Migration Characteristics Of Cu、Cd In Municipal Sludge Amended Soil

Municipal sludge is rich in organic matter and nutrients for plant growth such as N, P、K and different kinds of trace elements, which are lack in loess, so municipal sludge can be used as fertilization to supply these nutrients for loess. At the same time, it is one of the effective ways to dispose sludge. This article applied municipal sludge into the loess, it was referred to as municipal sludge amended soil. On the one hand, a adsorption-desorption experiment was carried out to investigate the ability of municipal sludge amended soil holds Cu, on the other hand, with the test of growing plant in pot to study migration characteristics of Cd in municipal sludge amended soil-plant ecosystem. The main conclutions are as follows:(1) In the designed concentration range of Cu(0-400 mg·L-1), the adsorption capacity for Cu of the amended soil that municipal sludge and loess were mixed in certain ratio were all reached the maximum, and the higher proportion of municipal sludge in amended soil, the higher maximum adsorption of Cu by amended soil; Under the same adsorption quantity, the amended soil that with higher proportion of municipal sludge, its desorption amount is smaller. This showed that:the amended soil that with higher proportion of municipal sludge, the adsorption capacity of Cu is higher. So when the municipal sludge was applied in loess, the Cu fixation capacity of loess is intentive, and lowers the activity of Cu.(2) pH of the amended soil with municipal sludge was less than that of loess, as the application of municipal sludge, organic matter content, EC, nitrogen content of the soil amended with municipal sludge rose 31.8%,35.9%,11.5% than that of loess. These improved that municipal sludge can supply nutrients for plant growth. Contents of Cu、Zn、Pb、Ni、Cd in the amended soil with municipal sludge were increased, but they were less than the threshold of soil contamination.(3) Under the same processing concentration of Cd, the wheat in the amended soil with municipal sludge, their emergence rate, plant height, dry weights of root, dry weights of stem and leaf, dry weights of ear, output are all higher than that of loess, dry weights of ear rose 59% than that of loess. Hence it may be concluded that:the 0.5% content of municipal sludge may promote wheat growth.(4) As the application of municipal sludge, exchangeable Cd content decreased of 0.2309 mg/kg, but carbonate-bonded Cd content, Fe-Mn oxides bound Cd content and organic Cd content increased of 0.3320 mg/kg,0.06 mg/kg and 0.0029 mg/kg, residual Cd content decreased of 0.1033 mg/kg. Considered the soil environment of this research, draw a conclution that: as the application of municipal sludge, the activity of Cd was enhanced.(5) As the application of municipal sludge, Cd contents in stem and leaf, shell and grain were all higher than that of loess, the application of municipal sludge promoted accumulation of Cd in aerial part of wheat. Therefore, apply municipal sludge in farmland may lead to serious health risks.