Experimental investigation on heavy metal distribution in soil-crop system with irrigation of treated sewage effluent

Treated sewage effluent(secondary effluent) is becoming one of the important water resources for irrigation, especially in arid and semi-arid areas. Experiments of irrigation with treated sewage effluent were conducted from 2000 to 2004 in Yongledian irrigation experimental station, Beijing, China. During the period of experiments, fresh water and secondary treated sewage effluent were used for irrigation, respectively. The water quantity for each irrigation was about 450 m³/hm². With data sets of the four years' experiments, the distribution pattern of heavy metals in soil-crop system was investigated. Results indicated that no accumulation evidence of heavy metals was found in soils irrigated with treated sewage effluent, and the concentrations of heavy metals in crop seeds were found much lower than the critical values of Chinese National Standard. It therefore implies that short-term irrigation with treated sewage effluent cannot result in environmental hazard both in soils and field crops in the study area. Meanwhile, no significant difference can be detected for the contents of heavy metals in soils irrigated with different quantities of treated sewage effluent, and the recovery of heavy metals at harvest of winter wheat showed much higher than the total heavy metals added to the soils by irrigation with treated sewage effluent during the winter wheat growing season.