Based On Fuzzy Mathematics, Taiyuan Basin, Soil Geochemical Environmental Quality Evaluation

In this dissertation, the eco-geochemical characteristics of the soil in Taiyuan Basin is studied to find out the distributive and statistical features of 54 elements and indexes, for the first time, to evaluate the soil quality and its distributive patterns systematically, completely, and synthetically by utilizing the Fuzzy Mathematics comprehensive evaluation method, and to classify the soil contaminative grades using the evaluative results.According to the first period regional investigation, the geochemical characteristics of Taiyuan Basin is studied by comparing geochemical diagrams of the soils between the deep layer and the superficial layer. The research shows that the contents of heavy metals such as Cu, Zn, Ni, Cd, Cr, As, U, and Th are enriched in the basin centre universally, and Pb and Hg abnormal along the main highroad and near towns. The value of pH reduces in the city and the sewerage irrigation region of Fen River universally, rises toward the side mountain direction obviously, which indicates that irrigation with sewerage have developed the soil acidification obviously, and the human economic activities of Taiyuan Basin have been changing the geochemical characteristics of the earth's surface largely.Researching on the total characteristics of elements of the soil in Taiyuan Basin, we have discovered that the geochemical characteristics of the superficial inherit mainly from the deep layer, though there is obvious reformation. The surface layer has enriched some poisonous and harmful elements(Cl, Cu, Ga, Hg, I, N, P, Pb, S, Se, C, Au, and Cd), which caused the descent of soil fertility, deteriorated the cropper output and quality, influenced the human health by the food chain, and would destroy the originally fragile environment of Taiyuan Basin.Factor Analysis of 54 elements and indexes presents 23 factors under 90% of accumulative variance. When explained the various abnormality of each index, we can discussed the comprehensive index factors which deduced the changeable regulation of all indexes emphatically, thus provided the certain theory basis for the choice of thesoil quality evaluation indexes.For comprehensive evaluation, 46 evaluative indexes are chosen according to the soil distributive characteristics of the Taiyuan Basin and the recent research purpose, which are divided into 7 major types by the Chovalitsky's geochemical classification of elements, that is petrogenetic elements, iron group elements, lithophile rare and rare earth elements, dispersed elements, solvent elements, radioelements, and sulfophilic elements. On the basis of preliminary evaluation with Fuzzy Mathematics method, we achieve the comprehensive evaluation of soil quality of Taiyuan Basin and classify the contaminative grades finally. It is suggested that the membership degree of unpollution, light-degree, moderate, heavy-degree and severe pollution are 0.27956, 0.5954, 0.06245, 0.04494, and 0.01765 respectively. The membership degree of light-degree pollution is the biggest, which implies that the soil quality of Taiyuan Basin is light-degree pollution as a whole.