Pollution Risk of Heavy Metals to Soil after Sewage Sludge Land Application

Land application is an important way for treatment of sewage sludge both in China and the world.Many domestic and foreign studies about the effect of sewage sludge land application on the soil were analyzed and summarized.The results showed that the heavy metals in the sewage sludge could migrate to soil after its land application.However,most of the heavy metals were accumulated in the topsoil.The heavy metals could be redistributed in the soil upon entry,which would result in an increase in the contents of available heavy metals.There was no pollution risk to soil if the sewage sludge was applied for a short period with a small quantity.The conclusion that sewage sludge land application for a long period could lead to heavy metals pollution to the soil did not accord with China's case.The quantities of sewage sludge application and the concentrations of heavy metals in sewage sludge were notably higher abroad.In China,there is lack of study on the long-term effect of sewage sludge land application on the potential pollution risk of heavy metals.Study on this field should be strengthened urgently.