Abstract:Based on the case study of Longyou County, Zhejiang Province, an approach was introduced to deducing and expressing spatial distribution of soil organic matter.This is a kind of data mining method or classification tree modeling method, which associates soil OM content with some extensive easily observable landscape attributes, such as landform, geology, landuse and remote sensing images, thus transferring the soil OM related information into a clear, quantitative, landscape factor-associated regular system.This system can be used to predict continuous soil OM spatial distribution.By analyzing the factors such as elevation, type of the rock, type of the soil, PC₄, PC₂, land uses, PC₃, PC₁, upslope contribut ing area, slope, exposure, plane curvature and profile curvature, the classification tree can predict distribution of soil organic matter levels.Among the factors, elevation, type of rock, type of soil, landuse, PC₄ and PC₂ (two indexes of vegetation coverage) are considered as the most important variables for predicting soil OM.Results of the prediction show a quite close relationship between soil OM contents and types of the landscape sorted by the classification tree with an accuracy of 81.1%.

Abstract:The system of wind defense and sand dune stabilizat ion, which crossed the Tengger desert and was began to construct in 1956, has insured the Baotou-Lanzhou railway straightway for almost half century.During succession of soil-plant system for decades, a artificial system of Hedysarum scoparium + Caragana korshinskii + Artemisia Ordosica-Ari-Sandic Entisols has developed into a semi-natural and natural system of Artemisia Ordosica+ Bassia dasyphylla + Eragrostis poaeoides-Hap-Orthic Aridisols.Development of biocrust and crust horizon changed redistribution of precipitation.A drought horizon formed in 20~500 cm depth because of shrub transpiration.Low plants began to compete water with grasses and shrubs.Shrubs with deep roots obtained hardly rainfall supply and dropped out protection system gradually.Soil-plant system went to a thinner active horizon.All of the changes were affecting the structure and function of the whole protection system.

Abstract:Planting tea is a typical way of land use of hillside fields in hilly regions of South Jiangsu Province.But the resultant soil erosion and its ecological impacts there should not be ignored.In order to measure soil erosion, the ¹³⁷Cs tracer method is a useful tool at present.However it is necessary to find out the background value of ¹³⁷Cs in the region and set up an applicable model for this method.After careful study the ¹³⁷Cs background value of the study area is 2 200 Bq m^-2 and a model for estimating erosion of cultivated soil is set up as h=Hc×(C_ref-C_t)/(C_ref-C_in).Based on the above work, the soil erosion rates are estimated and both direct and secondary ecological impacts of soil erosion are further discussed.The direct ecological impacts are thinning surface soil layers, deteriorating soil structure and decreasing soil nutrients.The secondary impacts include increase in fertilizer application and energy consumption, entrophication of waterbodies and change in landuse adaptability.In order to reveal seriousness of the damage of soil erosion to cultivated sloping fields in south Jiangsu Province by comparing with that in the Loess Plateau and red soil regions, an equivalent erosion module is put forward as index.

Abstract:Soil erosion has been a worldwide environmental problem.Soil erosion results in not only degeneration of soil productivity, but also floods and pollution of water resources.Soil erosion and its controls have been studied extensively.Many researches revealed that the rill erosion accounts for a large amount of total erosion on slope.But, few researches have studied the mechanism of the rill erosion occurred on slope.In this study, by using runoff scouring on the definite roughness glass flume under the different slope gradients(16.5°, 20.5°, 27°) and the different flow discharges (0.2 L s^-1, 0.3 L s^-1, 0.4 L s^-1), the rill erosion mechanism were studied.The results show that the runoff on the slope moves in the form of roll waves under the given experiment condit ion.The number of roll waves and the superposing of roll wave are heavily influenced by the discharge of flow and the slope gradients.The larger of flow discharge and the greater of slope gradients, the more decrease of the number roll waves.At the same time, the scouring ex-periments were conducted on the soil bed flume under the different flow discharge(2.5 L min^-1, 3.5 L min^-1, 4.5 L min^-1, 4.5 L min^-1, 5.5 L min^-1, 6.5 L min^-1) and the different slope gradients(6°,9°, 12°).The relationship between the soil detachment and the runoff energy consumption was studied by using the law of conservation energy in this article.The soil erosion rate model was built, and a new rill erosion critical index was put forward.Based on the analyzing the data of experiment, the author got that the rill erosion occurred when the energy consumption exceed 7.38 J.

Abstract:Nonequilibrium transport of pesticides is frequently reported to greatly affect their transport and mobility in soil.Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is a kind of herbicide that is widely used for selective control of grassy weeds in corn production but poses potential danger to the quality of ground water in China.Consequently, there is interest in predicting its mobility in agricultural soils.The objective of the present study was to apply the one-dimensional convection-dispersion equation based on the local equilibrium assumption model (LEA model) and nonequilibrium assumption model (NEA model, including the two-site model and two-region model) for describing nonequilibrium sorption characteristics of atrazine during miscible displacement in water-saturated homogeneous soil.Soil column experiments were conducted in duplicate with a sandy loamy soil under steady-state flow at a specific pore water velocity.A nonlinear least-squares optimization approach (CXTFIT 2.0) was used to fit breakthrough curves (BTCs) for bromide and atrazine in Exp.1.The symmetrical BTC for tracer bromide was best described by the LEA model, indicating that there were no significant effects of immobile water on transport of bromide (i.e., no significant physical nonequilibrium in this system).The asymmetrical shape and tailing of atrazine BTC showed that atrazine was mainly influenced by chemical nonequilibrium during transport and the best fit to observed atrazine BTC was obtained with the two-site model.Model verification procedures were based on bestfit parameters optimized from the first displacement experiment (Exp.1), and then these fitted parameters were used to simulate the transport of atrazine in the duplicate experiment (Exp.2) by the chemical nonequilibrium model.The results showed that there was a good agreement between measured and simulated concentration variations for atrazine leaching in this soil column.In addition, dynamics of the flux concentration and the cumulative leaching quantity of atrazine at different depths of the soil column in Exp.2 were simulated.This study suggests that the two-site model based on the nonequilibrium theory can be used as a useful approach to better quantifying environmental fate of atrazine in a given scenario.

Abstract:The environmental impact of phosphorus on surface water quality by a long-term applying fertilizer P in the upland fields of yellow soil areas and its risks evaluation was studied in Guizhou province.The results showed that the contents of algae-available P (NaOH-extractable P) and labile P (CaCl₂-extractable P) in the soils correlated significantly with the quantities of Olsen-P or total P in the soils, while P application increased both soil P and its corresponding potential of P loss from soil to water bodies at the same time.The results also showed that the contents of CaCl₂-extractable P, Olsen-P, NaOH-extractable P in the soils and the phosphorus sorption of index (PSI) or the degree of soil saturation with phosphorus (DSSP) correlated significantly with the concentrations of dissolved active P, particulate P and bioavailable P in runoff, respectively.CaCl₂-extractable P, Olsen-P, NaOH-extractable P, PSI and DSSP were used as indices to estimate agriculture P impacting on surface water quality.As a result, three environmental risk groups were constructed in the upland fields from yellow soil area.

Abstract:Four variable charge soils from south China and one constant charge soil from Nanjing were used to examine the effects of ionic strength and pH on the surface charge of soils and adsorption of Cu²⁺ ions.Adsorption of Cu²⁺ was measured at different pH in water, 0.01 mol L^-1, 0.1 mol L^-1 and 1 mol L^-1 of NaNO₃ solutions was measured respectively.In the soils studied, the net surface charge decreased with an increase in pH.The pH at which the net surface charge was zero (pH₀) differed between the soils.The pH₀ was higher for soils dominated by variable charge components.For all soils studied, the adsorption of Cu²⁺ increased with an increase in pH and was closely related to the negative surface charge.The effect of ionic strength on Cu²⁺ adsorption differed between the soils.For constant charge soils, the adsorption of Cu²⁺ always decreased with an in crease in ionic strength irrespective of pH.For variable charge soils, the effect of ionic strength on adsorp tion of Cu²⁺ was much smaller than that for constant charge soils.The higher the content of iron oxide in soil, the smaller the effect of ionic strength on Cu²⁺ adsorption.For iron oxide, the amount of Cu²⁺ ad sorbed in 0.01 mol L^-1 NaNO₃ solution was larger than that in water.The results suggest that the Cu²⁺ ions were retained by both non specific and specific bonding.For constant charge soil, non specific bond ing played an important role in the adsorption of Cu²⁺;whereas for variable charge soil, specific bonding played an important role in the adsorption of Cu²⁺ ions.

Abstract:Manganese oxide minerals are important scavenger of heavy metals and oxidants of changeable valent elements in soils and aquatic environment Previous studies on redox reaction between Mn oxides and Cr (Ⅲ) were mainly achieved by using synthetic Mn oxides, and little literature is available on redox reaction of Cr(Ⅲ) and Mn oxides from soils Fe-Mn nodules were major depositing forms of Mn in soils Influences of pH, ion strength and temperature on the oxidation of Cr(Ⅲ) by Fe-Mn nodules from soils were investi gated by means of chemical analysis and equilibrium techniques The results showed that the amounts of Cr (Ⅲ) oxidized by Fe-Mn nodules increased as pH decreasing, ion strength and temperature increasing It was related to charge properties and electric potential of Mn oxide surface, and coexistence of Fe oxides besides consumption of H⁺ during redox reaction The ranging amounts of Cr(Ⅲ) oxidized by N2-1 and N4-1 contained birnessite and lithiophorite were larger than that by N5-1 contained todorokite and lithio phorite under above conditions These diversities were related to crystallinity, crystal structure, and Mn (Ⅲ) content of Mn oxides in Fe-Mn nodules These data are useful for predicting chrome transport in the environment, and understanding functions of Mn oxide minerals in soil and sediment particles.

Abstract:The microbial reduction of ferrihydrite, lepidocrocite, hematite, goethite and Aluminum-subst ituted iron oxides were examined under anaerobic incubation by slurry experiment.The variation of the partial pressure of H₂, CO₂, CH₄ and the acetate concentration were determined.The results indicated that different iron oxides had been shown different reduced ability in slurry.The ferrihydrite and lepidocrocite were easily to be reduced, which had almost same reduced level, meanwhile in the addition of ferrihy-drite, there was a reduced hysteresis.The goethite, hematite, Al-substituted goethite and Al-subst ituted hematite were difficult to be reduced, which showed a same characteristic of iron reduction with control.Iron reduction can cause the decrease of H₂ and acetate concentration, and then methane production was inhibited.By ferrihydrite and lepidocrocite addition, the contribution (%) of electron-transfer belong to iron reduction were respectively increased to 63.32% and 46.90% from 18.30% (control), however, the contribution (%) by methane production were respectively decreased to 35.85% and 52.32% from 80.92% (control).Because of election compet ing consummation of iron reduction, the methanogenesis was greatly inhibited.

Abstract:A field experiment was carried out in Yancheng to assess CH₄ and N₂O emission rate in such two different cultivation systems of rice as traditional paddy production and aerobic production with different covers.There were four treatments, i.e., three treatments designed in aerobic rice production system such as the plots covered with plastic film (Ⅰ), straw mulch (Ⅱ) and bare (without any cover) (Ⅲ) and one treatment in waterlogged rice production (as CK).The emission of N₂O and CH₄ was measured during the entire cultivation period in the two completely different cultivation system.The results obtained were as follows.The total N₂O fluxes in aerobic condit ion was five to six times higher than that in paddy soil, while the total emissions of CH₄ in paddy soil was eight to nineteen times higher than that in aerobic condition.The total N₂O emissions during the growth period of rice within the three treatments in aerobic condition were significantly different.They were in the order of Ⅰ> Ⅲ>Ⅱ, whereas the order of the total CH₄ emissions was Ⅲ>Ⅰ>Ⅱ.The maximum emission rate of CH₄ (5.0 mg CH₄ m^-2 h^-1) from water-logged soil was found in the tillering stage of the rice crop.Fertilization was the primary factor affecting the N₂O emissions in aerobic condition.The peaks of the emission rates of N₂O from aerobic soil were observed in the eleventh day, the ninth to tenth day and the sixth day after N applied as basal fertilizer, applied at tillering and booting stage, respectively.

Abstract:In the present study, changes in soil physical, chemical and biological properties in paddy fields of a cultivation chronosequence were observed by field sampling in a typical red soil region in subtropical China, Jiangxi Province.After cultivation, clay (< 0.002 mm) content decreased from 39% of the orig-i nal uncultivated wasteland to 17% of the 80 a paddy field, while silt (0.02~0.002 mm) content increased.Soil pH increased generally by 0.5~1 units, the 0~10 cm soil organic C and total N contents increased respectively from 4.58 g kg^-1 and 0.39 g kg^-1 of the original to 19.6 g kg^-1 and 1.62 g kg^-1 of the 30 a paddy field, and then remained stable.With 3 a cultivation for paddy field, total P content increased from 0.5 g kg^-1 to 1.3 g kg^-1, which suggested that fertilizer application can accelerate phosphorous accumulation in paddy field.0~10 cm soil total K content showed a decrease by 80% with a 80 a cult ivation.Total Fe and free Fe contents also showed a decreasing tendency.Bacterial population in-creased and urease activity intensified obviously.In this chronosequence it appeared that it took 30 year to raise fertility to a relatively constant value, seen after 80 a cultivation.

Abstract:Two field experiments were conducted on Andisols in Japan to evaluate changes in natural ¹⁵N abun-dance in the soil profile and to estimate whether the values of δ¹⁵N can be used as an indicator of fertilizer sources or fertilizer fate.The 6-year experiment at the National Agricultural Research Center (NARC) consisted of the following treatments: swine compost (COMPOST), slow-release nitrogen fertilizer (SRNF), readily available nitrogen fertilizer (RANF), and no fertilization (CONTROL).Experimental plots at the Nippon Agricultural Research Institute (NARI) received cattle compost at different rates for 12 years;a forest soil at this site was sampled for comparison.Swine compost greatly changed δ¹⁵N distribution pattern in the soil profile, with the highest δ¹⁵N values occurring in the top 20-cm layer of the COM-POST plot, decreasing in the sequence of CONTROL\RANF> SRNF, mainly due to relatively high δ¹⁵N value of swine compost and its subsequent decomposition.In contrast, SRNF resulted in the lowest δ¹⁵N values in soil, indicating small nitrogen losses relative to input and low nitrogen release rates.Values of δ¹⁵N increased with compost applicat ion rates at NARI, and, for the unfertilized soil, the values of the FOREST plot at NARI were 1~2 δ units larger than the CONTROL plot at NARC.In leachate collected at 100 cm depth, δ¹⁵N values decreased in the sequence of COMPOST> RANF\CONTROL> SRNF.The lowest δ¹⁵N values of leachate of RANF plot was observed in the depth of 200~250 cm.These results in-dicated that δ¹⁵N values in upper soil or leachate may help us infer pollution sources of organic or inorganic nitrogen qualitatively in Andisols.

Abstract:In this study soil microbial biomass nitrogen (SMBN) in 6 soil samples were initially labelled with the ¹⁵NO₃^- in the incubation experiment.Then the NaOH hydrolyzable method was adopted to measure the alkali hydrolyzable-N in the soils, and winter wheat was grown on the soils in a greenhouse to evaluate the availability of SMBN to plants.It found that the extractability ratios of the NaOH hydrolyzable-N to the SMBN were in the range of 147 to 283, with an average of 201;there was about 30.1%~61.6% (averaging 42.9%) of NaOH hydrolyzable-N in the soils derived from SMBN.The atom % of ¹⁵N in the plant shoots grown on the soils ranged from 0.749% to 1.162%, which were higher than the natural atom % of ¹⁵N in soil, indicating the release of ¹⁵N immobilized by SMBN in soils.Therefore, it is concluded that the chemical and biological availabilities of SMBN are high.

Abstract:Rice (Oryza sativa L) had been traditionally recognized as the typical plant preferred NH₄⁺-N as its N source.But more and more reports have shown that plant growth and yield is superior on mixtures of NH₄⁺-N and NO₃^--N compared with provision of either nitrogen alone and only a few species actually perform well when NH₄⁺-N was provided as the only N source.NO₃^--N had become the important N source for rice crop cultivated in aerobic condition because of most the inorganic N in soil existed in this fom.To evaluate the effects of mixed nitrogen nutrition on growth and water use efficiency of rice cult ivated in aero-bic condition, a pot experiment was conducted under different rates of NH₄⁺-N and NO₃^--N application from 3-leaf stage to earring stage of the crop.The mixed nitrogen solution of NH₄⁺-N and NO₃^--N was carefully injected into Typicudi Alluuvic Primosols in potevery other two days at the ratio of 100/0,75/25, 50/50, 25/75 and 0/100.The amount of water irrigated everyday photosynthesis rate of functional leaves and yield of rice were measured and counted.The results showed that the total requirement of water by rice could be significantly reduced by proper application of NH₄⁺-N and NO₃^--N in aerobic cultivation.Meanwhile the photosynthesis of the functional leaves after earring was improved greatly and the dry matter and grain product ive efficiency of water by transpiration was raised by utilizat ion of NO₃^--N at a suitable ratio.The highest biomass production and maximum grain yield was obtained when 50% of nitrogen fertilizer as NO₃^--N was applied.Both root weight and ratio of root and shoot would be reduced when the proportion of NO₃^--N was ≥50%.

Abstract:A pot culture experiment was carried out in glasshouse to investigate effect of soil moisture and phos-phorus (P) on water consumption and water use efficiency by paddy rice cultivated in aerobic soil.The results obtained were as follows.Soil water and P fert ilization rate had significant effect on water consumption and water use efficiency by paddy rice, and there was also a significant interaction between them.The highest water consumption is at middle soil moisture to high soil moisture and middle P supply to high P supply.Thus, water consumption percentages in the total water consumption during the whole growth stages were 15%~18%, 63%~68% and 16%~21% at early growth stage, middle growth stage and later growth stage, respectively.The highest water use efficiency(1.25~1.60 g L^-1) by rice in seedling period was got at low to middle soil moisture and low to middle P supply while the highest water use efficiencies by rice in middle(2.22~3.56 g L^-1) to later stage (1.68~2.08 g L^-1) were found at low to middle soil moisture and middle to high P supply.The order of water consumption and water use efficiency by rice in different growth stages were as follows: growth middle stage> later stage> early stage.The results obtained in this experiment could provide the theoretic base of water and P management of paddy rice grown in aerobic soil in the southern hillock areas of China.

Abstract:In this experiment, characteristics of phosphorus fixation and release were studied with added different concentrations of P (water soil is 20 1) and by sequential extraction.The results showed that, fixing P capacity of red soil is higher than that of fluvo aquic soil, and fixing P capacity of paddy soil is lowest among three soils.Fixing P capacities of three soils are 2.84 g kg^-1, 2.53 g kg^-1 and 2.08 g kg^-1 soil under treatment of P 2.97 g kg^-1 soil.Ratio of P fixed to P added reduces with increase of added P.In release experiment, capacities of P release reduce with increase of extract ing times, and change insignificantly after 8 times of extraction.In three soils, maximum of P release of paddy soil (124.07 mg kg^-1) is higher than that of red soil (60.46 mg kg^-1) and fluvo aquic soil (19.74 mg kg^-1), the similar results were obtained in total amount of P released.At the beginning of experiment, the ratio of P released to P fixed increases gradually and then reaches equilibrium with increase of extracting times, and that of P released in paddy soil is higher significantly than that of red and fluvo-aquic soils.Ratio of P released to P fixed of soils treated with 1.98 g P kg^-1 soil is higher than that of soils treated with 2.97 g P kg^-1 soil in paddy and fluvo-aquic soils, but the contrary result was obtained in red soil.

Abstract:The potential risk of surface and ground water contaminat ion by heavy metals leached from contaminated soils have caused considerable concern.Understanding the accumulat ion and chemical forms of the elements in soils is necessary to predict long term leaching behavior of the heavy metals in the soils.The objective of this study was to evaluate heavy metal leachability of urban soils in Hangzhou City, Zhejiang Province, China.A total of twenty urban soils and twelve suburban agricultural soils were collected from the urban and suburban areas in the Hangzhou city for fract ionation and leaching test of heavy metals.An optimized European Community Bureau of Reference three-step sequential extraction procedure was applied to heavy metal fractionation of the soils.Four operationally defined fract ions were identified: acid extractable, reducible, oxidizable and residual.The soils were also subjected to determination of potential leachability of heavy metals using a method developed by the Netherlands Energy Research Center.The results showed that the urban soils in the Hangzhou City had been anthropogenically contaminated by heavy metals to a great extent, and heavy metals in the urban soils, including Cd, Cr, Cu, Ni, Pb, Zn, and Mn, were higher than those in the suburban agricultural soils.About 70% of Cd, Co, Cr, and Ni were associated with residual fraction indicating relative low mobility of the metals in the soils.Of the four remaining heavy metals, Cu and Pb were dominantly associated with oxidizable and reducible fractions with low acid extraction fraction.Zinc and Mn had only one-third of their total concentrations in the residual fraction, but one-fourth in the acid extractable, which is susceptible to release.Potential leachability of all the measured eight heavy metals, defined as the maximum metal pool that may become available for leaching at a constant pH 4, was low and decreased in the following order: Cu > Mn > Cd > Ni > Zn > Pb > Co, Cr.Low potential leachability of the heavy metals in the urban soils was due to their low percentage of acid-extractable fraction of the heavy metals, and relatively high organic matter, iron oxides as well as clay contents that could adsorb heavy metals released from dissolution processes.Measured data indicated a low risk for surface and ground water contamination from the urban soils in the Hangzhou City.

Abstract:The urban soils are affected greatly by human activity and characterized by significantly anthropogenic enhancement of heavy metals.It will be helpful for us to protect and to remedy the ecosystem of urban soils better if we are learn the relation between the abundance and the form of heavy metals in soil with the physical and chemical properties of soils and the factors of surrounding environment.This study was conducted to examine the content and the forms of heavy metals in urban soils in Nanjing, applying the theory of grey system to analyze the factors influencing the pollution of heavy metals.Such factors as soil organic matter content, soil clay content, soil pH, the distance from industrial zone, the automobile flow, and the fraction of residue in soils were concerned in this paper.Grey-relational analysis showed that the most important factor is the distance from industrial zone.The factors such as soil clay content and soil pH are also important.Other factors are relatively unimportant.

Abstract:The effect of different sewage sludge levels (0%, 1%, 4%) on mycorrhizal infections, spore dens-i ties, root and shoot biomass, Cu uptake by maize inoculated with three arbuscular mycorrhizal fungi (A.laevis, G.caledonium and G.manihotis) in the red soil was studied.Mycorrhizal infection, spore densities, root and shoot biomass were increased by 1% sewage sludge in comparison to no sewage sludge when the maize was inoculated with A.laevis, however, mycorrhizal infection, spore densities, and root and shoot biomass were greatly reduced in the three other treatments (p < 0.05).When the red soil was amended with 1% sewage sludge the Cu concentrations in the shoot of the maize were NM (noninoculation) > G.manihotis> G.caledonium> A.laevis, and the total Cu content in the root of the maize infected with the three mycorrhizal fungi was higher than that under nonmycorrhizal treatment.The results showed that the tolerance of different arbuscular mycorrhizal fungi to heavy metals varied and A.laevis could remediate heavy metal contaminated soil when the heavy metal concentrations were not very high.

Abstract:Seasonal dynamics of soil microbial biomass C and N were measured under six vegetations restored for 10 years on degraded red soils.Vegetation increased soil microbial biomass(C and N) markedly in comparison with the eroded bare soil (CK).Soil microbial biomass expressed by seasonal means in 0~5cm soil layer differed significantly (p < 0.01) among vegetations, and they were decreased in the following order: protected grassland (G2) > slightly disturbed grassland (G1) > deciduous broadleaf woodland (Qc) > coniferous-broadleaved mixed woodland (Sm) > evergreen broadleaf woodland (Ss) > coniferous woodland (Pm).Compared with microbial biomass C, microbial biomass N was more sensit ive to the vegetations type.Soil microbial biomass showed a high degree of seasonality, and seasonal fluctuations were not consistent under different vegetations.ANOVA and Discriminant analysis indicated that vegetations had greater impact on soil microbial biomass than seasons.Stratification of microbial biomass was evident with sharply declined at lower depths.Changes of soil microbial biomass imposed by vegetations and sea-sons mainly happened in the surface layer of soil (0~5cm).Soil microbial biomass was significantly and positively correlated with soil organic matter and other biological properties, also it was capable of discrim-inating different vegetations distinctly.So soil microbial biomass had great potential as an indicator of red soil quality.Using soil microbial biomass to monitor the recovery of degraded red soil, soil sampling in spring was suitable and at least 0~10cm soil layer should be analyzed separately.Some possible high-lights in future study of red soil microbial biomass were also briefly given.

Abstract:The relationship of urease act ivity with Hg and Cd was studied.Results showed a similar effect of Hg and Cd on urease regardless of its state whether solute, clay or soil.Hg+Cd's treatment was the highest in inhibition effect when Hg and Cd remarkably inhibited urease activity, meanwhile Hg was the strongest in ecot-oxicity.Urease activity could be used as an index of Hg or Hg+Cd pollution of the soil.Urease activity was influenced not only by Hg or Cd singly, but also by their interaction.The single-factor effect was still in dominance.Their effects on urease varied sharply because of the difference in its carrier, which plays an important role in protecting the enzyme and buffering the heavy metals.The solute-state urease did not have carriers and hence was more sensitive and susceptible to damage of heavy metals than the other two.Besides, temperature and concentration of urea enhanced the inhibition effect of Hg and Cd on urease activity.

Abstract:Chlorsulfuron is a kind of herbicide that is used all over the world for the control of broad-leaved weeds in the field of cereal crops Increasing attention is being paid all over the world for its persistency and high toxicity Bioremediation is an effective and economic method to treat the environment that has been polluted by hazardous organic compounds So researchers paid much attention in this area;most of this research has been focused on the isolating and characterizing bacteria with abilities to degrade particular pollutants or transformation of metals. At the same time people have begun to explore genetic manipulation of genes encoding degradability of specific chemicals and applied genetic engineered microorganisms in the waste treatment of cleaning up Environmental biotechnology has become an indispensable component of our current society dealing with pollution reduction and cleaning up the contaminated sites A strain of Chlorsulfuron degrading bacteria was isolated from soil samples collected from field with frequent application of herbicide The strain was designated LHL-1 and preliminary identified as Xanthomonas sp About 62% of Chlorsulfuron was degraded when the strain was cultured in a mineral salt medium containing 20 mg L^-1 Chlorsulfuron under the condition of 30, 150 r min^-1, 40 h Among the tested metal ions, Pb²⁺ and Ag⁺ inhibited its growth, while Ba²⁺, Al³⁺, Zn²⁺ and other metal ions have no effect on its growth.

Abstract:地表温度是农业生态环境研究中的一个重要参量.监测地表温度对适时播种、因土施肥等农业生产活动具有重要的指导意义,对研究城市热岛效应也非常关键.本文利用气象卫星AVHRR数据,运用劈窗技术反演方法提取地表温度,为大范围实时监测地表温度提供新的技术途径.1劈窗技术原理传统地表温度获取主要采用水银温度计测量法,方法简单但易受微地形影响,且监测范围小^[1];后来采用红外测温,实现远距离非接触式监测,精度也有所提高.近20多年来,由于遥感技术的发展,气象卫星监测地表温度方法得到了广泛应用.

Abstract:建立在数据库基础上的土壤施肥决策系统或专家系统开始步入实用化的水平^[1,2],在指导和帮助土地使用者在生产过程中合理施肥、恢复和提高土壤质量方面发挥着重要作用.这种决策系统没有将土壤空间信息(位置、大小、土壤养分空间分异等)同决策支持有机地结合起来.在GIS支持下针对土壤施肥分区进行施肥推荐,部分考虑了土壤养分空间上的差异,相比单纯数据库基础上的施肥推荐系统进了一步^[3],但它仍不能对地块给出推荐施肥方案.

Abstract:农药在土壤表面的光化学降解是决定农药在环境中转归、消失的重要途径,研究农药土壤光解具有重要的环境学意义^[1,2].长期以来,由于土壤组成的复杂性和土壤的非匀质相体系,给农药土壤光解研究带来很大困难,农药在土壤表面光解情况了解甚少^[3～6].苄嘧磺隆是20世纪80年代中期美国杜邦公司开发的一种新型的磺酰脲类除草剂,是目前广泛用于稻田杂草防治的主要除草剂之一^[7].本文选用不同质地、不同有机质含量的土壤,研究苄嘧磺隆在土壤中的光解产物和光解动态,可为评价苄嘧磺隆在土壤中的药效和残留状况提供科学依据.

Abstract:应用分子化石探讨古植被、古气候等全球变化问题的研究日益开展.研究的载体已经涉及到海相沉积物^[1]、湖相沉积物^[2]、欧洲泥炭^[3]、雪冰^[4]、黄土^[5]等沉积物,并且取得了许多重要的成果.有机化合物种类众多,分子结构精细,其中包括着丰富而形式众多的与古气候、古生态、古植被和古环境有关的信息,因而在全球环境研究中分子有机地球化学有着广阔的应用前景^[6].然而,应用以上这些载体中的分子化石对其进行古植被、古气候等的恢复有赖于现代分子有机地球化学的研究成果.