In light of the works on soil environment in China,three important issues worth exploring in the research of soil environmental quality in China are discussed,i.e.definition of soil contamination,revision of soil environmental quality standards,and legislation of soil contamination prevention law.In view of ambiguity of the definition of soil contamination,a definition is developed by the authors summarizing various principal views at home and abroad.It is suggested that a risk-based soil environmental quality standard system be set up in China,consists of three standards: a target value for soil environmental quality,guideline values for soil(for agricultural,residential and industrial soils,respectively) environmental quality,and a threshold value for soil pollution.Methodologies for setting up those values are suggested.Development of the soil contamination prevention law is an essential requirement for establishment of an effective soil environmental management system in China.Therefore,technical issues are discussed in formulating the soil contamination prevention law in China.

Stationary observation of CO₂ emission and fixation in paddy ecosystem was carried out during the late rice growing season,using the closed static chamber technique in a red soil hilly region.It was found that CO₂ flux varied with the weather condition（sunny,rainny,cloudy） from day to day.The daily net CO₂ fixation fluctuated sharply during the season,peaking up to 10.35 g·m^-2·d^-1,and dropping down below zero,-0.92 g·m^-2·d^-1,at the maturing stage of the crop.The CO₂ accumulative emission from the paddy ecosystem reached 20.4 t·hm^-2 and from the soil through respiration 6.3 t·hm^-2.The former was in an extreme power function relationship with the crop biomass.During the entire growing season of late rice,the paddy ecosystem fixed 3.85 to 4.00 t·hm^-2 C from the atmosphere.

Responses of soil quality indexes to land use of different patterns were explored.Results show that by using the Main Factor Analysis Method the 22 soil quality indexes in the Beibei karst mountain region of Chongqing could be sorted into 4 categories represented,respectively,by organic matter,available soil water,aeration porosity,and percentage of bacteria. The 4 categories reflect basically comprehensive conditions of soil quality.Path analysis shows that soil water holding(capacity) under different patterns of land use is mainly correlated with organic matter,and >0.25 mm water stable aggregates,and their effects are higher than that of clay.When land use patterns changed,changes in soil quality were embodied in content of organic matter,soil water holding and supplying capacity,soil structure and soil microbial characteristics.

Conservation of ecological functions is a hotspot of researches the world over.The concept of eco-function reserve has been expatiated,and methods for establishment and classification of eco-function reserves in Jiangsu Province have been discussed.Strategies are brought forth for protection and management of the eco-function reserves.

In the spring of 2006,nine greenbelts in Shanghai,i.e.evergreen woods（A） and grassland（B）in school;grassland in a dwelling district（C）;roadside ecological woods in Pudong（D）;woods（E） and grassland（F） in the Shanghai Arboretum;woods（G） and grassland（H） in an industrial area;and woods in deserted land,Laogang landfill（I）,were investigated for soil macro-invertebrate communities.A total of 1 930 soil macro-invertebrate individuals were found belonging to 18 orders,8 classes,and 3 phylums.Among them,Mesogastropoda,Isopoda,Oligochaeta opisthopora and Hymenoptera,were dominant orders,and Coleoptera,Oligochaeta plesiopora,Hemiptera,Araneae and Lithobiomorphy,common orders,with the rest being rare orders.Soil macrofauna community varied significantly in composition and population from site to site.To be an indicator of complexity and diversity of the communities,the intensity index(I_DG) and the complexity index（C） of community was better than the Shannon-Wiener index（H′）,and could adjust influence of the number of individuals of different communities on diversity.Results of hierarchical clustering of soil macrofauna using PC-ORD software show that the nine communities could be classified into six groups:（D,E,G）,（F,H）,C,A,B and I.

A typical area of habitat fragmentation in the Thousand-Island Lake,Zhejiang Province,was selected as subject to study effects of habitat variation as a result of island forming,on arbuscular mycorrhizae infection rate and its correlation with phosphatase activity in the rhizosphere of Castanopsis sclerophylla.Results show that with habitat acreage as the factor in one-way variance analysis(ANOVA) AM infection rate was not significantly different between islands,while in Pearson′s correlation analysis,infection rate was significantly negatively correlated with acreage of an islands.Acid phosphatase activity in the rhizosphere of Castanopsis sclerophylla varied sharply with the size of an island,but was not significantly related to AM infection rate.

GLEAMS model was introduced to calculation of nitrate leaching in an agricultural small catchment in Southeast China.Field experiments were carried out in farmlands under different land uses,such as paddy, banana,and vegetable cultivation,at Wuchuan catchment,Fujian Province.Lysimeters were set up in 8 plots different in land use to monitor nitrate leaching from April to December in 2002.After calibration and validation,the model displayed an acceptable performance in simulating nitrate leaching in all plots,except for the plot of paddy field.Results of the simulations show that nitrate leaching in the catchment varied from 4.64 to 38.39 kg·hm^-2 with land uses.Sugarcane,banana and vegetable fields had maximum nitrate leaching and peaked in July and August.Rainfall,land uses and management were significant factors influencing nitrate leaching in the catchment.The model simulations can be used to specifically establish best management practices for nutrient management and pollution mitigation in the catchment.

Soil environmental quality and its impact on safety of agro-products has been one of the research targets concerning regional environmental quality and sustainable development in the last decade.Based on a geologic survey and grid sampling of North Jiangsu including six counties and cities,Fengxian,Peixian,Tongshan,Suining,Chuzhou and Donghai,a total of 98 pairs of soil and rice grain samples were taken randomly in areas of two major soil types,Huangchaotu(Motudic Entisols) and Shajiang black soil(Vertisols) for analysis of contents of total Cu,Zn,Pb,Cd,Cr,Ni,As and Hg with an atomic adsorption spectrophotometer and an atomic fluorescence spectrophotometer,separately.Pollution levels of the soil and rice samples were assessed against the standards for green food production bases and hazard-free food production bases, and the background values of the region of the 1980s,and heavy metal exposure risk assessment of the rice produced in the region was conducted with R_fD values recommended by USEPA and/or WHO as benchmark.Results show that the environmental quality of the soils from the studied region basically meets the requirements set for green food production base in terms of heavy metal pollution,and on the whole falls into the category of "No Significant Pollution".Nevertheless,R_fD values calculated based on USEPA indicate that rice grown in all the soils of the region does pose some significant As and Cr exposure risk to food safety and rice from some areas does Cd exposure risk.Fortunately,it still falls into the category of "Safe" due to low Cd/Zn ratio.In order to further guard food safety,it is essential to amend and modify criteria for soil environmental quality,take positive measures to control soil pollution,and endeavor to improve the quality of the atmospheric environment.

In order to understand heavy metal(including Pb²⁺,Cu²⁺,Zn²⁺,Cd²⁺) adsorption characteristics of purple soil in the water-level-fluctuating zone of the Three-Gorge reservoir region,an experiment was carried out to study heavy metal adsorption behavior of acidic,neutral and calcareous purplish soils under different conditions with the batch sorption method.Results show that(1)with a certain pH,a soil adsorbed heavy metals with strength varying in the order of Pb²⁺>Cu²⁺>Cd²⁺≈Zn²⁺;(2)with a certain pH,the three soils absorbed the same heavy metal with strength in the order of calcareous purplish soils>neutral>acidic,which is in line with the order in surface charge density;(3)Pb²⁺and Cu²⁺ adsorption on the surface of the three soils existed in both static and specific patterns.The specific pattern accounted for 56%,67% and 50% respectively,in the case of Pb²⁺.Static pattern was in dominancy in the case of Zn²⁺and Cd²⁺. 

In order to investigate cycling and burial of phosphorus and nitrogen in Chaohu Lake,the sequential extraction method was used to measure different forms of phosphorus and nitrogen in sediments of the lake.It was found that total P in the sediment ranged from(0.1110.655) g·kg^-1,averaging 0.358 g·kg^-1,and was composed mainly of inorganic P(65%-72%),dominated with Fe-bound P.Total N in the sediment ranged from 0.220-0.922 g·kg^-1,averaging(0.532) g·kg^-1,and was composed mainly of organic nitrogen(94.7%).All these indices signify that Chaohu Lake is in the state of cleanness and almost cleanness.The very close linear relations between organic matter,total phosphorus and total nitrogen in the sediments indicate the nutrients in Chaohu Lake come from the same source.The mean TOC/N ratio of the sediment suggests that the organic matter in Chaohu Lake originates from land.

In the peri-urban river network area of Wuxi,which could be classified into 5 parts,i.e.watercourses in the residential area,main river course in the industry area,main river course in the farming area,ditches of the farming area and fishpond area.Sampling was carried out in both autumn(dry) and summer(rainy) seasons.Concentrations of nitrogen,phosphorus and Cu,Zn,Pb,Cr,Cd in samples of surface water and sediment were determined and their spatial variations were studied.Results show that 1) industrial wastewater and domestic sewage were the main contributors of nitrogen and phosphorus pollution in the surface water,rather than agriculture fields.And they were scattered in distribution and extensive in impact.2) Concentrations of heavy metals in the water and sediment were elevated to varying extents in the above-listed 5 types of water zones.Heavy metal pollution was induced mainly by industrial activities and urban surface runoff.However,heavy metals in the surface water were transported mainly along the main river courses.In both dry season and rainy season,heavy metal concentrations in the main river course were higher than that in ditches of the farming area and heavy metal concentrations in the sediments of the main river courses decreased sharply with increasing distance away from the town,which indicates that the range of river water affected by heavy metal pollution was small.3) The prominent problem of the water environment in the Taihu Lake region was still nitrogen and phosphorus pollution,rather than heavy metal pollution.However,the potential risk of heavy metal pollution in the water should not be overlooked considering the high concentrations of heavy metals in the river sediments in and around towns.

Submersed plant Potamogeton crispus was used to construct a holistic system connecting the shallow layer to the deep layer of water.When sandy water flows through the shallow layer to the deep one,effect of P.crispus on concentration of suspended mud and sand(MS) in different depth layers and sedimentation of MS.Results show that P.crispus reduced content of MS,and the longer they stayed with the flow,the greater the effect.The average settlement of MS in P.crispus system was 65.7 g·m^-2,39.4% higher than in CK.MS sorption on the surface of P.crispus is a dynamic process of "adsorption-settlement-adsorption" ranging from 3.26 to 5.69 g·kg^-1,which was related to biomass per unit area of P.crispus.Therefore,submerged plant P.crispus may play an important role in self-purification of water bodies in winter.

Earthworm(Eisenia foetida) was used in an experiment to test toxicity of carbofuran and to study its effects on death rate,protein content,SOD activity and AChE activity of the earthworm under different temperatures.Results show that when temperature was set at 10 ℃ protein content of earthworm increased slightly at the beginning and then decreased with the exposure time in treatment 30 mg·L^-1 and it also decreased with the rise in concentration of carbofuran.SOD activities of the earthworms exposed to carbofuran were all lower than the check.ANOVA analysis indicated that the effects of exposure time and concentration were significant(P<0.01).But when temperature was fixed at 20 ℃,no obvious regularity was observed in variation of protein content and SOD activity.AChE activity of the earthworms was significantly inhibited by mono-pollution of carbofuran with the maximal rate reaching up to 90%.All the physiological and biochemical indexes were significantly influenced by temperature.As a stable index,AChE activity of Eisenia foetida can be regarded as a biological indicator to monitor and evaluate effect of carbofuran contamination to the soil environment.

An experiment was conducted with cucumbers（Cucumis sativus） of ’Gai Liang Jin Chun No 2’ growing in a nutrient solution culture system and effects of extraneous nitric oxide on growth and active oxygen metabolism were analyzed and studied.Results show that addition of 100 μmol·L^-1 extraneous sodium nitroprusside（SNP）,a nitric oxide donor,significantly alleviated the injury that NaCl stress brought to the plants,increased obviously plant growth,and activity of SOD,POD,CAT and APX,and accelerated accumulation of proline（Pro） in the roots.Meanwhile,extraneous nitric oxide markedly decreased membrane permeability,O^-·₂ producing rate,MDA and H₂O₂ content of the roots.

Atrazine is one of the most widely used herbicides in China and worldwide.Being highly persistent,it exists for long in surface and ground waterbodies,threatening nontarget organisms,such as fish,and contaminating drinking water for human beings.An experiment was conducted on Carassius auratus to study effect of atrazine on glutathione S-transferases(GSTs) activity.Groups of fish were exposed to atrazine varying in concentration,i.e.0,0.1,0.5,1.0,5.0 and 10.0 mg·L~(-1),respectively.The GSTs activities in liver,kidney and muscle of fish exposed to 1.0 and 10.0 mg·L^-1 were measured after Day 3,6,10,14,19 and 24,respectively,to study time-response relationship between atrazine and GSTs activities in these organs.At the end of the experiment(24 days),GSTs activities in the three organs of fish in all treatments were evaluated to explore dose-response relationships between atrazine and SOD activities in these organs.Results indicate that atrazine had strong influences on GSTs activities in the three organs;long exposure(24 days) to atrazine induced activities of GSTs in liver and muscle,with a maximum rate being 110.81% and 32.54%,respectively;and their dose-response relationship was significant,when the concentration ranged from 0.1 to 5.0 mg·L^-1 and from 1.0 to 10.0 mg·L^-1,respectively.Long exposure(24 days),however,inhibited renal GSTs activities,with a maximum rate being 14.42%,and their dose-response relationship was distinct in all the treatments in the experiment.When the fish was exposed to atrazine,10.0 mg·L^-1 in concentration,on Day 6-14,the time-response relationships existed between atrazine and activities of GSTs in liver and muscle,but did not in any organs in any other treatments.

Investigation was made of groups of tombs of the ancient Tuguhun kingdom in Dulan County,Qinghai Province with a land coverage of 3 600 km².It was found that grassland tourism possesses four functions: nurturing of eco-mentality,appreciation of eco-culture,physiological enjoyment of primary ecology of nature,and sightseeing of achievements in grassland ecological agriculture.On such a basis,suggestions are brought forth for orientation of the construction of grassland eco-tourism.

Some researchers claim that organic farming can theoretically and practically contribute to maintenance and conservation of farmland biodiversity.To arouse concerns among the scientific community over relationship of organic farming with farmland biodiversity,a review is presented of the effects of organic farming on species richness,abundance and diversity of weeds,epigeic arthropods,soil organisms and birds in the farmland ecosystem.

Establishment of nature reserves is one of the most important strategies for conserving biodiversity and restoring ecosystems′ services,while the mechanism of ecological compensation plays a very important role in the construction and sustainable management of nature reserves.Based on the literature available,development of the concepts and theories of ecological compensation are summarized,and researches and practices in this aspect both at home and abroad are analyzed.Results show that the government and the market are the two leading factors in implementing ecological compensation of nature reserves,and common payment is a major means regardless countries both developed and developing,and community participation promoted through ecological compensation is an effective approach to nature reserve management.Issues,such as principles,approaches,standards and measures,in the establishment of ecological compensation mechanism in China are also discussed.

As extensive use of carbofuran seriously threatens the wetland birds in China,a brief introduction is presented to the status quo of the progress of in situ protection of wetland birds and the use of carbofuran in China,toxicity and poisoning path of the substance to the birds,and major affected areas.On such a basis some useful countermeasures are put forward, including strengthening the management of wetland nature reserves;screening out a first group of cities or counties where use of carbofuran should be prohibited;consummating the laws and regulations related to wetland bird reserves and natural reserves;readjusting the structure of pesticide products;demonstrating and promoting new pesticides high in effectiveness and low in toxicity;improving the management level of natural reserves;enforcing exsisting laws against birds poisoning;and intensifying control of sales and use of pesticides.

Field studies were conducted to investigate effects of rice straw incorporation and nitrogen application models on process of nitrogen uptake by rice paddy ecosystem and fertilizer-N use efficiency in the double rice cropping system.Results show that rice straw incorporation coupled with N application at a proper rate could increase nitrogen uptake by rice plants and nitrogen cycling in the rice field ecosystem.In the treatment high in N application rate,nitrogen uptake by rice increased,but the amount of N transferred to the ears was limited and the rest still remained in the vegetative organs.N recovery rate,regardless of treatment,ranged between 26.7% and 30.7%,and N agronomic efficiency,between 10.5 and 12.2 kg·kg^-1.Obviously,fertilizer-N use efficiency is low,and it decreased with rising nitrogen application rate.Straw incorporation improved slightly use efficiency of applied N,including N agronomic efficiency,N physiological efficiency,and partial productivity,except for N recovery rate.According to the nitrogen absorption and transformation,the nitrogenous fertilizer use efficiency,and the fact that 7 500 kg·hm^-2 rice straw is incorporated annually,it is recommended that 185 kg·hm^-2 of N be applied a year in the red earth-paddy system.

More than 200 kinds of organic pollutants were detected in water samples collected from different depths of five monitoring sections in estuary of the Yangtze River in dry and flood seasons.Among the 53 quantitatively measured kinds,36 kinds were in the list of venomous organic compounds specified by EPA of the USA for control,and 16 kinds in the blacklist of China for priority control in environment protection.In the dry season,N-dimethylnitrosamine was the highest in concentration with the maximum value reaching up to 11.2 mg·L^-1,while in the flood season,2,4-dinitrophenol and butylbenzyl phthalate were high in concentration with the highest to be 1.3 and 1.0 mg·L^-1,respectively.The concentration of organic pollutants in the deep water layer was higher than in the surface and middle layers.