Abstract:Soil aridization has turned into an important restricted factor on ecological construction in Loess Plateau.It is believed that loess in China is an indicator of the arid and semiarid climate.The development of loess deposition is a symbol existing the general tendency of climate aridization in North China from the Early to the Late Pleistocene.Loess as the parent material of modern loess soil has a significant influence on soil development and its properties can be reflected in modern loess soils. Taking environment aridization with loess deposition and three weathering type of loess formation as a start ing point,loess geologic origin of soil aridization in Loess Plateau was explored through comparative analysis between the old and present time.Soil physical cause of soil aridization is discussed in the paper.Soil aridization in Loess Plateau is the result of common influence of transient and immanent condition.Soil water physical properties,including water retention property and evaporation property, show an obvious regional directional change dealing with loess grain size composition,It means that soil water retention property gradually increases and soil evaporation property gradually drops from northwest to southeast.If the field capacity is taken as an index,and then soil water deficiency is discovered frequently in Loess Plateau.Arid soil-layer is the ecological aftermath of strengthened soil aridization resulted from the disturbing and breaking alignment of plant succession and ecological foundation of soil water.Based on analysis of climate change,prediction of soil aridization tendency in Loess Plateau is presented in the paper.

Abstract:The study of the loess-paleosol sequence of the Lingtai Section in the Loess Plateau,Northwest China,indicates that free iron(Fe_d),active iron(Fe_o)and organic matter contents in the sequence are highly significantly correlated with magnetic susceptibility(χ)(p<0.01).The influence of Fe_d on magnetic susceptibility indicates that the degree of pedogenesis will affect the formation of ferromagnetic minerals in the paleosols.The significant correlation between organic matter and magnetic susceptibility may be attributed to the processes of biogenetic magnet.In addition,the contribution of organic matter to the formation of maghemite in the pedogenetic processes and it interfering with the ageing of maghemite to hematite afterwards are also important reasons.The highly significant correlation between Fe_o and magnetic susceptibility is mainly related to the close relationships between Fe_o and Fe_d,and Fe_o and organic matter.

Abstract:Soil and water loss is one of the most vital environmental issues in China.Since the 1930 s,soil scientists have been observing the role of soil crusting and sealing in the processes of soil erosion.They have found that the existence of soil crust always decreases the land in infiltration rate and roughness of the surface,thus increasing runoff rate and anti-splash ability of the soil.Some studies have demonstrated that erosion modulus and cumulated sediment yield increase several or even dozens of times as much on crusted soils because soil crust augments kinetic energy of runoff,resulting in rill erosion.Unfortunately,critical values and related factors that affect forming process of soil crust are still not well understood.In order to clarify processes and factors of soil crusting,several types of soils were studied through art ificial precipitation,micro-conformation observation and physical and chemical analysis,and extents of different factors affecting soil crusting were also analyzed by SPSS.Results indicated that soil texture is the main factor for crusting,and soil clay minerals composition may be another main factor.Surprisingly,they also demonstrate that indexes of soil configuration and soil colloid have no obvious relationships with crusting and sealing.

Abstract:Conventional soil mapping is generally based on the conceptual models which reflect the relationship between soil genetic factors and its spatial variability,and usually appears to be qualitative and subjective as it is difficult to gather suffi cient data to examine these models over large areas.However,with the development of geostatistics and Geographic Information Systems(GIS),methods of mapping soil properties have also been improved.In this paper,a geostatistic method combined with GIS was applied to characterize and map the spatial variability of total nitrogen(N)in topsoil in the typical area of Taihu Lake watershed.The results showed that the spatial variability of total N were apparent in isotropy within the maximum lag extent of 40 km and its anisotropy had little influence on kriging.The isotropic semivariogram through lags of 40 km indicated that the total N in the studied area had a relatively good autocorrelation,and the range of autocorrelation extended to about 16 km.The maps of the total N made by block kriging based on the fitted exponential model depicted that the soils in Jiangyin and Yixing county gen erally had more N than that in the other two counties and the hot spots of high N were apparent in low-lying polderland.High estimate standard deviations of the kriged estimates occurred where data were sparse and additional samples from the sparse places would increase the accuracy of the total N map which would be useful to conduct optimal fertilization and develop management practices to control the non point sources of N pollution.

Abstract:In recent years,the tracing method of rare earth element(REE)has been used to study the dynamic processes of soil erosion,such as its initiation,development and distribution upon the hill slope.A series of laboratory rainfall simulation experiments were conducted with eight REEs,namely Dy,La,Sm,Yb,Ce,Eu,Nd and Tb.The experiments involved 3 rainfall intensities:50 mm h^-1,100 mm h^-1 and 150 mm h^-1;4 slope gradients:8.74%,17.63%,36.4% and 46.63%,with 3 replicates.The REE experiments revealed soil erosion distribution and its relation to the development of eroding rills.Analysis was made to relate the fluctuation in soil erosion upon the slope to the energy in the runoff flow.With quantitative determination of soil erosion along slope by REE tracers,the critical distance at which rill erosion initiated was determined,and the critical shear stress of soil were estimated accordingly.Regression analyses of maximum rill detachment rate and shear stress and stream power of runoff were made.

Abstract:Soil organic C plays an essential role in carbon cycle and carbon storage in a native ecosystem reflects that ecosystem.s capacity to sequester carbon.Based on soil map of China(1:4 000 000)combined with a soil database from the second soil survey of China,soil organic carbon storage to the depths of 100 cm and 20 cm were estimated for China using geographical information system.Carbon density of different soil types ranged from 1.19 kg m^-2 to 176.46 kg m^-2 at depth of 100 cm,and from 0.27 kg m^-2 to 53.46 kg m^-2 at depth of 20 cm.In total,about 84.4 Pg was stored in 0~100 cm,and 27.4 Pg in the 0~20 cm soil layer.The amount of carbon varied significantly at different districts in China.Northeast China, the south and east of Qinghai-Tibet Plateau and southwest China had high carbon density.Tarim Basin,Caidam Basin,Junggar Basin and other desert ification districts had low carbon density.This distribution showed an important climatic influence.Soil organic carbon would diminish with decreasing precipitation and increasing temperature.On the other hand,the activities of human beings may affect the range of soil carbon.

Abstract:Deserted farmlands in the Qaidam Basin are mostly of alkali soil with pH value around 8,high in salt content. Salts concentrate mostly in the 0~10 cm surface layer,ranging within 1~45 g kg^-1,and decrease in content with depth of the profile.Cations in the soil are dominated with K⁺,Na⁺,Mg²⁺ and Ca²⁺,whereas anions are in a decreasing order of Cl^- > SO₄^2- > HCO₃^- > CO₃^2- in terms of content in the 0~10 cm,10~20 cm and 20~30 cm soil layers.The correlation between total salt and Cl^-content is positive and extremely significant(p<0.01),and that between total salt and Mg²⁺,Ca²⁺ content significantly positive,too(p<0.05),but that between total salt and HCO₃^- content negative,whereas,the correlation between Cl^- and Mg²⁺,Ca²⁺ content is positive and extremely significant(p<0.01),and that between CO₃^2- and SO₄^2- content also significantly positive,but that between Cl^- and HCO₃^- content negat ive.All these findings further suggest that the soils are heavy chloride saline soils.Organic matter contents of the soils are low averaging 11.46 g kg^-1 in the 0~30 cm soil layer.The content of total N and P of the soils are also very low,but the soils are rich in K. The results obtained from experimental area indicate that degradation and salinization of the soils is closely related to the local natural conditions and irrational human activities in the region.

Abstract:Effects of planting on soil salt and water transport in silt loam soil were studied by means of big column experiment in the Laboratory of Water and Salt Regime,Fengqiu Agroecologic Experimental Station,Chinese Academy of Sciences. Models of soil salt and water transport were developed separately.Also,parameters such as saturated transmissibility(Hs),hydraulic conductivity(K),water characteristic curve h(θ)and coefficient of soil hydrodynamic dispersion(D)were measured indoors or in fields.The simulated and the measured results were analyzed and compared in detail,showing that the simulated results were very ideal.The rise of the groundwater table was of advantage to movement of salt and water in the silt loam soil column,which obviously leading to redistribution of salt in the soil column.As a result,the salt content of the soil at the depth of 20 cm was higher than that of the surface soil.So it is practicable to do numerical simulation of the soil salt and water transport by this model.Furthermore,if the actual movement of salt and water in fields should be described in detail,further study must be conducted.

Abstract:NO₃^--N content of groundwater in fields and wells at Tianfu village of Chengdu plain was monitored by using NO₃^--N electrode method for more than one year.Results showed that:a.NO₃^--N concentration of groundwater in fields in winter and spring was higher than that in summer and autumn.The former ranged from 0.36 to 2.62 mg L^-1 with an average of 2.59 mg L^-1,and the corresponding figure for the latter was 0.84~5.48 mg L^-1 and 1.10 mg L^-1,respectively.b.Rate of applied N in wheat cropping season greatly affected NO₃^--N concentration of groundwater in the fields of subsequent rice cropping season.The NO₃^--N concentration of groundwater averaged 17.9 mg L^-1 when N application rate was 375 kg hm²,and the average of NO₃^--N concentration was only 1.3 mg L^-1 when 150 kg hm^-2 was applied.c.NO₃^--N in 3 wells was in the range of 0.14~16.5 mg L^-1 with the mean value of 2.54,3.60,and 6.52 mg L^-1,respectively,higher than the average(1.81 mg L^-1)of NO₃^--N concentration of irrigation water in the region.d.Level of groundwater was not correlated to NO₃^--N content of wells.

Abstract:In this work,typical soil profiles developed from early Paleozoic stratum in Daba Mountains were selected as our investigative objects.The concentrations and distributions of Se and F in those soils were studied.It was found that the concentrations of Se and F in soil of Daba Mountains were far higher than those in control soils and those of background value in Chinese soils.The average Se and F concentrations in Daba Mountains soils are 6.65±14.25 μg g^-1 and 670±451 μg g^-1,respectively.Zn in abundance and Fe-deficiency help to enrichment of Se and F in the soils.Se and F concentrations in soils are governed by the distribution of stratum and the lithology of parent rock.Otherwise,environmental geochemical processes,biologic processes and denudation physiognomy also profoundly affect the redistribution of them in soils.

Abstract:In the present work,desorption of copper ions adsorbed by variable charge soils was studied.Four variable charge soils,i.e.,Ali-Haplic Acrisol,Ferrali-Haplic Acrisol,Rhodic Ferralsol and Hyper-Rhodic Ferrasol collected from south China,were used.As contrast,two constant charge soils,i.e.,Haplic Luvisoil and Phaeozems collected from Nanjing and Harbin respectively,were also used.The results showed that the copper ions adsorbed by variable charge soils could be desorbed by deionized water.When the adsorbed copper ions were desorbed at different pH,a pH~desorption rate curve could be ob tained.A peak with maximum desorption rate could occur on the curve at a certain pH value.When the pH of soil suspension was higher than this pH value,the desorption rate decreased with the increase in pH.When the pH was lower than this pH value,the desorption rate decreased with the decrease in pH.For different variable charge soils,this pH value was related to the content of iron oxides in soils.The higher the content of iron oxides,the higher this pH value.After removal of copper ions which could be desorbed by deionized water,the residual copper ions adsorbed could be desorbed by dilute solution of NaNO₃. For different variable charge soils,the higher the content of iron oxides and the higher the concentration of electrolyte,the more difficult the desorption of the residual copper ions adsorbed.On the contrary,the copper ions adsorbed by constant charge soils could not be desorbed by deionized water,but could be desorbed by electrolyte solution.The higher the concentration of electrolyte,the greater the ability of desorption of electrolyte.It is suggested that the mechanism of adsorption of copper ions by variable charge soils was different from that by constant charge soils.

Abstract:Kinetic and thermodynamic characteristics of cadmium adsorption on humic acid were studied using ion-selective electrode.Results show that the characteristics of cadmium adsorption on humic acid differed with the medium pH at the adsorption data were best described by Freundlish equation at pH 3.0~3.5 and by Langmuir equation at pH 4.0~6.5,respectively. Significant correlations existed between cadmium adsorption amounts and the medium pH at the range of pH 3.00~6.50 under the experimental conditions. The increase of temperature resulted in a decrease of the cadmium adsorption amount on humic acid, suggesting a heat-release reaction between humic acid and cadmiumions. The adsorption heat was pH-relevant with an increased adsorption heat at higher medium pH. The adsorption forces of cadmium on humic acid varied substantially with the change of medium pH,with ligand exchange being dominating at pH 6.5 and hydrogen bond and dipole force being the main forces at pH 5.5. The adsorption processes involved partly electrostatic force without the release of hydrogenions. The logarithm of the adsorption distribution coefficient(log K_f)positively correlated with the medium pH at low cadmium concentration. An initial fast reaction stage followed by as slow reaction between humic acid and cadmium ions were observed and it took at least 500 min for the reaction equilibrium to be established. The reaction rates were accelerated with the increase of medium pH and the adsorption kinetics were best described by Elovich equation followed by double-constant equation.

Abstract:By adding NaOH or HCl,one neutral soil and one weakly alkaline soil was respect ively adjusted to a series of samples with different pH.After addition of NO₃^- the soil samples were anaerobically incubated with or without glucose for 24 h. After that N₂O production rate was measured.The results show that without glucose the optimum pH for the greatest N₂O production rate is about 5.25 for the neutral soil series,and 5.90 for the weakly alkaline soil series.With glucose,however,the optimum pH for N₂O production is different,at about 6.50 and 6.90 for the neutral soil series and the weakly alkaline soil series, respectively,demonstrating that the addition of easily available carbon source has raised the optimum pH for N₂O production. The experiment results also show that acidic condition could increase the ratio of N₂O to total reduced gas,as for the absolute value of N₂O production,however,the neutral condition is still more favorable.

Abstract:Nitrogen mineralization of soil and soil particle fractions with long-term annual combined application of manure and chemical fertilizer in a wheat/rice rotation system was monitored during a 112-day laboratory incubation NH₄⁺ and NO₃^-in leachates were measured after soil samples were incubated for 1,2,4,6,8,10,12,14 and 16 weeks at 25 Nitrogen mineralization potential(N₀)and mineralized rate constant(k)were fitted using a first order equation N₀ value of soil and soil particle fractions was significantly increased after 14-year incorporation of pig manure and straw,however,there was no significant effect on k value The N mineralizability in different soil particle fractions increased in the order:0~2 m>2~10 m>50~100 m>10~50 m A pot experiment was also conducted to determine the basic nitrogen supply of the soil and soil particle fractions during 16-week growth of ryegrass The results showed that the amount of N mineralized during the incubation was greater than those taken up by ryegrass,suggesting that it is worthwhile making some modifications when we make comparison of the results obtained from incubation and pot experiments.

Abstract:This paper deals with the influences of herbicide mefenacet on soil respiration and the activities of dehydrogenase,catalase,urease,proteinase and phosphorylase in paddy soil.The results showed that after application of mefenacet with concentration of 0.067,0.100,0.133,0.200 and 0.267 g g^-1 dried soil,soil respiration was stimulated at the beginning but reduced slightly afterwards,and the activity of dehydrogenase was enhanced in paddy soil.The soil catalase was less active than dehydrogenase,even inhibited within the first two weeks.The soil urease was strongly depressed and the activity of proteinase took on the slight inhibition within the whole period of experiment.The activity of phosphorylase,however,was raised with the increase of mefenacet concentrations within the first 18 days.Mefenacet had lower effects on soil respiration and enzyme activities than butachlor,an old generation of herbicide.

Abstract:Effects of pesticide-contaminat ion on population and activity of sulfat-ereducing bacteria(SRB)were invest igated in three paddy soils,Huangsong paddy soil developed from shallow-marine deposit of intermediate lake deposit,Red paddy soil developed from alluvial deposit and Purple paddy soil developed from parent material of neutral purple sandstone and shale,4 weeks after the soils were applied with insecticide(carbofuran),fungicide(carbendazim)and herbicide(butachlor)at different concentrations.The results showed that population and the sulfate-reducing activity of SRB in Purple paddy soil,Huangsong paddy soil and Red paddy soil ranged(66.83~127.81)×10⁴,(45.87~105.07)×10⁴,(3.81~61.62)×10⁴ cells per gram dried soil,respect ively,and S^-2(7.14~11.57),(6.84~9.07),(1.91~6.67)Lg d^-1g^-1 dried soil,respectively,and that the sulfate-reducing activity was positive relativity to the population of SRB in paddy soil.The population of SRB and the sulfate-reducing activity were increased by addition of carbofuran(1 mg kg^-1 dried soil)or butachlor(1 mg kg^-1 dried soil)in paddy soils,but significantly inhibited by addition of butachlor(50 mg kg^-1 dried soil),carbofuran(5 mg kg^-1 dried soil)and carbendazim(50 mg kg^-1 dried soil)in paddy soil till 7 d,14 d and 7 d,respectively.Then the inhibition effects of the contaminants were gradually attenuating.Eventually pesticide or metabolism of pesticide became contributive to the population of SRB and their sulfate-reducing activity.

Abstract:The inability to culture most microbe from soil samples is a fundamental obstacle to understanding soil microbial ecology and diversity Therefore,amplification of DNA from soil and a rapid,preferable DNA extract ion method involving necessary purification is needed for rapid and thorough analysis of microbial diversity in environmental samples The method extracting fungi DNA that is applicable to two kinds of forest soil types in Australia is developed in this research,and result showed that extracted DNA purity and size is reasonable and suitable for PCR amplification At the same time,a framework for soil microbial diversity analysis with T-RFLP(Terminal restriction fragment length polymorphism),a recent molecular approach that can be used to assess subtle genetic differences between DNA samples as well as provide insight into the structure and function of microbial communities in soils,is presented here Generally,PCR amplification of extracted DNA sample from soil is conducted by using a set of fluorescent tagged specific primers of the bacterial 16S rDNA or ITS of fungal rDNA,and then products are digested with a four base restriction endonuclease,as maximizing the resulting number of terminal fragments Finally the entire terminal fragments are detected and sized by the ABI automated sequencer The technique has both high sensitivity and throughput making it an ideal choice for comparative community analyses.

Abstract:Twenty three single colonies of actinomycetes were isolated from a soil sample collected from Changshu Agroecological. Experimental Station,Institute of Soil Science,Chinese Academy of Sciences Among 10 strains distinguished from each other by morphological properties,9 were further identified as Streptomyces sps. All strains showed capability of reducing nitrate into N₂O under anaerobic pure culture conditions. Three strains were selected and denitrification rates were measured. Nitrous oxide product ion rate of these strains ranged from N 1.2 to 187.7 g g^-1 min^-1. The strains were shown not only to grow well but also to be able to reduce nitrate to N₂O in sterile soil,indicating that these strains were able to use soil organic carbon as electron donor for nitrate reduction. Acetylene showed inhibitory effect on N₂O production of most strains isolated. Stressed under continuous strict anaerobic condition,strains of Streptomyces sps still showed considerable denitrification capacities.

Abstract:In this study,the microbial activity and structure of microbial communities in soils polluted by tailings from Pb,Zn,Ag mine area were studied.The results showed both total and soluble metal loadings in these soils increased with proximity to the mine tailing reserve.Indictors of soil microbial features varied significantly because of heavy metal contamination stress.Soil microbial biomass and viable population size(plant counts)were negatively affected by the elevated metal levels,but the size of soil basal respiration rate and microbial metabolic quot ients were positively influenced by the increasing heavy metal pollution levels.Microbial community structure also changed with increasing contamination,as indicated by Biolog data and principal component analysis of Biolog community metabolic profiles.Soil microbial metabolic profiles(AWCD)values,community richness and diversity index in mine-soils decreased remarkably as compared with adjacent non-mine soils(p<0.01).It was suggested that the decline of soil microbial community functional diversities would occur in soils polluted by heavy metals from mine tailing,decreased microbial number used energy carbon and utilization ability of microbial communities for carbon substrates.The microbial activities and community functional diversities can effectively indicate soil environmental quality transition from mine area to non mine conditions.

Abstract:This paper reported soil microbial characteristics of Elsholtzia harchowensis-soil system in Lipu Copper mine tailings,Zhejiang Province,and correlations between the metal element contents of E. harchowensis and soil were also analyzed The results indicated that metal element contents of E. harchowensis in sequence were:Cu>Zn>Pb>Cd There were significant correlations in Cu contents between E. harchowensis and soil in Copper mined tailings region,and the next was in Zn contents Compared with the control,the E. harchowensis-soil system possessed obviously different soil microbial features:intensiver in microbial basal respiration strength,and higher microbial eco-physiological parameters Cmic/Corg and qCO₂,but lower in soil microbial biomass Biolog data showed that soil microbial community structure was obviously changed in the E. harchowensis-soil system,and much more consumed rapidly carbon sources,but the lower in the ratio of utilization compared with the control.

Abstract:Subalpine coniferous forest in western Sichuan is an important part of Sichuan forests. Because it mainly distributes in Jinshajiang River of upper reaches of the Yangtze River and its branches,Yalongjiang and Minjiang River and so on, it takes very important role in water conservation and soil protection in these area. Moreover,it also has a tremendous influence on economy and balance of ecosystem in this region and also as far as to the middle and lower reaches of the Yangtze River. Since 1940 s,natural coniferous forest was felt in grand scale,then spruce forests were planted on clear felled areas in succession. At present,there are 4.3×10⁴ hm² spruce plantation in these regions. But simple structure of artificial plant community had led to the degradation of forest ecosystem function. The soil organic matter and nutrient pool were studied under subalpine spruce plantation in western Sichuan. The results indicated that the soil organic matter and nutrient pool under spruce plantation degradated greatly. Decay rate and recycling period of spruce plantation were slower than those of secondary broad forest and natural coniferous forest,which led to that dry matter of forest floor and nutrients stored in the litter layer can't enter soil. Soil OM content,total N,total P and alkali-hydrolyzable N abruptly decreased with increasing of forest ages. The unitary composition of spruce plantation with less litter and nutrient returned to soil and the slower decay rate of litter were crucial factors inducing the degradation of the soil organic matter and nutrient pool in this area. In addition,human-induced disturbance,especially clearingout of litters and shrubs under plantation were another factor of the degradat ion of the soil organic matter and nutrient pool. It was suggested that the degradation of the soil organic matter and nutrient pool could be controlled by planting coniferou-shardwood and the rational thinning down after spruce plantation matured.

Abstract:侵蚀、搬运和沉积过程是土壤侵蚀过程中相互影响又相互制约的三个子过程。自从20世纪40年代Ellison^[1～4]将水蚀过程分为四个子过程,即雨滴侵蚀过程、径流侵蚀过程、雨滴搬运过程和径流搬运过程以来,许多学者从不同角度对其进行了研究。Meyer和Wischeier^[5]及Meyer和Foster^[6]基于Ellison的四个侵蚀过程,提出了输沙量受侵蚀量和输沙能力的制约和细沟间侵蚀以降雨侵蚀为主、细沟侵蚀以径流侵蚀为主的侵蚀概念模型。此模型即为美国新一代水蚀预报模型(WEPP)的物理基础^[7]。

Abstract:波涌灌溉(Surge irrigation,即间歇灌溉)是美国学者于70年代末提出的一种新型地面灌溉方式^[1,2],曾被称为是地面灌溉的一次“革命”。与传统地面连续灌溉相比,主要是供水的间歇性。在灌水间歇期湿润区地表易形成密实层,以减少第二次灌水时的入渗速度,增加行水速度,具有减少深层渗漏、提高灌水均匀度的作用。面对内蒙河套灌区5.667×10⁵hm²低效的地面灌溉耕地,提高地面灌水效率,是减少引黄量、降低地下水位、防止土壤次生盐碱化的根本途径。为此,在室内研究了波涌灌溉对当地典型土壤的作用效果。

Abstract:铝毒是酸性土壤上植物生长不良的主要限制因素,铝的生物毒性与铝离子的化学形态有密切的关系^[1,2],而铝的化学形态又受包括低分子量有机酸在内的多种因素的影响^[3,4]。低分子量有机酸是土壤中广泛存在的一类非常活泼的物质,植物在生长过程中其根系会不断分泌出各种有机酸,植物残体分解过程中和土壤微生物代谢过程中均会产生有机酸^[5,6]。一些有机酸阴离子可以被可变电荷土壤吸附,并影响土壤的某些表面化学性质;另一方面某些有机酸阴离子能够与铝形成稳定的络合物从而改变铝离子在溶液中的存在形态,这两方面的原因都有可能对可变电荷土壤中铝的吸附产生影响。

Abstract:当前,对有机物污染土壤进行修复成为环境科学研究热点之一^[1],常用的修复方法有化学修复、生物修复、化学与生物相结合的修复;但迄今仍没有经济有效的有机污染土壤修复的实用技术。因此,利用在土壤中注入阳离子表面活性剂形成吸附区,截留有机污染物,阻止有机物迁移,并对固定污染物进行修复,无论对土壤及地下水有机物污染防治,还是生产优质农产品都具有现实意义。近年来,相关研究主要集中在截留非极性有机污染物^[2～7],而对溶解度较大且易于迁移的极性有机物截留研究较少;并且认为表面活性剂增强土壤截留有机物的机理由土壤表观有机碳含量增大所致。

Abstract:水稻是一种喜水或嗜水植物,具有半水生或湿生的习性,淹水栽培使水稻种植不仅耗水量巨大而且水资源浪费严重。因降雨量在地区间、季节间、年际间分配不均,加之受水源多少、引水灌溉难易等的影响,使不少稻田由于水资源短缺以及水分供需矛盾的原因往往造成水稻产量低而不稳甚至改种其它作物。水稻旱作是克服水分不足的高效节水稻作技术,作为一种抗旱手段,水稻旱作为水资源不足的地区、高亢地及低洼易涝旱作区、干旱所致的缺水地区扩种水稻、减少灌溉用水,加快种植业结构调整、提高农民收入有着重要意义^[1,2]。

Abstract:咪唑烟酸(其英文通用名称为imazapyr,商品名有arsenal、assault、灭草烟、阿时拉等)是由原美国氰胺公司研制的一种具有较长残留活性的广谱性苗后除草剂^[1]。它对一年生和多年生的禾本科、阔叶科、莎草科杂草及多种灌木和落叶树有活性。自20世纪80年代中期商品化后,咪唑烟酸已被广泛用于森林、铁路、公路等多种类型的非耕地除草。目前,咪唑烟酸已经在世界上22个国家登记使用,是目前国外使用量较大的一个灭生性除草剂品种^[2]。关于该除草剂环境归趋的研究,引起了世界各国的关注。