Influence of Eutrophication on the Distribution of Total Mercury and Methylmercury in Hydroelectric Reservoirs

Abstract

The distribution of mercury (Hg) and the characteristics of its methylation were investigated in Wujiangdu (WJD) and Yinzidu (YZD) reservoirs in Guizhou province, China. The two reservoirs are characterized by high and low levels of primary productivity, respectively. Mercury species in water samples from depth profiles in both reservoirs and from interface water in the WJD were analyzed each season during 2007. The concentrations of total Hg (HgT(unf)) and methylmercury (MeHgT(unf)) in unfiltered water samples from the WJD varied from 3.0 to 18 pmol dm(-3) and from 0.17 to 15 pmol dm(-3), respectively; ranges were 2.0 to 9.5 pmol dm(-3) for HgT(unf) and 0.14 to 2.2 pmol dm(-3) for MeHgT(unf) in the YZD. Elevated methylmercury concentrations in water samples from the bottom water and water-sediment interface demonstrated an active net Hg methylation in the downstream reach of the WJD. There was no discernable Hg methylation occurring in the YZD, nor in the upstream and middle reaches of the WJD. The results suggest that high primary productivity resulting from cage aquaculture activities in the WJD is an important control on Hg methylation in the reservoir, increasing the concentrations of MeHg in water in the Wujiang River basin Southwestern China.

Atmospheric mercury deposition and its contribution of the regional atmospheric transport to mercury pollution at a national forest nature reserve, southwest China

“…As many researchers have shown, atmospheric deposition of Hg depends upon Hg speciation; highly soluble Hg 2+ species are quickly stripped from the atmosphere and deposited locally, whereas PHg emissions are transported regionally, and elemental emissions are transported globally (Demers et al 2007;Porvari and Verta 2003). On the issue of atmospheric transport and deposition at this study area, which are described in detail in BPotential source identification for transport of atmospheric Hg^section, RHg concentration in litterfall of the study area was slightly higher compared with other studies (Meng et al 2011); no obvious Hg activation effect was observed.…”

Synthesis of current data for Hg in areas of geologic resource extraction contamination and aquatic systems in China

“…Wujiangdu and Yinzidu Reservoir;Feng et al, 2009aFeng et al, , 2009bMeng et al, 2010b). Furthermore, total-Hg concentrations in the Hongfeng Reservoir impacted by a coal-fired power plant were elevated and slightly increased with depth in water columns (He et al, 2008a(He et al, , 2008b.…”

“…However, to an increasing extent the reservoirs are affected by human activities, such as the cage aquaculture, that significantly add to organic matter in the sediment over time, feasibly stimulating the process of methylation. Feng et al (2009aFeng et al ( , 2009b and Meng et al (2010b) demonstrated that the primary productivity and also the water residence time are important factors that control the potential of net Hg methylation in the Wujiang River reservoirs. Compared to lakes and reservoirs located at higher latitudes, the premises and evolution of methylation in Chinese hydropower reservoirs appear different.…”

“…Concerning the elevated Hg levels observed in fish from North America and northern Europe, Lucotte et al (1999) suggested that the decomposition of flooded organic matter (OM), which generates favourable conditions for bacterial methylation of inorganic Hg to MMHg, could be the primary driving process underlying high MMHg in fish. It is evident that the conditions in newly constructed Chinese reservoirs with comparatively different type and low availability of organic matters are not in favour of net in-situ methylation (Meng et al, 2010b;Yao et al, 2011;Larssen, 2010). Another important factor is that the most common fish species in Chinese reservoirs are herbivorous species, which grow fast and have a limited time to bioaccumulate MMHg before being consumed.…”

Intake of predatory fish in Amazonia is a driver of toxicological risk for susceptible exposure groups

“…In Amazon region, mercury levels are of even greater concern, in this particular region when factored with the effects of a hydroelectric facility being constructed in the area, and continued gold mining in the region (Meng, 2010).…”