Objective To understand the pollution levels of heavy metals in surface sediments of the Huaihe River (Anhui Section), evaluate their potential ecological harm, and provide scientific references for water environment protection and restoration of heavy metal pollution in the Huaihe River.
Methods Samples of surface sediments were collected with grab samplers in 17 sampling sites of the Huaihe River (Anhui Section). Chromium (Cr), cadmium (Cd), copper (Cu), and lead (Pb) in surface sediments were tested by flame atomic absorption spectrometry, and arsenic (As) by atomic fluorescence. Geoaccumulation index and potential ecological risk index were applied to assess the ecological risks of the five heavy metals.
Results The mean levels (range) of Cr, Cd, Cu, Pb, and As in surface sediments were 69.12 (21.89-114.14), 6.61 (3.14-11.66), 51.73 (23.77-93.63), 46.54 (19.28-103.37), and 0.74 (0.16-2.57) mg/kg, 1.10, 78.97, 2.68, 1.79, and 0.09 times of the soil background values of Anhui, respectively, and the severity order of heavy metal pollution from high to low was Cd > Cu > Pb > Cr > As. The geoaccumulation index of Cd was the highest (5.72), indicating very high environmental risk. The indices of Cr and As were -0.44 and -4.08, respectively, indicating no environmental risk. The indices of Cu and Pb were 0.84 and 0.26, respectively, indicating low environmental risk. The potential ecological coefficients of Cr, Cd, Cu, Pb, and As were 2.30, 396.56, 8.62, 9.31, and 0.50, respectively, with a high-to-low order of Cd > Pb > Cu > Cr > As. The comprehensive ecological indices of the five heavy metals of different sampling sites ranged from 197.65 to 738.58, and the mean was 417.30. The sampling sites showing medium, strong, and very strong ecological risks account for 18%, 59%, and 23% of total, respectively, and the comprehensive potential ecological risk was strong.
Conclusion The average levels of heavy metals, except As, in surface sediments of the Huaihe River (Anhui Section) are higher than the soil background values of Anhui Province, showing varied degrees of pollution, especially Cd. Both geoaccumulation index and potential ecological risk index indicate that Cd has the highest potential ecological risk.
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