Bioaccumulation of mercury in Crassostrea sp. exposed to waste seawater discharged from a coal-fired power plant equipped with a seawater flue-gas desulfuriaztion system

A field experiment was conducted to study mercury (Hg) bioaccumulation in Crassostrea sp. exposed to waste seawater discharged from a coal-fired power plant equipped with a flue gas desulfurization system. Oysters were cultured in the discharge outlet of the power plant (studying site) and a control site, respectively. The total Hg (THg) concentrations (all counted as dry weight) of seawater in the studying and control sites were determined as (120.6 +/- 55.5) ng x L(-1) (n = 5) and (2.7 +/- 1.0) ng x L(-1) (n = 5), respectively, while methyl Hg (MeHg) concentrations were (0.30 +/- 0.44) ng x L(-1) (n = 5) and (0.28 +/- 0.31) ng x L(-1) (n = 5), respectively. The THg in oyster at the studying site increased dramatically from (138.3 +/- 14.3) ng x g(-1) (n = 6) to (3 012 +/- 289) ng x g(-1) (n = 6) within 7 d, and remained at high levels of 2 935-4 490 ng x g(-1) for the next 34 d. In contrast, the THg in oyster at the control site showed no significant change, and kept at low levels of 60.7-137.5 ng x g(-1). After 41 d exposure, the MeHg in oyster at the studying site had no significant change, ranging from 55.4 ng x g(-1) to 73.1 ng x g(-1), and the content at the control site showed a slight decrease, ranging from 15.6 to 55.6 ng x g(-1). The study showed that THg in the waste seawater discharged at the coal-fired power plant could be quickly bioaccumulated by oyster to a great extent, the potential risk can thus not be ignored. MeHg concentration in the waste seawater was quite low, and no obvious bioaccumulation was found in oyster. Under the study conditions, no self-synthesis of MeHg or transformation of inorganic Hg into MeHg was found.