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

Whether heavy metals can be enriched in crops after sewage sludge land application is a significant concern.By summarizing a large number of studies undertaken at home and abroad,it was found that the contents of heavy metals in crops did not exceed the agricultural products quality and safety standards adopted by different countries if the sewage sludge was applied for a short period.However,if large quantity of sewage sludge was applied for a long period,the contents of heavy metals in some crops exceeded those agricultural quality standards.Nevertheless,the conclusion that sewage sludge land application for a long period could lead to the heavy metals pollution to crops does not necessarily apply to China because the quantities of sewage sludge application [60 to 510 t/(hm2·a)] and the concentrations of heavy metals in the sewage sludge are notably higher abroad.