Metal Contamination in Sediment of One of the Upper Reaches of the Yangtze River: Mianyuan River in Longmenshan Region,Southwest of China

Metal contamination in sediment of the Mianyuan River (one of the major upper reaches of the Yangtze River) in Longmenshan Region (China) was investigated in 2012. Means of metal concentrations in sediment (<74μm) were Cr: 59.93 ± 19.8% mg/kg; As: 7.21 ± 50.2% mg/kg; Se: 0.45 ± 66.3% mg/kg; Pb: 19.89 ± 29.3% mg/kg; Zn: 78.98 ± 31.9% mg/kg; Cd: 0.69 ± 28.3% mg/kg; Ba: 0.71 ± 34.0% g/kg; Mn: 0.55 ± 62.2% g/kg. This study suggested: (1) concentrations of Cd, As, Cr, and Pb in Mianyuan River sediment were lower than those of the middle and lower reaches of the Yangtze River; (2) the increase of metals during the period from 2006 to 2009 was probably related to the destruction of tailings piles by the Wen Chun earthquake in 2008; (3) organic materials decided the distribution of Cd, Se, As, Ba, and Mn in the upstream sediment, while the iron and manganese minerals controlled the distribution of Ba, Cr, and Zn in the downstream sediment; (4) sources of Cd, Se, and As were geogenic, while sources of Cr, Zn, Ba, and Mn were anthropogenic; (5) the source of Pb in the upstream sediment was probably automobile exhaust, but that of Pb in the downstream sediment was geogenic.