Ecological Geochemical Features Of Land In Tuojiang Town, Neijiang City

As the source for all producing and exsiting, land is the material basis of human's living and development. With the acceleration of urbanization and industrialization since 1970s, the size of cultivated land has decreased while the population has increased, which made the contradiction between land supply and human need become more serious. Since then, land has become a worldwide issue that has been influencing the sustainable development of human being.By the methods of geology and geochemistry, this thesis carried out agro-geological survey in Maopengsi Village, Lanjiasi Village, Zhongxin Village, Longmen Village of Tuojiang Town, Neijiang City, to find out the geochemical features of land's composing elements like soil, water, air, and plants in this area.Through studying the content of geochemical elements in soil, it indicated as follows: the soil in this area was mainly neutral or light alkaline, and the content of elements distributed unevenly. Compared with the background contents of elements in soil of the whole country, that of Cd, Mg, P in this area were higher, with the enrichment coefficients of 3.18, 1.79, 1.43 respectively, while that of As, CaO, I, Se were lower, with the enrichment coefficients of 0.31, 0.66, 0.22, 0.68 respectively, and that of other elements were close to the national background value. In the topsoil, the contents of heavy metal elements As, Cu, Cr, Hg, Ni, Pb, Zn in 85% of samples were lower than the first order of national soil quality standard. The content of Cd in 85% of samples was within the sencod order, which attributed to the affect from huaman activities. Contents of macroelements N, P were comparatively short, while that of K was morderate. Contents of Ca, S were relatively low while that of Mg was high. Microelement Zn was rich, Cu, Fe and Mn were moderate while B, Mo were insufficient. Juding from availability, the available contents of B, Mo, Mn, N were inadequate, those of P, Cu were moderate while those of Zn, Fe, K were abundant. In the vertical direction, organic matter, S, I, Se, N, P enriched while B and Mo lacked in the topsoil.Testing of irrigation water and drinking water in the area indicated: the irrigation water was out of pollution, with low contents of heavy metal elements in the mud, which satisfied the quality standard of irrigation water; the drinking water suited the drinking water quality standard in general.By testing the dust and rain in the area, it indicated: the quality of air in most places was good, only a little part of area with As, Cr, Hg, Pb a little high; the rain in some parts was acid sometimes.Through testing plants and the soil around the root in this area, it indicated as follows: rice and maize, whose As, Cd, Hg, Pb contents were lower than the value of pollution-free food standard, were safe foods; tuber mustard generally suited the safety food standard, but with two samples having Cd content a little high. In the soil of cultivation area, content of Cd in some parts was a little high. In the background environment, rice and maize had strong ability to enrich Zn, Se, I and Cu, while tuber mustard had high enrichment coefficients of Cd, Ca, Se, Zn.