The Pollution Status And Health Risk Assessment Of Heavy Metals From The Sewage-irrigated Wheat And Corn In Shijiazhuang

Objective: To explore the impact of different irrigation methods, including sewage, groundwater and mixed groundwater with sewage, on the contents of heavy metals in crops, and to analyze and evaluate the pollution levels and human health risks for Cu, Zn, Cr, As, Cd, Pb and Hg in wheat and corn from sewage irrigation in Shijiazhuang. This can offer a scientific basis for reducing the contamination of crops and carrying on safety evaluation.Methods:1 Sample collectionCollecting wheat and corn from farmer’s home, within 5km along the drain in Luancheng. To ask the type of irrigation and number the samples.2 Sample pretreatmentThe samples were packed in the bags with the labels after air-dried and sample grinding. The wheat and corn were taked the wet digestion by HNO3-HCl O?.3 Sample determinationContents of Cu, Zn, Cr, As, Cd and Pb were measured by ICP-MS, Hg by an Automated mercury analyzer.4 Sample analysisWhile classifying crops by different irrigation methods, that is sewage, groundwater and mixed groundwater with sewage. Applying one-way ANOVA to analyze the differences among heavy metals because of irrigation methods. We can use the single and comprehensive pollution index to analyze the heavy metals contamination of crops. Learning from the U.S. Environmental Protection Agency(USEPA) recommended risk assessment models of health risk assessments for adults and children. While the comprehensive evaluation was measured in principal component analysis.Results:1 The exceeding rate of heavy metals in cropsThe rates above standard values for Cr and Pb in wheat were 100%, those of Zn, As and Cd were 96.23%, 92.59% and 24.07% respectively; Cu and Hg were not exceeded. The rates above standard values for Cd, Pb, As and Zn in corn were 96.0%, 92.0%, 66.7%, and 12.5%, respectively. Cu, Cd and Hg were not exceeded.2 The analysis of differences among heavy metals in wheat and corn from different irrigation methodsThe contents of Zn and Cd in wheat from sewage irrigation were higher than those from mixed groundwater with sewage and groundwater irrigations(P<0.05).The contents of Cu, Cr, As, Pb and Hg were not changed obviously from different irrigation methods(P>0.05); In corn, the contents of Zn from groundwater irrigation was lower than those from mixed groundwater with sewage and sewage irrigations(P<0.05), others were not significantly different(P>0.05).3 The single and comprehensive pollution index evaluationThe single pollution index for wheat were followed by the order of: Pb>Cr>Zn>As>Cd>Cu>Hg, the values were 3.32, 2.08, 1.61, 1.27, 0.78, 0.71, 0.08, respectively. And those for corn were: Pb>Cr>As>Zn>Cd>Cu>Hg; 2.28,2.14,1.20,0.82,0.38,0.25,0.12, respectively.Among them,the single pollution index of Pb in wheat were greater than 3, it have reached the heavy pollution levels. The comprehensive pollution index of wheat and corn were greater than 1, the values were 2.59 and 1.54.4 The health risk assessment for adults and childrenThe average daily dose for adults and children showed that Zn is the largest, following Cu and Hg is minimum. The average daily dose of carcinogenic heavy metals(Cd, As) for adults were greater than those for children besides in wheat, other values showed children less than for adults. About health risk assessments, the carcinogen of arsenic and cadmium were much higher than other non-carcinogens, but within the maximum acceptable level of risk(non-carcinogenic:7 ? 10-5, carcinogenic: 3.5 ? 10-3).5 The comprehensive evaluation of different irrigation methodsTo evaluate three kinds of irrigations effected on the content of heavy metals in crops.In wheat, the order is sewage>mixed groundwater with sewage > groundwater, the corn is mixed groundwater with sewage >groundwater>sewage.Conclusions:1 The pollution index of wheat was higher than that of corn. That is moderate and light pollution. The pollution of Cr and Pb were more serious than other heavy metals in wheat and corn.2 The contents of Zn in wheat and corn, Cd in wheat from sewage irrigation were higher than those from groundwater, mixed groundwater with sewage.3 In wheat, the health risks were higher than in corn. As and Cd were greater than Cu, Zn, Cr, Pb and Hg. The non-carcinogen risk assessments for children were more than adults. The carcinogen risk assessments for adults were higher than children.4 In wheat, the degree of heavy metal pollutions was followed by the order of sewage>mixed groundwater with sewage>groundwater, while corn was not distinct.