Distribution of Different Mercury Species in the Waterbody at Sanmenxia Reservoir

Abstract

In order to obtain the distribution of different species of mercury (Hg) in the water in the Sanmenxia Reservoir, cold vapor atomic fluorescence spectrometry (CVAFS) and aqueous phase ethylation derivatization-gas chromatography-atomic fluorescence spectrometry (GC-CVAFS) methods were used for the analysis of total Hg (THg) and methylmercury (MeHg) in water and sediment samples, respectively. It was found that the levels of THg, dissolved mercury, and particulate mercury in the water ranged from 1.65-9.65, 0.80-3.16, and 0.70-7.81 ng·L-1, respectively. The THg in the water could meet the requirement for the Class I criterion in the national surface water environmental quality standard (GB 3838-2002). The amounts of MeHg, dissolved MeHg, and particulate MeHg in the water samples were 0.05-0.36, 0.02-0.14, and ND-0.26 ng·L-1, respectively. No evident seasonal or spatial patterns for Hg were observed. The THg and MeHg in the Sanmenxia Reservoir were within the ranges for those in uncontaminated waterbodies worldwide. The amount of THg in the sediments was (92.96±10.65) ng·g-1 and (80.06±19.14) ng·g-1, while the amount of MeHg in the corresponding sediment samples was (0.33±0.14) ng·g-1 and (0.50±0.19) ng·g-1 for wet and dry seasons, respectively. The ratios of MeHg/THg in the sediment of the Sanmenxia Reservoir were relatively small in comparison to those in other aqueous systems, indicating that methylation might play a minor role in the biogeochemistry of Hg in the Sanmenxia Reservoir. This might be attributed to the high dissolved oxygen levels of the bottom water and low organic carbon content of the sediments.