Abstract:Variation of Xiashu Loess-Paleosol of Zhenjiang in rare earth element(REE)composition was studied,and the findings show that ∑REE varied in the range from 193.7 to 214.9μg g^-1 with an average value of 207.7μg g^-1.Compared with the Loess of the Loess Plateau,Xiashu Loess were significantly higher in REE absolute abundance,because of its higher content of clay that adsorbed REEs(especially LREEs).But they showed similar REE distribution patterns and characteristic parameters,and they were also quite similar to the upper continent crust(UCC)in REE composition.The REE distribution patterns of Xiashu Loess samples of different ages were almost identical,which displays uniformity of Xiashu Loess in material composition of the profile.The above-mentioned features provide new geochemical evidence of the aeolian origin theory for Xiashu Loess,and indicate that the materials of Xiashu Loess might come from an open and broad area and get highly mixed as aeolian dust during the process of transportation.The REE characteristics of Xiashu Loess are inherited mainly from its source materials. Even though the aeolian dusts has undergone stronger weathering and soil-forming process after they were settled and accumulated,the fractionation between LREE and HREE in Xiashu Loess is more apparent than in the loess of the Loess Plateau.On the whole,chemical weathering does not show any remarkable influence on REE fractionation,and the Paleosol does not vary much from the loess in REE composition or show any apparent Ce-depletion and Eu-depletion.

Abstract:Forty soil profiles in the hilly region of Xuan Lang Guang,Anhui Province were identified and classified according to the keys to the Chinese Soil Taxonomy(CST)(the 3rd edition).The placement of 11 taxa,formerly sorted on the sub-group level of the Chinese Soil Genetic Classification System(CSGC),in CST was elucidated in the paper.All these soils studieds are classified into 5 CST Orders:Anthrosols,Ferrosols,Argosols,Cambosols and Primosols,5 CST Suborders:Stagnic Anthrosols,Udic Ferrosols,Udic Argosols,Udic Cambosols and Orthic Primosols,15 CST Group and 23 CST Subgroups.The correlation of Soil taxa between CSGC and CST was so complicated that there is almost no one-to-one correlation of soil taxa.The taxonomic soil classification of the hilly region of Xuan Lang Guang was proposed in the paper.And correlation of taxa between CSGC and CST was also discussed.The results of the study are of high reference value to proper correlation of soil taxa between CSGC and CST and development of CST.

Abstract:Soil water deep leaching and nitrate(NO₃^--N)distribution in the soil profile and NO₃^--N leaching losses below the root zone were investigated in fields under a local traditionally managed wheat-maize crop rotation system in the North China Plain.Coupled with the soil water balance method,soil water deep leaching and NO₃^--N concentration in suction samples were determined.The results indicate that water leaching,NO₃^--N distribution and leaching losses exhibited pronounced spatial and temporal variability.Events of water leaching and NO₃^--N leaching loss were prone to occur during the summer maize growing season(rainy season),after each irrigation operation and significant rainfall.Annual soil water deep leaching reached 33～48 mm(averaged 39 mm)in 1998/1999 cropping year and 90～92 mm(averaged 90.7 mm)in 1999/2000,accounting for 10% and 19% of the total amount of irrigation plus rainfall,respectively.The amount of NO₃^--N leached below the root zone (including leaching loss of soil-and fertilizer-N)averaged NO₃^--N 12 kg hm^-2 a^-1(ranging from NO₃^--N 6 to 17 kg hm^-2 a^-1) in 1998/1999 and NO₃^--N 61 kg hm^-2 a^-1(ranging from NO₃^--N 30 to 84 kg hm^-2 a^-1)in 1999/2000,equivalent to 1.4%～4.1% and 7.3%～20.3% of the N fertilizer applied,respectively.The results indicate that during the summer maize growing season,potentials do exist of reducing water and fertilizer inputs,so as to improve water and fertilizer use efficiency in this region.

Abstract:Karst rocky desertification is a land degradation process,involving serious soil erosion,extensive exposure of basement rocks,drastic decrease in soil productivity,and appearance of a desert-like landscape.As it is a serious problem in Guizhou Province,studies were carried out on succession of the vegetations on lands under karst rocky desertification and its impact on chemical composition of runoffs from the lands in this region through vegetation surveys and analysis of soil and runoff samples.The results show that with development of karst rocky desertification,the soil was losing organic matter rapidly, becoming clayey in texture,decreasing in soil capillary porosity and in water-holding capacity in the surface or subsurface soil layers significantly during dry seasons,thus altering the law of water movement in karst ecological system.The analysis of chemical composition of surface runoffs show that in terms of concentration,anions and cations in the surface runoffs were in the order of HCO₃^->SO₄^2->Ca²⁺>Mg²⁺>K⁺、NO₃^-、Cl^->Na+>NH₄⁺>PO₄^3-.With karst rocky desertification going on, the output of PO₄^3- in the surface runoff increased significantly,and that of Ca²⁺ and NO₃^- followed,thus leading to decrease in soil fertility and affecting environmental quality of the recipient waterbodies.The variation of chemical composition of ground runoff was similar to that of the surface runoff,but the concentrations of HCO₃^-,Ca²⁺,and Mg²⁺ were higher than that in the surface runoff,respectively,while the concentrations of NH₄⁺ and K⁺ lower than that in the surface runoff.The concentrations of HCO₃^- and Mg²⁺ were reduced obviously with karst rocky desertification proceeding on,thus weakening karstification,while the concentrations of NH₄⁺ and NO₃^- were increased significantly,thus affecting the quality of ground-water,to some extent.

Abstract:This study took Nanjing as a target area and aimed to establish relationships between compaction and soil water characteristic parameters by determining soil bulk density,porosity and soil water characteristic curves as affected by different land uses,including function zones,vegetation types and years of land use.Function zones were differentiated as residential area,park,campus,road greenbelt in the city zone and vegetable garden in the suburb.Vegetation types included lawn,lawn and tree,arbor and shrub,vegetable and no vegetation.Land 2use ages varied from the newly transported soils(used for less than 5 years)to the old soils(used for more than 20 years in the studied areas).Therefore,the studied soils were typical and could show the major soil uses in Nanjing.Bulk density and porosity were selected as the indicators of soil compaction.Water characteristic parameters included field moisture capacity,wilting point moisture content and available moisture content.The results show that urban soils were severely compacted as compared to surrounding suburb soils.The bulk density of most soils in the city exceeded that of normal soils(1.30 g cm^-3).The porosity decreased significantly,especially aeration porosity.Bulk density and aeration porosity were good indicators of soil compaction,showing significant relationship with field moisture capacity.Wilting point moisture content was also related to bulk density and aeration porosity.With the increase in soil compaction degree,field moisture capacity and wilting point moisture content of the soil increased,while potentially available moisture content decreased obviously.So compaction weakens the capacity of soils in regulating water supply and makes plants more vulnerable to drought.

Abstract:To investigate influences of intensive human activities on soil environment dynamics in the peri-urban zone,the study was conducted in an area of 14km² in the vicinity of the Meishan Steel Industrial Corp.area.Totally 93 samples of topsoils were collected according to an aerophoto-based gridding design and concentrations of heavy metals Cu,Zn,Pb,Cr,Cd,Hg and As in the soil samples were determined.First of all,statistical analysis of the test results indicated that concentrations of the heavy metals in the studied soils did not exceed the safety values of the national soil quality criteria with the exception of Hg and Cd.Although the concentrations of a few metals in the some sampling sites slightly exceeded their average background values, the spatial variations of the concentrations of those metals,however,paralleled the pedo 2geochemistry of the study area.Hg concentrations in 61.3% of the soil samples were higher than the environmental safety criteria of the national soil quality standard,suggesting that Hg might be considered as a dominant element causing soil heavy metal pollution in the study area. Furthermore,the spatial variability of soil pollution in terms of heavy metals was investigated by combining pollution evaluation with geostatistical methods,and potential sources and possible entrance paths of heavy metal pollutants in those plots with measurable pollution were discussed.

Abstract:Determination of soil organic C content at steady state is of important significance for evaluating potential of C sequestration of the soil and developing a measure for rational organic material utilization.In this study,change in soil organic C content of paddy fields in a typical red soil region over a period of time,dynamics of the organic C content in the paddy soils across a chronosequence of cultivation,and the input and output of soil organic C,were investigated in order to determine the organic C content at steady state and then potential of C sequestration in the paddy soils of subtropical China.In the past 20 years or so,soil organic C content of the paddy fields in Yujiang County of Jiangxi Province increased generally but it remained stably at 18.5 g kg^-1 in paddy soils with high productivity.After 30 years of rice cultivation,soil C content of the paddy field reached to 19.0(±1.20)g kg^-1 and varied insignificantly afterwards.If the high level of soil organic C formed recently is settled in equilibrium,the soil organic C content will be 19.2(±1.10)g kg^-1.As a whole,at the present high level of productivity,the soil organic C content at steady state of paddy soils in subtropical China would be 18～20 g kg^-1 with an average of 19.0 (±1.0)g kg^-1.In the past 20 years,the storage of organic C in the paddy soils of Yujiang County increased by 6 955 (±1 116)kg hm^-2.Based on this,it was figured out that the paddy soils in subtropical China sequestrated 555.1(±88.7)Tg of atmospheric CO₂ in the past 20 years,demonstrating an important function as a sink of CO₂.Today there are still large areas of paddy fields that have less soil organic C content than that at steady state.It is estimated that they could sequestrate on average 5 150(±1 063)kg hm^-2 more of carbon.Therefore,at the present high level of productivity,the paddy soils in subtropical China would sequestrate an extra of 411.0(±84.7)Tg of atmospheric CO₂ in future.

Abstract:Soil heterotrophic respiration(HR)was investigated in one tract of native Castanopsis kawakamii forest(NF), a 33-year-old Castanopsis kawakamii plantation(CK)and a Cunninghamia lanceolata(Chinese fir,CF)plantation of the same age in Sanming,Fujian Province,China.Soil CO₂ efflux was measured in situ in a 2-year period with the alkali sorption technique.Respirations of root-free soils(R_RF)and litter layer(RL)were measured separately by trenching and removing litter, respectively.Both R_RF and R_L in the three forests showed a similar seasonal pattern with o ne single peak occurring during May or June and a valley during December or January.R_L averaged CO₂ 79188,44137 and 21102 mg m^-2 h^-1,and R_RF averaged CO₂ 21714,85185 and 94104 mg m^-2 h^-1 in NF,CK and CF,respectively.The model R=ae^bTW^c (R stands for soil CO₂ efflux, T for soil temperature and W for soil water content at 0~10 cm soil depth,and a,b,c for the constants)indicated that soil temperature and soil water content together could explain 82%~85% and 85%~92% of R_L and R_RF,respectively,with soil temperature being the dominating factor affecting soil respiration rate in 2002 and soil humidity in a dry year of 2003.R_L was more sensitive to variation in soil temperature and humidity than R_RF.Annual R_L averaged C 3176,2163 and 1123 t hm^-2 a^-1, and annual R_RF averaged C 3144,2179 and 1149 t hm^-2 a^-1,respectively,in the NF,CK,and CF.Differences in soil heterotrophic respiration between forests were associated with differences in quantity and quality of organic inputs,biomass and activity of roots,and content and components of soil organic carbon.R_L in CF showed higher sensitivity to drought than in CK and NF,and the sensitivity of soil organic C to drought was higher in the plantations(CK and CF)than in the native forest (NF).

Abstract:A field experiment was conducted to investigate gaseous losses from N fertilizers applied to a tomato field and affecting factors.Ammonia volatilization was measured by the enclosure chamber method.Denitrification loss(N₂+N₂O)was measured by the acetylene inhibition-intact soil core technique,and N₂O emission was also measured in the absence of acetylene.Results show that ammonia volatilization was not detected in all the treatments during the tomato growing season.It was presumed that ammonia partial pressures on the surface soil were lower than the detection limit of the method,as a result of the low ammonical N concentration and low pH in the surface soil.During the tomato growing season,in the CK treatment denitrification loss and N₂O emission were relatively high,which amounted to 29.6 kg hm^-2 and 7.76 kg hm^-2,respectively.Application of N fertilizer significantly increased denitrification loss up to the range of N 40.8~46.1 kg hm^-2,or 5.50%~6.01% of the applied N;and N₂O emission up to the range of N 13.6~17.6 kg hm^-2,or 2.62%~4.92% of the applied N in the three fertilized treatments.Application of polymer coated urea didn't show any significant effect on reducing denitrification loss and N₂O emission in comparison with urea.In the two urea treatments soil nitrate peaks were observed after each topdressing event, and subsequent flux peaks of denitrification loss and N₂O emission were found.There was a significant positive correlation between denitrification fluxes and wate-rfilled pore space(WFPS).It is concluded that ammonia volatilization is negligible,where-as nitrification-denitrification is an important pathway of N losses during the tomato growing season.

Abstract:Aimed at the unfavorable impact of mono-cropping cultivation on farmland environment,in paddy field,a five-year field experiment was carried out.Ecological analysis in the experiment was conducted to compare crop rotation with mono-cropping cultivation in soil physical and chemical properties,yield,incidence of crop diseases and pests,energy flow and nutrient balance.The results show that the former significantly improved soil physical and chemical properties and yield by 384.8%,226.2% and 3.0%,respectively.Moreover,crop rotation not only altered the environment for pathogen bacteria, but also built up plant resistance to diseases and pest,and suppressed crop diseases,insects,and weeds,etc.and increased the overall initiative productivity,light energy use rate and auxiliary energy use rate by 17.47%,9.87% and 5.0%,respectively,N,P and K use rate as well.Therefore,reasonable optimized multi-crop rotation systems are presented in the paper.

Abstract:Through field investigation and soil fertility index analysis,causes and mechanism of fertility degradation of black soil in the Songliao Plain were explored.The results show that the interface between the cultivated layer and the plough sole in the soil profile was undulated under the current cropping system mainly using small-sized four-wheeled tractors and flat under the cropping system of deep plowing annually in the fall.Besides,the two systems were significantly different in soil nutrient content and soil physical and chemical properties.The study also discovered that both the present fertilization system based on inorganic N and inorganic P and the present system of continuous cropping of corn had greats effect on balance of soil nutrients. It thus follows that the present improper systems of cultivation,fertilization and continuous corn cultivation are the main causes of fertility degradation of black soil in the corn belt of the Songliao Plain.

Abstract:A study on exchange-adsorption of aluminium and manganous ions under conditions close to the field was carried out.The principal results were shown as follows:The exchange-adsorption between aluminium/manganous and calcium/potassiumions acted still in accordance with the universal rule of ion exchange,but remained contradictory to the ratio law;The mechanisms of adsorbed/displaced mole rat io being less than 1 between aluminium/manganous and calcium/potassiumions and for exchange of potassium by calciumion were discussed;Parameters k,r,1/n,K and $F were also explained,and in this regard k and K were much higher and lower in value respectively.In view of $F,the natural tendency of acidification as a result of aluminium transformation in red soils was further proved in thermodynamics,and the energy characteristics for exchange-adsorption of aluminum and potassium by calciumion was revealed.

Abstract:华南酸性森林土壤分别在pH值为3.46、4.24和4.84条件下用含不同浓度盐基离子(Ca²⁺)的酸性浸提液浸提,以查明降水中盐基离子对土壤水中Al和H+的影响。实验结果表明:随着Ca²⁺浓度的增加,土壤浸出液中H+和Al都有增加的趋势。随着Ca²⁺浓度的变化,H+和Al有不同的来源:当Ca²⁺<0.5mmol L^-1时,土壤主要通过Ca-H交换机制释放H+,浸出液中Al主要来源于土壤活性铝的溶解;当Ca²⁺>0.5mmol L^-1时,由于Ca-Al交换反应,浸出液中Al随Ca²⁺浓度增加而显著增加,此时H+主要来源于Al的水解反应。浸出液中pH-pAl关系也随pH值(或Ca²⁺浓度)的变化有显著不同:当浸出液pH>3.7(Ca²⁺<0.5 mmol L^-1)时,浸出液中Al3+活度随pH的变化幅度较小,这可能是酸性土壤中活性铝已显著流失的缘故;当pH<3.7(Ca²⁺>0.5 mmol L^-1)时H+对于Al浓度具有较强的依赖性,故pH随Al3+活度增加而显著降低。因此,降水中盐基离子的增加能够引起土壤水乃至地表水中酸性阳离子(特别是Al)的迅速增加,可能造成对水生生物的突发性影响。

Abstract:Effects of organic acids(acetic acid,tartaric acid and citric acid)on adsorption of Cd²⁺ and Pb²⁺ by goethite and bentonite were studied with the batch method.The results show that Cd²⁺ and Pb²⁺ adsorption by the tested minerals was promoted by organic acids low in concentration(<0.6 mmol L^-1),whereas the adsorption was inhibited with the concentration of the organic acids rising.The inhibiting effect of the organic acids on Pb²⁺ adsorption by goethite and bentonite were stronger than on Cd²⁺ adsorption when the concentration was >1.0 mmol L^-1.The effect of change in concentration of the organic acids on Cd²⁺ and Pb²⁺ adsorptions varied with minerals,and was more obvious on goethite than on bentonite.The effect of the organic acid on Cd²⁺ adsorption intensity on bentonite was greater than on goethite even if the concentration of added Cd²⁺ varied.The effect of low concentration organic acid promoting Cd²⁺ adsorption by bentonite was more obvious when the concentration of Cd²⁺ was high(8.0 mmol L^-1)than when it was low(0.4 mmol L^-1),but the inhibiting effect of high concentration organic acids on Cd²⁺ adsorption by bentonite remain approximate whether the concentration of Cd²⁺ was high or low.The Cd²⁺ adsorption by goethite was more obviously promoted by tartaric acid and citric acid than by acetic acid when they were low in concentration (<0.6 mmol L^-1),but the promoting effects of the three organic acids on Cd²⁺ adsorption by goethite were similar.When the concentrations(>1.0 mmol L^-1)of the organic acids were high,their effects on Cd²⁺ adsorption by goethite were stable,but the Cd²⁺ adsorption by bentonite was more obviously restricted by citric acid than by acetic acid or tartaric acid.The effects of the three kinds of organic acids on Pb²⁺ adsorption on two minerals were almost the same.

Abstract:From the angles of modification rate,soil layers,and temperature,CrO₄^2- adsorption characterist ics were studied of the soil samples gathered from the tillage layer(TLLS)and clay layer of lou soil(CLLS)modified with cetyltrimethylammonium bromide(CTMAB)and cetyltrimethylammonium bromide+sodium dodecylsulphonate(CTMAB+ SDS)mixture at various rates.The results show that CrO₄^2- equilibrium adsorption amounts(EAA)in the soil samples increased with the CrO₄^2- equilibrium concentration;the adsorption isotherms appeared in the shape of L in the modified soils and of S in the unmodified soil.In terms of adsorption of CrO₄^2- the soil samples from both layers were in the order of 100CB>120CS>50CB>CK.CrO₄^2- adsorption in unmodified TLLS increased faster than that in unmodified CLLS with the increase in CrO₄^2- equilibrium concentration.The EAA of CrO₄^2- in modified CLLS were higher than that in modified TLLS,however,the difference in soil affinity to CrO₄^2- between modified CLLS and modified TLLS decreased with the increase in modification rate.CrO₄^2- adsorption in unmodified soils increases with the temperature,and the effect was stronger on unmodified CLLS than on unmodified TLLS,indicating increase in temperature promotes CrO₄^2- special adsorption on clay mineral.The CrO₄^2- adsorption rate from 20 to 40 on modified soils did not vary much with the increase in CrO₄^2- equilibrium concentration.With rise in temperature,CrO₄^2- adsorption on modified TLLS decreased while the CrO₄^2- adsorption on modified CLLS was related to both modifier and modification rate.

Abstract:Differences were studied between wild type and transgenic rice overexpressing barley peroxisomal type ascorbate peroxidase(HvAPX1)under excessive cadmium condition in growth,physiological characters and accumulation of cadmium.The results indicate that with increasing HvAPX1 transcript in transgenic rice,elongation rate of the main root,total biomass, chlorophyll content and activity of the APX(ascorbate peroxidase)all got obviously higher than that of the wild type of rice, respectively.The transgenic plants were significantly more tolerant to cadmium stress as compared with the wide-type plants and accumulate more cadmium.

Abstract:A bacterial strain GM6 with high capability of accumulating poly-P was isolated from aerobic activated sludge in a municipal sewage treatment plant and identified as Pseudomonas putida.This strain could grow in conditions with pH ranging from 5.5 to 8.5 and the most favorably in solution being 6.5 in pH.But its capability of accumulating poly-P peaked when pH was at 7.0.When pH was either below 5.5 or above 7.5,this capability descended distinctly.Aeration tests showed that volume of liquid did not influence much growth of GM6.But when the volume was 100 million,its P removing effect was the best and while the volume is over 150 ml,the effect became less.The optimal temperature for its growth was 27℃.When the temperature was either lower than 5℃ or higher than 37℃,it grew slowly and its P removing effect was poor.The optimal temperature for its phosphorus removal was 20℃.After GM6 incubation in synthesized sewage,LB,YG and MOPS medium for 24 hours, phosphate concentration in the liquid media declined sharply,showing a phosphate removal rate ranging from 63% to 96.6%, which were significantly higher than that of E.coli.Its phosphate accumulating capacity was also investigated aerobically in media LB,YG,MOPS and synthetic wastewater.The results show that the total phosphorus in the GM6 cells harvested from four media was in the range of 6.80%～9.32% while that in the E.coli cells was in the range of 0.98%～2.31%,indicating the former had a higher level of phosphorus accumulation.Strain DM6 showed the characteristics of a typical phosphate accumulating organism as it displayed apparent phosphorus accumulation and release in a SBR process.Its phosphate release and accumulation rate was 4.5 mg L^-1 h^-1 at the end of anaerobic stage and 2.73 mg L^-1 h^-1 at the end of subsequent aerobic stage, respectively.

Abstract:An 8-year in-situ experiment was carried out to study spontaneous nutrient supply capacity and crop responses in vertisol,Huaibei.The data obtained indicated that,in the absence of N fertilizer,N supply capacity of vertisol declined to 64% of the original in the first investigated year,and sharply down to 22% in the second year,and then fluctuated around 20% in the years that followed.And,without P fertilizer application,P supply capacity of the soil decreased gradually throughout the 8 years of the experiment,from 95% in the first year to 45% in the last year,and so was soil 1K supply capacity,but from 90% in the first year down to 60%～70% in the 8th year of the experiment with holding K containing fertilizers1And,P and K supplying performances of vertisol,however,differed significantly from crop to crop,wheat and maize.The 8-year mean yields of wheat and maize in Treatments CK,N,NP,NK and PK were 26.9%,54.3%,85.2%,53.2%,31.8% and 21.4%,68.9%,73.5%,81.6%,28.0% of that in Treatment NPK,respectively,suggesting strong responses of the crops to fertilization models1Detailed analysis showed that,element concentrations of N and P in the seeds and straws of the crops significantly increased in the treatments with N and P fertilizer application 1K concentration in the crop's seeds,however,showed no obvious change while increased evidently in the straws in the treatments with Kfertilization.After 8 years of experiment,the total N content of the tested vertisol decreased by 5%～10% in the treatments without N fertilization,by contraries increased by 12%～16.5% in the treatments with N fertilization.And,the total P content of the soil decreased by 20% in the treatments without P fertilization,and only slightly increased in the treatments with P fertilization available.The available P content of the soil,however,varied very strongly during the experiment period,depending on P fertilization status.As for the total Kcontent of the soil,there was no obvious variation between treatments with or without Kfertilization.The content of available Kin the soil decreased by 35% in the treatments without Kfertilizer,decreased by 5.9% in Treatment NPK,and increased 10% in Treatments NK and PK1The content of soil organic matter decreased by 10% in Treatments CK and PK,and remained stable in the other treatments after the 8-year experiment.The cumulative apparent recovery rates of N,P,K fertilizers on the crops of wheat and maize were 59.8%,47.3%,50.2% and 51.1%, 33.2%,49.5% respectively during the experiment period.The equations correlation coefficients between gain and loss of soil available phosphorus and between gain and loss of soil available potassium were y(ebb and flow of soil available P)=0.113 8 x(balance of gain and loss of P)-0.406 1(n=6,r=0.959 4)and y(ebb and flow of soil available K)=0.107 5 x(balance of gain and loss of K)-8.787 1(n=6,r=0.902 1)respectively.

Abstract:Spectroscopic measurement(Fourier transform infrared differential spectroscopy,Carbon 13 nuclear magnetic resonance spectrometry,Matrix-assisted laser desorption/ionization-time of flight mass spectrometry)and elemental analysis were performed of fulvic acids(FA)extracted from soils applied with corn plant residues.The results show that after corn plant residues were applied into the soil,C,H and N contents increased,O content decreased,and rat ios of C/H,O/C and C/N all declined in soil FA.The carboxyl groups and aromatic carbon were comparatively lower,suggesting a low degree of oxidation and a low aromaticity of FA.Structural changes in soil FA showed a trend of becoming simpler in structure and smaller in molecule size.At the same time,amide,alkyl C and O-alkyl C contents increased significantly.Combining capacity of soil FA with inorganic minerals was gett ing weaker.Carboxylic groups in soil FA were turning from carboxylates into free carboxyls.Polysaccharide components in FA also increased The changes in composition and structure of FA varied from treatment to treatment.

Abstract:Soil pollution is deteriorating due to rapid urbanization and industrial development.Once released into soils, pollutants are transferred to other environmental media such as water,air and biota.They pose health risks to humans via various exposure pathways including drinking water,inhalation,food,dermal contact etc.As a new environmental management tool, health risk assessment(HRS)of polluted soil forms the base for establishing soil environmental quality standards.So far,limited research work has been done in China in relation to HRS of polluted soils.As an effort to boost its development in China,this article reviewed the advance in related research,methodology,existing problems and future trends.HRS of polluted soils is moving towards multi-media,multi-pathways and multi-pollutants risk assessment.Model simulation will be widely used in HRS. Currently,many uncertainties still remain in the quantification of HRS.To make it reliable,future research should focus on developing quantitative methods including pollutants transport models,dose-response relationship,and time-activity patterns of population etc.

Abstract:在毛乌素沙地,其主要地貌为各种大小不一的流动沙丘、半固定沙丘和固定沙丘。沙丘高度一般在5~10 m之间,大小因沙丘类型不同而不同,地形起伏不大。不同沙丘类型以及沙地微地形对沙地土壤水分运动影响很大^[1,2]。固定程度不同的沙丘,植被的生长状况不同,对水分的消耗不同,使不同类型沙丘的土壤水分存在明显的差异,从而造成景观异质性变大^[3]。

Abstract:自1954年召开的第五次国际土壤学会代表大会上介绍了土壤磁性研究工作^[1~3],磁化率在环境科学研究中得到了广泛应用^[4~8]。一些学者讨论了沉积物磁性与物源之间的关系,并将其用于河流底移质泥沙运动和沉积物来源的示踪^[9~10]。该方法的优点是简便易行,省时省力、廉价,对大、小土壤团聚体、泥沙均适用,近来此法用于监测和评估山坡地的土壤侵蚀和沉积也有成功的先例^[11~13]。本文选择粉煤灰施入土壤中作为磁示踪剂,研究坡面土壤侵蚀,取得了初步成果。

Abstract:据报道,全世界每年因腐蚀而报废的金属材料和设备的量约为金属年产总量的1/4到1/3。可见,研究金属的腐蚀与防护是一项非常重要的工作。金属的腐蚀,一般可分为化学腐蚀、物理腐蚀和电化学腐蚀三种^[1]。其中,又以电化学腐蚀现象最为普遍,造成的危害也最为严重。大量埋设在土壤中的油管、气管、电缆等地下金属构筑物的腐蚀属于电化学腐蚀,与土壤性质关系极为密切^[2~9]。

Abstract:植被是防止水土流失的主要因素。大量研究表明,许多因素如土壤紧实度、容重、水稳性团粒、渗透性、水分状况以及有机质含量的动态变化,均影响土壤的抗蚀性。这些因素的变化受制于覆盖于其上的植被类型^[1],早在20世纪60年代,朱显谟先生就指出,生物措施是水土保持中最有效和最根本的方法^[2]。他认为土壤抗冲性的增强,主要取决于根系的缠绕和固结作用。李勇等人对植物根系与土壤的抗冲性进行了系统的研究,但这些研究多集中于西北地区及林木上^[3~5]。在我国南方对植物根系—土壤抗蚀性—水土保持的研究极少。

Abstract:稻麦轮作是我国南方一种传统的耕作模式,有关该体系下作物的生长和土壤氮素的转化已有较多报道^[1]。近年来,随着水稻种植方式的多元化,除传统的水稻水作外,还诞生了水稻旱作,即水稻在全生育期不建立水层的条件下生长,土壤的理化性状均有别于水稻水作,石英等^[2]发现水稻旱作条件下不同覆盖物和常规淹水种植水稻条件下水稻生育期间土壤NH₄⁺-N和NO₃^--N的动态变化规律不同,殷晓燕等^[3]则报道水作水稻和旱作水稻的覆盖地膜、覆盖秸秆种植对土壤氮素盈亏的影响是不同的,然而有关这些改变对后茬作物生长的影响与传统的水旱轮作体系有何不同的研究还鲜见报道。

Abstract:土壤胶体带有表面电荷,对阳离子和阴离子的吸附与解吸都受电荷性质的制约。土壤表面电荷中的可变电荷易受环境条件的影响,使人们有可能用某些措施调节环境条件,以改变可变电荷的数量,使之影响土壤的性质。由于电荷特性对土壤的分散、絮凝、膨胀和收缩,以及离子在土壤中的移动和有机无机复合体的形成等一系列性质有重要意义,从而使土壤电荷性质的研究倍受关注^[1~3]。