Field Trials For Chemical Regulation Of Heavy Metal Contaminated Soils

The cultivated soil of China have been polluted seriously by heavy metal, and this problem seriously threats the safety and healthy of our people. Heavy metal pollution has a wide range of area, long enduring time, easy to accumulate in plants and animals and harm to human's health. Remedy of contaminated soils has always become one of the hot topics and the key issues of today's environmental pollution prevention in society, and also is the focus of attention of many scientists. Added amendments into the pollution soil to reduce the activity of heavy metals in the soil, reduce crops absorbing heavy metals, is an effective way to remedy of heavy metal polluted soil.The subject established an experimental base for this subject in the typical pollution area of heavy metal contaminated soils, through a large number of field trials, to study the effects by using calcium magnesium phosphate (FCMP), peat, sepiolite, lime. Moreover, planting the common crops which adapted to the local environment, such as soybeans, rice, sweet potato, cabbage, to study the law of the cumulative distribution of heavy metals in plants and explore the best type of amendments and fertilizer ratio. Mainly the following conclusions:(1) Through the BCR extraction experiments under different soil conditions, amendments can effectively reduce the high bioavailability of acid extractable fraction Cd contents in crop, so that conversion to low-bioavailability form. The ordering of four amendments according to reduce Cd acid extractable fraction is FCMP>sepiolite>lime>peat, the effects of reduce Cu acid extractable fraction is FCMP>sepiolite≈lime≈peat, the effects of Zn acid extractable fraction is FCMP>sepiolite>peat>lime. Moreover, the effects by applying amendments to Cd acid extractable fraction are paddy field greater than the dry land, and transformed into the extract and residual reducible.(2) All the four kinds of amendments can reduce the content of heavy metals in plants, the best effects to reduce the Cd content in rice or sweet potato tubers, soybean grain of Cd and Cu content, cabbage of Cd, Cu and Zn content is FCMP, second is sepiolite. The best effect to reduce Zn content of soybean grain is peat, second is sepiolite. The correlation analysis showed that there is a significant relationship between the content of heavy metal in the crop, the available of soil and the content of acid extractable fraction. So reduce the content of the activities of heavy metals is the key to reduce the content of heavy metal in plants. The content of bioavailability of heavy metal is a primary evaluating indicator for levels of pollution.(3) FCMP and peat or sepiolite using on Chinese cabbage are the best to reduce the content of heavy metal. The order of the best treatment to reduce the Cd is FCMP≈FCMP+peat>FCMP+sepiolite, reducing the best effect for Cu, Zn is FCMP≈FCMP+sepiolite>FCMP+peat. In engineering applications, the cost of the FCMP is higher than peat and sepiolite. Using peat or sepiolite together with FCMP can ensure the significant effects; also can reduce the cost and the risk of secondary pollution of phosphorus.(4) The accumulation volume of heavy metals in the organ of the metabolism is bigger. Nutrient storage organ was less, such as fruits and seeds. The distribution order of heavy metal in soybean is leaf> stem> grain, the rice is straw> rice, the sweet potato is leaves> tuber.