| Three Gorges Reservoir system is "natural-social-economic" composite system. It is a transitional connection between land and water areas, both land and water area of some two ecosystem functions, structure and unique characteristics of the environmental landscape. However, due to the reasons for natural and human factors, Gorges Reservoir wetland ecosystems showing strong instability and ecological fragility, resulting in the formation of Gorges Reservoir with fragile ecological environment of wetland. Scientifically and rationally develop and utilize, Fragile ecological environment in the water-level-fluctuating, such as establishing a diversified ecological system, must be based on clear recognizing soil quality. In some specific regions, heavy metal environmental conditions which is important the study of human activities on soil quality, soil quality evolution and the rational exploitation and utilization of land resources is a reflection of environmental quality. Second, with the development of industrial and agricultural development heavy metals into the soil through a variety of ways, resulting in the accumulation of pollution. due to its universality, concealed, surface concentration and irreversibility characteristics, investigating and researching in a special position in the heavy metal content fluctuation zone is of great practical significance.This essay focuses on a tributary of Xiaojiang Water-level-fluctuating Zones, which is locating in the center of the Three Gorges Reservoir Area. The concentrations of soil heavy metals in Water-level-fluctuating zone are directly associated with water safety and human health. In this study, the concentrations of Cu, Cr, Ni and Zn in Water-level-fluctuating zone soils of the Three Gorges Reservoir (TGR) area were determined, and their influencing factors and characteristics of distribution were researched. The result of the first method shows that this area is polluted by Cd, Zn, and Pb to some extent but is relatively clear of Cu, Cr, Ni; The results of the two comprehensive assessment methods are consistent, indicating that in a whole the zone is in a light pollution state while some areas lie in heavy pollution state. There is a certain cumulative effect along Xiaojiang river.Specific conclusions are as follows: (1)The statistic of soil heavy metal concentrations in Water-level-fluctuating Zones is Cd 0.387mg/kg; Cr 57.196mg/kg; Cu 28.685mg/kg; Ni 27.910 mg/kg; Pb 35.567 mg/kg; Zn 126.028 mg/kg. From the point of coefficient of variation, Pb> Cd> Cr> Cu> Ni> Zn. One of which, Cu. Zn, Ni are of weak variation, reflecting the relatively uniform spatial distribution, human factors is weak. Cr is medium variant. Cd and Pb are the strength variable, indicating a larger spatial variation.(2) Correlation and stepwise regression analysis showed that organic matter was a major impact on the concentrations of the heavy metal; pH and mechanical composition impact the heavy metal also by the content of organic matter; The concentration of heavy metals were influenced by pH, organic matter and mechanical composition, the order of influence degrees is:Cr> Cu> Ni> Zn. Zn was not affected by everyone factors, Cr, Ni was mainly affected by soil particle content; Cu is mainly affected by sand content.(3) The content of heavy metal in the distribution of different segments in water-level-fluctuating zone as follows:Cr:River> middle> lower> upper; Cu:middle and lower> middle> lower> upper; Zn:River> River> downstream> upstream; Ni:the River> Downstream> middle> upper. Cd:River> lower> middle> upper; Pb:upstream> River> River> River. ANOVA showed that there were significant differences of total concentrations of soil heavy metals in each section of the Water-level-fluctuating zone, where the concentrations of soil heavy metals increased gradually from the upper stream to the middle and decreased in the downstream. There was no significant difference in their distributions at different altitudes.(4) It shows that the acid soluble fraction, the reducible fraction, the oxidizable fraction and the residual fraction of Zn in this area are respectively 3.60mg·kg-1,5.44mg·kg-1,10.59mg·kg-1 and 106.40 mg·kg-1 on average. The study suggests that the total contents of Zn and its speciation character contents distribute the most in the middle stream while less in the upstream and the middle and lower reaches of the river. This is related to the geological background of each section of Water-level-fluctuating zone. The different chemical speciation of Zn was affected in the different levels of significance by the total content of Zn and soil properties. Its reducible fraction of Zn is mainly affected by its total contents, the oxidizable fraction by sediment contents, and the residual fraction by its total contents together with organic content. The acid soluble fraction is markedly affected by neither its total quantity nor its physical and chemical properties.(5) According to a standard of soil environmental quality standard, We tries to test the heavy metal pollution levels of Ni, Zn, Cr, Cd, Cu, Pb by applying such methods as single-factor pollution assessment method, Newerow integrated pollution index method and fuzzy comprehensive evaluation method and by using single-factor equation analysis to analyze the factors that affect the spatial distribution of the five heavy metals in the soil. The result of the first method shows that this area is polluted by Cd, Zn to some extent but is relatively clear of Cu, Pb, Cr, Ni; The results of the two comprehensive assessment methods are consistent, indicating that in a whole the zone is in a light pollution state while some areas lie in heavy pollution state. (6)According to water-level-fluctuating zone stands a special place in the environment, functions and principles of sustainable using of land resources, leading to elevation and slope factors for the water-level-fluctuating zone land use planning were discussed. Utilization in the water-level-fluctuating zone of protection based on the recommendations put forward:①Speeding up land-use legislation about water-level-fluctuating zone;②Water-level-fluctuating with the development of ecological environmental protection measures;③Actively carrying out publicity and education;...
|
PDF Full Text Request