Ecological risk assessment and source tracing of heavy metals in surface sediments of a hilly riverine reservoir in Chongqing, China

Background This work conducted quantitative and qualitative analyses on the heavy metals in 32 surface sediment samples collected from eight sampling sites across four seasons in the Yutan reservoir, a typical mountainous hilly riverine reservoir in Southwest China. Results Nine heavy metals were identified: (Cr, Cd, Pb, Cu, Zn, Hg, As, Ni, and Co). The concentrations varied within the ranges of 23.16 ~ 34.62, 0.53 ~ 1.09, 31.88 ~ 59.04, 51.94 ~ 85.84, 106.76 ~ 227.69, 0.08 ~ 0.15, 12.57 ~ 25.60, 12.06 ~ 27.64 and 11.04 ~ 14.56 mg/kg, respectively, following a decreased concentration order of Zn > Cu > Pb > Cr > Ni > As > Co > Cd > Hg. Except for Cd, which accumulated in winter, and Hg, which reduced in spring. The concentration of heavy metals showed no significant seasonal variation and generally had higher contents at the river mouth and lower concentrations in open water areas and branches. The geoaccumulation index ( I geo ) assessment also indicated that the reservoir was uncontaminated by Cr and Ni ( I geo