The Contamination Assessment And Stability Analysis On Heavy Metals In Minerals From Soil, Dabizhuang, Dongli District, Tianjin

The main mineral composition of soil, include a large number of clay minerals, as well as natural iron-manganese oxides and aluminum hydroxide, silicon oxide, carbonate minerals and so on.A large number of heavy metals are exist in these minerals, and distribute, migrate and transform between different minerals. Absorption and fixation of heavy metals by the minerals is the root of soil self-purification.This paper analyses soil contamination and the possible reasons of the study area - Tianjin dabizhuang areas. It educes the form distributing of heavy metals in minerals, and also further discusses its stability. I divided the soil into 7 grades, and used the X-ray powder crystal diffraction analysis method, semi-definite measured the mineral composition and content of the soil. Then I used the Chinese geology Investigation Bureau geological investigation technical standard to carry on the morphological analysis, and unified the heavy metals in mineral adsorption and the analysis rule, in order to definite the condition and the distributed situation of heavy metals in minerals. At last, I further discussed its stability by using the environment mineralogy theory and the method. What I did is also the evidence of using the mineral to handle metal pollution for future.After more than a year of experiments and analysis, there are some conclusions as follows:First, Reference to soil pollution standards constituted by State Environmental Protection Administration of China, the content of heavy metals in the soil in Dabizhuang are: Hg> Cd> Pb> Zn> Cu> Cr> Ni. Hg and Cd are the most serious pollution metals. other heavy metal elements are also exceed the highest standards of safety. the most polluted areas is near Tianjin second gasworks and around sewage river as well as sewage irrigation area. So we can conclude the major sources of pollution is atmospheric deposition and sewage irrigation.Second, It is positive correlation between the heavy-metal contamination and layered silicate minerals (Mica, chlorite), while it is negative correlation between heavy-metals and quartz , feldspar as well as other minerals. The result proved that the contamination are main exist in layered silicate minerals. Which own great layer domain, and it is conducive to the absorption of other substances.Third, through the analysis of the two typical elements of the pollution Hg and Cd, I found that Hg is mainly bonding adsorbed in the minerals, and mainly located in between the layers of clay minerals and mineral structure channels, which is relatively stable. Cd is mainly no bonding adsorbed or weak bonding adsorbed, and it mainly in the surface of minerals or mineral structure channels, so it is very unstable.Fourth, the pH value of soil in research area is around eight, and the elements Hg and Cd are more stable in the right weak basicity environment, so it is advantageous for this area to use minerals to remove the pollutions, and we may consider that we could get rid of the heavy metals by using mineral method.