巨牡蛎(Crassostrea sp.)对燃煤电厂脱硫海水中汞的生物累积

研究了巨牡蛎(Crassostrea sp.)对配备烟气海水脱硫装置电厂的脱硫海水中汞(Hg)的生物累积.在电厂的排水口(实验点)和参考点分别吊养牡蛎群,定期采集样品,测定海水中的Hg浓度和牡蛎的Hg含量(均以干重计).实验点和参考点海水中的总汞(THg)浓度分别为(120.6±55.5)ng.L-1(n=5)和(2.7±1.0)ng.L-1(n=5),甲基汞(MeHg)的浓度分别为(0.30±0.44)ng.L-1(n=5)和(0.28±0.31)ng.L-1(n=5).在7 d内,实验点牡蛎体内THg含量从(138.3±14.3)ng.g-1(n=6)迅速增加到(3 012±289)ng.g-1(n=6),且在后来的34 d内,一直保持在2 935～4 490 ng.g-1的高含量水平;而参考点牡蛎对THg未见明显累积,为60.7～137.5 ng.g-1之间.暴露期间实验点牡蛎体内MeHg的含量未发生显著变化,保持在55.4～73.1 ng.g-1之间.而参考点牡蛎MeHg含量呈略微下降的趋势,但变化幅度不大,在15.6～55.6 ng.g-1之间.本研究表明,燃煤电厂排放的脱硫海水中的THg可被牡蛎迅速累积至很高的含量水平,有不容忽视的潜在风险.脱硫海水中MeHg的浓度很低,其在牡蛎体内未见明显累积;在本研究的条件下,未观测到牡蛎自身合成MeHg或将无机汞转化为MeHg.

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·L^-1 (n=5) and (2.7±1.0)ng·L^-1 (n=5), respectively, while methyl Hg (MeHg) concentrations were (0.30±0.44)ng·L^-1 (n=5) and(0.28±0.31)ng·L^-1 (n=5), respectively. The THg in oyster at the studying site increased dramatically from (138.3±14.3)ng·g^-1 (n=6) to (3012±289)ng·g^-1 (n=6) within 7 d, and remained at high levels of 2935-4490 ng·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·g^-1. After 41 d exposure, the MeHg in oyster at the studying site had no significant change, ranging from 55.4 ng·g^-1 to 73.1 ng·g^-1, and the content at the control site showed a slight decrease, ranging from 15.6 to 55.6 ng·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.