Study On Immobilization Remediation And Soil Enzyme Activities Of Lead-Zinc Mine Tailings

In recent years, the problem of soil heavy metal pollution to the environment was increasingly prominent. China’s Total Dietary Study (CTDS) have shown that heavy metal pollution in China has a huge potential harm to human health. The 12th Five-year plan put forward the management of heavy metal pollution of soil, which is imperative. Soil incubation experiment and pot experiment were conducted to compare the influence on physiochemical properties of soil, soil enzymatic activities and phyto-availability,which were tested on the soil of lead-zinc mine tailings of Huanjiang river basin in Hechi, Guangxi. The organic material of silkworm excrement, coconut chaff and inorganic material of red mud, sepiolite were used as chemical passivators. The major research results are as follows:(1) The soil pH value had been significantly improved after adding red mud and silkworm excrement, which belong to alkaline substances. The effect of composite passivator of them were extremely striking. Coconut chaff slightly reduced the soil pH value, but the influence of sepiolite on soil pH value was not significant. The content of soil organic matter were greatly improved after adding silkworm excrement and coconut chaff,which are rich in organic matter, improving the soil quality.The result of Toxicity Characteristic Leaching Procedure(TCLP) showed that the content of TCLP extraction condition of lead and zinc with single organic material was lower than single inorganic material, and the content of TCLP extraction condition of lead and zinc with composite materials were lower than the single materia. The effect of the best on reducing weak acid soluble lead and zinc were silkworm excrement and red mud-silkworm excrement,respectively, and red mud-silkworm excrement composite treatment had the best effect on increasing the content of residual Pb and Zn.(2) Among all treatments, silkworm excrement and its composite passivators had significant effects on urease activity, this may be related to three kinds of treatment just ranged soil pH value of application on urease. The sucrase activity were recoveried best when added coconut chaff. All composite treatments had activated effects on sucrase activy. Catalase activity improved significantly after adding amendments. Therefore, improving soil pH value within a certain scope, increasing the content of organic matter and reducing the available heavy metals state can effectively restore soil enzyme activities.(3) The results of Brassica Chinensis L. pot experiment showed that Chinese cabbage grew in soil added composite passivators were better compared with added single passivator, and passivation effect were high pH materials better than low pH materials. The treatment of silkworm excrement and its composite passivators had the best effect on inactivating heavy metal lead and zinc, and the content of heavy metals in Chinese cabbage vivo were the lowest. It also improved Chinese cabbage production the most obviously. But the Chinese cabbages were still not safe to eat even after soil had been dealt with, it suggetion that plant some economic crops of non-edible or high resistance to heavy metal instead.(4) The correlation analysis showed that, increasing soil pH value and the content of soil organic matter of soil can reduce the content of weak acid soluble Pb and improve the content of residual Pb in a certain extent, and then reduce the mobility and biological effectiveness of heavy metal Pb. But the real soil are not just influenced by soil pH or organic matter, the complexity of soil and multiple factors are needed to consider in practical application.