Impact of domestic wastewater irrigation on heavy metal contamination in soil and vegetables

In this study, the impacts of domestic wastewater irrigation on the concentration of heavy metals such as lead (Pb), zinc (Zn), cadmium (Cd), and copper (Cu) in soil and vegetables were investigated by monitoring an experimental area irrigated with effluent from a domestic wastewater treatment plant. The risk of people consuming vegetables that may contain heavy metals was also assessed. Three replications were performed on 10 x 2-m test plots, and heavy metal concentrations in soil and vegetables were monitored from 2005 to 2007. The risks to human health from consuming vegetables containing heavy metals were assessed using the hazard quotient, which is defined as the ratio of average daily dose to the reference dose. The monitored results showed that the concentrations of Cu, Cd, and Pb in soil during the experimental period were lower than the initial soil levels before irrigation, whereas Zn increased. However, the ranges of Zn, Cu, Cd, and Pb in soils were below the soil pollution standards of the Republic of Korea. A risk assessment indicated that vegetables grown with domestic wastewater are safe for human consumption with respect to heavy metal concentrations.