Abstract:Relationships of soil aggregates stability with soil loss,runoff and sediment characteristics were studied under simulated rainfall in red soils derived from Quaternary clay,Shale and Granite.Results show that soil loss and runoff rate were significantly related to aggregate stability,but the relationship varied with the aggregate stability indices.Among them,mean weight diameter with wet-sieving method and content of water stable aggregates lager than 0.25 mm were the highest in relativity.As for Le Bissonnaisπmethod,soil loss and mean runoff rate were also significantly correlated with the normalized mean weight diameter of aggregates (1～0.5 mm in size) in the fast wetting treatment and aggregates (2～1 mm in size) in the wet stirring treatment.A significant relationship (partial correlation analysis) was found between particle size of sediment and mean weight diameter (r=0.8283),water stable aggregates >0.25 mm (r=0.8209).In Le Bissonnais' method,the NMWD of aggregates (1～0.5 mm) in the fast wetting treatment and aggregates (2～1 mm) in the wet stirring treatment showed close but not significant relationship with particle size of sediments (r=0.7458,r=0.6859).However,the stream power and particle size of sediments did not show much (r=-0.1852) in this study.

Abstract:Suburbs of Nanchang City and Yujiang County in Jiangxi Province,a typical area with rapidly developing intensive agriculture in city suburbs and a typical one with intensive traditional agriculture,respectively,were selected in a red soil region of Jiangxi Province for study of effect of intensive agriculture on soil fertility and environmental quality and countermeasures.Results show that twenty years of vegetable cultivation increased soil organic matter by 21153%,readily available phosphorus by 13115~18186 times,readily available potassium by 1115~1135 times,but did not increase much total soil nitrogen and nitrate nitrogen in the suburbs of Nanchang.In Yujiang County,the trend of soil acidification was obvious,with 90% of the soil falling in pH by 0.5 unit,meanwhile some farmlands were polluted by heavy metals to a certain extent.,Readjustment of the agricultural structure,increased application of chemical fertilizer,P and K fertilizers in particular,and application of barnyard manure were found to be the major factors leading to soil nutrient enrichment/unbalance and soil acidification,and industrial production the main source of soil pollution.Reducing fert ilizer input for a short term,using nutrient accelerant and applying slow-release fertilizer are positive measures to improve utilization efficiency of fertilizer,control excessive enrichment or unbalance of soil nutrients to some extent.Proper application of lime or other alkaline soil amendment is a major practice to prevent soil acidification.For slightly polluted soil,application of chemical ameliorator and cultivation of super-accumulating plants can be used to remedy the soils.

Abstract:In this experiment carried out in 1998 when the Three Gorges Project was about to start,soil faunae in different habitats and at different altitudes were investigated in the Three Gorges Reservoir Region,including Zigui County,Wanxian County and Shennongjia region.Results show that in the region,Nematoda was the predominant group,and Acarina,Collembola,Tardigrada and Harpact icoida were common groups.Soil faunae under different vegetations at the same location displayed certain similarity and difference as well.Correlation tests demonstrated that altitude and habitat had little effect on the correlation between the numbers of soil arthropod individuals and groups.It was also discovered that the lower the more favorable the habitat (altitude and vegetation),the higher the biodiversity index.Comparison between communities in similarity showed that fauna communities under similar vegetations at the same elevation were quite high in similarity.In Zigui Country,the numbers of Nematoda,Acarina and Collembola individuals were not much affected by habitat and elevation,while in Wanxian Country,the numbers of Acarina and Collembola were by elevation.In Shennongjia region,distribution of Nematoda varied significantly with vegetation.Acarina and Collembola were widely distributed in various soil layers under different vegetations,whereas the number of Acarina in the litter layer varied significantly with habitat and elevation.

Abstract:Human health risk assessment has been extensively employed to derive guidelines/standards for soil environmental quality around the world.Various threshold values for Bezo[a] pyrene (B[a]P) concentration in soil for protection of human health were introduced.Exposure scenarios and parameters of three different patterns of land use were defined to quantify health risk of human exposure to soil B[a]P.A human-health-based methodology for deriving threshold values for B[a]P concentration in soils was proposed for the first time in China,which should be further used to derive threshold concentrations for other persis tent organic pollutants.Four exposure pathways,i.e.soil ingestion,dermal contact,soil inhalation,and consumption of contaminated vegetables,were considered in modeling for calculation.Threshold concentrations of B[a]P at cancer risk levels of 10^-5 and 10^-6,were calculated for agricultural,residential and industrial soils,respectively.Threshold values for B[a]P concentration in soil for protection of groundwater quality were also derived based on the guidelines/standards for protection of groundwater quality.

Abstract:Xishan City,a typical area of the Yangtz River Delta,was selected as a case for study of responses of 7 soil fertility indices,such as soil pH,organic matter (OM),total nitrogen (TN),total phosphorus (TP),available nitrogen (AN),available phosphorus (AP),and available potassium (AK),to changes in land use,i.e.from dry-land to unused land (DCU),from paddy field to vegetable field (PCV),from paddy field to dry-land (PCD),from paddy field to forest land (PCF),and from paddy field to unused land (PCU),in Yangtze River Delta.Results show that changes in land use did significantly affect soil properties to a varying degree.1) PCV,PCD and PCF led to decrease in soil pH by 0.47,0.78 and 0.17,respectively,while DCU and PCU to increase by 0.24 and 0.74,respectively;2) PCU,PCV and PCF led to decrease in content of OM by 3.83,3.18 and 0.35 g kg^-1,respectively,while PCD and DCU to increase by 7.58 and 1.07 g kg^-1respectively;3) DCU,PCV and PCU led to decrease in content of TN by 0.31,0.08 and 0.11 g kg^-1,while PCD and PCF to increase by 0.41and 0.04 g kg^-1,respectively;4) DCU led to decrease in content of TP slightly by 0.01 g kg^-1,while PCV,PCD,PCF and PCU to increase by 0.23,0.08,0.23 and 0.09 g kg^-1,respectively;5) DCU and PCU led to decrease in content of AN by 2.38 and 7.62 mg kg^-1,while PCV,PCD and PCF to increase by 11.61,34151 and 18.26 mg kg^-1,respectively;6) DCU led to decrease in content of AP by 3.70 mg kg^-1,while PCV,PCD,PCF and PCU to increase by 45.16,7.54,40.55 and 10.94 mg kg^-1,respectively;and 7) DCU,PCV,PCD,PCF and PCU led to increase in content of AK by 8.75,77.44,32.28,160.4 and 27.59 mg kg^-1,respectively.

Abstract:To study spatio-temporal variation of soil available phosphorus in farmland soils may provide some scientific basis for rationalizing fertilization and identifying key regions for control of agricultural non-point phosphorus pollution.Rugao County,Jiangsu Province was chosen as an object for a case study to analyze spatio-temporal variation of soil available P at three time periods.Results show that spatial distribution of soil available P varied remarkably in the 20 years' period from 1982 to 1997 and to 2002,on the whole showing a continuous rising trend,which,however,differed from soil series to soil series.In the Loam Aquatic cambosols (Yinfang) in the southern part of the area,soil available P increased in recent years after experiencing a decrease in the middle of the 1990s,and in the other soils it showed a rising trend,different in extent within each time period.In the sandy Aquatic Cambosols (Motou and Taoyuan) derived from river alluvium in the mid-western part of the area it increased more slowly than in the other soils in recent years,meanwhile in the loam Aquatic Cambosols (Dongchen),also developed from river alluvium,in the northeastern part and the loam Aquatic Cambosols (Banjing) derived from lacustrine sediment in the northwestern part of the area it increased very fast.Fertilization,land utilization and soil properties were found to be the main factors affecting spatio-temporal variation of soil available P.Based on the data of soil available P figured out with a certain fitting equation,it is anticipated that soil available P in the area may reach the critical value undermining the water bodies in the region in another 24 years.

Abstract:Surface soil samples collected from Shilong coal mining area were tested for saturated hydrocarbons by means of GC-MS,and 85 representative kinds of chemical compounds including normal alkanes,steroids,terpenoids,etc.,were detected.Composition and distribut ion characteristics of the saturated hydrocarbons in soils of different functional zones were analyzed and their sources were explored,with their molecular organic geochemical parameters taken into account.Results show that the soils in the areas affected by coal mining were much higher in content of saturated hydrocarbons than those in non affected areas,especially higher in soils around the gangue damping grounds and coking plants;with normal alkanes,the portion high in carbon number was small,but the portion low in carbon number was great,and their C_max were at 16 or 18,and their Pr/Ph and hopane/moretane ratios were high;and the content of sterane of geological configuration type and C₂₉ααα20R-sterane were high,too.These geochemical characteristics were quite close to those of raw coal,suggesting that the surface soil layer of the Shilong area is not of contemporary sediments or naturally formed surface soil.Deposition of large volumes of coal slack or dust generated from the coal mining operation,such as dumping,storage,transport and processing of coal and gangue may be the major source of organic manure in the soils of the coal mining area.

Abstract:Samples of airborne dust and soils around the two steel factories in Nanjing were collected and their element concentrations were analyzed by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and their magnetic susceptibility determined by magnetic susceptibility analyzer.Results indicate that the deposition flux around the two steel factories was 190 t km^-2a^-1 and 407 t km^-2a^-1,respectively and the annual accumulation in soil surface due to dust deposition could reach up to 0.3 mm,which is an important contribution to soil formation in a long run.The contents of Al,K,Na,Ti,and V in the dust were lower than that in the surface soils,but Ca,Fe,Zn,Mn,Pb and Cu were much higher.The magnetic susceptibility (MS) of the surface soils was over 100×10^-8m³kg^-1 except that in the paddy field,and the MS of the roof dust was much higher than that of the surface soils.MS decreased sharply with depth in the several centimeters of soils around the factories,indicating an obvious surface enrichment of magnetic materials and heavy metals.The study reveals that the dust from industrial sources has a strong impact on the soils around,by causing enrichment of heavy metals in the soil surface and sharp rise in magnetic susceptibility.

Abstract:Effects of organic acids (acetic acid,tartaric acid and citric acid) on Cd²⁺ and Pb²⁺ adsorption on goethite and bentonite were studied with the batch method.Results show that pH decreased with the increase in concentration of Cd²⁺ and Pb²⁺ in the goethite and bentonite isothermal systems when the concentration of Cd²⁺ and Pb²⁺ was lower than 0.2 mmol L^-1 and 4.0 mmol L^-1,respectively.The decrease of pH in bentonite system was more obvious than in goethite system.The effect of pH on Cdand Pbadsorption of goethite and bentonite varied sharply with organic acids added.Cd²⁺ sorption rate was small with goethite when pH was in the range from 3 to 4.5,but it went upward sharply when pH was higher (4152+ sorption rate began to increase when pH was 3 with goethite,and it leveled off to 95% at pH 5.5.Affected by three organic acids,Cd²⁺ sorption rate increased slowly from 40% at pH 3 with bentonite,and approached close to 90% at pH 8.Pb²⁺ sorption rates were around 60% in bentonite systems added with different organic acid.They increased to 80% when citric acid was added and 95% when other organic acid added.Cd²⁺ and Pb²⁺ sorption rates varied from 40% to 90% with bentonite at different pH,but from 3% to 90% with goethite.In terms of effect of organic acids on Cd²⁺ and Pb²⁺ adsorption of goethite,the three acids were in the order of citric acid > tartaric acid > acetic acid,but the effect was not clear with bentonite.

Abstract:Charcoal derived from incomplete combustion of vegetation is ubiquitous and potentially effective for sequestra tion of environmental contaminants.To demonstrate effects of this type of charcoal on sorption and desorption of pesticides in soil,synthetic charcoal from burning of red gum chips was mixed into soils at different rates,sorption and desorption behavior of diuron in the charcoal amended soils were determined by means of batch equilibrium and consecutive dilution techniques,respectively.For comparison,sorption and desorption of diuron in three natural soils with known contents of organic carbon and charcoalwere also measured.The sorption and desorption isotherms were fitted linearly with the Freundlich equation,and the ratio of sorption Freundlich exponent coefficient (N) and that of desorption (N_f) was used to indicate degree of sorption/desorption hystersis.Results of the sorption determination show the sorption capacity of the soil newly amended with charcoal increased with the rate of charcoal amended.The Freundlich sorption coefficient K increased from 4.08 to 500,while the other Freundlich coefficient (N) that shows the non linearity of sorption isotherm decreased from 0.83 to 0.16,when the content of charcoal in soil increased from 0% to 1.0%.The diuron sorption capacity of natural soils was related to the content of organic carbon,while the isotherm non-linearity was closely related with the relative content of organic carbon and charcoal.The higher the proportion of charcoal in total organic carbon,the higher the isotherm non-linearity.Results of the desorption experiment in soils newly amended with charcoal show that the desorption hystersis index H increased rapidly in value from 1.14 to 14.92 when the content of charcoal increased from 0% to 1.0% in the soil,and H values of natural soils SS7,SS8 and SS6 were 2.49,1.61 and 1.42,respectively,when the content of charcoal was 2.145%,0.819%,and<0.07%,respectively.The results indicated that the hysteresis effect of charcoal on desorption of diuron seemed to be closely correlated with the content of charcoal in the soils.

Abstract:Interactions between bacteria and clay minerals are ubiquitous in soil and sediments.Previous studies on bioad-sorption of bacteria focused mainly on large particles like quartz sands.Few methods for investigation of bacteria on clayey soil components are available.This study aims to establish a method for determination of adsorption of bacteria on clay minerals.Kaolinite and B.thuringiensis were used as the test bacterial strain and clay mineral.Nycodenz—density gradient solution was used to separate free bacterial cells from those adsorbed.Correlation between total protein and count of bacteria was analyzed.Suspending and separating effects of Nycodenz solution on bacteria and minerals were tested.Appropriate ranges of bacterial number and clay mineral,and equilibrium time were determined.Results show significant correlation between total bacterial protein and count of bacteria (R²=0.9919).Total protein of bacteria could be used to represent the amount of bacteria adsorbed on minerals.Data reveal that Nycodenz solution,60% (w/v) in concentration and 1.31 g ml^-1 in density,is an efficient density gradient medium to separate free bacteria from those adsorbed on clay minerals.No interferences were observed of the 12% (v/v) Nycodenz solution on protein measurement by the Bradford method.Maximum adsorption of bacteria on kaolinite occurred 60 min after getting in contact and then leveled off.The method could be extended to the study on interactions of minerals and microorganisms.

Abstract:Morin was employed as complexing reagent in determining inorganic monomeric Al in acidic soil solution using a reversed-phase high-performance liquid chromatograph and a fluorescence spectrophotometer in this study.Three different methods,varying only in molar ratio of morin:Al,dissolving medium of the complexing reagent,and pH of the buffer solution,were proposed for comparison in linear range,accuracy,and precision,and analyzed for correlation between them.Results showed that Method Ⅲ (1.0×10^-4 mol L^-1 Morin dissolved in ethanol reacted with inorganic monomeric Al in pH 410 acetate buffer solutions,and fluorescence was recorded by fluorescence spectrophotometer (Ex=403.3nm,Em=490nm) ) was the most suitable one for determing inorganic monomeric Al in acidic soil solution.

Abstract:Decomposition and transformations of added organic substrates (¹⁴C labeled glucose and rice straw) in upland soil and paddy soil and their influences on mineralization of native soil organic C with soil samples collected from the red earth region of China were investigated under incubation at 25℃ and 45% water holding capacity (WHC) for 100 days.During this period,49.6% and 46.7% of glucose-C were mineralized in the upland soil and in the paddy soil,respectively,and the correspon sive values for straw-C were 25.2% and 21.8%.The influences of these amendments on soil microbial biomass C (B_C) and on the mineralization of soil native organic C were larger in the upland soil than in the paddy soil.The maximum percentages of glu cose-C assimilated by the microbial biomass were 23.5% and 21.6% for the upland soil and the paddy soil,respectively,and the corresponsive values for straw-C were 10.4%and 11.3%.Under the conditions,the turnover time of B_C,calculated from the gross turnover rate of ¹⁴C B_C in the treatment with glucose,was 329 days and 127 days for the upland soil and the paddy soil,re spectively.These results demonstrated that under soil moisture of 45% WHC,the decomposition rate of glucose and rice straw was faster in the upland soil than in the paddy soil,but the turnover rate of B_C was in reverse.

Abstract:Physical fractionation and chemical analysis were conducted of upland red soils different in fertilization combination to study variation of organic carbon fractions in aggregates >2000,250～2000,53～250 and <53μm in particle size.Results show that long-term combined application of organic manure and inorganic fertilizer could significantly increase content of total organic carbon in soil (TOC) and content of organic carbon in light fraction (LF-C),coarse fraction (CF-C),inside particle organic carbon-fine (FF-C) and mineral-associated organic carbon (mSOC) in aggregates of all sizes.And organic carbon contents in various fractions of aggregates were significantly related to TOC.Content of organic carbon in aggregates decreased with the decreasing particle size of aggregates.Application of livestock manure significantly improved SOC content,dominated with mineral-associated organic carbon.Application of organic manure reduced turnover rate of macro-aggregates,and incorporation of crop residues contributed more than application of organic manure to formation and stability of aggregates.In the red soil region,the effect of long-term combined application of organic manure and inorganic fertilizer on formation and stability of aggregates should be intensified.

Abstract:A solution culture experiment was conducted to study effects of NH₄⁺-N/NO₃^--N ratio on growth,food-safety and nutrition of spinach.The following results were obtained. (1) Fresh weight of spinach shoots gradually increased with the percentage of NO₃^--N in the total nitrogen,and spinach supplied with NO₃^--N as its sole nitrogen source was the highest in biomass,but there was no significant difference (p<0.05) in dry matter weight between treatments,25:75 and 0:100 in NH₄⁺-N/NO₃^--N ratio. (2) Contents of nitrate and nitrite in spinach shoots increased linearly with the decrease in NH₄⁺-N/NO₃^--N ratio.A significant quadric relationship was observed between the percentage of NO₃^--N in the total nitrogen and soluble oxalate content of the spinach shoots,and in Treatment 25:75 in NH₄⁺-N/NO₃^--N ratio,the soluble oxalate content was the lowest.Obviously,proper partial replacement of NO₃^--N by NH₄⁺-N is beneficial to decreasing contents of nitrate,nitrite and oxalate in spinach. (3) Proper partial replacement of NO₃^--N by NH₄⁺-N increased Vc content in spinach shoots,and it was the highest in Treatment 50:50 in NH₄⁺-N/NO₃^--N ratio.Content of soluble sugar in spinach shoots gradually decreased with the NH₄⁺-N/NO₃^--N ratio,and content of crude protein was the highest in Treatment 25:75 in NH₄⁺-N/NO₃^--N ratio.

Abstract:Pot experiments were carried out to investigate effect of application of amino acid fertilizer (AAF) on biological properties of cucumber plants (Cucumis sativus) and soil microorganism under continuous mono-cropping.Results show that application of AAF increased chlorophyll content,leaf area,photosynthesis rate,and dry weight of the cucumber plants.Moreover,after the application of AAF with high-quality carbon,the number of actinomycetes was increased by 1.57～2.18 folds,fungi by 2.22～8.43 folds,while the number of Fusarium oxysporum,a witling disease causing fungi,was significantly decreased.The ratio of Fungi/Bacteria was significantly increased while the ratio of F.oxy.to fungi was significantly decreased.The rate of protection of fusarium wilt was more than 80%.The results suggested that AAF application could significantly promote the growth of cucumber plants,stimulate microbial activities in the soils,and alleviate the adverse effect of continuous mono-cropping of ucumber.

Abstract:A total of 40 soils samples of different soil types from all over the country were analyzed for total N,organic matter,fixed ammonium,remaining organic matter (OM in the soil after treatment with KBOr),and residual organic matter (OM in the soil after treatment with KBOr-HF).Results show that in soils containing 2:1 clay minerals,residual organic matter is closely related to fixed ammonium in soil at an extremely significant level (r=0.831^**),and the organic matter existing in lattice is at a significant level (r=0.832^**),while in soils containing 1:1 clay minerals neither residual organic matter or lattice organic matter are related to fixed ammonium.The mean content of the remaining organic matter and residual organic matter in the 40 soils samples was 2.59 g kg-1and 3.70 g kg-1,accounting for 10% and 16%,respectively of the organic matter in the soils.

Abstract:Effects of fertigation strategy on nitrogen (N) uptake by cotton and N use efficiency (NUE) were invest igated through a pot experiment under greenhouse conditions.According to t iming of irrigation and fertilization,four fertigation treatments were designed,nitrogen applied 1) in the beginning of the irrigation cycle (N-W),2) at the end (W-N),3) in the middle (W-N-W),and 4) throughout the irrigation cycle (N-N) in a completely randomized layout,each with four replications.Cotton was grown in plastic containers,84 L in volume,filled with a clay loam soil and fertilized at a rate of N 6.44 g per pot as ¹⁵N-labeled urea Treatment N-W was significantly higher than Treatment N-N in total dry matter (DM) and N content,but did not differ much from Treatment W-N and Treatment W-N-W Plants in Treatments W-N and N-W were found to have a significantly higher content of nitrogen derived from fertilizer (NDFF) than those in Treatments W-N-W and N-N Fert igation strategy had a consistent effect on total NUE:Treatment N-W was the highest in total NUE,and followed by Treatments W-N and W-N-W,which were quite similar to each other,and Treatment N-N was the lowest After harvesting,the residue of fertilizer N in soil was highest in Treatment W-N,and the lowest in Treatment N-W,but did not vary much between Treatment N-N and Treatment W-N-W The difference between the four treatments in total ¹⁵N recovery was not statistically significant From the aspect of nitrate leaching losses from the root zone,Treatments N-N and W-N may lead to an increase in soil residual nitrates and hence a higher risk of nitrate leaching.In contrast,Treatment N-W tends to reduce potential leaching loss of nitrate from the root zone In this study,the fertigation strategy,Treatment N-W (nitrogen applied in the beginning of the irrigation cycle) increased DM accumulation,N uptake and NUE of cotton Therefore,NUE could be enhanced by optimizing fertilization strategies with drip irrigation.

Abstract:Effects of long-term application of N fertilizer on microbial communities in Mollisol,in Northeast China,were investigated by determining phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) of soil microbes,NLFA/PLFA ratio,and PLFA composition in soil samples different in nitrogen treatment with or without phosphorus and potassium fertilizer.Treatments Nil-fertilizer and Fallow were set as controls.Results of PLFA determination show that application of nitrogen coupled with phosphorus promoted microbial growth and immobilization of nitrogen in the soil,while application of nitrogen coupled with phosphorus and potassium did not show any similar effect.Application of nitrogen alone,however,inhibited growth of fungi,probably due to the excessive consumption of nutrients such as available phosphorus.Comparison between different microbial groups in PLFA ratio demonstrates that fungi were better adapted to nutritional stress than bacteria,while the latter accumulated more rapidly in biomass than the former in Treatment N or Treatment NP.NLFA content and NLFA/PLFA ratio varied sharply between treatments different in N rate,suggesting that they could be used as indicators of bio-physiological conditions of soil microorganisms and nutrient level of the soil.

Abstract:Impact of genetically modified or transgenic plants on the eco-environment has aroused great concerns.But little is known of their possible impacts on non-target organisms,such as microbial communities associated with their parent plants in the soil environment because of the complex structure-function relationships of microorganisms.A one-year field study was carried out by analyzing soil samples collected from the cotton field and the rhizospheres of cotton plants of transgenic cotton variety GK12 (expressing Bacillius thuringiensis insecticidal proteins) and its non-transgenic parent variety Simian No.3 at four different growth phrases (seedling,squaring,flowering and boll-forming,and boll-opening).Based on amplification of 16S rDNA retrieved from the soil microbial communities associated with both transgenic and non-transgenic cottons,terminal restriction fragment length poly-morphism (T-RFLP) analysis,clone library construction and sequencing were carried out to see changes in bacterial and archaeal community structures in the soils.Shannon-Wiener index analysis showed that bacterial diversity declined and a certain change occurred in archaeal diversity as well in bulk soil,indicating microbial communities were affected by season succession.According to the clone library and sequencing analysis,the dominant microorganisms in the soil were bacteria and archaea that have never been cultivated or known for their functions in the soil ecosystem.It remains unclear what causes these differences and whether these differences have any ecological threats and bio-risk to the soil ecosystem.Compared to bulk soil samples,the rhizosphere soil samples showed cultivation of cotton varieties remarkably affected bacterial and archaeal communities therein.Variation of bacterial and archaeal communities,especially the archaeal community,was significantly associated with both cotton variety and growth season in T-RFLP analysis,.Since archaeal community is less diversified than bacterial community,the study illustrates that the impacts of transgenic cotton on soil microorganisms varied with the microbial background and transgenic cotton affected the less diversified microbial community more.

Abstract:A strain of high-efficiency phosphorus accumulating bacteria,identified as Pseudomonas putida GM6,was used as research object,from which polyphosphate kinase gene was cloned and its roles in the phosphate transport system verified.A 528-bp fragment of ppk gene was successfully amplified firstly from GM6 genomic DNA using self designed primers corresponding to the well-conserved regions of reported ppk gene sequences.Then,its upstream and downstream sequences were cloned with the technique of self-formed adaptor PCR (SEFA-PCR).Three amplified sequences were put together and analyzed using the OMIGA program (version 2.0),and operon of the complete ppk gene ca.2220 bp was obtained (it has been deposited in the GenBank database under accession number DQ133537).The constructed recombinant expression strain of ppk gene E.coli BL21 (DE3) /pET29a-ppk was induced with IPTGfor three hours,and expression product,81 kDa in molecular weight,was observed.The strain removed 80% of the phosphorus in the solution while the CK strain only 18% in 12 h.Its P removing capacity,more than 40%,the sofar reported highest rate,indicates excessive expression of ppk gene in E.coli,which would lead to accumulation of a great deal of poly-P in E.coli in vivo,and removal of a large amount of phosphate from the medium.

Abstract:A strain of bacterium designated as Strain Dsp-2,capable of degrading chlorpyrifos efficiently,was isolated from sludge in a wastewater treatment installation that has long been treating chlorpyrifos polluted water.Strain Dsp-2 was identified preliminarily as Sphingomonas.sp based on its physiological and biochemical characters and the result of the 16 SrDNA homologue sequence analysis.Strain Dsp-2 can grow with chlorpyrifos as its sole carbon source,degrading 100 mg L^-1 of chlorpyrifos completely within 24 h.Results of its degradation characteristics show that the degradation rate of chlorpyrifos was increased considerably with the concentration.But when the chlprpyrifos concentration was higher than 200 mg L^-1,the strain Dsp-2 stopped degrading.Effects of initial inoculum size,yeast extract,glucose,peptone and metal ion on degradation of chlorpyrifos by Dsp-2 were also studied.Results show that large initial inoculum size and a proper amount of peptone could promote its degradation of chlorpyrifos.1 mmol L^-1 of Fe³⁺ and Ni²⁺ could restrain its degradation rate of chlorpyrifos.Addition of strain Dsp-2 to three test soils treated with chlorpyrifos resulted in a higher degradation rate of chlorpyrifos than in the control,soils without inoculation.However,the highest rate was showed in brown soil,which indicated moderate pH,moisture and nutrients could promote the degradation.The degradation rate reached to 85%～98% at 7th day when the concentration of chlorpyrifos ranged in 1～100 mg kg^-1.

Abstract:Effects of abamectin,applied at 1,5,10,50 or 100 mg kg^-1,on vegatable-growing soil microorganisms and their respiration,and the activity of urease,dehydrogenase and catalase,in vegetable fields were investigated.Results show that when it was low in application rate (1～10 mg kg^-1) abamectin,stimulated slightly activity of urease and dehydrogenase,but did not have much on soil respiration.And when it was high (50～100 mg kg^-1),it displayed strong inhibitive effects on respiration,and activity of urease and dehydrogenase.Regardless of application rate (1～100 mg kg^-1),abamectin reduced biomass of soil microbes to a varying extent and strongly stimulated activity of soil catalase.

Abstract:Transport of nonaqueous phase liquids (NAPLs) in soil and other porous media would pose a great threat to the environment of soil and underground water.Recent advancement in the study on retention characteristics,and permeation features of NAPLs,mathematic models of their transport and experimental technology and methods are reviewed.on such a basis direction and trend of the research on mechanism of NAPLs transport in porous media,and key issues for further study are also presented.

Abstract:LUCC(Land Use Cover Change)研究是IGBP(In-ternational Geosphere-Bioshpere Programme)和IHDP(In-ternational Human Dimensions Programm)的重要组成部分,日益重视区域尺度上土地利用变化对土地覆被状况影响的研究,如对地表植被的变化^[1]、土壤环境^[2]的影响等.当前,国内学者对区域土地利用变化对水资源的影响、土壤养分含量的影响及其驱动机制进行了深入分析^[3~8],也有学者从地块尺度上探讨了不同土壤类型不同土体构型中的土壤盐分含量的变化^[8],但总体看来缺乏区域尺度上土地利用变化和土壤耕层盐分之间关系的研究,特别是对人为影响显著区域的研究则更为鲜见.

Abstract:根际一般指绕根面1~2mm,性质受根分泌物影响的薄层土壤,是植物摄取养分的主要区域,已日趋受到人们的重视^[1].根际土壤环境在土壤体系中较为独特,它与本体土壤(非根际土壤)在物理、化学及生物化学性质等方面都有较大的差异^[2~4].根据土壤的表面电荷特征和表面化学行为,可将土壤表面划分为二种类型,即恒电荷表面和可变电荷表面,土壤表面带有电荷是土壤具有众多理化性质的根本原因^[5,6],了解土壤表面电荷性质对于土壤发生分类、改良利用以及污染控制等都有非常重要的参考价值^[7].于天仁等^[8]系统地研究了可变电荷土壤的电化学特征,但关于温带土壤胶体表面的电化学特征尚缺乏系统研究.

Abstract:苏打草甸碱土是松嫩平原西部盐渍土壤类型之一,碱化度大,pH达10以上,形成了寸草不生的光碱斑,造成了草场退化和生态环境的恶化.通过采用碱斑堆肥、覆盖等措施对盐渍土植被重建试验,能使光碱斑当年得到修复,覆盖率达到90%以上,pH下降到8.5以下.为进一步阐明改良效果,本文将对草甸碱土改良后的盐分变化及土壤酶活性进行探讨.由于土壤酶参与土壤各种生物化学反应过程,与土壤供应养分能力密切相关^[1~3],而且土壤中酶的种类繁多,本文选择具有代表性的酶(土壤过氧化氢酶、脲酶和磷酸酶)的活性进行研究.这主要因为土壤过氧化氢酶的活性可以表征土壤总的生物学活性和肥力状况.

Abstract:在植物-微生物-土壤三元关系中,根际微生物作为土壤和植物中介与桥梁,是最为活跃的因素,其活动规律对于土壤肥力、植物营养和植物病害都有举足轻重的作用^[1,2].植物促生细菌(Plant growthpromoting rhizobacteria,PGPR)在植物的根际普遍存在,应用某些优良菌株促进植物生长的试验也获得了不少好的结果,但这些试验多在人工控制的条件下进行,真正应用于大田生产的效果却很不稳定或无效果.其原因在于接种的细菌未能在植物根际存活或继续生长繁殖.到目前为止,人们只顾及单一因素,即通过增加在种子上的接种量来增加PGPR在根际的定殖.