Abstract:Relationship between contents of soil nutrient elements (N,P and K) and laboratory VNIR (visible-near infrared) spectra of the soil is analyzed in this article.Some spectra are pre-processed before calculation of four spectral indices,including inverse spectra (1/R),first derivative reflectance spectra (FDR),inverse-log spectra (log (1/R)) and Depth.Based on the partial least square regression method,statistical relationships between these indices and contents of soil nutrient elements are established by calibration set.Then the regression model is verified by test set.The results showed that VNIR (visible 2 near infrared) spectra of soil are potentially useful for rapid estimation of content of the nutrient elements in the soil.

Abstract:The behavior of persistent organic pollutants in soil environment largely depends on their adsorption to soil organic matter.Particle-size fract ionation is usually used to differentiate organic matter pools with different composition and turnover rates.In this research,phenanthrene (Phe) and benzo[a] pyrene (Bap) were used as representatives of low-and high-ring polycyclic aromatic hydrocarbons (PAHs),respectively.The distribution characteristics of them in different particle-size separates (clay,fine silt,coarse silt,fine sand and coarse sand) of nine agricultural topsoils (0~20 cm) from a contaminated district were studied.The results showed that the average contents of Phe in different particle-size separates decreased in the order coarse sand>fine sand>clay>fine silt>coarse silt,and those of Bap in the order coarse sand>fine sand>coarse silt>fine silt>clay.In the different particle-size separates,the contents of both Phe and Bap had significantly positive correlations with that of organic matter (p<0.01).The enrichment ability of organic matter for Phe in different particle-size separates decreased in the order coarse silt>fine silt>fine sand>coarse sand>clay,and for Bap in the order coarse silt>coarse sand>fine silt>fine sand>clay.

Abstract:Labile organic matter (LOM) in red soil under long-term fertilization was measured using the KMnO₄ oxidation method.The results show that LOM and carbon management index (CMI) decreased apparently in red soils in Treatment Zero-fertilizer (CK) or treatments applied chemical fertilizer (CK,N,NP,NK,PK,and NPK) after 10 years of cultivation,with the maximum drop (CK) by 40.5% in LOM and 48.1 in CMI;but increased significantly in the treatments applied with manure or with both manure and chemical fertilizers (M,MNPK,and 1.5MNPK),with the maximum rise (1.5MNPK) by 183% in LOM and 195 in CMI.LOM and CMI in Treatment SNPK decreased after 5 years by 25.2% and 31,respectively;but increased after 10 years by 17.9% and 13,respectively.These suggest that chemical fertilizers mainly increase non-labile organic matter content,while manure mainly improves quality of soil organic matter,and straws are slower in the effect than manure.The contents of three fractions of labile organic matter named as highly labile organic matter (HLOM),mid-labile organic matter (MLOM) and labile organic matter (LOM),respectively,were determined using 33 mmol L^-1,167 mmol L^-1 and 333 mmol L^-1 KMnO₄,respectively.Averagely,HLOM,MLOM and LOM accounted for 5.6%,9.6% and 14.5% of total organic matter,respectively.Significant correlations were found among the three with the coefficient between HLOM and MLOM being 0.478,between HLOM and LOM being 0.592^**,and between MLOM and LOM being 0.716^**.Crop yield was also found closely related to MLOM and LOM,with the correlation coefficient being 0.821^** and 0.602^**,respectively,but the correlation between crop yield and total organic matter was insignificant.At the same time,LOM and CMI showed significant positive correlations with cation exchange capacity (CEC),exchangeable potassium,exchangeable calcium,total base and microelement,etc..However,total organic matter was insignificantly related to those chemical indexes.So,LOM and CMI could more than total organic matter objectively reflect changes in soil fertility and soil quality,and should be used as indices to describe soil quality and assess soil management.

Abstract:Soil erosion and deposition influences accumulation and loss of soil organic carbon (SOC),yet it has never been an issue of proper attention in the study of soil carbon cycle.In this paper,the CENTURY model was used to simulate original organic carbon accumulat ion in black soil of a given soil texture in a typical rolling farmland in the Black soil region,Northeast China to get the initial value of SOC and its fractions;Then the model was verified through statistical comparison between the simulations and actual measurements with and without considering SOC enrichment with sediments;And then temporal variation of SOC and its fractions after reclamation,and contribution of soil erosion to SOC loss were assessed.The results show that SOC accumulation could be divided into two stages,i.e.fast accumulat ion in earlier stage and slow accumulation in later stage.The slow organic carbon accumulation in the former stage contributed the most to the SOC pool and passive organic carbon played a dominant role in SOC accumulation at the latter stage.When equilibrium was reached the content of organic carbon in the black soil in the study area was 7 240 g m^-2,of which slow and passive organic carbon accounted for 97.4%;The simulations tallied better with the actual measurements was better when the effect of sediments on SOC enrichment was taken into account;When natural black soil was cultivated,active and slow carbon was most likely to get decomposed by microorganism and mineralized,while passive carbon was losing with soil erosion.It was not so significant because soil erosion was not serious problem in the study area.

Abstract:Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are the main components of soil solution and involve in many soil processes.An experiment was carried out to study effect of wheat straw incorporation,nitrogen fertilization and transplant date management on dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in soil solution in paddy field.Soil solution samples were obtained by centrifuging fresh soil samples.Results show that the concentration of DOC in soil solution was significantly increased at the initial stage of flooding and then decreased gradually regardless of straw incorporation.Wheat straw incorporation significantly increased DOC in the first two months of flooding,and DON,too,in the initial period.Application of inorganic nitrogen led to a decrease in concentrations of DOC and DON.The concentration of DON decreased with fertilizer nitrogen application rate increasing.When the soil was flooded in the same time,delayed transplantation of rice seedlings for three weeks significantly decreased DOM.

Abstract:Structures and morphologies of goethite and its two synthesized Bloaded oxides,Ad-B-Goethite and Oe-B-Goethite,were characterized with the aid of IR,XRD and TEM,and their specific surface areas and Mn²⁺-adsorption capacities were measured with the BET method.It was found from IR that as compared with goethite,the two Bloaded geothites decreased in the bands of Fe-OH-Fe inplane bending at 888 cm^-1,the bands of Fe-OH inplane bending at 1 000 cm^-1,and the bands of free OH at 3100 cm^-1.The bands of bending modes of trigonal and tetrahedral boron were found at 458.5 cm^-1 with Ad-B-Goethite,and also at 527.2 cm^-1 and 476.5 cm^-1 with Oe-B-Goethite.XRD analysis showed that Ad-B-Goethite was still fine-FeOOH and Oe-B-Goethite was differed from goethite,suggesting that Oe-B-Goethite is probably a new mineral.Judging from TEM graphs,the particle of Oe-B-Goethite was smaller than that of goethite.The specific surface area of goethite,Ad-B-Goethite and Oe-B-Goethite was 108.4 m²g^-1,88.69 m²g^-1,and 120.5 m²g^-1,respectively.The increase in surface area means Oe-B-Goethite having more activity than normal goethite.This assumption is supported by the finding that the adsorption of Mn²⁺ on the surface of Oe-B-Goethite was the highest and that of goethite was the lowest in the three kinds of minerals.It was found that B in Oe-B-Goethite had replaced hydroxide ligands inside the crystal lattices,and inhibited crystal growth of goethite,thus resulting in weak crystallizability.It was also found that Mn²⁺ adsorption increased with the presence of Ad-B-Goethite,especially of Oe-B-Goethite.It is suggested that boron applied into soil functions is not only as a nutrient for plant,but also as a buffer against Mn²⁺ toxicity to the plant in the soil by forming B-loaded iron oxides.

Abstract:Six types of oxides,i.e.Goethite (G),Manganite (M) Ad-B-G (goethite treated with borax),Ad- B-M (manganite treated with borax),Oe-B-G (goethite treated with boric acid) and Oc-B-M (manganite treated with boric acid) were used as objects in the study on Mn²⁺ adsorption characteristics of B- loaded oxides in an isothermal condit ion with the adsorption equilibrium method.The results show that in terms of Mn²⁺ adsorption capacity,the 3 minerals of the goethite series followed the order of Oe-B-G>Ad-B-G>G,and the other 3 minerals were in the same order,O-c B-M>Ad-B-M>M.Their capacity rose with the pH of the solution,which,however,differed between the two series of oxides.It was believed that oxides treated with boron increased adsorption of Mn²⁺,and Mn²⁺ was more readily adsorbed by the manganite series of oxides than the goethite series.Electronic property PZC (Point of Zero Charge) of the minerals might be the main factor caused these differences.Mn²⁺ sorption increased with the concentration of Mn²⁺ in the solution.The ratio of proton-to-manganese stoichiometry on these minerals was in the order of Oe-B-M Ad- B-G>G.The decrease in release of H⁺ into solution was due to changes in surface charge and number of active sites on the surface or the micro-particle size of oxide.These results provided strong support for the phenomenon that application of boron to acidic soil could relax acidification of the soil.

Abstract:Points of zero charge (PZC) of goethite as control and several ores of manganese oxides were determined with different methods,e.g.potentiometric titration (PT),rapid potentiometric titration (RPT),salt titration (ST) and the improved salt titration (IST).Results showed PZC of birnessite,cryptomelane,todorokite was 1.18,1.98 and 3.98 respectively with PT and 1.75,2.10 and 3.50 respectively with RPT.With ST there was no point of intersection of pH of manganese oxides and x-axis.However,when 0.5 ml 2 mol L^-1 KCl was added into the solution and its equilibrium duration was set at 24 h,PZCs of the manganese oxides were determined to be 0.98,1.72 and 3.31,respectively.The PZCs of goethite obtained with the PT and RPT methods were both 8.00 showing no difference between the two methods,and with the ST and IST methods were 8.31 and 8.41 respectively,showing a minor difference.After the ST method was improved,it could be used to determine PZC of manganese oxides.This method was reliable,simple and convenient compared with the PT and RPT methods.

Abstract:A method for extracting,clearing off and determining residues of cypermethrin,fenvalerate and deltamethrin in soil has been developed.The method uses pertole mether-acecton (V/V,2:1) mixture to extract residues of the pesticides in soil samples,a column (20 cm×1.5 cm) packed with 3g Florisil to clear the mixture of the residues,and pertolem ether-ethyl acetate (V/V,9:1) to elute the residues from the column.Then the eluent is determined by gas chromatography (ECD-GC) with a HP-5 (30 m×0.32 mm×0.25 μ m) capillary column and quantified by the single pointexternal standard method.In an experiment of using this method,the recovery rates of cypermethrin,fenvalerate and deltamethrin were found to be 90.10%～93.02%,90.62%～91.07% and 89.67%～91.53% respectively with RSD being 2.02%～2.49%,2.51%～3.70% and 3.08%～3.42%,respectively in the operation.And the minimum detectable quantity was 1.00 pg.The relative standard deviations (n=5) of the equipment ranges from 1.37% to 2.88%.This method is proved to be easy in operation,and high in sensitivity,reproductivity and selectivity.

Abstract:A great deal of concern has been aroused among the scientific community about the extensive use of carbamate pesticides and their residues in vegetables.A method combining HPLC,a post-column derivation device and a fluorescent detector was used to determine residues of ten carbamate pesticides (aldicarb sulfoxide,aldicarb sulfone,oxamyl,methomyl,3-hydroxy carbofuran,aldicarb,propoxur,carbofuran,carbaryl and methiocarb) in 68 vegetable and 32 soil samples under four different cultivation systems (traditional kailyard,open field vegetable base,green house and paddy) were collected from a certain city in South Jiangsu.in March 2003 and July 2003.The results reveal that residues of carbamate pesticides were mostly found to be in the acceptable range from 0.1 μ g kg^-1 to 10 μ g kg^-1 in the soil samples and from 0.2 μ g kg^-1 to 23 μ g kg^-1 in the veg 2 etable samples.Residues of 3-hydroxy carbofuran and methiocarb were detected in all the soil samples with the highest value reaching 10 μ g kg^-1 and 1.64 μ g kg^-1,respectively,and residues of the rest were only in a few samples.What is even more noteworthy is that residue of 3-hydroxy carbofuran,a degradation product of carbofuran,was detected in all the soil and vegetable samples.And its concentration in water spinach,eggplant and celery ranged from 0.4 mg kg^-1 to 4.8 mg kg^-1,which may result from differences between vegetables in efficiency in bio-utilization of 3-hydroxy carbofuran.Meanwhile,under different cultivation systems residue of 3-hydroxy carbofuran in soils was related to that in some vegetables,like tomato,pepper and shang-haiqing,but not statistically significant.

Abstract:Behavior of pesticide adsorbed on soil and mineral surface is important for determining its environmental fate and risk.The adsorption of glyphosate [N-(phosphonomethyl)-glycine] (GPS;GLY) on six types of soils different in physico-chemical characteristics,and on minerals saturated with metal ions was investigated.The results indicate that the adsorption isotherms were well fitted with the Freundlich equation.Quantity of glyphosate adsorbed on the soils was related to soil characteristics.It increased with the contents of soil clay and Fe₂O₃,but decreased with the increasing soil pH.More glyphosate was adsorbed by kaolinite than by montmorillonite.When the minerals were modified with different metal ions,quantity of adsorbed glyphosate decreased on the minerals,which were in a decreasing order of Fes²⁺-montmorillonite>Ca²⁺-montmorillonite>Na⁺-montmorillonite and Fe²⁺-kaolinite>Ca²⁺-kaolinite>Na⁺ kaolinite.

Abstract:The amount and process of ammonia volatilization from nitrogen fertilizer in the rice field of Fe leachi Stagnic Anthrosols in the Taihu Lake region were investigated.The effect of some soil factors on N loss was also studied.The purpose of the experiment was to provide basic theory to reduce the amount of ammonia volatilization loss from nitrogen fertilizer and improve nitrogen use efficiency in rice field.Ammonia volatilization loss from urea applied was measured with the continuous airflow method in the experiment and the main influencing factors (NH₄⁺-N concentration and pH in flooded water,etc.) were also measured.Results showed that ammonia volatilizat ion loss varied from 3.7% to 11 7% of applied N,the highest N loss oc curred in the period of tillering top dressing,lower in ear bearing top dressing period,and the least in basal dressing period.Ammonia volatilization primarily occurred in one week after fertilization.And there was a significant correlation between the NH₄⁺-N concentration,pH in the flooded water and the amount of ammonia volatilization (the correlation coefficient was 0.791^** and 0.443^**,respectively).

Abstract:Phosphorus (P) is the limiting factor for agricultural production in red soil regions,so the study about P forms and transports can be meaningful to agricultural production in red soil regions.The forms and contents of phosphorus by upland red soils different in fertilization were studied with the P fractionation method proposed by Hedley.The results show: 1) All the inorganic P and most of the organic P are always lower in soil not fertilized with inorganic or organic phosphorus than in soil fertilized with phosphorus.2) Resin-P and NaHCO₃-P that can be utilized by plant easily are tiny,but P combined with ferric and aluminium and Residual-P are the greatest parts in upland red soil.So the P availability in red soil is low.3) NaHCO₃-P_i,P_i combined with ferric and aluminium,P_o existed in soil aggregates are the most contributive forms to available P(Bray=P).In a word,these results guide us to research on P availability and transformation of phosphorus by upland red soils different in fertilization.And then,they can be theoretical and practical guidance for phosphorus managment in upland red soil.

Abstract:Manganese deficiency has been a problem in agricultural practice in many soils in North China and manganese fertilizer also has been extensively used to correct the problem.In order to further understand behavior of manganese fertilizer in soils,a long-term field experiment was initiated in 1984 on continuous application of manganese fertilizer in dryland soils of the Loess Plateau.After 17 years,availability and fractions of manganese in the soil were investigated using a modified sequential extraction technique.The results showed that total manganese and DTPA extractable manganese were not increased much in the soil.But the latter did show an increasing trend with the time,no matter manganese fertilizer was added or not.In addition,the application of manganese fertilizer contributed little to increase of soil DTPA-Mn,which ranged from 0.4 to 1.7 mg kg^-1.Manganese fractions in all studied soils were greater in manganese fertilizer treatments compared with those in control.It was also found that mineral bonded manganese occupied about 87.3%~91.8% of the total soil manganese,while carbonate form and oxides form of manganese,and organic matter strongly bonded manganese shared similar percentages.In terms of content,the various fractions of manganese ranked in the order of mineral bonded>carbonate bonded>oxides bonded>organic matter strongly bonded>organic matter weakly bonded>exchangeable.About 91.1%~98.6% of fertilizer manganese was in the form of carbonate bonded,oxide bonded,or organic matter strongly bonded manganese,or in the mineral form,which were not readily available for the crop to use.Only 1.4%~8.8% of fertilizer manganese entered into exchangeable and organic matter weakly bonded forms,which were considered as available manganese in soils.The results of statistical analysis showed that exchangeable and organic matter weakly bonded manganese were the major sources of soil available manganese,carbonate bonded and organic matter strongly bonded manganese made little contribution to soil available manganese.

Abstract:Dynamic changes in content of chlorophll and proline,and activity of protective enzymes such as superoxide (SOD),peroxidase (POD) and chloramphenicol acetyltransferase (CAT) in the leaves of Trapa bispinosa treated,respectively,with Cd²⁺ at varying rates and Cd²⁺ plus 5 mg L^-1 Ce³⁺ were studied.Results show that chlorophyll contents decreased with increasing Cd²⁺ concentration,while the activity of both SOD and POD,and the content of proline increased when Cd²⁺ concentration was low and decreased when it was high.In contrast,CAT activity decreased when it was low and increased when it was high.Compared with the single ion treatments,the Cd²⁺+Ce³⁺ treatments increased cholorophyll contents,and stimulated activity of SOD and POD,especially,that of the latter,which was 8.33 times higher than its control when the combination was 5 mg L^-1 Ce³⁺ plus 1 mg L^-1 Cd²⁺.The results suggest that the addition of 5 mg L^-1 Ce³⁺ can relieve the toxicity of a low concentration Cd²⁺ on leaves of Trapa bispinosa.

Abstract:Two layers of ancient paddy soil were discovered in archeological excavation of Chuodunshan Relics in Kunshan,China.One of them could ascend to 6 500 a BP (prehistoric),and the other 3 320 a BP (Shang-Zhou Period).Two soil profiles,not far apart,named P-01 (containing both soil layers) and P-03 (containing only the latter) respectively,were fixed and soil samples were collected according to soil color and texture.The techniques of soil anaerobic incubation,Biolog analysis and PCR-DGGE of 16S rDNA gene fragments encoding Euryarchaeota variable V3 region were used to study microbial diversity of anerobic microbes,methane emission potential and the genetic diversity of methanogenic archaea communities in different soil layers.The aim of this study is to determine biological properties of the ancient paddy soils.The results show that among all the underground soil layers of the two profiles,the prehistoric ancient paddy soil layer still had quite a number of anaerobic microbes surviving in the soil,up to 7.0×10⁵ cfu g^-1 soil,and it also showed better carbon utilization capacity and diversity than the other soil layers.A tendency was noticed that the prehistoric ancient paddy soil showed slightly higher methane emission potential than its parent material-lake sediment and homochronous non-paddy soil-loess,though it was very weak compared with that of recent paddy soils.PCR-DGGE analysis revealed that the methanogenic archaea community made paddy soil layers different from the other soil layers,and paddy soils of different ages have their respective special predominant populations.

Abstract:A strain of FLDA capable of degrading metsulfuron-methyl aerobically was isolated from sludge collected from a pesticide (metsulfuron-methyl) plant.Based on analysis of its 16S rDNA,morphology,physiological and biochemical characteristics,strain FLDA was identified preliminarily as Pseudomonas sp.This strain of bactera could degrade 72.6% of 30mgL^-1 metsulfuron-methyl in liquid medium within 5days.The optimal pH and temperature for metsulfuron-methyl degradation was 7.0 and 30℃,respectively.The degradation rate was related positively to initial inoculation rate.Enzyme distribution experiment showed that the metsulfuron 2 methyl degradeing enzyme in the bacterium was endoenzyme.Strain FLDA could be used to degrade metsulfuron-methyl in soil.

Abstract:Influence of soil moisture regime (non-flooding,flooding-drying,and flooding) on microbial community diversity and activity was investigated by determining Biolog sole carbon source utilization pattern,phospholipid fatty acid (PLFA) profiles and enzyme activity indices.Increased dehydrogenase and invertase activities were observed in Treatment Flooding as compared to what in the other two treatments,which apparently led to enhanced soil basal respiration.The average well colour development (AWCD) of the carbon sources on Biolog plates was significantly lower in Treatment Non-flooding than in the other two treatments.The fungal indicator (18:2w6,9c) and the proportion of fungal biomarker (18:2w6,9c) to bacterial biomarkers (15:0i+15:0a+16:0i+16:1w5c+17:0i+17:0a+17:0cy+17:0+18:1w7c+19:0cy) were lower under flooding conditions.The relative abundance of cyclopropyl fatty acid 19:0cy was not affected by moisture regime,however,the relative abundance of 17:0cy was the highest in Treatment Non-flooding.Cluster analyses of the sole carbon source utilization and PLFA data demonstrated that Treatment Non-flooding differed from the other two treatments in soil microbial community.Although certain similarity was found between Treatment Flooding and Treatment Flooding-drying in structure and functional diversity of soil microbial community,the findings of the study suggested that there were some drastic changes in microbial community composition and activity associated with variation of soil moisture regime.

Abstract:Polyacrylamide (PAM) can enhance soil structural stability,however its influence on soil hydraulic conductivity is not very clear.Effects of PAM application rate and method on saturated hydraulic conductivity were studied in laboratory through a soil column leaching experiment.PAM was mixed with the soils (sodic and nonsodic soils),respectiviely,or spread over surface of the soils at a rate of 0,1/5 000,1/2 000,and 1/1 000 (PAM/dry soil in weight).The experimental results indicate that hydraulic conductivity of nonsodic soil was greater than that of sodic soil when no PAM was applied.PAM application through mixing obviously decreased steady hydraulic conductivity of the two soils,but its effect on sodic soil was greater than on nonsodic soil.PAM application through spreading decreased hydraulic conductivity of nonsodic soil.Steady hydraulic conductivity of sodic soil decreased with the increase in PAM application rate when the rate was low,but it increased when the rate was getting high.In order to maintain a great soil hydraulic conductivity,PAM application rate should be kept as lower as possible,or PAM is applied through mixing in nonsodic soil or through spreading on surface of sodic soil.

Abstract:Agricultural intensification plays an important role in stabilizing the food production in China,while bringing about an increasing negative impact on the soil and ecoenvironment as a result of the longterm highlyintensive land use and agricultural chemical overuse,thus leading to degradat ion of soil physical,chemical and biological properties,which are demon-strated as soil nutrient imbalance,soil acidification,pollutant accumulation,and biodiversity deterioration and posing serious stress and threat to the ecosystem per se and the environment.Under such an impact,the properties of the soil ecosystem characterized by nonlinear responses to forced conditions may show a tendency of catastrophe and trigger a more serious environmental risk.Recently,more attention has been given to researches on mechanisms of the formation and evolution,and spatiotemporal variation of soil degradation under highly-intensified agriculture,and countermeasures for its control and rehabilitation of degraded soil.

Abstract:Phospholipid fatty acids are major constituents of the membranes of all living cells,and different groups of microorganisms synthesize different varieties of PLFA through different biochemical pathways.Thus some PLFAs can be used as "bio-signatures" to analyze changes in microbial biomass and microbial community structure.Currently the PLFA method is more and more used in soil microbial analysis.An introduction was made by the authors to some PLFAs characterizing microorganisms,methods to extract PLFAs from soils and the principle of using GC-MS to analyze PLFAs.Besides,comparison of the PLFA method was conducted with some other commonly used methods.The traditional method,which analyzes soil microbial community structure,depends on culture technology and it is able to culture and separate a small number of microbial communities;the Biolog method is used to investigate physiological diversity of soil microbial communities,i.e.how the microbial communities potentially utilize a range of carbon substrates,but it is of high selectivity to the small fraction of microbial communities that grow fast or fit the Biolog experimental conditions;and the main shortcoming of nucleic acid analysis lies in that it can't make quantitative analysis of soil microbes.However,compared to those methods mentioned above,the PLFA analysis has a number of advantages.The characteristics of the PLFA analysis have been demonstrated in this article with several practical examples,and some disadvantages of the PLFA analysis have been analyzed.By using the PLFA method combined with some others,more comprehensive and integrated information about the diversity of soil microbial communities can be obtained.

Abstract:已有的研究表明,植物之间除了地上部之间的相互作用不可忽视外,地下部分的根系对养分和水分的竞争更为激烈^[1~3]。在判断竞争平衡、竞争强度和资源利用方面,地下部分的竞争作用明显重要于地上部分^[4],从根系生态学的角度来研究,才能了解种间关系的本质。因此根系之间的相互作用,成为种间关系研究的主要内容。Snaydon和Harris^[5]认为,间作作物根的生长动态在不同的单作作物间有差异,导致了根相互作用和竞争的程度不同,从而对营养物质和水分的利用产生影响。因此,改进根的空间分布和活性对提高间作系统中土壤营养资源的利用效率是非常有利的。

Abstract:硫是植物生长发育不可缺少的16种主要营养元素之一,目前已被认为是继氮、磷、钾后第4位主要营养元素。硫在植物体内许多功能与氮相似,其吸收量与磷大致相当,只有当作物吸收充足数量硫后才可能实现高产和优质^[1~3]。水稻上氮硫交互作用的试验结果表明^[4,5],在同等施氮水平下,施硫肥和不施硫肥相比,施硫能够显著促进作物对氮的吸收,提高氮肥利用率。在同样施硫情况下,氮肥也能够促进作物对硫的吸收。在施硫肥增产或不增产的情况下,可相对减少施氮量5%~10%。氮和硫在植物体内的生理功能有许多相似之处^[6],共同组成各种植物蛋白质中的含硫氨基酸。

Abstract:环境污染导致水和土壤中镉等重金属元素超标,是多年来造成农产品质量不合格的重要原因之一。农作物中的重金属元素最终会通过食物链进入人体,对人体造成危害。因此研究如何抑制农作物对镉的吸收在理论上和应用上都有重大意义,前人也做了一些相关的工作[1~3]。众所周知,硒和锌是对人体有益的微量元素。缺硒会得各种各样的疾病,研究还表明硒具有抗癌作用^[4],近年来人们对富硒食品做了大量的研究^[5];锌是许多金属酶的重要组成部分,并能激活多种酶,因此锌在生物的正常代谢过程中起着重要作用。当镉与锌、硒共存的时候,它们之间有复杂的相互作用。

Abstract:在实际的重金属污染体系中往往有多种重金属元素同时存在^[1,2],当这一污染体系与土壤作用时不同重金属离子对土壤表面存在竞争吸附^[3,4]。Cu(Ⅱ)和Pb(Ⅱ)是土壤中常见的2种重金属离子^[5,6],土壤和矿物表面对2种离子的竞争吸附或2种离子吸附亲和力的比较已有一些研究报道^[7~12]。一般认为土壤对Pb(Ⅱ)的吸附亲和力大于对Cu(Ⅱ)的吸附亲和力^[10],但在可变电荷土壤和矿物中情况有所不同。McKenzie的结果表明合成赤铁矿在pH3.0~6.0范围内对Pb(Ⅱ)的吸附亲和力大于Cu(Ⅱ),而针铁矿的结果相反^[7]。

Abstract:随着手性合成技术的发展,具有光学活性的农药品种将在市场上占有越来越重要的地位。但目前生产和使用的大部分手性化学物质仍为外消旋体(Racemate,对映异构体1:1混合物)^[1],研究手性污染物的环境行为、生态效应及潜在毒性时,一直以来都把外消旋体污染物视为单一化合物,几乎所有的环境法规也是如此^[2]。然而手性物质进入生态环境被生物摄取后,其各个对映体在体内的活性、代谢等一系列涉及生命活动的过程往往存在对映体选择性,它们潜在的生物效应大都具有对映体选择性^[3,4],即一个手性化合物中的不同对映体会有不同的毒性。

Abstract:运动场草坪的坪床建设方法目前主要分为两大类,一类是传统的土基坪床,其设计方案是将10~30cm的壤质土壤覆盖于透水较慢的坚实地基之上,作为草皮建植的基础,该类型运动场排水的主要途径是凭借坪床表面的坡度进行地表排水;另一类是逐渐被国外广泛采用的砂基坪床,砂基坪床的主要材料是粒径较均一、渗透速度快、抗板结能力强的石英质砂,其设计方案是将一定厚度的砂层覆盖于粒径更大,透水性更强的砾石层之上,在砾石层中铺设带孔的排水管道。这种方法主要的排水途径是使几乎所有的降水及灌溉水渗透进入砂基坪床剖面,然后再进入砾石排水层,通过其内部的排水管道排出场外^[1]。