Comprehensive analysis of mercury pollution in the surface riverine sediments in the Haihe Basin, China

The Haihe Basin extends over 318,000 km² or 3.3% of the total area of China, has a population of over 120 million, and is one of China's most polluted river basins. We investigated the pollution and risks from mercury (Hg) in surface riverine sediments of this basin and found that total Hg concentrations in surface sediments ranged from 0.001 to 1.05 mg/kg and averaged 0.054 mg/kg. Using the modified European Community Bureau of Reference standard method, we found that the exchangeable/acid-soluble, reducible, oxidizable, and residual fractions of Hg accounted for 9.86, 6.54, 11.0, and 72.6% of total Hg, respectively. The riverine sediments in the Da Qing He watershed had the highest anthropogenic enrichment of Hg (enrichment factor >1.5). There was a high potential ecological risk from Hg in the riverine sediments in the upper reaches of the Bei San He and Da Qing He watersheds, the middle reaches of the Luan He and Hei Long Gang watersheds, and the lower reaches of the Zi Ya He watershed. Comparison with risk assessment code showed that the riverine sediments in the Da Qing He, Luan He, and Tu-Hai Ma-Xia He watersheds represented a medium risk, with 16.6, 11.9, and 11.8% of Hg in the exchangeable/acid-soluble fraction, respectively.