Analysis of Heavy Metal Contamination, Distribution and Sources in Agricultural Soil of Yellow River Irrigation Area

ABSTRACT Heavy metal (HM) pollution in irrigated agricultural soil seriously affects the soil ecosystem, food security and human health. To investigate the HM pollution level, ecological risk, distribution and source in agricultural soil in the Yellow River Irrigation Area, 117 soil samples were collected from the farmland of Helan County, and the concentrations of HMs arsenic (As), cobalt (Co), chromium (Cr), molybdenum (Mo), nickel (Ni), lead (Pb), cobalt (Co), zinc (Zn) and cadmium (Cd) were measured. The single‐factor pollution index ( P i ), Nemerow comprehensive pollution index ( P c ) and potential ecological risk index ( RI ) were used to evaluate the pollution and accumulation characteristics of soil HMs. Then, the positive matrix factorisation (PMF) model was used to analyse the sources of the eight HMs. The results showed that (1) the mean contents of Pb, Ni, Co, Cr, As, Mo, Zn and Cd were 17.16, 39.51, 14.80, 69.19, 21.30, 0.90, 64.35 and 0.23 mg/kg, respectively, which were lower than the soil pollution risk screening value in soil environmental quality in China. (2) The trend of the mean values of P i for the eight elements was Pb < Ni < Zn < Cr < Co < Mo < As < Cd. As shown by P c , 72.65% and 25.64% of the sample sites indicated mild and moderate pollution, respectively. Through RI , it could be seen that 51.28% and 48.72% of the sample points showed moderate and strong ecological risk, respectively. (3) The PMF model indicated that Cr, Ni and Cd were mainly from agricultural sources, contributing 33.0%, 32.6% and 50.3%, respectively; the sources of As and Zn were mainly from atmospheric deposition sources, contributing 44.5% and 35.8%, respectively. Mo was mainly from industrial sources, contributing 80.9%; and Co and Pb were mainly from natural sources, contributing 45.1% and 64.5%, respectively. Overall, HM elements in the farmland of Helan were within the safe range, but more than 70% of HMs in the soil of the research area could be traced back to human activities. The results could provide data support to prevent and control HM pollution in soil and ensure food security and agricultural sustainable development in the Yellow River Irrigation Area.