Abstract:【Objective】The study is oriented to explore characteristics of the evolution of iron oxides and magnetic susceptibility in Stagnic Anthrosols, different in parent material, in subtropical China along chronosequence and their influencing factors. 【Method】Soil samples were collected for extraction of total Fe (Fe_t), free Fe oxides (Fe_d), amorphous Fe oxides (Fe_o) and organic-bound Fe (Fe_p) by the lithium metaborate fusion method, the dithionite-citrate-bicarbonate (DCB) method, acid ammonium oxalate (AAO) at pH=3 in the dark and Na-pyrophosphate at pH=10, separately. Magnetic susceptibility (MS) of the soils was measured at both low (0.47 kHz) and high frequencies (4.7 kHz) using a Bartington MS-2B meter with dual frequency sensor.【Result】Results show that along the chronosequence, weighted mean total Fe (Fe_t), free Fe oxides (Fe_d) and Fe_d/Fe_tin the 0~120 cm soil layer increased in the calcareous Stagnic Anthrosols, at a rate of 3.2 t hm^-2a^-1, 1.2 t hm^-2a^-1 and 0.04% a^-1, respectively, during the first 50 years and at a rate of 0.1 t hm^-2a^-1, 0.15 t hm^-2a^-1 and 0.01% a^-1, respectively, during the following 950 years (50 ~ 1000 years), but decreased in the acid Stagnic Anthrosols at a rate of 0.2 t hm^-2a^-1, 0.5 t hm^-2a^-1 and 0.03% a^-1, respectively, during the first 60 years and at a rate of 0.9 t hm^-2a^-1, 1.2 t hm^-2a^-1 and 0.06% a^-1 during the following 240 years (60 ~ 300 years), while weighted mean amorphous Fe oxides (Fe_o) and Fe_o/Fe_d in the 0~120 cm soil layer tended to decrease in the calcareous Stagnic Anthrosols, but did reversely in the acid Stagnic Anthrosols. Soil pH, Eh, and the balance between input of external Fe with irrigation and loss of internal Fe with leaching are major factors controlling the rates and pathways of Fe oxides transformation during the evolution of Stagnic Anthrosols. Along the chronosequence, the Stagnic Anthrosols derived from calcareous parent material underwent chronosequence demonstrated three phases of magnetic changes, i.e. the initial phase lasting a few decades dominated by rapid decreases in MS (magnetic susceptibility), SIRM (saturation isothermal remanent magnetization) and IRM_s (soft isothermal remanent magnetization); the second phase lasting a bit more than two centuries (50~300 years) demonstrating constant IRM_h (hard isothermal remanent magnetization) and slow decline in MS, SIRM, and IRM_s; and the third phase (300 ~ 1000 years), witnessing minimal changes in MS, SIRM and IRM_s but drastic decline in IRM_h, while the Stagnic Anthrosols derived from acid parent material did two phases, which in the 0~20 cm soil layer were completely different from those in the 20~120 cm soil layer: In the first phase (0~60 years), MS, SIRM and IRM_s declined but IRM_h increased rapidly in the 0~20 cm soil layer, while all the magnetic properties declined in the 20~120 cm soil layer; However, in the second phase (60~300 years), all the magnetic properties did not vary much in the 0~20 cm soil layer, while MS, SIRM, and IRM_s declined rapidly in the 20~120 cm soil layer after 150 years of paddy cultivation.【Conclusion】The overall magnetic depletion in the Stagnic Anthrosols, though different in parent material was attributed to the reductive dissolution of ferromagnetic minerals under artificial submergence.

Abstract:【Objective】To reveal the water loggogenic type of the fifth palaeosol in Xi’an area, and identify the water content, moisture balance and possible vegetation types when the S₅ developed.【Method】Field investigation, electron microscope observation and energy spectrum analysis were used to research relevant problem.【Result】The fifth palaeosol was composed of three layers, which was the best ancient soil in the loess. Based on the field investigation of the fifth palaeosol in Xi’an area, celadon spots were first discovered in the argillic horizon of this palaeosol, proving the accumulated water in the middle and upper paleosol and reducing environment during the development of S₅. The red ferruginous adhesive film developed very well, which has two kinds of micro structure under the electron microscope, one was crystal structure composed of newborn clay minerals, the other was amorphous colloid structure. According to the energy spectrum analysis, the content of Fe₂O₃、Al₂O₃ and SiO₂ in the red ferruginous adhesive film and celadon spots was between 12.85%～17.15%、20.45%～24.84% and 47.19%～54.17%, with average of 15.28%、23.07% and 52.13%, separately. Resulting from the deposition of green iron film on the surface of the red adhesive film, the difference of Fe₂O₃content between the red ferruginous adhesive film and celadon spots was quite small. The migration depth of red ferruginous adhesive film is 1.8m under the bottom of argillic horizon, and that was 6.3m from the top of the palaeosol.【Conclusion】These celadon spots in the fifth palaeosol were formed under the condition of deep ground water level. The major factor was abundant precipitation for reducing layer appearance above deep ground water level. The distribution depth of gravity water is up to 6.3m when the S₅developed and the climate would have been favorable to sustain forest development for a long period. At that time moisture content of reducing layer reached saturation state and that in the upper part of the soil was about 42%, generally speaking, soil moisture was quite adequate at then. During the development of S₅, the volume of receipts of soil water was more than the volume of expenditure, and the value of soil moisture balance was positive. Meanwhile, there was still sufficient atmospheric precipitation infiltrating to groundwater after evaporation, transpiration and surface runoff loess.

Abstract:【Objective】In this paper, two soil profiles at the Yangshao Village cultural relic site of Henan Province, one with obvious evidence of ancient human activities (cultural profile in short) and the other free of any ancient human disturbance (natural profile in short), were chosen for comparison. 【Method】 Through observation and analysis, the two profiles were compared in content of relics, physical and chemical properties and plant remain in an attempt to identify indicative characteristics of the soil in ancient human cultural sites. 【Result】Results show that the cultural profile was found to have some pottery shards, stone wares, ash pits, ash layers and cultural layers; its particle size composition tended to be sandy with sand content, on average, being 1.38 times as high as that in the natural profile and peaking up to 294 g kg^-1 in the ash layer; its average and variation coefficient of low frequency magnetic susceptibility（χ_lf）was 1.15 and 1.96 times, respectively, that of the natural profile with an abnormal peak of χ_lf appearing in Transition layer II, reaching up to 705.51×10^-8 m³ kg^-1; its average and variation coefficient of frequency-dependent magnetic susceptibility（χ_fd）was 0.99 and 0.78 times that of the natural profile, being obviously slightly lower than the latter; its average of redness (a*), yellowness（b*）and lightness（L*）was 0.83, 0.90 and 1.09, respectively, that of the natural profile; its variation coefficient of a*, b* and L* was 2.72, 2.83 and 0.97, respectively, that of natural profile; its a*, b* and L* fell down the bottom in the ash layer, being 2.45, 5.82 and 22.68, respectively; its average and variation coefficient of bulk density was 0.88 and 3.78 times, respectively, that of the natural profile; its bulk density was the lowest in the cultural layer, being 0.79 g cm^-3 , and higher than 1.00 g cm^-3 in all the other layers; its average and variation coefficient of total phosphorus was 4.95 and 1.18 times, respectively, that of the natural profile; its TP peaked in the ash and cultural layers up to 8734 mg kg^-1and 9879.6 mg kg^-1, respectively; The average content of Gramineae and Artemisia remains, including phytolith of setaria italic, panicum miliaceum, oryza sativa, was 2.56 and 1.27 times that of the natural profile; its δ¹³C tended to be more positive than the other’s; its indicative plants were dominated with C4; and its average content of carbon dust was 4.02 times that of the natural profile. 【Conclusion】Based on the above-listed findings, it is found that the soil under the influence of ancient human activities is apparently different from natural soils macroscopically in intrusive body and profile morphological; its main macro indicative feature is the existence of abundant relics, while its micro ones are being higher than natural soil in variation coefficients of particle size composition, magnetic susceptibility, chroma, total phosphorus, and bulk density, sandy in particle size composition, higher inχ_lf, slightly lower inχ_fd, lower in chroma, higher in total phosphorus, and lower in bulk density; the content and types of pollen and phytolith it contains are also different from those a natural soil has;, for instance, the former has rich Gramineae andArtemisia pollens and phytoliths identified to be of setaria italic, panicum miliaceum and oryza sativa. In addition, its content of carbon dust is higher with δ¹³C tending to be more positive.

Abstract:【Objective】Traditional soil surveyshave turned out huge piles ofconventional soil mapsvarious in scale and nature.Although these maps are not very high in spatial detail or accuracy, they contain large volumes of valuable expertise concerning soil-environment relationships in relevant regions. Data mining models can be used to extract from these maps information useful to updatingof the conventional soil maps. In using data mining models to extract the information of soil spatial distribution, selection of training samples is an essential step.Quality of training samples will affect to a great extent full expression of soil-environmental relationships and accuracy of the updatedsoil maps.The area-weighted proportion method was a common method for selecting of training samples. However, this method usually assigns too much weight to those soil types large in area, so that too many training samples would be selected. Meanwhile, random selection of training samples from polygons of the same soil type may bring in some “noise” samples, occurring ontransition areas between soil types,which make the accuracy of the updated soil maps not high.【Method】In this paper, a new method was developed to select training samples from conventional soil mapsbased on grading of soil types by area.The method consists of the following two steps. The first step is to specifytypical (representative)samples of each soil type based on conventional soil map, so as to avoid generation of “noise pixels” due to misplacement in delineating boundaries between soil polygons.It is assumed that most of the boundaries of the soil polygons of a certain soil type arecorrectly delineated, and then the peak of the histogram of a certain environmental factor enclosed in the polygons of the soil type represents the typical environmental conditionunder which the soil develops or exists. The pixels close to the selectedenvironmentalconditions or within the peak zone of the histogram are considered as representative samples. All the representative samples selected through histograms of various environmental conditions of a certain soil type are combined into a typical sample set of the soil type.The second step is to select training samples based on grading of soil type by area, with a view to keep the numbers of samples of each soil type in balance. Soil types in the samegrade should have the same number of training samples out of the typical sample set of each of the soil types.The random forest model adopted in this study is to update conventional soil maps based on the selected training samples. To evaluate the above-proposed method, comparison was made between this method and two other training sample selection methods.Oneis to randomly select trainingsamples from polygons of each soil type and the number oftraining samples for each soil type depended on proportion of the grade the soil type is in, while the other is the common area-weighed proportion method, which randomly selects training samples form the soil polygons of a soil type and the number of training samples for each soil type depended on the area-weighted proportion of the soil type.The study area was a small watershed inRaffelson, Wisconsin of USA.The three selection methods were tried repeatedly, each for 500 times, and validate mean precision of the inferential mapping and proportion of the updated conventional soil maps with 92 independent verification samples in the field.【Result】Resultsshow that based on the 500 trails, comparison of this method with the other two reveals thatabout 79.5%, 71.8% and 63.6% of the conventional soil maps could be updated, respectively. Meanwhile, the updatedsoil maps based on the proposed training sample selectionmethod are more consistent with the actual soil distribution inthe Raffelson watershed.【Conclusion】It is concluded that the proposed method is an effective training sample selection method for data mining model to update conventional soil maps.

Abstract:【Objective】Gully erosion is very severe in the Yuanmou Dry-hot Valley Region, dominated with headward erosion, which is characterized by steep gully headcuts. During the field investigations, headcut height is often regarded as one of the main indices of distinguishing the type of gully head activity. The abrupt drop of concentrated flow at headcut would cause a sudden change of the runoff in hydrodynamics, thus accelerating the headward erosion processes. It is, therefore, of great significance to carry out the preliminary study on effects of headcut height on characteristics of soil erosion and sediment yield in the gully headward processes, to the gully erosion research in this region as scientific supplement.【Method】To simulate different step heights, based on an in-situ active bank gully head, two experimental plots were constructed with the headcut height of 25 cm and 50 cm, separately. And in November 2015 a series of in-situ scouring experiments were carried out with the flow set at 120 Lmin^-1. The entire scouring test lasted 140 min, consisting of 5 test runs. During the scouring tests, cross-sections were set in the drainage area and along the gully bed at1 m intervals, for observation of changes of runoff in width, depth and velocity at regular intervals. Meanwhile, sediment samples were also collected at regular time intervals at the outlet of the drainage area and the plots, separately, for analysis of sediment content with the oven drying method. Besides, before and after the experiment, topographic data of the two plots were collected with the high-resolution close range digital photogrammetry measurements, for analysis of changes in landform, morphological parameters and net soil loss.【Result】Results showed that: (1)The scouring power of jet flow differed significantly between the two plots. When surface runoff turned into impinging jets, the mean potential energy transformation in the two plots was about 4.89and 9.78Js^-1, separately with shear stress reaching 25.9 and 53.5 Pa, on average respectively, both in multiple relations. And the velocity at the instance when the flow touched the bottom of the headcut reached as high as 2.28 and 3.18 ms^-1, separately, which was 4.1 and 5.6 times larger than that at the brink point respectively. (2) The two plots also differed significantly in morphological characteristics of plunge pools and soil erosion volume at lower end. At the end of the experiment, the incision depth of jet flow reached7.38 and 7.50 cm in maximum, and was 3.87 and 5.16 cm on average, separately, in the two plots. Especially, the growth of incision depth with the experiment going on varied sharply between the two plots. Furthermore, during the scouring tests, the soil erosion cumulative contribution rate at the gully headwall and in the bed at the lower end reached as high as45.1% and 64.9%, and was 41% and 54%on average. (3) The two plots also differed sharply in runoff sediment concentration (p< 0.1). Excluding the maximum concentration at the beginning of each test, the mean sediment concentration was 7.51 and 18.76 g L^-1, separately, about 1.5 times in difference. Especially, during the first previous 80 min of the scouring tests, when runoff flew over the headcut, the runoff sediment concentration increased by 25.28 and 108.78 g L^-1 in maximum and by 6.25 and 25.49 g L^-1on average, separately, in the two plots. 【Conclusion】This study has tentatively concluded that the effect of gully headcut height affecting runoff scouring force and characteristics of soil erosion and sediment yield is probably the key factor influencing the headward erosion process. However, it is still not very clear about how the effect would vary in the case of higher headcuts. More experiments with a variety of headcut heights should be conducted, in an attempt to supplement more complete meaningful theories to the study on dynamics and mechanisms of gully headward erosion in dry-hot valley regions.

Abstract:【Objective】The region of loess slopes covered with sporadic aeolian sand is the most serious erosion-stricken area in the aeolian-water erosion interlaced zone of the Loess Plateau. This project is oriented to study characteristics of the soil erosion in this region in an attempt to provide some principal theory for prediction and control of soil erosion in the aeolian-water erosion interlaced zone. Observations in this special region found that aeolian sand-covered loess slopes were different in runoff production pattern and erosion process from ordinary loess slopes. So far, a little has been reported about studies on soil erosion on this special type of slopes. 【Method】An indoor experiment with simulated rainfalls on soil erosion on sand-covered loess slopes was carried out. The experiment was designed to have only one rainfall intensity (90 mm h^-1), one slope gradient (15°), three levels of thickness for overlying aeolian sand (2 cm, 5 cm and 10 cm) and five patterns of particle size composition(100%<0.25 mm, 75%<0.25 mm 25%>0.25 mm, 50%<0.25 mm 50%>0.25 mm, original aeolian sand and 100%>0.25 mm). 【Result】Results show that overlying aeolian sand layers delayed the initiation of runoff and reduced the generation rate and volume of runoff, but increased the yielding rate and volume of sediment on loess slopes. The initiation of runoff on slopes covered with 2 cm, 5 cm and 10 cm thick of aeolian sand was 6~10 times, 12~20 times and 16~26 times later than that on the ordinary loess slope, respectively. Thickness of the aeolian sand layer is the main factor affecting delayed runoff and sediment yield. The thicker the overlying sand layer, the later the initiation of runoff, the lower the runoff rate and runoff volume and the higher the yielding rate and volume of sediment yield. During the rainfall process, runoff and sediment fluctuated sharply in rate and volume and the fluctuation intensified with the aeolian sand layer increasing in thickness. The effect of particle size composition of the sand layer on runoff and sediment yield varied with thickness of the sand layer. On slopes covered with a sand layer 2 cm in thickness, runoff and sediment yield tended to increase with the sand layer increasing in particle size during the initial period of rainfall, but no such a tendency was observed during the late period of rainfall. On slopes covered with a sand layer 5 cm in thickness, runoff increased in rate with the sand layer increasing particle size. The slopes covered with coarse sand was higher in erosion rate than the slopes covered with find sand during the initial period of rainfall, and it went reversely in the late period of rainfall. On slopes covered with a sand layer 10 cm in thickness, runoff and sediment yield did not vary much with particle size composition of the sand layer. There might be a reasonable range of aeolian sand thickness in which the influence of particle size composition of the sand layer on runoff and sediment yield existed. In short, thickness, particle size composition and their interaction significantly (p<0.05) influence the initiation of runoff, 60-min runoff volume and 60-min sediment yield. 【Conclusion】 The runoff production process on aeolian sand-covered loess slopes goes as vertical infiltration of rainwater - flow at the interface between sand layer and loess layer – seepage at the toe of the sand layer – overland runoff, while the erosion process goes as seepage erosion at the toe of the sand layer – retrogressive collapse caused by gravity and flow – surface runoff transport, which are completely different from the pattern of runoff yield under excessive infiltration and the erosion development process of splash erosion – sheet erosion - rill erosion on bare loess slopes.

Abstract:【Objective】Collapse of hills is a form of soil erosion widely distributed in South China. It occurs mainly in denudated granite hilly areas where vegetation has been destroyed. The collapses threaten the security of farmlands and residents, and cause huge economic losses. A typical collapsing hill contains five parts, that is, catchment slope, collapsed wall, colluvial deposits, gullies and alluvial fan. Colluvial deposits are poor in soil structure, posing the main source of erosion sediment in collapsing hills, weak in erosion resistance and very susceptible to runoff scouring. The traditional method of managing collapsing hills combines land leveling and planting of trees and grass. However, the method per disturbs the soil and besides, the benefits of revegetation come into being slowly. Soil particles in colluvial deposits are readily detachable with surface runoff. Now a new type of hydrophilic polyurethane, called W-OH, is available and good to intensify the cohesive force of soil particles between each other, and hence can be used to make up the weakness of the traditional method. 【Method】In this study a slope flume experiment was carried out to analyze effect of W-OH on soil detachment rate of colluvial deposits. The experiment was designed to have four W-OH concentrations, i.e. 2%, 3%, 4%, 5%, five slope gradients, i.e.8.8%, 17.6%, 26.8%, 36.4% and 46.6% and three flow rates, i.e.1.0 L s^-1, 2.0 L s^-1 and 3.0 L s^-1. The slope flume had a chamber to hold soil samples. Before the experiment, the soil samples were soaked in water for 12 hours to make the samples saturated and in the process of soaking, the water surface was kept slightly lower than the upper surface of the ring-knife. Slope gradient of the flume was regulated with a pulley system and water flow with a group of valves. Before the scouring process started, soil moisture content of the samples was measured, and soil detachment rate was calculated out of the difference between the soil samples before and after the experiment in dry weight. In order to facilitate the use of soil erosion models to estimate the effect of W-OH mitigating erosion, relationships of soil detachment rate with flow shear stress, stream power and unit stream power were analyzed. 【Result】Results show that as affected by a specific combination of slope gradient and flow rate, soil detachment rate decreased with the increasing concentration of W-OH. Such a trend was not obvious when the slope gradient was 8.8% and the flow rate 1.0 L s^-1 or 2.0 L s^-1。When the flume was over 8.8% in slope gradient, soil detachment rate displayed a clear gradient between the treatments and dropped by 1~3 orders of magnitude, as compared to CK, and the higher the W-OH application rate, the greater the descend gradient of the soil detachment rate. The analysis of relationships of soil detachment rate with hydraulic parameters shows that compared with CK, critical flow shear stress of the soil applied with W-OH increased. 【Conclusion】All the findings listed above indicate that the effect of W-OH reducing soil detachment rate is remarkable, and such an effect increases with increasing W-OH application rate. Under different circumstances, to reduce soil detachment rate decreases by two orders of magnitude, it is necessary to apply W-OH at a corresponding rate. Once W-OH is applied, a consolidated surface layer is formed with the surface soil of colluvial deposits, thus altering the process of soil erosion. When the consolidated surface layer is intact, soil erosion is very weak, and once the consolidated surface layer is ripped by surface runoff, soilerosion aggravates dramatically.

Abstract:【Objective】Safety of agricultural producing areas has become an extensive concern. Heavy metal pollution of agricultural soils not only brings about adverse effects on the soil ecosystem, but also is closely related to food safety and potential health hazard. How to assessment the risk of heavy metals pollution of agricultural soils is of some practical and far-reaching significance. Therefore, it is a very urgent task to investigate the status of heavy metals in agricultural soils and assess the risk with a variety of assessment methods. The findings in this study may help decision-makers select appropriate assessment methods for rational assessment and zoning of the agricultural producing area and remedy contaminated soils scientifically.【Method】Taking the agricultural soil in Baguazhou Town of Nanjing as an example, this study focused on the five heavy metal elements, i.e. As, Cd, Cr, Hg and Pb, that are relatively more harmful than the others to the human body and analyzed the soil samples collected from the surface soil layer (0~20cm) in 2015. In October 2015, the Chinese Ministry of Agriculture promulgated the “National technical regulations for safety assessment of heavy metals in agricultural producing areas” (Standard Methods for Producing Areas), which has modified the criteria of some relevant elements and specified the use of a new method called the maximum single factor index method for assessing integrated risk of heavy metals in agricultural soils. It is necessary to adopt the specific standard and method to do the assessment. The study used the Traditional Standard Method (T-SM) and the Standard Method for Producing Areas (PA-SM) to assess the risk of heavy metals in the study area and compared the two methods for differences. Furthermore, an Improved Geo-accumulation Comprehensive Index Method (IG-M) was created to assess the ecological risk of heavy metals in the study area. With the aid of GIS geostatistics, spatial distribution of different heavy metals risk levels was characterized. The inverse distance weighting interpolation method was used in this study.【Result】Results show that the average concentration of As, Cd, Cr, Hg and Pb was11.0, 0.38, 92.1, 0.08 and 34.5 mg kg^-1, respectively. All of them, except for Hg, were beyond their background values in Nanjing. The elements of Cd, Cr and Pb exceeded the criteria for soil quality to a varying extent, especially Cd, which should be paid more attention to. The use of PA-SM found that over 80% of arable land in Baguazhou was risk-free and Cd and Pb were the main factors that posed a low risk. Risk areas scattered across the southwest, south and east parts of Baguazhou, which may be associated with the distribution of large and medium factories and plants, while the use of T-SM displayed that only Cd exceeded the standard. The use of PA-SM revealed that the risks of Cd, Cr and Pb were relatively high due to human activities, while the use of the IG-M disclosed that the study area as a whole was good in ecology.【Conclusion】Generally speaking, the agricultural environment of Baguazhou was good, but the risk area in the south needs intensive monitoring and adoption of pollution control measures. T-SM and PA-SM can work together to identify risk-free region, but PA-SM can better evaluate and divide risk areas. Therefore, it is recommended to use PA-SM in conjunction with IG-M to assess risk levels, spatial distribution and ecological risk of the heavy metals in the agricultural soil of the region.

Abstract:【Objective】This paper is to illustrate the status quo of soil lead contents and potential risk of soil lead in Guangxi. 【Method】By searching various important databases (China National Knowledge Infrastructure, Wanfang Data, Vip, Science Direct, Web of Science, Springer, etc.) for papers on soil lead contents in Guangxi published at home and abroad since the 1990s. A total of 57 papers were retrieved involving 5 807 soil samples from 20 areas in Guangxi. As the areas covered varied in background and function, the soil samples were sorted into five groups (clean soil, soil from urban zone, soil from industrial and mining zone, soil from farmland in non-industrial and mining zone, and soil from farmland in industrial and mining zone). To make the data comparable with the prevailing criteria of the Standard for Soil Environment Quality (GB15618-1995), means it the target papers tallying with normal distribution or data acquired from the tables and/or figures in the papers were collated. 【Result】Results show that lead concentration in the soil of Guangxi varied in the range of 18.80 ~ 6 350 mg kg^-1, with geometric mean being 147.9 mg kg^-1 or 7.86 times as high as the background value. Obviously it was lower than Grade II Criterion of the Standard for Soil Environment Quality (GB15618-1995). The soil in the Siding lead-zinc mining area was 6 350 mg kg^-1 or the highest in lead content, with pollution accumulation index reaching up to 278.5. Soils in different function zones varied sharply in soil lead content distribution. The lead content in clean soil, soil in urban area, soil in industrial and mining zone, soil in farmland of non-industrial and mining zone and soil in farmland of industrial and mining zoneswas26.17, 32.88, 244.5, 42.93 and 347.6 mg kg^-1, respectively, or 1.391, 1.747, 12.99, 2.281 and 18.47 times, respectively, the background value in Guangxi. Soil lead content in clean soil, soil in urban area, and soil in farmland of non-industrial and mining zone was moderate in spatial variability, but in the other two groups, it was high in spatial variability. The coefficient of variation (CV) of the soil in Guangxi as a whole was 220.8%. Of the total soil samples, 23% were ＞ 1 in lead pollution index and about 7% fell into the category of “heavily polluted”. The heavily polluted soil samples were collected mainly from Nandan, Rongan, etc., where the mining activities were very intensive. 【Conclusion】Based on the distribution of lead mines and areas not covered by the survey, it is suggested that positive management measures be adopted in those highly polluted areas, such as Nandan, Jinchengjiang, Huanjiang, Rongan, Yangshuo, Chongzuo, etc., and further in-depth investigations be made of the areas relatively rich in lead and zinc resources, such as Daxin, Wuxuan, Cenxi and Hezhou.

Abstract:Contamination of farmland soils with persistent organic pollutants (POPs) is still a problem of environmental concerns. Take hexachlorobenzene (HCB) and 1,1,1-trichloro-2,2-bis-4-chlorophenyl ethane (DDT) for example, pollution of farmland soils is generally characterized by being low in concentration and vast in area, and new pollutants flow in unceasingly from non-point sources. Farmland soils are rich in microorganisms, which potentially play a significant role in degrading such POPs. In this study, HCB and DDT were selected as representative of highly chlorinated and low chlorinated POPs, respectively, and soils were collected from a years-long paddy field and a years-long sugarcane field for use to study potentials of the soils naturally attenuating HCB and DDT. ¹⁴C-labeled HCB and ¹⁴C-labeled DDT were used for tracing mineralization, volatilization, metabolites, and bound residues to overcome the shortage of the traditional methodsfor studying the degradation of compounds. Traditional methods merely monitor the concentrations of the mother compound and/or the metabolites which may be sheltered in soil matrix via adsorption, and result in overestimating of the degradation extent. ¹⁴C-HCB and ¹⁴C-DDT were spiked respectively into the paddy soil and the sugarcane field soil, then incubated aerobically under the optimal water content (63% for paddy soil, 35% for sugarcane field soil) in an attempt to get the highest mineralization rate. Both the ¹⁴CO₂ and the ¹⁴C-volatiles were trapped by specific liquid in a closed systemand measured with a scintillation counter. ¹⁴CO2 production corresponds to mineralization degree of the compounds. After 84 days of incubation, only 0.14% of ¹⁴C-HCB and 3% of ¹⁴C-DDT were mineralized. ASE extraction showed that penta-chlorobenzene was the only detected metabolites of HCB. DDD, DDE and DDMU were found to be the main metabolites of DDT. In the paddy soil samples, DDD was relatively higher in concentration,whereas in the sugarcane field soil samples DDE was. The extremely low mineralization extents indicate that soils are very low in potential of attenuating HCB and DDT naturally. Mere aerobic treatment is not adequate to remove HCB and DDT from soil. It is thereby inferred that it is necessary to treat the polluted soil anaerobically to remove such compounds, because in anaerobic incubation HCB would undergo reductive dechlorination which favors aerobic hydroxylation of benzene rings by dioxygenase or lignoltic enzymes, and anaerobic incubation may probably promote the growth of potential DDT degraders, like the benzene- and phenol-mineralization microorganisms that can trigger ring-cleavage reaction. Comparison between HCB and DDT in the total mineralization indicates that under aerobic conditions, high chlorinated compounds are much more persistent than the lower chlorinated compounds. HCB and DDT were quite low in volatilization, being in the range 0.1% ~ 0.6%, which indicates volatilization is not an important process of HCB and DDT in environment. Besides, compost from garden waste was introduced into the DDT incubation experiment to simulate effects of exogenous carbon on mineralization and volatilization of DDT. Results show that the compost increased the mineralization and the non-extractable bound residues of DDT, but reduced the volatilization of the substance; however, the effects were not statistically significant. From an engineering application view, the use of compost to enhancing DDT mineralization was not cost effective. All the findings in this study may serve as reference of good reasons for understanding the natural attenuation of the chlorinated organic compounds in natural soils, and for remediation of soils polluted with such compounds. Since paddy soil and sugarcane field soil have their own specific dominant degradation mechanisms, it is more advisable to design case-specific strategies, anaerobic, aerobic or anaerobic-aerobic alternation, to have the pollutants degraded the most efficiently.

Abstract:【Objecivet】Paichongding, a neonicotinoid type of insecticide recently developed in China, is easily absorbed by plant and transferred inside the plant. Now it is used mainly for controlling insects of homoptera and expected to have a bright future as a promising new pesticide. Once pesticides enter into the soil, they readily get adsorbed, desorbed and leached in the soil. Their sorption and desorption are the main factors influencing fate of the pesticides in the soil, and seriously affecting their behaviors, like chemical and microbial degradation, volatilization and leaching, and moreover, it is an important index in pesticide environmental safety assessment. The study on its adsorption and leaching characteristics is of important significance to prediction of its environmental behavior and pollution in the soil. 【Method】In order to provide a scientific basis for the study of environmental behavior, migration and transformation, of paichongding in the soil, the batch oscillating equilibration method and column leaching method were adopted to explore adsorption and leaching characteristics of paichongding in three typical soils, that is brown soil from Tai’an, red soil from Fujian and black soil from Northeast China, and effects of three soil amendments on leaching of the substance in the soils. Residue of the pesticide in the soil was determined with SPE-HPLC. As in the leachate, the concentration of paichongding was low, the solution underwent concentration and purification with SPE before determination of residue of paichongding in the leachate with HPLC. 【Result】Results show that the adsorption equilibrium time of paichongding was 12 h, 9 h and 12 h in the red soil, brown soil and black soil, respectively, by absorption dynamics. The Freundlich model and the Linear isothermal adsorption model can well be used to describe the adsorption processes of paichongding in soil. Of the pesticide, distribution coefficient, Kd, was 23.16、11.24 and 4.68, and adsorption constant was 22.03、11.69 and 5.05 in the black soil, red soil and brown soil, respectively. Among the three soils, black soil was the highest in paichongding adsorption capacity and brown soil was the lowest. The adsorption isotherms of paichongding in three different soils fitted fairly the Freundlich model and Linear model at 25℃, with Koc being 1 619、2 094 and 495, respectively, and the absolute values of free energy in all the three soils were less than 40 kJ mol-1, so the adsorption of paichongding in these soils belonged to physical adsorption. Leaching of paichongding varied in the three soils. In the brown soil, paichongding migration rate was the highest, and slightly increased with rising dosage of the pesticide, and the variation with dosage was not significant; In the red soil and black soil, dosage did not have much effect on leaching rate of the pesticide, either, and Only a slight difference in leaching rate was found in the red soil between treatments applied with 200 μg and 500 μg of paichongding. One-way ANOVA analysis of the black soil shows that the effect of dosage was not significant. In the leachate from the brown soil, red soil and black soil, paichongding residue accounted for 16.69~16.86%, 11.55~13.52% and 8.98~9.35% of the total applied, respectively. As the black soil was the highest in adsorption capacity, pesticide in the soil was the lowest in mobility. Residue of paichongding in the red soil and black soil decreased with soil depth, but by a little margin. Once activated carbon was added into the soils, it reduced not only migration and leaching rate of paichongding significantly, but also extractable residue by 34.8%, 36.79% and 16.93%, respectively, in the brown soil, red soil and black soil; No residue was detected in the leachates from the red soil and black soil, while 76.4% less residue was found in the leachate from the brown soil in the treatments amended with activated carbon. The addition of 0.5% humic acid and peat, separately, reduced the leaching rate of the pesticide by 25.1% and 17.1%, respectively, in the brown soil, by 29.7%% and 23.3%, respectively, in the red soil, and by 42.1% and 27.6 %, respectively, in the black soil. 【Conclusion】 In brief, the amendment of 0.5% activated carbon, humic acid and peat into the paichongding-contaminated soils can significantly reduce leaching rate of the substance, and hence its risk of polluting the groundwater.

Abstract:【Objective】How to monitor and assess soil Cd pollution and bioavailability is currently an issue of great concern. However, measurements of soil available Cd contents using the conventional chemical methods may only serve as certain reference, because they are not good enough to intuitively and truly reflect the damages soil Cd²⁺ does to plants. Bryophyta are simple in structure, free of any cuticle on their surface and quite sensitive to pollutants, so they are usually used in monitoring environmental pollution. In this paper, an effective method was preliminarily studied to monitor and evaluate soil Cd pollution and Cd bioavailability using Pogonatum inflexum, a species of bryophyte highly sensitive to soil Cd. A mature plant of the sporophytic generation of Pogonatum inflexum could be as high as 10 cm. Besides, it is simple in surface structure with no vascular bundle differentiation, but with sporophytes parasitizing on gametophytes. Furthermore, the various organs of Pogonatum inflexum are homogeneous in cell structure and mostly monolayer cells.【Method】In the experiment to validate effectiveness of the method, the tested soil was prepared into media, different in Cd contamination degree (1~5 mg kg^-1), for culture of Pogonatum inflexum. Growth, Cd enrichment, chlorophyll content, soluble protein content and MDA concentration of the bryophyte was observed and/or determined. Soil available Cd contents extracted with acetic acid were cited as indicator parameter for soil Cd bioavailability, and then analysis was done of correlations of the above described indices with content of soil total Cd and content of soil available Cd, separately.【Result】Results show that in the test soil, bioavailable Cd accounted for about 20%~40% of total Cd. All the indexes of Pogonatum inflexummentioned above were closely related to soil Cd stress, especially when soil Cd concentration was higher than 3 mg kg^-1. Pogonatum inflexum was low in Cd enrichment and in tolerance to Cd as well. It could enrich as high as Cd 1.627 mg kg^-1, with enrichment coefficient being 63.9% and Cd concentration in Pogonatum inflexum was more closely related to soil bioavailable Cd than to soil total Cd. Pogonatum inflexum responded quite apparently to soil Cd pollution, with visible symptoms such as damaged sporophytes and gametophytes. When soil Cd concentration was higher than 1~2 mg kg^-1 (available Cd concentration was higher than 0.559 mg kg^-1), leaves ofPogonatum inflexum turned yellow and brown; when soil Cd concentration got up to 5 mg kg^-1, seta softened and kinked, till the plants withered dead. Changes in physiological and biochemical indexes of the tested plants, such as contents of chlorophyll, soluble protein and MDA, were apparently related to soil Cd stress, especially to soil bioavailable Cd contents, and corresponded well to changes in soil Cd pollution level.【Conclusion】Therefore, the contents of chlorophyll, soluble protein and MDA in Pogonatum inflexum can be used as indicators to monitor and evaluate soil Cd pollution and bioavailabilty. Pogonatum inflexum is an ideal material to be used to effectively monitor soil Cd pollution thanks to its high sensitivity to soil Cd²⁺ and its readiness and intuitiveness in displaying damage symptoms.

Abstract:【Objective】 Soil aggregates are an essential material foundation of soil structure and an important carrier of soil nutrients. Rhizosphere is the most active region of matter and energy exchanging between crop and soil, and it differs from the bulk soil in many of physical and chemical conditions and biochemical processes, thereby influencing soil aggregation. A number of studies have been reported paying attention mostly to effects of organic manure application, tillage management and some other regulatory measures on soil aggregates during fallow seasons, rather than to differences of rhizospheric soil from bulk soil in dynamic variation of soil aggregate composition during the rice growing seasons. It is of great significance to study changes in volume of soil aggregates and contents of organic carbon and nitrogen therein in the rhizospheric and non-rhizospheric soils during the rice growing season to revelation of impacts of artificial cultivation on the changes and in-depth understanding of interactions between plant and soil and variation of soil quality.【Method】A field rhizo-bag experiment using two types of red paddy soils different in fertility was conducted in the Yingtan National Field Observation and Research Station of Farmland Ecosystem, Jiangxi Province, China. The soils were collected from the topsoil layers (0~15 cm) of two typical paddy fields near the station in March 2012. Two-layered root bags were used to separate rhizosphere from non-rhizosphere and bulk soil. During the experiment, root bags and the soils around were collected before rice transplanting and at the tillering, booting and maturing stages of rice, separately. The rhizosphere and non-rhizosphere soils were saved individually and separated into five aggregate-size fractions (>2 mm, 1 ~ 2 mm, 0.25 ~ 1 mm, 0.053 ~ 0.25 mm and <0.053 mm) using the wet sieving method. Mass fraction, percentage of aggregate destruction (PAD) and mean weight diameter (MWD) of water-stable macro-aggregates were calculated to determine stability of the aggregates. Organic carbon and total nitrogen in the aggregates were measured.【Result】 Results show that the aggregates in the low fertility soil were dominated mainly with the fraction of >0.25 mm macro-aggregates (56.2%~64.0%), and the amounts of 0.25~1 mm size was the highest. Except for the aggregates 1~2 mm in size, all the fractions of aggregates in the rhizosphere soil changed significantly in content during the rice growing season. Sampling time and interactions between sampling time and rhizospheric effect remarkably affected the amounts of the fractions of 0.25~1 mm and 0.053~0.25 mm. In the high fertility soil, <0.25 mm micro-aggregates accounted for 59.8%~72.0% of the total soil aggregates, and the 0.053~0.25 mm fraction made up the largest proportion. Sampling time affected the content of >0.25 mm macro-aggregates the most, while interactions between rhizospheric effect and sampling time did the content of >2 mm fraction the most. Compared with non-rhizospheric soils, rhizospheric soils were low in PAD, but high in MWD, which indicates that rice cultivation helps improve stability of rhizosphere soil. Contents of organic carbon (SOC) and total nitrogen (TN) were the highest in the 1~2 mm fraction of aggregates and the lowest in the 0.053~0.25 mm fraction, and obviously much higher in macro-aggregates than in micro-aggregates. The SOC content in rhizosphere aggregates during the crop maturing period did not have much difference from that before rice transplanting. But SOC contents in rhizosphere aggregates did fluctuate significantly during the tillering and booting stages of rice. The SOC content in the 0.053~0.25 mm fraction was significantly influenced by sampling time. In the low fertility soil, there was no significant difference in aggregate-associated SOC contents between rhizosphere and non-rhizosphere soils. But in the high fertility soil, SOC contents in the >2 mm fraction at the tillering stage, in the 1~2 mm fraction at the booting stage and in the 0.053~0.25 mm fraction and <0.053 mm fraction at the maturing stage were significantly lower in the rhizospheric soil than in the non-rhizospheric soil. The growth of rice decreased the content of TN in macro-aggregates. The effect of rice growth was more significant in the high fertility soil. 【Conclusion】In the low fertility soil, rhizospheric effect affects mainly the composition and stability of aggregates, while sampling time does contents of SOC and TN in aggregates. In the high fertility soil, composition of aggregates and distribution of SOC and TN vary under the joint impact of rhizospheric effect and sampling time.

Abstract:【Objective】How to reasonably use of corn stover has become an important topic in the agricultural regions of China. Corn stover incorporation into the field is the best way in corn stover utilization. However, the method of corn stover incorporation used to either overcast the corn stover on the surface of the field like mulching or incorporate the corn stover into the shallow topsoil layer, which would obviously bring about some problems, like impeding rise of soil temperature, seedling growth, favoring incidence of insect pests. Corn stover deep incorporation (CSDI) refers to burying corn stover deeply into the subsoil layer and it is believed to be a sustainable utilization model to solve the problem of burning of corn stover and degradation of soil fertility. But with the days going on, it is not clear that the dynamic change in composition and structural characteristics of soil humus caused by CSDI. This paper mainly deals with the effect of the corn stover applied duration on components of soil humus and structural characteristics of humic acid in the soil, so as to provide some theoretical basis for determining the interval of CSDI.【Method】A field experiment was conducted in a mono-cropping corn field of black soil at the Experiment Station of the Jilin Agricultural University, with four treatments, that is, CK (No corn stover incorporated), CSDI-2014 (One year after the corn stover deep incorporation), CSDI-2013 (Two years after the corn stover deep incorporation) and CSDI-2012 (Three years after the corn stover deep incorporation). Humus, including fulvic acid (FA), humic acid (HA) and humin (HM) with the modified humus component extraction method for analysis of composition and then HA was further extracted with the IHSS method for analysis of element composition, infrared spectrum, thermogravimetry, and structure with differential thermal analysis. 【Result】Results show that in Treatment CSDI-2014 significantly increases the content of organic carbon by 23.7%, 30.5%, 27.3% and 46.1% in the soil, HA, FA and HM, respectively, and especially in the subsoil; but it did not affect PQ much; however, it reduced condensation degree and oxidation degree of the HA significantly and (O+S)/C ratio by 14.31% and 14.68%, while raising H/C ratio by 27.74% and 28.86% in the topsoil and subsoil. Moreover, it increased the content of aromatic-C and aliphatic chain hydrocarbon, reduced thermal stability and made simpler the structure of HA. The effects, however, varied with the time going on, in Treatment CSDI-2012, organic C decreased in content in the soil, FA and HM, but increased in HA, while PQ changed significantly; HA displayed an increasing trend in condensation and oxidation degrees and became lower in aliphaticity, higher in aromaticity, and more complicated in structure. 【Conclusion】With the days going on, the deep-incorporated corn stover in the soil gets mineralized and decomposed steadily, weakening its effects on composition of the soil humus and structural characteristics of the humic acid in the soil.

Abstract:【Objective】This study is to explore how soil carbon, nitrogen and phosphorus were distributed vertically along the slope of the Taibai Mountain and elaborate eco-stoichiometric characteristics of these soil nutrient elements relative to elevation from 1 700 m to 3 500 m.【Method】Soil samples were collected along the slope at an interval of 100 m in elevation and soil physicochemical properties were mensurated for analysis. 【Result】Results show as follows. (1) Soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) in the soil varied in the range of 23.56~83.59 g kg^-1, 2.00~5.77 g kg^-1 and 0.32~0.47 g kg^-1, respectively, and averaged 40.58 g kg^-1, 3.11 g kg^-1 and 0.39 g kg^-1, respectively. Soil organic carbon and TN displayed a trend of rising-first-and-declining-later with the rising elevation and a peak appeared at 3 000 m. The content of SOC was obviously higher in the middle section of the slope, 2 200~2 300 m in elevation than in the upper and lower sections of the slope and TN varied similarly in vertical distribution. So soil carbon and nitrogen content were quite consistent in spatial variation. However, TP varied much less spatially and along the altitude gradient. Along the slope of the Taibai Mountain, stand different types of forests in belt. In these different forest belts, regardless of type, the distributions of soil carbon, nitrogen, phosphorus were somewhat coupled. Soil C:N, C:P and N:P varied in the range of 7.17 ~ 18.41, 60.61 ~ 190.4 and 5.81 ~ 12.26, respectively, and averaged 12.99, 102.2 and 7.90. With rising elevation, soil C:N decreased in the broad-leaved forest belt and increased in the coniferous forest; soil C:N was quite close to the average (12.4) of the global forest soil (0~10 cm); soil C:P varied in a trend similar to what soil C:N did, and peaked in the section of the slope, 2 200~2 300 m in elevation, getting higher than the average (81.9) of the global forest soil (0~10 cm); and soil N:P was similar to soil C:N in variation. (2) SOC, TN and TP varied in the range of 23.84~49.54 g kg^-1, 2.42~3.62 g kg^-1 and 0.36~0.42 g kg^-1, and averaged 39.82 g kg^-1, 2.97 g kg^-1 and 0.39 g kg^-1, respectively, in the studied slope under whatever type of forest. SOC was obviously lower in the fir forest belt than in the broad-leaved forest ( Quercus acutidentata forest, liaodong oak forest, birch forest) belt; soil TN in the coniferous forest belt was significantly lower than that in the Quercus liaotungensis forest and alpine meadow belts, and similar to those in the others; and soil TP differed slightly between forest belts. Soil C:N, C:P and N:P varied in the range of 9.80 ~ 15.49, 67.01 ~ 119.44 and 6.32 ~ 9.21, and averaged 13.36, 100.81 and 7.54, respectively. The two broad-leaved forests ( Quercus liaotungensis forest belt and birch forest belt) and the alpine meadow belt were the highest in content of soil carbon and nitrogen and their ecological stoichiometric ratio, while the fir forest belt was the lowest. (3) Temperature, water content, elevation and vegetation may quite well explain the variation of the ecological stoichiometry of soil carbon, nitrogen and phosphorus. Redundancy analysis shows that the points of Ⅰ and Ⅰ on the sequencing axis may explain 57.94% and 9.21% of the variation of the contents of soil nutrients and their stoichiometric characteristics, and the four factors, temperature, water content, elevation and vegetation, may explain 25.7%, 22.5%, 20.9% and 18.7%, respectively, of the system variation. Obviously, elevation is the major factor that directly determines vegetation type and environmental conditions, which in turn affect distribution and eco-stoichiometry of soil nutrients. 【Conclusion】All the findings in this study may serve as scientific basis for determining soil nutrient supply and its limiting factors in these forest soils and evaluating quality of these soils. However, more effects should be made to further discuss the issue of soil nutrients and their eco-stoichiometric characteristics, and to expose stoichiometric characteristics, mutual relationships and spatial variation of the forest system of vegetation-litter-soil.

Abstract:【Objective】Straw biochar is a kind of carbon-rich material prepared through pyrolysis under high temperature in anoxic condition. Its application may directly or indirectly affect availability of soil phosphorus in the soil through altering soil physicochemical properties or soil environment during the crop-growing season. Freezing and thawing alternation is a common climate phenomenon in Northeast China. Frequent occurrence of such a phenomenon in the spring causes changes in soil properties like soil structure, thus leading to drastic variation of soil available phosphorus content. However, so far little has been reported about the effect and mechanism of biochar affecting availability of soil phosphorus during the freeze-thaw season. In this study, an indoor simulation experiment was conducted to explore rule and mechanism of biochar affecting availability of soil phosphorus in the brown earth of Northeast China during the freeze-thaw cycle and its impact on soil nutrient suppling capacity during the early crop growing season in the region. The findings in this study may have some significance to guiding the theoretic study on use of biochar practice of and theoretic study of use of biochar in Northeast China. 【Method】Soil samples were collected from a maize field in the Comprehensive Field Experiment Base of the College of Water Conservancy, Shenyang Agricultural University, after the harvest in 2015, and then air-dried and sifted for future use. Biochar was prepared out of maize stalk and ground to pass a 1mm sieve. Then the biochar was blended with air-dried soil samples at a rate of 0% (0﹕100), 2%, 4% and 6%, separately. The mixtures were them packed, separately, into 20 cm×20 cm×15 cm plexiglass boxes, 2.5 g each, constituting four treatments and three replicates each. All the samples in the boxes were incubated under room temperature for 60 days. During the incubation, the samples were kept wet with soil moisture content being 50﹪ of the soil water holding capacity by adding distilled water weekly. After the incubation, the soil samples were subjected to 30 cycles of simulated freezing-thawing with temperature varying between -10 ℃ and 7℃. A set amount of the soil sample in each box was retrieved after 0, 1, 3, 5, 10, 20 and 30 cycles of freezing-thawing for determination of soil properties, including content of readily available phosphorus, pH, organic matter, electric conductivity and activity of phosphatase.【Result】 (1) The effect of the alternation of freezing and thawing was extremely significant on content of soil available phosphorus during all the phases of the treatment (0 ~ 5 cycles, 5~30 cycles and 0 ~ 30 cycles), relative to number of freeze-thaw cycles, biochar application rate and their interactions, except for the first five cycles. (2) After the incubation, the content of available phosphorus was increased by 24.0%, 25.7% and 42.5% in Treatments 2%, 4% and 6% as compared with CK separately. Obviously the effect increased with rising biochar application rate. The effect peaked during the 5th cycle, however, the increment declined with rising biochar application rate. Around the 20th cycle, the contents of available phosphorus in all the treatments dropped down to relative valleys, available phosphorus and even lower that that in the treatments applied with biochar and incubated under room temperature, which indicates that biochar increased the content of available phosphous under room temperature, while the freeze-thaw cycles helped boichar fix soil phosphorus, as compared with CK, thus reducing the risk of phosphorus loss with melting snow. (3) The analysis of responses of biochemical properties of the soil, such as soil pH, EC, organic matter and phosphatase activity, to freezing and thawing cycles and relationship of soil available phosphorus with phases of the freeze-thaw cycles reveals that the content of organic matter varied sharply with the freeze-thaw cycle going on and was closely related to soil available phosphorus.【Conclusion】Through enhancing the stability of soil aggregates, biochar helps soil organic matter hold soil phosphorus by reducing its release. During the freeze-thaw cycles, biochar helps fix soil P and reduce P loss with thawing snow.

Abstract:【Objective】 To cope with the trend of global warming, CO₂ capture and storage （CCS）is one of the major technologies for reduction of CO₂ emission. And then the captured CO₂, nil in commercial value, is injected underground to raise the output of petroleum or coalbed methane, so as to maximize its economic profit. However, the prevailing technologies are far from being capable of guaranteeing zero leakage of the stored CO₂ during the processes of CO₂ storage and transportation, geological activities and human misoperation. Once the risk of potential CO₂ leakage becomes real, the leakage will pose an enormous threat to the near surface ecosystem. It is, therefore, essential to explore in depth effects of underground CO₂ leakage on farmland soil environment, especially tolerance and sensitivity of soil microbial communities to different concentrations of CO₂. So the study was conducted. 【Method】 An experimental platform to simulate underground CO₂ leakage was constructed in an idle farmland, in the South Lake Campus of the China University of Mining and Technology. The platform was used to simulate leakage of CO₂ varying in intensity, i.e. 400 g m^-2d^-1, 800 g m^-2d^-1, 1 200 g m^-2d^-1and 2 000 g m^-2d^-1 for 60 days, thus forming four treatments, i.e. L-400, M-800, H-1200 and E-2000. Besides, the experiment also had a control group and a recovery group. Soil samples were collected from the four treatments and their 3 replicates on the 14th, 30th and 60th day after the start of simulated leakage, from the control group on the day before the start of leakage (C1) and at the end of the experiment (C2), and from the recovery group, which was actually Treatment E2000, 60 days after the stop of the leakage. The soil samples were analyzed for soil physical and chemical properties, concentration of occluded soil, structure and α and β diversities of soil microbial community with the conventional physicochemical analysis method and the Illumna second generation gene sequencing method based on the Miseq platform.【Result】 Results show that CO₂ leakage decreased soil pH, electrical conductivity and nitrate nitrogen content and the effect was enhanced with rising CO₂ concentration whereas it had an opposite effect on soil organic matter content. In all the four treatments. Soil CO2 concentration increased till it reached saturation in 24 h, when soil CO₂ gas concentration leveled off at 1.60%, 4.80%, 10.80% and 19.60%, respectively. Along with increasing CO₂flux, soil microbial community decreased in diversity, Chao index and Shannon index, by 17.00%~27.80% and 6.10%~9.50%, respectively. In contrast, soil microbial community increased in β diversity (NMDS index) in Treatments L-400 and M-800 (low CO₂ concentration) but decreased in Treatments H-1200 and E-2000. Some bacteria, like Bacteroidales, varied extremely, either rising up or falling down in relative abundance with increasing CO₂ leakage. 【Conclusion】 The structure, diversity and abundance of soil microbial community varied significantly from treatment to treatment. Soil pH and CO₂ flux were the two most important environmental factors affecting soil microbial diversity. Bacteroidales was very sensitive to CO₂stress so that it can be used as a key indicator in monitoring and evaluating ecological risk of underground CO₂leakage. The 60 d short term recovery experiment indicates that the soil microbial community recovered well in diversity and richness, but it is still unclear whether it did in function. Therefore, in future studies, focuses should be laid on impacts of underground high concentration CO₂ leakage on functions of the soil ecosystem.

Abstract:【Objective】Dry-wet alternation is a common phenomenon existing in nature, especially in paddy soil. But it is still unclear about rule of the response of soil microorganisms to such variation of soil moisture in complex soil, because of limitations in technology. This study was aimed to investigate rules of changes inabundance and community of archaea in a typical paddy soil derived frnom lacustrine sediment, in Changshu of Jiangsu, experiencing three cycles of drying and wetting in lab. 【Method】Soil samples of the typical paddy soil from Changshu were subjected to three consective cycles of drying and wetting in lab. Each of the drying or wetting period lasted 7 days. Real-time quantitative polymerase chain reaction (Real-time PCR) and high-throughput sequencing of 16S rRNA genes were performed to analyze how the archaea in the soil samples changed in biodiversity, abundance and community in response to the dry-wet alternations at DNA and RNA levels. 【Result】The Real-time PCR analysis suggests that the abundance of archaeal 16S rRNA genes copy number changed in response to dry-wet alternation, dropping at DNA level by 149 ~ 468 times, but only by 2.06 times on RNA level during the process from wet to dry, and rising by 147 ~ 360 times at DNA level, but only by 2.95 times at RNA level during the process from dry to wet. These findings indicate that the change of archaea in 16S rRNA genes copy number was far greater at DNA level than at RNA level. Based on the high-throughput sequencing of 16S rRNA genes, it was found that the archaea community changed significantly in structure at both DNA level and RNA level after three consecutive dry-wet cycles and the changes may be described by non-metric multidimensional scaling (NMDS) (p<0.05). The archaea in the paddy soil could be sorted into 3, 10, 13, 14 and 10 groups at either DNA or RNA level, when classified at phylum, class, order, family and genus level, respectively. The alternation caused significant changes in the archaeal community, especially the six groups at order level, including mainly Methanogenicarchaea and ammonia-oxidizing archaea, like Methanobacteriales, Methanosarcinales, Methanomicrobiales and Nitrososphaerales. The change varied by 2.1%, from 2.82% to 0.69% in total abundance and by 3.79 times, from 0.54% to 2.60%, in maximum fold. 【Conclusion】The Real-time PCR analysis demonstrates that the abundance of archaeal 16S rRNA genes copy number changed significantly in response to the alternation. The high-throughput sequencing of 16S rRNA genes indicates that the archaeal community in the soil changed significantly in structure with the soil alternating in soil moisture condition from dry to wet and from wet to dry. As in environment free extracellular RNAs decompose rapidly, while free extracellular DNAs may remain intact for quite a long time, it is quite probable that archaeal RNA sequence may come from intact microbial cells, and these archaeal cells are able to adapt to severe moisture changes in paddy soil. As the process of drying or wetting does have some impacts on abundance and composition of archaea communities, it is more advisable to unfold studies on changes in soil archaea at DNA and RNA levels simulataneously so as to expose rules of the soil archaea responding to dry-wet alternation of the soil.

Abstract:【Objective】Biochar is a carbon-rich product of pyrolysis of biomass and can be used to ameliorate soiland promote crop growth.Recently,studies show that biochar has some good effects on control of soil-borne diseases. Researches in the past already demonstrated that straw biochar could effectively control Phytophthora blight of chilli pepper, through improving soil physic-chemical properties and microbiological properties, but little has been reported on how application rate affectsthe effect ofbiocharcontrolling the disease of Phytophthoracapsici.【Method】In this study, a pot experiment, designed to have 5 treatments concerning application rate, i.e. Treatment 0, 1, 2, 3 and 4 (0%, 0.33%, 0.66%, 1.33% and 2% w/w, respectively), was carried out to investigate effect of straw biochar controlling Phytophthora blight of chilli pepper, relative to application rate of biochar.The soils in the pots were analyzed separately for chemical properties (soil pH, electrical conductivity, organic matter, ammonium N, nitrate N,available Pand readily available K) and soil micro-biological properties (soil enzyme activity, microbial population, microbial community structure and soil microbial carbon utilization features).Soil microbial populationwasdetermined with the dilution plating method and real time PCR; soil microbial community structurewith PCR-DGGE andsoil microbial carbon utilizationfeatures with the Biolog system. Correlation analysis was done of biochar application rate, soil properties and disease control effect.【Result】The disease controlling efficiency in Treatment1, 2, 3 and 4 was -9.8%,8.6%,56.7% and 35.1%, respectively, forming an inverted U-shape curve. So the application rate of 1.33% (Treatment 3) was the optimal for disease control.With increasing biochar application rate, soil pH and organic matter content increased gradually, electrical conductivity, available P content and readily available K content did significantly, but ammonium and nitrate nitrogen contents did only slightly.Urease and β-glucosidase activities gradually decreased, FDA Hydrolase and sucrase activities increased firstand then decreased,total bacteria, total fungi and four groups of functional microorganisms gradually increased in population, and P.capsici first increased and then decreased in population with increasingapplication rate of straw biochar.Microbial metabolic ability, microbial diversity and microbial community evenness all displayed an inverted U-shape curve in response to the varying application rate of straw biochar, with peaks appearing all in Treatment 3(1.33%).DGGE profiles show that biochar at low application rates (0.33% and 0.66%) had little effect on microbial community structure, but when at high application rates (1.33% and 2%) it did significantly alter microbial community structure, significantly increasing the abundance ofPseudomonas, Sphingomonas, Ascomycota and Basidiomycota.【Conclusion】This study demonstrates prominently the importanceofapplication rate of strawbiochar in disease control.The control efficiency increases as application rate of straw biochar increaseswithin a certain range, which may be attributed to the function of biochar to improve soilchemical and biological properties.But when the application rategoes beyond the range, straw biocharcould weaken in control efficiency, which may be explained by the fact that too much biochar has some negative influences on soil carbon and nitrogen recycling, microbial activity and diversity.In addition,the effect of biochar controlling Phytophthora blight of chilli pepperis not much related to the population of P.capsici in the soil.

Abstract:【Objective】Tobacco bacterial wilt is one of the most serious soil-borne pests affecting tobacco production in Southwest China. Biocontrol of tobacco bacterial wilt has been a hot research topic in recent years. For control of the pest, a kind of biomanure prepared out of microbes antagonistic to the pest is used together with some proper agronomic measures, so as to achieve sustainable and healthy development of tobacco production.【Method】In this study, a three-year long field experiment was conducted in a severely wilt infected tobacco field in Guizhou Province to explore effects of the pest control measures. The experiment was designed to have four treatments or measures, that is, T1 (Conventional fertilization), T2 (Conventional fertilization liming), T3 (Conventional fertilization L-25 Biomanure) and T4 (Conventional fertilization liming L-25 Biomanure). High-throughput sequencing was done of the microbial genome in the rhizosphere to explore effects of the integrated control measures on soil microflora.【Result】The experiment indicated that in 2013 Treatment T4 was significantly (p<0.05) higher than Treatments T2 and T3 in controlling effect during the entire tobacco growing period, and in 2014, Treatment T4 was significantly higher than Treatments T2 and T3 in controlling effect,60 days after transplanting and 6.26 and 1.99 times as high as Treatments T2 and T3, respectively, 90 days after transplanting. At the end of the experiment, the pest controlling effect reached up to 61.30%. In 2013, Treatment T4 was significantly higher than all the other treatments in tobacco yield or 3.71, 1.61 and 1.13 times as high as Treatment T1, T2 and T3, respectively. In 2014, Treatment 4 was the highest in tobacco yield and output value and Treatment T3 was significantly higher than the other two, which were more or less the same. In 2013, although the pathogen in the treatments amended with biomanure slowly increased in population, the counts of antagonistic bacteria in the treatments were higher than those of pathogen during the initial 70 days after transplanting, while in 2014, the population of pathogen in Treatment T4 was always kept below the level of 10⁶ cfu g^-1 soil, but the counts of pathogen in all the other treatments grew beyond the level of 10⁷ cfu g^-1 soil, 90 days after transplanting and on. Treatment T4 was higher than Treatment T1 in microbial species abundance, operational taxonomic unit (OTU) and Shannon index. Principal component and cluster analysis shows that Treatments T3 and T4 were quite similar, but significantly different from Treatment T1 in microfloral structure. 【Conclusion】The integrated measure, (like Treatment T4) can effectively control tobacco bacterial wilt and significantly improve yield and output value of cured-tobacco, and soil microflora as well, which demonstrates that the measure has a promising application and extension prospect.

Abstract:【Objective】The study was oriented to explore characteristics of phosphate-dissolving microbial (PDM) in peanut rhizosphere dissolving Ca₃(PO₄)₂ (Ca-P), FePO₄ (Fe-P) and AlPO₄ (Al-P) as affected by fertilization in a 28-year long-term fertilization field experiment designed to have three fertilization treatments, i.e. NPK (pure chemical fertilizer-NPK), NPKM (combined fertilization of chemical fertilizer and pig manure) and NPKS (combined fertilization of chemical fertilizer and rice straw) in the red soil region. 【Method】Soil samples were collected from the three treatments of the long-term field experiment for preparation of soil suspensions with NBRIP (National Botanical Research Institute Phosphate) (containing 10 g L^-1 glucose, 2.5 g L^-1 MgCl₂, 0.25 g L^-1 MgSO₄.7H₂O, 0.2 g L^-1 KCl, 1 g L^-1 (NH₄)₂SO₄, 15 g L^-1 agar, pH 7.0, and 5 g L^-1 Ca₃(PO₄)₂ for the Ca–P test, 4.86 g L^-1 FePO₄ for the Fe–P test, and 3.93 g L^-1 AlPO₄ for the Al–P test), separately. Then the suspensions were incubated in lab and analyzed for variation of available phosphorus (AP) in and pH of the suspensions relative to treatment of the long-term fertilization experiment. In the experiment field of acidic soil, N, P and K was applied at a rate of 110 kg hm^-2, 29 kg hm^-2, 142 kg hm^-2 in the form of urea, (NH₄)₂HPO₄ and KCl, respectively, and combined fertilization was done at a ratio of 7:3 on N input basis (chemical fertilizer and composted pig manure or straw). Each fertilization treatment had three replicates, 34.6 cm² in plot size. The plots were laid out randomly and separated with cement boards (20 cm above ground, 30 cm below ground). 【Result】Results show that the treatments of combined fertilization stimulated propagation of PDM. In Treatments NPKM of the Ca-P and Fe-P types, PDM was 6.15 and 5.80 log (cfu g^-1 dry soil) in density, respectively, higher than in all the other treatments. Among the treatments, Treatment NPKM was the highest in phosphorus solubilizing capacity and reached up to 221.8 mg kg^-1 in Fe-P and 205.5 mg kg^-1 in Al-P, or 134.6%~144.6% and 10.48%~153.2% higher than that in the other two treatments after 3 and 5 days of incubation, while Treatment NPKS was unique in ability to dissolve Ca-P, which was 21.33% and 24.57% higher than that in Treatment NPKM and NPK. Comparing to a single strain of bacteria, PDM did not show any absolute advantages, but it did reflect the real phosphate-dissolving effect under complicated field conditions and the effects of different fertilization treatments on phosphate-dissolving bacteria groups.【Conclusion】 Therefore, it is found that long-term combined fertilization is more capable of stimulating propagation of PDM groups and hence dissolving more inorganic phosphorus in peanut rhizosphere soil. Consequently, soil P supply is improved and biomass/yield of peanut raised.

Abstract:【Objective】Species abundance distribution is a classic cutting-edge research field in the study on community ecology. Niche apportionment models are commonly used to simulate relative abundance distribution of species, but quite rarely applied to the study of soil fauna. Moreover, little has been reported in the past on how soil fauna responds to environmental changes in community construction relative to feeding guild. A field investigation was carried out of relative species abundance (individuals and biomass) distribution of the litter-dwelling fauna as a whole as well as each feeding guild (including omnivores, phytophage, predators, and saprovores) in a Quercus wutaishansea forest with an elevational gradient in the Dongling Mountain, Beijing. 【Method】Five commonly used niche apportionment models, that is the broken stick model (BSM), niche preemption model (NPM), niche overlapping model (ONM), random assortment model (RAM), and dominance preemption model (DPM), were used separately to simulate abundance distribution of the fauna. Adequacy of sampling is the prerequisite for the models to simulate species relative abundance distribution and judged by species accumulation curves. Rank-abundance plots were used to show richness and evenness of the species contained in the litter-dwelling soil fauna and each feeding guild. 【Result】 Results show that sampling in this study was adequate for fitting of the soil fauna community and feeding guilds. The distribution of the soil fauna in individual number disagreed with that in biomass. The dominance preemption model was not fit for either the whole litter-dwelling fauna community or each feeding guild based on chi-square test. The broken stick model was the optimal one for fitting the whole litter-dwelling fauna community, free of any impact of changes in elevation. The overlapping model and the niche preemption model were also good enough in fitting. When individual number was used as the index for abundance, elevation did not affect much fitting of the models for each feeding guild of the litter-dwelling soil fauna according to the chi-square test, but the chi-square test did vary from guild to guild. For omnivores, only the dominance preemption model failed the chi-square test, but for phytophage and predators, the random assortment model and for saprovores, the niche preemption model did, too. When biomass was used as the index for abundance, elevation did not have any impact on the chi-square test of the models fitting omnivores and predators, but did on that of the dominance preemption model fitting omnivores, and of the dominance preemption model and the niche preemption model fitting predators. The chi-square test of the models fitting saprovores and phytophage varied with the elevation. For saprovores, the dominance preemption model was good in the section low or moderate in elevation, while in the seciton high in elevation, the dominance preemption model and the random assortment model were. For phytophage, the dominance preemption model was good in the section low in elevation, the dominance preemption model and the random assortment model were in the section moderate in elevation, but the dominance preemption model, the niche preemption model and the random assortment model all failed the chi-square test in the section high in elevation. Abundance distribution of the various feeding guilds of the fauna was very sensitive to changes in elevation. For omnivores, the optimal model changed from the niche preemption model to the broken stick model with rising elevation, while for phytophage, it did reversely. Fitting with individual number as the index of abundance indicates that the optimal model for predators changed from the niche preemption model to the broken stick model and the niche preemption with rising elevation. For saprovores, the optimal model was the random assortment model in the sections low and high in elevation, while it was the broken stick model in the section moderate in elevation. When biomass was used as the index of abundance, the broken stick model replaced the random assortment model as the optimal one for predators, and the niche preemption model for saprovores. The use of biomass was better than that of individual number as index for the models to fit abundances of various feeding guilds of soil fauna. 【Conclusion】To sum up, elevation and selection of index does not affect much the models in fitting abundance distribution of the soil fauna as a whole, but does in fitting abundance distribution of the various feeding groups of the soil fauna. Future studies should consider modern theory of species coexistence and the neutral theory to examine the relative importance of stabilizing mechanism and equalizing mechanism in community assembly.

Abstract:【Objective】The turnover of liable organic carbon (C) sources in soil is a key component of the cycle of soil carbon. Liable C sources (i.e. glucose), derived from C deposition in rhizosphere and other extraneous C inputs, are important sources of the C pool in the soil. Therefore, studying the turnover of liable C sources as affected by stoichiometric ratio of soil nutrients may help reveal mechanisms of the eco-stoichiometric regulation of the turnover of extraneous C in paddy soil. 【Method】In this study, an in-lab incubation experiment was conducted using ¹³C-glucose as extraneous organic C typical in paddy soil to explore quantitatively dynamics of decompositing mineralization and priming effect of glucose as affected by C/N/P/S stoichiometric ratio. 【Result】Results show that glucose was rapidly mineralized in the paddy soil so that 65.5% to 74.6% of the added glucose-C was mineralized after 60 d of incubation. The addition of nutrient elements not only increased glucose mineralization rate, but also raised the proportion of glucose-C available to soil microbes from 58% to 65%, thus accelerating glucose turnover rate in the soil. The amount of nutrient elements added was found significantly and positively related to both proportion of the microbe-available C pool in and mineralization rate (R ² = 0.63, p<0.05; R ²= 0.83, p< 0.05) of glucose C, which suggests that the addition of nutrient elements promoted the microbial utilization of extraneous C in the soil, and stoichiometric ratio of the nutrient elements regulated the dynamic of glucose mineralization. With the addition of glucose-C, the decomposition of the soil native organic matter was inhibited, and the cumulative negative priming effect was -370 to -570 mg kg^-1. The higher the amount of nutrient elements added, the stronger the negative priming effect observed, and the two were obviously in negative correlation (R ² = 0.66, p< 0.05), indicating that the soil microbes preferentially utilize the added glucose-C to sustain their growth. The supply of N, P and S reduced the dependence of microbes on nutrient elements in the soil native organic matter, and thereby slow down the decomposition of soil organic matter. 【Conclusion】Mineralization of liable C in paddy soil is affected by C/N/P/S stoichiometric ratio. The addition of a high ratio of nutrient elements promotes mineralization of liable C in paddy soil, inhibits decomposition of native soil organic matter, and intensify negative priming effect. All the findings in this study demonstrate that application of liable C and fertilizers to paddy soils could effectively inhibit decomposition of soil native organic matter, and stimulate accumulation of soil organic matter, thus building up soil fertility.

Abstract:【Objective】 Coastal soils in North China are extremely susceptible to salinization because of the geographical and meteorological conditions of these areas. Nowadays, soil bioremediation has proved to be an effective and economical way to ameliorate saline soils and hence been extensively applied. However, researches in this aspect are mostly focused on phytoremediation by planting salt-tolerant plants, and little has been done on use of earthworms or other soil animals. The first phase of this study demonstrates that the introduction of earthworms Eisenia fetida using composted green waste as its food source could help lower salinity of the coastal saline soil in North China. 【Method】 In order to improve the efficiency of using E. fetida and composted green waste to ameliorate saline soil, a field experiment was conducted on addition of phosphogypsum, the conventional soil amendment, and brown sugar in an attempt to determine whether they may help improve the efficiency of the bioremediation. The experimental site was located on a tract of typical coastal saline soil in the Lingang Economic and Technological Development Zone of Cangzhou, Hebei, China. The field was divided into plots. Each plot, covering an area of 12 m², was amended with 6.5 kg m^-2 of composted green waste and earthworms at 50 individuals per m² (average weight 0.334 g). In addition, the plots were applied with 0 kg m^-2, 1 kg m^-2, 2 kg m^-2, or 3 kg m^-2 of phosphogypsum, along with 0 kg m^-2, 0.2 kg m^-2, 0.4 kg m^-2, or 0.6 kg m^-2 of brown sugar, separately. 【Result】 The experiment went on for one year, with results showing that the addition of phosphogypsum could significantly decrease pH of the soil in the treatments applied with the same rate of brown sugar, however, the effect did not vary much with the amendment rate of phosphogypsum. As Ca^2﹢ and SO₄^2- are the major component of phosphogypsum, application of the substance significantly increased the content of soluble Ca^2﹢ and SO₄^2- in the soils the same in brown sugar treatment. The Ca^2﹢ in phosphogypsum helped formation of soil structure and promoted desalination of the saline soil, while reducing the content of soluble Na^﹢ and Cl^- significantly; the amendment of brown sugar stimulated activities of the earthworms, thus facilitating formation of soil aggregates and hence leaching of salts, and eventually intensifying the effect of bioremediation. So in the treatments the same in phosphogypsum amendment rate, addition of brown sugar significantly lowered the content of soluble Na^﹢ and Cl^- in the soil. As affected by the contents of soluble Ca^2﹢, SO₄^2-, Na^﹢ and Cl^- in the soil, in the treatments amended with 0 kg m^-2 or 1 kg m^-2 of phosphogypsum, addition of brown sugar significantly lowered the content of total salt, but the effect did not vary with its amendment rate; however, in the treatments the same in the amendment rate of brown sugar, the content of total salt in the soil increased rather than decreased if too much phosphogypsum was used. 【Conclusion】 Aiming at lowering the content of total salt, it is recommended that in addition to 6.5 kg m^-2 of composted green waste and 50 individuals per m² of E. fetida, 1 kg m^-2 of phosphogypsum and 0.4 kg m^-2 of brown sugar should be amended in bioremediation of the coastal saline soil in North China. Compared with CK (nothing amended), the amendment of composted green waste and E. fetida significantly decreased the content of total salt, and the effect was further enhanced when phosphogypsum and brown sugar was added at a recommended rate. The cost of soil amelioration with the above-described method is only 10.60 Yuan per m², and it would be lowered if brown sugar is replaced by some by-products from the sugar industry, such as beet pulp, bagasse, and molasses.

Abstract:Effects of phosphorus (P) and citric acid (CA) on Pb²⁺ adsorption by goethite and kaolinite were studied through a batch isothermal equilibrium experiment and Zeta potential analysis. Results show that the Pb²⁺ adsorption by goethite and kaolinite rose with rising citric acid concentration and peaked when citric acid concentration reached 0.5 mmol L^-1. The effect of citric acid was enhanced to a varying extent by the presence of phosphorous regardless of concentration. With rising P concentration, Pb sorption by the two minerals increased and leveled off when P concentration reached 1 mmol L^-1 and 0.6 mmol L^-1for goethite and kaolinite, respectively. When citric acid was spiked in addition to phosphorus, Pb sorption by the two minerals increased with rising citric acid concentration added, which indicates that phosphorous and citric acid would jointly enhance lead sorption by the minerals. In the kaolinite system, the addition of phosphorous and/or citric acid moved the Zeta potential-pH curve towards negative, displaying an order of 1.0 mmol L^-1 P +0.5 mmol L^-1CA > 0.5 mmol L^-1CA > 1.0 mmol L^-1P, in terms of intensity of the effect, which indicates that the increased negative charges on the surface of kaolinite are responsible partially for the increased electrostatic adsorption of Pb²⁺. Both P and citric acid decreased Zeta potential of goethite significantly, and Zeta potential did not vary much with rising pH, which indicates that both phosphorous and citric acid increase specific adsorption Pb mainly by getting adsorbed on the surface of goethite.

Abstract:Through consultation of literature and field survey, data were collected of the conventional rice, wheat, vegetable and fruit production, the economic benefit of the production under the model of cleaner production and the nitrogen loss in the Zhushanwan catchment, a subwatershed in the northwest of the Taihu Lake Region, and other relevant social-economic data. An attempt was made to readjust the planting structure of the catchment in line with five simulated scenarios (I, II, III, IV and V), separately, high to low in total nitrogen loss, using the linear optimization model (Software Lingo 11) and taking into full account maximal economic benefit and total volume control of pollution discharge. In Scenario Ⅱand Ⅲ, the total N input was found to be 6 267 t and 5 567 t, respectively, and the total N loss 511 t and 447 t, respectively, which indicates that both scenarios meet their respective intended targets of reducing total N input by 20% and total N loss by 30% as compared with that in the conventional planting structure. Besides, the two scenarios may generate a relative net economic profit of 845.6 million yuan and 796.6 million yuan, respectively, both higher than that (787.3 million yuan) the conventional planting structure does. So among the five scenarios, Scenario Ⅱ is the optimal one and Scenario Ⅲ the second to follow for readjustment of the planting structure of the region. The quota of eco-compensation was calculated according to opportunity cost and ecological benefit reward, and the compensation policy and mechanisms were suggested to facilitate implementation of cleaner production. The ecological compensation funds, excluding transaction cost, about 15% of the total compensation for Scenario Ⅱ and Ⅲ is estimated to be 9.61 and 35.07 million yuan (RMB), respectively, according to the standard for compensation, 739 and 2 696 Yuan hm^-2, respectively. Implementation of the policy and its matching eco-compensation measures may effectively help control non-point source agricultural pollution and expedite the process of transformation or escalation of the farming industry in the region from the traditional one to the one of cleaner production.