[Distribution and health risk assessment of heavy metals of groundwaters in the irrigation district of the lower reaches of Yellow River].

In order to investigate the contamination levels of groundwater in the irrigation districts of the lower reaches of Yellow River, fifty-nine groundwater samples collected from the irrigation districts of Henan and Shandong provinces, were analyzed. Health risks associated with eleven metals (Ba, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se and Zn) were assessed using water pollution index and USEPA health risk assessment model. The average concentrations of Fe with 0.496 mg x L(-1) and Zn with 0.445 mg x L(-1) were higher than the concentrations of other heavy metals. Concentrations of Fe, Mn, Se and Zn exceeded the relevant standards and the over-standard rates by 27.12%, 27.12%, 15.25% and 5.09%, respectively. Inverse distance weighted method was applied to estimate the unobserved points and their distribution maps were obtained, which indicated that areas of over-standard heavy metals were Wucheng country, Fan country, Dong'e country, Yucheng city and Guan country. Health risks of ingestion of water for all non-carcinogenic metals are higher than those of dermal absorption, while health risks of ingestion of water for carcinogenic metals is lower than those of dermal absorption. Among the health risks caused by the carcinogenic metals in drinking water and dermal absorption, the highest risks associated with Cr, are seven times and twenty-eight times as that of Cd, respectively, but both were significantly lower than the maximum allowance levels recommended by ICRP (5 x 10(-5) a (-1)). The non-carcinogenic metal risks( Ba, Cu, Fe, Mn, Mo, Ni, Pb, Se and Zn), ranging from 1.73 x 10(-13) to 3.46 x 10(-10) a(-1) in dermal absorption and from 1.13 x 10(-9) to 6.06 x 10(-8) a(-1) in drinking water, were much lower than the maximum allowance levels.