Tianrong He

Tracing Mercury Contamination Sources in Sediments Using Mercury Isotope Compositions

Mercury (Hg) isotope ratios were determined in two sediment cores collected from two adjacent reservoirs in Guizhou, China, including Hongfeng Reservoir and Baihua Reservoir. Hg isotope compositions were also analyzed in a soil sample collected from the catchment of Hongfeng Reservoir and three cinnabar samples collected from the Wanshan Hg mine. Baihua Reservoir was contaminated with runoff from Guizhou Organic Chemical Plant (GOCP) when metallic Hg was used as a catalyst to produce acetic acid. Hongfeng Reservoir, located upstream of Baihua, receives Hg from runoff and atmospheric deposition. We demonstrated that delta(202)Hg values relative to NIST 3133 of sediment in Baihua Reservoir ranging from -0.60 to -1.10 per thousand were distinctively different from those in Hongfeng Reservoir varying from -1.67 to -2.02 per thousand. While sediments from both Baihua and Hongfeng Reservoirs were characterized by mass dependent variation (MDF), only Hongfeng Reservoir sediments were characterized by mass independent variation (MIF). Moreover, by using a binary mixing model, we demonstrated the major source of Hg in sediment of Hongfeng Reservoir was from runoff due to soil erosion, which was consistent with the conclusion obtained from a previous Hg balance study. This study demonstrates Hg isotope data are valuable tracers for determining Hg contamination sources in sediments.

The concentration and distribution of different mercury species in the water columns and sediment of Aha Lake

In order to find out whether Aha Lake was polluted by the acid wasted mining water or not, the concentration and distribution of different mercury species in the water columns and sediment porewater collected from the Aha Lake were investigated. The concentrations of HgT ranged from 2.08 to 19.14 ng ·L -1, DGM ranged from 0.04 to 0.09 ng·L -1, HgR ranged from 0.2 to 1.1ng·L -1 and MeHgT ranged from 0.002 to 0.43ng·L -1 in the Aha Lake water columns. In the sediment porewater , however, the concentrations of HgD varied from 1.72 to 19.12 ng·L -1, and MeHgD ranged from 0.03 to 1.57 ng·L -1. The results indicated that highly elevated MeHgD concentrations in the porewater were obtained at the depths from 2 to 5 cm in the sediment profile, and decreased sharply with depth. A positive correlation has been found between MeHgD formation and sulfate-reducing bacterial activity. These highly elevated concentrations of MeHgD obtained in the intersurface between waters and sediments suggesting a favorable methylation conditions. Moreover,even under the conditions of high SO 2-_4concentrations, reaching up to 1100mg·L -1, a strong correlation beteen MeHgD and SO 2-_4was observed as well.

Contaminations, Sources, and Health Risks of Trace Metal(loid)s in Street Dust of a Small City Impacted by Artisanal Zn Smelting Activities

To investigate the impact of artisanal zinc smelting activities (AZSA) on the distribution and enrichment of trace metal(loid)s in street dust of a small city in Guizhou province, SW China, street dust samples were collected and analyzed for 10 trace metal(loid)s (Cr, Co, Ni, Cu, Zn, As, Cd, Sb, Pb, and Hg). Meanwhile, the health risks of local resident exposed to street dust were assessed. The result showed that the average concentrations of 10 elements were Zn (1039 mg kg−1), Pb (423 mg kg−1), Cr (119 mg kg−1), Cu (99 mg kg−1), As (55 mg kg−1), Ni (39 mg kg−1), Co (18 mg kg−1), Sb (7.6 mg kg−1), Cd (2.6 mg kg−1), and Hg (0.22 mg kg−1). Except Ni, Co, and Cr, other elements in street dust were obviously elevated compared to the provincial soil background. Pb, Zn, Cd, Sb, and Cu were at heavy to moderate contamination status, especially Pb and Zn, with maximums of 1723 and 708 mg kg−1, respectively; As and Hg were slightly contaminated; while Cr, Ni, and Co were at un-contaminated levels. Multivariate statistical analysis revealed AZSA contributed to the increase of Pb, Zn, Cd, Sb, As, and Hg, while, natural sources introduced Ni, Co, Cr, and Cu. The health risk assessment disclosed that children had higher non-carcinogenic risk than those found in adults, and As has hazardous index (HI) higher than 1 both for children and adults, while Pb and Cr only had HIs higher than 1 for children, other elements were relatively safe. For carcinogenic risks, the major concern was As, then a lesser concern for Cr. The study showed that although the scale of AZSA was small, the contamination of heavy metal(loid)s in street dust and associated health risks were severe.