Health risk assessment of heavy metal of different treatments for roots and straws of crops in wastewater irrigation area

In order to evaluate the health risk of different treatments for roots and straws of crops in Tianjin wasterwater irrigation areas, authors estimated contents and distribution patterns of Cd, As, Pb, Cu, Zn in crops respectively. The contents of heavy metals in roots were more than those in stems. Health risks caused by returning field, burning and returning field plus burning of crops roots and straws were evaluated by using the environmental health risk assessment model. The contents of heavy metals in roots were higher than those of straw. For returning filed, the combined carcinogenic hazard index for child and adult were 6.08×10-9 and 1.95×10-8, respectively, and the combined noncarcinogenic hazard index were 1.01×10-5 and 6.45×10-6, respectively. It resulted negligible health risk for people. However, for burn treatment, the combined carcinogenic hazard index for child and adult were 2.89×10-8 and 4.67×10-8, respectively, and the combined noncarcinogenic hazard index were 1.76×10-3 and 9.43×10-4, respectively. The combined carcinogenic hazard index for child and adult were 2.05×10-8 and 4.28×10-8, respectively, and the combined noncarcinogenic hazard index were 8.88×10-4 and 3.78×10-4, respectively for returning filed plus burning. The noncarcinogenic hazard was unacceptable for burning or returning field plus burning. Considering large amount of heavy metals in crop straws, the top-priority treatment are suggested by returning field, then carefully considered by burning. These results made scientific suggestions for agricultural solid waste management.