Distribution And Influence Of Heavy Metals In The Soil-vegetable System Around Different Enterprises In Nanchang Area

This paper selected the soil-vegetable system which was around four kinds of enterprises in six plants, such as chemical industry, iron and steel, electroplating and plastic in Nanchang area, as the research object. Some physical and chemical properties of the soils, such as pH, organic matter, available phosphorus and heavy metals content were analyzed. The statistical and GIS software were used to study the pollution and spatial distribution of heavy metal in soils with small interval around different plants. Also, heavy metal content in vegetables, the transformation and impact factor in the soil-vegetable system around different plants were analyzed. The main results are described as follows:1. Compared to the second grade standard in the Chinese Environmental Quality Standards for Soils, Cd concentrations in all test soil samples exceeded the standard. At the same time, Cu and Zn concentrations in the soils also exceeded the standard in some plants. Among them, Cu concentrations of 17.4% soil samples around Chemical industry had exceeded the standard. Cu concentrations of 19.2% and Zn concentrations of 65.4% soil samples around iron and steel enterprises had exceeded the standard. Both Cu and Zn concentrations of 43.8% soil samples around electroplating enterprises had exceeded the standard. Cu concentrations of 60% and Zn concentrations of 50% soil samples around plastics enterprises had exceeded the standard. Pb content of all the soil samples did not exceeded the standard. The soil pollution degree was in order of electroplating enterprise> iron and steel enterprises> plastic enterprise> chemical enterprises.2. The correlation analysis result of Cu, Zn, Pb and Cd in the test soils showed that the four heavy metals were significantly related to each other. Their homology was good. Principal component analysis results showed that the main influence factor to the test soil environmental quality was factitious heavy metals from human activity, which was followed by the natural background characters of the soil such as pH and the land use. The spatial analysis results showed that the spatial distribution of basic physical &chemical properties and heavy metals of soils were good. The highest concentration appeared at the south-east direction. Heavy metals in the region had reached heavy accumulation. May be industrial production and atmospheric pollution were the main factors. 3. The results of morphology analysis of soil samples from soil-green vegetable system (n=32) showed that: the main fractionation of the four heavy metals were the residual form and Fe-Mn oxide combined form, and the next were carbonate combined form and exchangeable form. The last was the organic combined form. Except the residual form, the other four forms absorbed easily by plants were named as the potentially harmful forms. The most potential harmfulness element was Pb.4. According to the Hygienic standards for food (vegetable) security of P.R. China, the vegetables were mainly contaminated by Zn and Pb. And some of the samples were also contaminated by Cd. Among them, Pb concentrations of 9.09% vegetable samples around Chemical industry had exceeded the standard. Zn concentrations of 12.5% and Pb concentrations of 6.25% vegetable samples around iron and steel enterprises had exceeded the standard. Zn concentrations of 13.3% and Cd concentrations of 6.7% vegetable samples around electroplating enterprises had exceeded the standard. Zn concentrations of 30% and Cd concentrations of 20% and Pb concentrations of 40% vegetable samples around plastics enterprises had exceeded the limit. So, the degree of pollution was in the order of plastic enterprise > electroplating enterprise> iron and steel enterprises> chemical enterprises.5. The contents of Zn, Pb and Cd between the green vegetable and the soil samples showed significant positive correlation. The correlation between the contents of Cu, Zn, Pb and Cd in green vegetable samples and the contents of soil chemical extraction were significant. And the citric acid (0.1mol / L) was tested to be the best chemical extraction for those tested soils.