Land Quality Geochemical Assessment In The Dongting Lake Region Of Hunan Province

The land is a sort of basal resource, and with the fast development of global industrialization, we are faced with the drying up of resource and environmental pollution, which is a serious problem. Land quality assessment is not only the main technique foundation and decisive factor in land use area division, but also the important part of land use programming. Land quality assessment, according to which grade of land quality can be defined by quality index, has an important practical meaning in harmonizing the relationship between human and sustainable use of land.In this paper, land quality geochemical assessment in Dongting Lake region in Hunan province is carried out by single factor standard, analytical hierarchy process(AHP), gray related comprehensive evaluation.The ecological efficiency of elementary abnormity in soil was carried out according to content of heavy mental in paddy and National Food Health Standards. The result shows that the most serious pollution of heavy mental in paddy is Cd among different area, especially in Miluo and Xiangyin.The concentration of Cd of 23% samples were unqualified according to National Food Health Standards.With grade evaluation about nutrients of N, P, K, B, Mo, Mn in soil of Dongting Lake area, the result shows higher content of N, P, K in a majority of investigated area, while lower content of P in large area west form Changde city. The content of B was high in almost all the area, and the only lower B was distributed in east area. Available Mn was thin in investigated area, especially in crop field. High content of available Mo was inspected in most investigated area, while lower Mo in mid plain area.Compared to GB15618-1995, the degree of heavy mental pollution in investigated area shows that Cd was over standard in 87% area, which is zonally distributed along Xiangjiang River. Pb, As, Hg were respectively over standard in 32.76%, 18.51%, 14.10% area.Land quality comprehensive assessment by AHP shows that soil in research area mostly is graded as fine, which accounts for 44.80% in the whole region. Worse grade area which accounts for 14.58% in the whole region may develop agriculture production restrainedly. Excellent grade area accounts for 13.36% in all and is suitable to develop green agriculture production. Other area which is graded as common accounts for 13.36% in the region .According to the results of Grey Relative comprehension assessment, soil in Dongtinghu Lake region is sorted into excellent, fine, common and worse, the percentage of these four kinds of soil is respectively about 6.71 , 43.34, 35.75 and 12.20.The results of these kinds of assessment are approximate because that the percentage of fine grade soil is close and the division of restricting area is similar. And the results of these two kinds of assessment are objective and credible.The contents of some toxic elements such as Cd or Pb in the aqueous and exchangeable form increase with soil acidification enhancement. Especially in alkalescence or weak acidity soil, the bioactivity of the element Cd increases sharply, which is harmful to crop security production. Moreover, soil acidification causes electropositive ions such as K, Na, Ca, Mg, etc. to eluviate loss much, and causes the available beneficial elements to decrease rapidly. Thus results in reducing the soil fertility, nutrient and quality.In order to reduce the effects of soil acidification.