Experiment Research Of Heavy Metal Pollution In Environmental Impact Assessment Of Lead-Zinc Mining Activities

In the environmental impact assessment of lead-zinc mine development project, to find out the approach of Pb, Zn and other heavy metals join into the environment, quantify the pollution sources which are heavily, evaluate its degree of pollution, which is the key to judge the feasibility for environment of the project. It often uses the analogy, the material balance analysis and other technical means to analyze the original data and carry out the assessment in actual evaluation work that reach to the mentioned problems which lack empirical basis about the key data. This paper aimed to find out the activities of heavy metals such as Pb and Zn in pollution sources by carry out ore dressing experiments and balance of heavy metals analysis, tailings and waste rock of the acid leaching experiment, simulated rainfall leaching experiment which selected a lead-zinc mine development project for research. This paper attempted to provide important experimental data which can make evaluation more scientific and point out the reference method for lead-zinc mine the environmental impact assessment.The main research results were as follows:As elements balance analysis for small dressing closed-circuit test of Pb, Zn, Cu, Cd and As, it showed that the enrichment of Pb and Zn in the ore is mainly to the lead concentrate and zinc concentrate. Compared with mine ore, the enrichment ratio about Pb and Zn were about32.633and32.460respectively, and about1/3and1/2in zinc sperm tailings and1/8and1/13in zinc scavenging tailings to mine ore, while the total tailings about1/7.5and1/12to mine ore. Cu mainly enriched in lead concentrate and the enrichment ratio was about22.571. It was equal in zinc sperm tail and ore, and about1/4in the tailings to mine ore while the total tailings about1/3.5. Cd mainly enriched in zinc concentrate and zinc sperm tailings, the enrichment ratio about20.909and10.000respectively, and it was smaller slightly in zinc scavenging tailings to mine ore while the total tailings about a quarter. As mainly enriched in zinc concentrate and zinc sperm tailings, the enrichment ratio about17.200and22.000respectively, and about1/6.25in zinc scavenging tailings to mine ore, while it enriched in the total tailings about5.400times. As the contents of heavy metals and metalloid about Pb, Zn, Cu, Cd and As in zinc sperm tailings were higher than in zinc scavenging tailings and total tailings, in order to reduce the risk of heavy metals into the environment, the need of processing zinc sperm tailings accordingly before discharge to the tailings is necessary.Carry out chemical analysis for carbonate and silicate in the alkaline minerals of mineral sulfide minerals, the results showed that the main enrichment sulfur minerals to concentrate, while tailings mainly enriched about carbonate and silicate alkaline minerals, with the pH values of tailings was above7.5, so that tailings itself did not produce acidic mine drainage.Acid leaching toxicity test of tailings and waste rock with evaluation of tailings ecological risk level, it showed that tailings and waste rock did not belong to the hazardous waste. However, the ecology harm coefficient and ecology risk index about Cd of tailings were tremendous as Pb, Zn, Cu and As following. So that we not only need to pay attention to the pollution of Pb and Zn in the lead-zinc mine acquisition, but also more to Cd about it’s pollution hazard and risk of ecological environment.In order to explore the release characteristics and their influence factors of main heavy metals in mineral above-mentioned under water or simulated rainfall, this study carried on the static simulation experiment and dynamic simulation rainfall leaching experiments of tailings and waste rock. Results showed that the pH value of soaking had evident effect on the heavy metals ion releasing, and the stronger the solution acidity was, the more the Pb and Zn ions and dissolution rate would release. Zn ion was easier release than Pb ion as well as and the high temperature was advantageous to the dissolution of heavy metal ions, but the effect was not obvious. As K+and Na+with simulated rainfall could increase the leaching solution and promote the dissolution of minerals, heavy metals such as Pb and Zn could release quantity more by simulating rainfall than water under the same conditions.