Abstract:Application of remote sensing data in landuse classification often comes cross some difficulties and problems that originate from various types of uncertainty associated with image information extraction and ambiguity of the linguistic rules involved in the context information concerning dependency between features and landuse.Fuzzy classification system,as one of the most powerful soft classifiers,is capable of incorporating inaccurate sensor measurements,vague class descriptions and imprecise modeling in the analysis process,and outputting classification results that better demonstrate the limitation of human knowledge and the real world.Therefore,fuzzy classification is considered as a better method in landuse mapping based on remote sensing data.In this paper,a case study of the periurban Nanjing was carried out to extract landuse information by means of the supervised fuzzy classification,based on object-oriented segmentation and the resultant so-called image object information of not only spectral values,but also feature space using shape and topological features.Results indicte that fuzzy classification of landuse based on remote sensing data could achieve a more reasonable and meaningful result,in comparison with conventional rigid methods.

Abstract:Eight soil profiles in soils derived from purple-red sand rocks at different time periods in south Anhui Province were identified and classified according to the keys to the Chinese Soil Taxonomy (CST) (the 3rd edition).The placement of 2 taxa,the eight soil profiles were formerly sorted into on the subgroup level in the Chinese Soil Genetic Classification (CSGC),in CST was elucidated in the paper.All these soils studied are classifed into 3 CST Orders: Isohumosols,Cambosols and Primosols,3 CST Suborders: Udic Isohumosols,Udic Cambosols and Orthic Primosols,4 CST Group and 6 CST Subgroups.With CSGC-Purple 2 Soil as object for classification,references between the CST,the U.S.Soil Taxonomy (ST) and the World Reference Base for Soil Resources (WRB) were discussed.Environmental conditions for development of Isohumosols from purple-red sand rocks in south Anhui Province were also studied.Meanwhile some amendments were suggested of the Keys to the CST in classifying CSGC-Purple-Soils.

Abstract:For areas with no soil survey experts or soil maps available,knowledge about soil-environment relationships is a key to predictive soil mapping using knowledge-based approaches.An approach based on an unsupervised fuzzy clustering method (FCM,fuzzyc-means clustering) is recommended to acquire the knowledge.The method consists of four steps:1) define those environmental factors which play decisive roles in formation and development of soil,then build up environmental database;2) identify environmental niches (combination of environment conditions) by running FCM on the environmental database;3) allocate field efforts to relate unique environmental factor combinations to soil types;4) establish a soil-landscape model by analyzing the relationship established from the field samples.The model is then used to predict spatial distribution of soils.The method was applied in a study area in Northeast China and a soil map at the subgroup level was created for the area.The derived soil map was accurate up to 72% when verified using an independently collected field sample set.Comparing this method with the conventional soil mapping method (50%～60%) in USA in accuracy,it could be concluded that the approach is effective for prognostic soil mapping over areas with no local soil experts available.At the same time,the clustering method can improve efficiency of the field sampling.

Abstract:Samples were collected from anthropogenic forest soil and cultivated soil at Bailuyuan site to observe and quantitatively analyze their micromorphological features with the aid of a polarizing microscope and the Qwin software.Results show that the two soils are quite similar in mineral composition.Their coarse granules are mainly formed of quartz and feldspar,but some-what different in size and shape of particles.The anthropogenic forest soil is characterized by smooth pores,packed voids and continuity in succession of micromorphology,whereas the cultivated soil by intricate rough pores and obvious changes in succession of micromorphology with depth of the profile,particularly at 20 cm and 35 cm in depth.The existence of a large amount of cryptocrystal calcite suggests that the soil environment has been subjected to frequent changes,of acicular calcite in the mid and lower part of the plow pan that the soil environment has undergone a short stable period,and of microlitic calcite that the soil environment has been maintained stable for quite a long period.

Abstract:As a result of soil forming process and human activities,rock fragments or detritus exist in soils,different in contents and sizes.Their presence does have some effects on some physical properties of the soil as well as water infiltration process.Based on the experiment of vertical infiltration in lab,effects of content of rock fragments (0%,10%,20%,30%,40%,50% and 60%) and size of the detritus(0.2～0.5cm,0.5～1.0 cm,1.0～3.0 cm and 3.0～4.0 cm) on water infiltration were studied.The purpose of this study is to determine effect of rock fragments different in content and size on water infiltration process and find out its mechanisms.

Abstract:Virus-adsorbing behavior of soil,to a large extent,determines the risk of viruses polluting drinking water.Batch sorption experiments were carried out with bacteriophages MS2 and φX174 to compare 6 different soils with contrast properties in virus-adsorbing behavior,and to expound effect of the presence of indigenous microorganisms on the behavior.In general,soils were more adsorptive to φX174 than to MS2.Among the studied 6 soils,clayed red soil showed the greatest adsorption capacity,while sandy Chao soil the lowest,Effect of the presence of indigenous microorganisms on soil virus-adsorbing behavior varied with soil and bacteriophage.Sterilization increased soil adsorption of MS2 in all the soil samples,except in clayed red soil,whereas it did not affected their adsorption of φX174 except in clayed red soil,where adsorption of φX174 decreased significantly,which suggests that clayed red soil or materials with similar properties may be used as an ideal virus sorbent to purify virus-contaminated water.In areas dominated with sandy Chao soil,the possibility of "natural disinfection" through soil adsorption is rather limited.In soils may exit some microorganisms and some special groups of microorganisms that may control the process of virus adsorption by soils.It is,therefore,essential to further study mechanisms involved in this process.

Abstract:Distribution of polycyclic aromatic hydrocarbons (PAHs) among soil organic matter pools different in activity may influence their mobility and bioavailability in the soil.In this research,the distribution characteristics of 15 kinds of USEPA priority PAHs in soil light fractions,heavy fractions and different fract ions of combined humus of soil heavy fractions were studied by the fractionation method for soil organo mineral complexes.The results showed that the contents of total PAHs in light fractions ranged from 1.30 10⁴ to 1.07 10⁵g kg^-1,far greater than in heavy fractions,ranging from 221.7 to 297.8 g kg^-1,Al though the light fractions accounted for only 0.4% to 2.3% of the soil,they got associated with 31.5% to 69.5% of the PAHs in soils.The PAHs in heavy fract ions were mainly associated with tightly combined humus,account ing for 71.2% to 87.2% of total PAHs in heavy fraction.The contents of PAHs in different fractions of combined humus of heavy fractions had significantly positive correlation with their organic carbon contents (p<0.01),The enrichment ability of tightly combined humus was signifi cantly greater than that of stably combined and loosely combined humus.Environmental risk of PAHs polluted soils probably comes mainly from the PAHs combined with soil light fractions.

Abstract:A total of 2 631 soil samples were collected from 10 counties of the Taihu Lake region of North Zhejiang Province,China,in the study to characterize spatial variability and environmental risks of Hg,Cd,Cr,Pb,Cu and As.Results clearly show strong spatial variability of Hg and Cd,suggesting its close relationship with anthropogenic factors.Meanwhile,statistical analysis of the test results indicate that concentrations of the heavy metals in the soils were in the range of the safety values of the national soil quality criteria with the exception of Hg and Cd.Compared with Cd (2.62%) slight in risk,Hg in 10.34% of the soil samples exceeded the environmental safety criteria of the national soil quality standard,suggesting that Hg might be considered as a dominant element causing soil heavy metal pollution in the study area.The disjunctive kriging technique was thus used to quantify the risk of Hg pollution,and revealed that polluted areas were concentrated around cities and towns and industrial plants and mining,suggesting that the pollution is closely related to air-particle deposition as well as discharge of industrial solid waste and urban garbage.The results of this study provide some insight into risk assessment of environmental pollution and decision-making for agriculture and industry.

Abstract:Sewage irrigation has been paid more attention due to its adverse effects on soil and crops.An experiment was carried out in a greenhouse equipped with a drip irrigation system to investigate the distribution patterns of heavy metals (Hg and As) and tomato development,yield and fruit quality under sewage irrigation.Results showed that significant spatial variation of heavy metal contents was observed in soil profiles.Hg and As were enriched in the 10~30 cm layer,showing close correlation between them,which indicated that the soil environment was seriously affected by external pollutants.Generally,sewage irrigation influenced growth of tomato fruits and its quality,as shown by a lower growth rate,7 68% lower yield,46.2% higher soluble solid content,76.76% higher Vccontent,55.84% lower protein content and similar contents of the acidity and total soluble sugar than with freshwater irrigation.Sewage irrigation also increased Hg content by 28% and As by 112%,but not above the food safety criteria.

Abstract:During the 6th excavation of Chuodun site (E120°50'41",N 31°24'07"),22 pieces of prehistoric farming lands were discovered within 300 m²,Each field was surrounded with bands in between,and ditches or water pools (wells) constructed for irrigation,and some pots wearers (belong to Majiabang culture periods) for water transfer from ditch to field were found in these ditches or fields;more.000 fossil rice grains were screened out,and about 10 to 60 thousands rice phytolith (opal) per gram soil were detected in these ancient lands,all facts above are strong proof indicating these small piece of ancient lands were irrigated paddy fields for rice cultivation by ancient human beings settled in this site.The age of these paddy fields were about 5 907 a BP to 6 280 a BP determined by ¹⁴C analysis.It is in Neolithic period and in agreement with Majiabang culture period identified by archaeological method.The small size of each field which only 0.4 m² to 16 m² and various shape etc.morphological characteristics were reflect the very low production capacity at that time.A soil monolith (P-01) was studied and described,results indicated that there were two buried paddy soil profile piled together.One is prehistoric paddy profile with age of 6 280 a BP (Majiabang cultural period) in the layer of 103～200 cm depth and the other was ancient paddy profile with age of 3 320 a BP (about Maqiao cultural periods to Early Shang dynasty period) in the layer of 42～103 cm depth.It proved that there were several times of flooding or sea water invade resulting to break off agricultural civilization.Another monolith (P-03) only 15 m apart from the above monolith (P-01),but it was not found the prehistoric paddy profile in the layer of 103～200 cm depth indicating early human beings settled in Chuodun site during that periods had no capacity to use hill land for rice planting yet,because of P-03 monolith was located at the foot of Chuodun hills,they had no technology to level it to construct terrace for rice planting,while the same buried paddy profile in the layer of 40～103 cm aged as Maqiao cultural period to Early Shang dynasty period was there same as in P-01.Both buried paddy soils have developed most of the typical characteristics of modern paddy soils.

Abstract:Routine analyses and new biotechnologies,such as sole carbon source utilization tests (Biolog),were applied to investigate changes in physico-chemical properties and microbial ecology of petroleum contaminated soil,Results show that petroleum contamination did not affect much soil hydrolysable N,total N,total P,available K and total K.But the observed increases in soil organic matter and decreases in soil pH,might have led to changes in microbial ecology of the soil,Although there was no significant difference found between the clean and the contaminated soils in numbers of cultivable heterotrophic bacteria and actinomycetes,hydrocarbon-degraders and PAHs-degraders in the contaminated soil were about 100 to.000 times higher in number than in the clean soil,Community level physiological profile using Biolog sole carbon source utilization tests was used to investigate effect of petroleum on soil microbial diversity.Diversity indices,such as Gini index,McIntosh index,and McIntosh evenness,increased in the contaminated soil,The above results indicate that petroleum contamination increased microbial diversity of the soil,Besides,the acute bio-toxicity test by the luminous bacteria method showed that the DCM/DMSO extract from the petroleum contaminated soil is toxic to the bacteria and only.950 μ g ml^-1 in EC50.

Abstract:Microbial community composition in PCBs-contaminated paddy field soils was analyzed by PCR-DGGE.Impacts of PCBs and soil physico-chemical properties on soil microbial composition were investigated by canonical correspondence analysis.Results show that soil microbial community composition varied with soil PCBs level,and soils relatively higher in PCBs content (64.0～484.5 ng g^-1 dw) were quite close in community structure.Moreover,PCBs contamination affected more significantly (p<0.05) bacterial species composition in comparison with other soil physico-chemical factors such as available phosphorus,pH,organic matter,etc.,suggesting that under the stress of PCBs,the entire soil microbial community changed.In conclusion,PCBs pose a potential ecological risk to the microbial ecosystem in contaminated paddy soils.

Abstract:Phosphorous fractionation is a method developed to estimate sizes of readily soil available P pool,and soil P sub pools and their ability to replenish the available P pool.Three types of acid soil (laterite red soil,yellow red soil and brown red soil),of which the first two were sampled from Yunnan Province and the third one was sampled from Hubei Province,were used in pot experiment under a rain shelter condition to investigate the effect of lime amendment on P fractions and their bioavailability by plant of broad bean.A new phosphorus fractionation scheme was developed and used to study P bioavailability in the tested soils compared with the two typical soil P fractionation schemes,Chang Jackson on acid soil and Jiang Gu on calcareous soils.The new phosphorus fractionation scheme used a series of sequential extractants,such as 0.25 mol L^-1 NaHCO₃,1 h (for Ca₂-P),0.5 mol L^-1 NH₄F (pH8.5),1 h (for Al-P),0.7 mol L^-1 NaClO,pH 8.05,85 & water bath 30 min (for Org-P),0.1 mol L^-1 NaOH 0.1Na₂CO₃,4 h (for Fe-P),1 mol L^-1 NaOH,85 & water bath.h (for O-Al-P),0.3 mol L^-1 Na citrate 0.5 g Na₂S₂O₄-0.5 mol L^-1 NaOH,80 & water bath 15 min (for O-Fe-P),0.25 mol L^-1 H₂SO₄,1 h (for Ca₁₀ P),Results showed that Ca₂ P,Al-P and Fe-P were the main available P sources in acid soils.O-P was potentially available phosphorus source,which could be subdivided into O-Al-P and O-Fe-P with the new phosphorus fractionation scheme,and the latter reflected difference be tween CK and lime treatment in plant availability.The size of the labile organic fraction was relat ively invariable and could be transformed into a highly available P source to plant.Further study may be needed on extractant for labile organic phosphorus in determining soil P availability in acid soils.

Abstract:Effects of concentration(0~80 mmol L^-1) and pH(2.5~7.0) of the solution of tartrate,a simulative rhizo spheric exudate on adsorption and specific activity of acid phosphatase on goethite,kaolinite,and colloids in yellow brown soil and latosol were studied.Results suggest that the adsorption of enzyme on soil colloids and minerals exhibited a sharp downfall (0~5 mmol L^-1),which was soon leveled off with rising tartrate concentration from 0 to 80 mmol L^-1,The effect of tartrate concen tration on enzyme adsorption was the most remarkable (the adsorption percentage reduced from 96.2% in referenced system to 33.7% in 80 mmol L^-1 tartrate system) on goethite,but much lower (the adsorption percentage reduced from 76.3%~60.6% to 56.2%~41.6% in 80 mmol L^-1 tartrate system) on soil colloids composed of phyllo aluminosilicate mineral and kaolinite.The pH value triggering the maximum adsorption of enzyme was on the acid side of the IEP of the enzyme,which may probably be related to the change induced by tartrate in electric charge property of the minerals.In the tartrate system,specific activity of the enzyme was much higher on goethite than on the colloids.The most proper specific activity point of the enzyme did not vary much with the type of colloid.

Abstract:An experiment was carried out in 2005 in Yixing and Changshu,part of the Taihu Lake region,to study roles of buffer strips (BS) in reducing nitrogen (N) and phosphorus (P) concentrations in surface water,leachate,and irrigation water of paddy fields different in fertilization level during the rice-growing season,and their effect on yield of the crop,Results show that Treatment BS differed slightly from Treatment Fertilization in rice yield,but significantly reduced N and P loss by intercepting runoff,The total net N intercepted ranged between 20.6 and 51.9 kg hm^-2,accounting for 31.7%～50.9% of the total dis-solved N in the surface water,and the total net P intercepted did between 4.7 and 5.1 kg hm^-2,accounting for more than 1/2 of the total dissolved P in the surface water.Its role in intercepting N and P in leachate in soil profile was also apparent,reducing N and P transfer into water bodies.N and P concentrations in the profile display a declining trend with the depth,suggesting that paddy field can filter out N and P from irrigation water.

Abstract:Through use of the principal component analysis (PCA) and cluster analysis (CA) methods,sensitivity was analyzed of characteristic indices of changes in organic carbon in soils subject to straw application and earthworm (Metaphire guillelmi) activity in a long-term rice- wheat rotation field experiment,Results show that these indices varied in response to straw application and earthworm activity.When all the indices chosen were used,the changes in content and composition of soil organic carbon could be reflected relatively inextenso,but too much information and inconsistency of the information embarrassed further analysis.According to the principal component analysis (PCA) and cluster analysis (CA) methods,these indices could be divided into two groups,one related to soil organic carbon content,including dissolved organic carbon (DOC),hot water extractable carbon (HWEC),potentially mineralizable carbon (PMC),basal respiration (BR),acid extractable carbon (AEC),readily oxidation carbon (ROC),particulate organic carbon (POC),light fraction organic carbon (LFOC),total organic carbon (TOC),and the other related to microbes and having some potential influence on soil organic carbon,including microbial quotient (Mq),qCO₂ and microbial biomass carbon (MBC),The former could be used to evaluate effect of straw application on soil organic carbon,and the latter to evaluate potential effect of earthworm activity on soil organic carbon.

Abstract:With GPS and GIS method,the distribution of soil nitrogen at microscale,mesoscale and macroscale was studied in Lianshui Basin,Xingguo County,Jiangxi Province.The results suggest that both the total nitrogen and available nitrogen showed normal or lognormal distribution at the three different scales,but their means increased along the scale up,In the multi-scales,mean total nitrogen contents were 0.60 g kg^-1,0.73 g kg^-1 and 0.83 g kg^-1 respectively,and mean available nitrogen were 64.8 mg kg^-1,66.3 mg kg^-1 and 80.2 mg kg^-1,respectively.The spatial variability of soil total nitrogen and available nitrogen showed obvious scale effect with the different semivariogram parameters and spatial distribution for the multiscales.The combined sampling method of griding with stratifying is suitable for the study of spatial variability of soil nitrogen at the multi 2 scales in hilly area.Their reasonable sample points were 82,6%,71.2% and 58.1% of the initial sampling points under the 90% confidence level,and those were 95.7%,94.2% and 89.2% under the 95% confidence level,separately.

Abstract:A two-year field experiment was conducted to investigate ammonia volatilization from Gleyed paddy soil in the Taihu Lake region.The experiment was designed to have four N levels (0,180,255,330 kg hm^-2) and four P₂O₅ levels (0,30,90,180 kg hm^-2),forming six NP combinations (CK-N₀P₀,LN-N₁₈₀P₉₀,OPT-N₂₅₅P₉₀,LP-N₂₅₅P₃₀,HP-N₂₅₅Psub>180 and HN-N₃₃₀P₉₀),Ammonia volatilization was measured with the enclosure method.Results show that ammonia emission occurred within the first 6 days after fertilizer application,and it was less after the basal dressing and the first top-dressing than after the second top-dressing.N loss through ammonia emission accounted for 0.4%～12% of the total nitrogen applied for the basal and the first top dressings.However for the second top-dressing the percentage was 5.8%,9.7%,25.6%,15.6%,11.6% during the 2002 rice season,and 27.4%,26.2%,30.0%,35.1%,27.6% during the 2003 rice season for Treatments LN,OPT,LP,HP and HN,respectively.Ammonia loss was low when fertilization was followed by rainy days or was done right at the elongating or booting of the rice crop,Positive correlation was observed between NH₃ loss and NH₄⁺-N concentration in the surface water in all the three fertilization periods.When the rate of phosphorus fertilizer remained the same,NH₃ loss increased with N fertilizer rates,whereas when at the rate of N fertilizer stayed unchanged,NH₃ loss was higher in treatments higher and lower in P rate treatments than in treatments optimum in P rate,suggesting that ammonia loss would be greater when NP combination is unbalanced.P₂O₅ is recommended to be no more than 90 kg hm^-2 for rice.

Abstract:A hydroponic experiment was carried out to study effects of increased ammonium (NH₄⁺) on growth of pakchoi under light low in intensity.Results obtained show: 1) Biomass,photosynthetic rate and leaf area of pakchoi cultured in complete nitrate solution decreased by 63%,31% and 13%,respectively,in treatment 50% in light intensity and by 76%,33% and 24%,respectively,in treatment 25%,compared to those under natural light;2) Total length,surface area and volume of roots were decreased by low light intensity while average diameter was increased,but did not differ much between the three treatments different in light intensity;3) When 0.75 mmol L^-1 NH₄⁺ was added into the solution,biomass,photosynthetic rate,and leaf area of the plant peaked in treatment 50% in light intensity and increased by 90%,12% and 19%,respectively In treatment 25% in light intensity,addition of 0.50 mmol L^-1 NH₄⁺ increased the biomass,photosynthetic rate,and leaf area of pakchoi by 33%,15% and 27%,respectively;4) Root morphological parameters of pakchoi were significantly improved when a proper rate of NH₄⁺ was added,showing thatNH₄⁺ helps promote root growth.Pakchoi growth was inhibited by low light intensity through de creasing photosynthetic rate and leaf area.But addition of some NH₄⁺ into the solution could significantly offset this inhibition effect.

Abstract:A pot experiment was conducted with three treatments (T1,295 ng g^-1;T2,3 723 ng g^-1;T3,6 109 ng g^-1 in concentration of DDT) and one control (CK,31 ng g^-1),When peanuts were mature whole peanut (Arachis hypogaea) plants were harvested and divided into four parts,roots,stems,husks and kernels.Concentrations of DDT in these parts were determined separately by GC ECD.Results show that the concentration of DDT in the kernels was about 200 ng g^-1 in T2 and T3,exceeding the maximum residue limit for DDT residue (100 ng g^-1) set by WHO/FAO.In general,the concentration of DDT in peanut ker nels is not likely to exceed the maximum residue limit in current environment,but the concentrat ions of DDT in the husks and stems,especially in the roots,of the plants were rather high,which causes more concerns.The total amount of ΣDDT in the roots was the highest,indicat ing the roots are the dominating part of the plant that takes up and accumulates DDT.Fairly high bioaccu mulation factors of the roots and the stems suggest the peanut plant is great in capacity of absorbing and accumulating DDT.Fur thermore,the results suggest that the high oil content in peanut kernels might facilitate the uptake and accumulat ion of lipophilic DDT.

Abstract:Impact of soil spatial variability on spatial distribution pattern of Locusta migratoria manilensis eggpods in Nandagang reservoir,Hebei,were studied by means of geostatistical analysis and GIS techniques.Results show that soil properties,such as salt content,water content at 5 cm depth,organic matter and pH,displayed significant spatial heterogeneity,but the first two demonstrated close spatial correlation and the last two moderate spatial correlation,and the distribut ion of locust egg pods,significant spatial auto correction.Locust eggpods were mainly distributed in the central and eastern parts of the study zone,where the soil was low in salinity (<9%) and moderate in water content (10.1%~29.9%),but they were rarely found in the western and northern parts,where the soil was high in water content (>30%) and in salinity (>3%).The find ings indicate that the spatial distribution pattern of locust eggpods is mainly related to spatial variability of the soil in the study area.

Abstract:Pedometrics is a new branch of soil science,which originated and developed in Europe,Australia and America over the last 30 to 40 years.The International Union of Soil Sciences (IUSS) had its Pedometrics Commission established following the 17th World Congress of Soil Science in 2002.This commission,together with others (e.g.soil geography,soil genesis,and soil classification),belongs to the first division of the IUSS (Soils in Space and Time).In this paper,attempts are made to introduce the theoretical and technical backgrounds of the genesis of Pedometrics and the course of its development and summarize and discuss works that have been done in this aspect in China.

Abstract:Urban soils act functionally as an ecological screen in protecting urban environment.Their degradation,however,is in essence a process of providing ecological services,such as sink of all kinds of pollutants,at the cost of their own quality.Therefore,as a result,they often come across a variety of environmental problems.Besides physical degradation,such as compaction,enrichment of various elements associated with human activities,heavy metals,and organic pollution are the major problems with urban soil environment.The main features of urban soil contamination are characterized firstly by strong accumulation of socalled ‘urban elements' such as Cu,Zn,Pb and Hg,but less of other heavy metals;and secondly by spatial isolation,which means the contamination is not spatially continuous.During the process of urban development,heavy metal contamination of urban soils happens not only nowadays,but also did in the past,especially when primitive mining and metal processing prevailed.Furthermore,urban soils are often polluted by organic pollutants,especially polycyclic aromatic hydrocarbons (PAHs),with roadsides and industrial sites being the major vulnerable areas.PAHs therein have normally 2～6 rings and predominantly 2～4 rings,strongly suggesting their pyrogenic background,including motor vehicles,industrial activities and coal burning. So far,studies on urban soil contamination and other related environmental problems have concentrated mainly on three aspects,firstly source,status and diffusion patterns of urban soil contamination;secondly impact and risk assessment of soil contamination on environment,ecology and biological health;thirdly better use and management of urban soils.More researches are expected in the coming near future on environmental capacity of urban soils,threshold values and dynamics of translocation of these contaminants,interactions between soil,water and organisms,and biological effects of pollution. These studies are important to the establishment of a science-based risk assessment system for urban soil environment,soil pollution control and better management of urban soils and environment.

Abstract:In wind erosion research,Bagnold's threshold equation,applicable to determination of relationship between threshold wind velocity and particle size of loose dry sediments,is widely accepted.However,soil moisture is also an active factor influencing the threshold wind velocity because the tension of water molecules will increase the inter-particle cohesion between sediment particles,and hence the threshold wind velocity.To accurately and quantitatively estimate wind erosion and dust emission,it is essential to establish relationship between threshold wind velocity and soil moisture content,but so far the research in this field lags far behind the need of the reality.The review sums up research findings on relationship between threshold wind velocity and soil moisture content in the last five decades,into three categories,i,e.semi-quantitative description,empirical model and theoretical model,and cites some representative examples for each category.Comparison analysis reveals that conclusions of these researchers are various and diversified,especially concerning quantitative relationship,except for the connotation of nature determination.The authors attribute the differences to the lack of a clear understanding of the relationship between inter-particle cohesion and moisture content,definition of threshold wind velocity and moisture content,and physical and chemical properties of tested soil samples.It is suggested that further work be done in this research field.

Abstract:空间异质性为系统的某种属性在空间上的复杂性和变异性^[1]。土壤学家将土壤特性在不同空间位置上存在明显差异的属性称为土壤特性的空间异质性^[2],不论在大尺度上还是小尺度上,土壤的空间异质性均存在。自从20世纪60年代Martheron^[1]建立地统计学以来,土壤特性的空间变异定量化研究一直是一个被关注的热点问题,土壤特性的空间格局及其产生空间变异的主要影响因素成为异质性研究的一个重要领域。

Abstract:根系三维结构的确定对研究原位状态下根系吸收水分、养分有重要的意义^[1,2]。国内外很多研究者已经将定量化模拟与分析根系三维结构作为培育资源高效利用的作物新品种、提高SPAC系统中物质、能量运移与分布模拟精度的重要突破手段与方法^[2~5]。

Abstract:烤烟是我国重要的经济作物,2006年全国种植烤烟的面积达114.5万hm²,总产量为2163t^[1]。烤烟生产分布在全国23省市,是2000多万农户、约一亿多烟农主要的经济来源^[2]。特别是在我国经济尚欠发达的西南地区,烟叶生产是重要的支柱产业之一。吸烟有害是世人共识的,在卷烟没有完全退出市场和部分人群的生活之前,提质降害是卷烟工业和科研工作者的首要任务。烤烟生产是卷烟工业的第一车间,卷烟的提质降害必须从田间抓起。