北京市场4种食用淡水鱼的总汞和甲基汞的含量分析

Analysis of total mercury and methylmercury concentrations in four commercially important freshwater fish species obtained from Beijing markets

目的研究北京市场经常食用的四种淡水鱼的总汞和甲基汞的含量,评价普通人群汞暴露的风险。方法从市场购买4种人们经常食用的代表不同品种的淡水鱼:鲤鱼、草鱼、鳙鱼和黑鱼,取其肌肉、肝脏和鱼鳃,利用超声波辅助溶剂萃取-电感耦合等离子体质谱测定其总汞和甲基汞,样品加入6mol/L HCl超声2h,取部分上清直接稀释测定总汞,另一部分加CH2Cl2萃取并用水反萃测量甲基汞。通过测定标准参考物质DORM-2和DOLT-3用以评价方法的可靠性。结果按各种鱼肉中总汞和甲基汞平均含量最高值,可排出如下顺序:黑鱼>鳙鱼>草鱼>鲤鱼,表明鱼体中汞的蓄积是与食物链密切相关的。其中甲基汞所占的百分比均值为80%,甲基汞的浓度与总汞的浓度是成正比的。研究了鳙鱼和黑鱼的肝脏和鳃的总汞和甲基汞含量及甲基汞所占的百分比,其中汞的含量是肌肉组织>肝脏>鳃,而甲基汞所占总汞的比例为:肌肉组织>鳃>肝脏,甲基汞主要蓄积在可食用的肌肉组织中。结论根据我国国家淡水鱼食品卫生标准,北京市场的四种淡水鱼的汞含量均低于国家标准,因此对于人们食用是安全的。

Objective The present paper makes an attempt to evaluate the risk of mercury exposure to human by analyzing the total mercury and methylmercury concentrations of four commercially important freshwater fish species in Beijing markets. Methods Fish samples of common carp, grass carp, bighead carp, and snakehead were purchased from Beijing market. Then their muscle, liver and gills were taken out. The total mercury and methylmercury concentrations were determined using ultrasonlc-assisted solvent extraction coupled with inductively coupled plasma-mass spectrometry. Samples were digested with 6mol/L HCl and sonicated for 2 hours. Subsequently, some aliquots were directly diluted for determination of total mercury concentrations ; the remained extracts were extracted with CH2Cl2, and then back extracted with H2O for determination of methylmercury concentrations. To evaluate the validity of the method, the standard materials of DORM-2 and DOLT-3 were also measured. Results According to the concentrations of total mercury and methylmercury in the muscles, an order was obtained as： snakehead 〉 bighead carp 〉 grass carp 〉 common carp, which showed that the accumulation of mercury in fish was closely related to food chain. Methylmereury were about 80% of the total mercury, whereas there was a positive relationship between total mercury and methylmercury. The mercury distributions in the bighead carp and snakehead fish showed that the order of mercury concentrations was ： muscle 〉 liver 〉 gill, the ratio of methylmercury to total mercury was ： muscle 〉 gill 〉 liver. Methylmercury was mainly accumulated in the muscle of fish. Conclusion mercury concentrations of the four fishes in Beijing markets were all below the standard level according to the National Standard of China, therefore, it is safe to human health.