Study On The Farmland Soil Geochemica Characteristics Of Tongzi Town In Jiangan County, Yibin, China

The soil is a result of combining the actions of oxygen and microbe to erode the mother rocks, it also is the stockpile-storeroom and the exchange-storeroom of the farmland ecosystem nutrient cycle. Along with modern industrial development and human oneself activity's increases, a great lot of materials-bearing heavy metal elements, such as waste water, exhaust gas , waste residue,inorganic fertilizers, pesticide pullution and so on, is brought to the earth's surface environment and accumulated in the soil, it's not only destroyed agro-ecosystem, but also affected the security of agricultural productions and has brought a series of ecology problem.The geological environment is an important physical condition for agro-ecosystem and a carrier for the survival of crops. Through the geological and geochemical investigation mapping of soil, water and atmosphere quality in the soil consolidation zone, the project has found out the characteristics of dispersion and enrichment of element distribution in the soil; The understanding of the relevant geochemical indicators, distribution and migration law of elements, which can provide basic data and scientific basis for improving the land utilization, stipulation of fertilization scheme by testing soil formulation, optimization of harmless agricultural products and green food base, adjustment of the agriculture planting structure and ensure the safety of agricultural products . Through the implementation of this project, it can set an example for applying effectively the results of agro-geological environmental survey to soil consolidation, development of agricultural production and improving life quality of both urban and rural residents.The "Golden Land Project", which is a concrete project that the Sichuan provincial government carries out for implementation of the national policies concerning agriculture, countryside and farmers. This project is a comprehensive improvement project for improving filed, water, road, forest and residence of countryside , improving utilizing structure of land and conditions of production and living , recovering ecological environment, newly adding effective arable land and improving the quality, land-use ratio and output capability of them. The agro-geological environmental survey is an important and basic part for the research and study of this project and a basic work serving for the sustainable development of local economy.For this reason, the thesis studies the farmland soil geochemica characteristics of Tongzi Town in Jiangan County, Yibin, China. The study covers regional geological setting; soil mineralogy; soil element geochemistry; soil nocuousness element geochemica characteristics; geochemica appraises of the farmland soil quality and so on.Baced on analytical data and synthetical studies, some conclusions can be drawn as follows:①The mother rocks of the soil-forming are purplish red mud sandstone and siltpelite of the Suinin Group, and deep-grey feldspathic-debris sandstone of the Shaximiao Group.②The compositions of purplish red farmland soil is similar to the mother rocks it, but the rice soil is not so. The rice soil is poor CaO and Na2O, and enrich Cd, Hg and S.③The heavy metal element Pb, Ni, Cu, Cd is enrichment in the farmland soil, and poor N, P and organic matters.④The acidity-alkalinity of the farmland soil: pH=6.5～8.5 in the Paoshadatu area, the Huangnitian area; pH<5.5 in the Shatu area, the Shatian area.⑤Here, Cd is enriching in the soil and surpassing I level of the State farmland soil, so it is belong to II level of the State farmland soil.As a whole, due to heavy metal Cd in the topsoil of the study area surpasses the first class standard of soil environment quality, it makes the soil environment quality in the study area become the national second-level soil. In the summated evaluation, the soil quality of study area is excellent.Based on the agrogeological investigation subproject of the "Golden Land Project" - the land consolidation zone in Tongzi Town of Jiang'an County, Tibin City and through the geochemical methods, this paper studies the geochemical characteristics of the farmland in this area. It lays heavy stress on topsoil, lateral longitudinal profile soil and vertical section plane soil. The characteristics and distribution of soil macroelement, microelement, nocuousness element and mineral composition are analyzed.During one-year implementation of this project, we have carries out the works of surface soil sample of the study area, lateral generalized section, longitudinal (shallow well) profile, the dust-fall of atmosphere, water environment measurement and the plant sampling. In view of this paper laying stress on farmland soil, it doesn't involve the measurement results of dust-fall of atmosphere, water environment and plants. Through the test analysis of the collected soil sample, we have gotten comparatively profound knowledge about the soil macroelement, the microelement, the nocuousness element and other element and also understand the distributing characteristic and existing condition of them in the study area. It provides us a foundation for studying the soil quality.The agriculture geological investigation project of the land consolidation area in Tongzi Town of Jiang'an County, Yibin City is based on the spirit of No. 234 official letter of Sichuan people's government [2005], No. 150 official letter of the Sichuan provincial financial investments department [2006] and NO. 1256 official letter of Sichuan Municipal Bureau of Land and Resources [2006] and regulation on carrying out agriculture geological investigation work in the "Golden Land Project" area , Sichuan Geological Investigation Institution undertake this project. It provides financial aid for this study. This paper is under the instruction of Prof. He Mingyou.