Investigation And Configuration Analysis Of Heavy Metals Pollution In Wasted Lead Smelting Plant Site

A wasted lead smelting plant is located under the normal water level of a planned reservoir. To protect the water supply safety of the reservoir, this paper takes the site soil of the abandoned lead smelting plant as the research object to investigate and evaluate the pollution statue of heavy metals, thus to provide the basis for soil remediation of the contaminated site.According to the distribution of the contaminated site, eight mixed soil samples were collected and the total content of eight heavy metal elements（lead, cadmium,arsenic, mercury, zinc, nickel, chromium, copper） in the soil were determined. Based on the primary standard value of the " Environmental quality standards for soils"（GB15618-1995）, the major heavy metal pollution elements in soil were determined.At the same time, the main sources of heavy metals were analyzed by pearson correlation analysis, and the soil pollution characteristics of the site were identified by leaching procedure of sulphuric acid & nitric acid and pure water method. In the evaluation of soil heavy metal pollution in the site, the pollution status of heavy metals in soil was evaluated by single factor index method and the ground accumulation index method by taking the soil environmental background of Henan province as the reference, and the potential impact of heavy metals on the soil ecological environment of the site was analyzed by the potential ecological risk assessment method. At last, the distribution of heavy metals in the field was studied by XRD technology, based on which, the leaching property of major heavy metals was analyzed. The main conclusions of this study were as below:（1）The main pollution elements of the site soil were cadmium, lead, arsenic and mercury, and the biggest overweight multiples were 34.6 times, 3.8 times, 0.4times and 0.24 times respectively. While the other heavy metal elements zinc, nickel,chromium and copper were not exceed the standard; The correlation analysis of variation coefficient and element content showed that lead, arsenic, mercury and cadmium were exogenous pollution, and their sources were consistent;（2）The results of pure water leaching show that the site soil was a risk towater quality of the planned reservoir, so the site soil must be remediated. When the landfill process is used to repair the site soil, with the soil was not hazardous waste and was similar to the heavy metals pollution of category I of general industrial solid wastes, therefore, it can be handled according to the category I of general industrial solid waste.（3）The results of three different evaluation methods all showed that, the most serious pollution element is cadmium which grade is extremely serious pollution grade, Followed by lead, arsenic, mercury, and zinc, copper, nickel, chromium were lighter pollution grade.The highest pollution level of sampling points were2-1,followed by 1-1, 2-2, 3-1, and 3-3, 3-4, 2-3 and 3-2were relatively lightest.Overall,the assessment area was polluted seriously by heavy metals,and the pollution degree was reduced with the increase of distance to the pollution source of the wasted lead smelting plant.（4）In the site soil, lead mainly existed in the form of boulangerite(Pb₅S₁₁Sb₄)and jordanite(Pb₁₄As₆S₂₃), and cadmium existed in the form of spinel(Ga-_--2Cd_0.75 Cu_.025O₄). Since the solubility of cadmium oxide and lead sulfide are below the detection limit, and the terminal p H of sulphuric acid & nitric acid leaching solution was 5-6, cadmium and lead below the detection limit in the pure water and sulphuric & nitric acid leaching was not effectively detected. Arsenic mainly exists in the urusovite（Cu Al As O₅）and jordanite(Pb₁₄As₆S₂₃). As₂S₃ can obtain the effective leaching within the detection limits in pure water and sulphuric & nitric acid. While arsenic sulfide can only get effective leaching in the sulfuric acid, the leaching concentration of arsenic in the sulphuric & nitric acid is higher than that in the pure water.