Spatial distribution and potential ecologic risk assessment of heavy metals in the sediments of the Nansi Lake in China

The contamination levels and ecological risks of heavy metals in the sediments of the Nansi Lake were investigated. The contents of Cd, Cr, Cu, Pb, Zn, Ni, and Co in the surface sediments collected at 20 sites ranged from 0.08 to 1.12, 58.92 to 135.62, 38.09 to 78.65, 24.51 to 53.95, 110.51 to 235.36, 11.30 to 65.40, and 4.12 to 20.14 mg/kg, respectively. The results of partitioning analysis revealed that the proportions of soluble and exchangeable fraction were less than 1 %, the proportions of carbonate, amorphous oxides, organic matter, and crystalline oxides fraction were less than 10 %, and 10.52 % of Cd was associated with carbonate. The average proportions in the residual fraction ranged from 48.62 % for Cu to 73.76 % for Ni, indicating low mobility and bioavailability. The geoaccumulation index (I _geo), relative enrichment factor (REF), sediment pollution index (SPI), and potential effect concentration quotient (PECQ) values of the heavy metals in the sediments were not in agreement with each another. The average REF values of Cd and Zn were higher than those of other metals. However, the average PECQ values were higher for Cr and Ni than those of other metals, indicating that these two metals would cause higher adverse biological effects. Therefore, it is suggested that future management and pollution control might focus on Cd, Zn, Cr, and Ni in the sediments of the Nansi Lake.