Pollution and health risk assessment of heavy metals following repeated biogas slurry application in two vegetable fields

Repeated biogas slurry application in soil may cause accumulation of heavy metals. In the experiment, repeated biogas slurry application for 4 (N1) and 10 years (N2) in two vegetable fields, to detect heavy metal content (Zn, Cu, Cr, Pb) and assessment the risk of shortand long-term fertilizing on ecology and health. The result showed, long-term fertilization has increased the content of heavy metal. Zn and Cu in topsoil (0-20 cm) in field N2 exceed the standard, resulting in mild contamination. The value of hazard quotient ( HQ ) in the same land were as follows: Cr>Pb>Cu>Zn. In general, the noncarcinogenic risk and carcinogenic risk index in N2 were higher than those of N1. In the survey area, there was no noncarcinogenic risk and carcinogenic risk for adults and children. However, children are more sensitive to environmental changes than adults and should pay more attention to protect their health. Longterm monitoring and evaluation of heavy metal hazards is necessary to ensure the safety of biogas slurry used in farmland.