Biogeochemical Cycle of Mercury in Reservoir Systems in Wujiang River Basin, Southwest China by Xinbin Feng Bo Meng Haiyu Yan Xuewu Fu Heng Yao & Lihai Shang

Author:Xinbin Feng, Bo Meng, Haiyu Yan, Xuewu Fu, Heng Yao & Lihai Shang
Language: eng
Format: epub
Publisher: Springer Singapore, Singapore

2.Distribution of mercury species in water columns

(1)THg, DHg, and PHg in water columns

Spatial and temporal distributions of THg and DHg at Houwu and Daba are presented in Fig. 7.6. The THg concentrations ranged from 2.49 to 13.9 ng L−1, with an average concentration of 6.89 ng L−1. The DHg concentrations ranged from 1.19 to 7.96 ng L−1, with an average of 3.98 ng L−1. The mercury concentrations in the HF water were distinctly higher than those in other natural waters reported for Europe and North America (e.g., Bloom et al. 2004; Sullivan and Mason 1998). THg and DHg showed no discernible vertical distribution trends throughout all of the water columns across the sampling areas. However, we found spatial and seasonal variations in the THg and DHg concentrations in the water column of the reservoir. These spatial variations suggest that the two basins of the reservoir have been affected by different mercury contamination sources. The highest average concentrations of THg and PHg were observed at Houwu in May 2004 (up to 11.43 and 5.95 ng L−1, respectively), while lower average concentrations of THg and PHg (6.06 and 3.84 ng L−1, respectively) were found at Daba at the same time. Similarly, elevated average concentrations of TSP were found at Houwu in May; the TSP levels averaged at 15.67 mg L−1 compared to a value of 2.1 mg L−1 found for the Daba at the same time. This difference is attributed to the appearance of large algae populations at Houwu in May due to aquaculture activity and the addition of wastewater enriched with N and P. The distribution of mercury found also shows that macroalgae may be able to bind mercury and may represent a substantial pool of mercury in the aquatic system. The levels of total and dissolved mercury recorded in September were fairly low relative to those recorded in November and February. This seasonal distribution of mercury could be a result of wastewater contamination. In May and September, high runoff volumes were due to abundant precipitation-diluted mercury concentrations in the water, whereas there was very little precipitation in February and November, thus causing mercury concentrations in the water to increase.

Fig. 7.6THg, DHg, and PHg in water columns of the Hongfeng Reservoir from 2003 to 2004 (redrawed from He et al. 2008c, with permission from Elsevier; redrawed from He et al. 2010, with permission from Journal of Lake Science; redrawed from He et al. 2008d, with permission from Chinese Journal of Geochemistry)

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