汞在小浪底水库的赋存形态及其时空变化

为了解小浪底水库汞的赋存状况,采用冷原子荧光光谱法测定了小浪底水库水体、表层沉积物、沉积物间隙水以及鱼类肌肉样品中的总汞,采用乙基化衍生-气相色谱-原子荧光法测定了上述样品中的甲基汞,进而分析了小浪底水库鱼体中汞的富集状况.结果表明,小浪底水库水体中丰、枯水期总汞浓度分别为0.71~1.42 ng·L-1和0.90~2.49 ng·L-1,均符合国家地表水环境质量标准(GB 3838-2002)一类水汞浓度标准限值,水样中未检出甲基汞.丰、枯水期沉积物中总汞浓度分别为51.74~90.42 ng·g-1和95.66~172.52 ng·g-1,甲基汞浓度分别为0.09~0.26 ng·g-1和0.18~0.39 ng·g-1,甲基汞浓度较低,这可能与水体底层溶解氧浓度较高以及沉积物中有机碳浓度较低有关.丰、枯水期沉积物间隙水总汞浓度分别为4.27~9.49 ng·L-1和5.46~41.04 ng·L-1,甲基汞浓度分别为0.09~0.99 ng·L-1和0.07~1.01 ng·L-1,间隙水中总汞和甲基汞浓度明显高于上覆水体,与水体间存在汞浓度梯度,可能存在从沉积物间隙水向水体中的扩散.鱼体肌肉总汞浓度在43.47~304.98 ng·g-1之间,甲基汞浓度为10.77~265.23 ng·g-1,甲基汞低于食品安全国家标准规定的污染物限量(GB 2762-2012)(非肉食性鱼500 ng·g-1和肉食性鱼1 000 ng·g-1).水库鱼体总汞的生物富集系数分别为鳙鱼1.3×105,梭鱼9.3×104,鲫鱼4.7×104,白条5.0×104,黄颡鱼1.7×105,弓鱼3.9×104.

Speciation and Spatial-temporal Variation of Mercury in the Xiaolangdi Reservoir

In order to investigate the occurrence status of mercury in Xiaolangdi Reservoir, water, surface sediments, pore water and fish samples were collected and analyzed for the contents of total mercury(THg) and methylmercury(MeHg). Cold vapor atomic fluorescence spectrometry and aqueous phase ethylation derivatization-gas chromatography-atomic fluorescence spectrometry methods were used for the analysis of THg and MeHg, respectively. Bioaccumulation of THg in fish of Xiaolangdi Reservoir was then discussed. It was found that THg contents in water were 0.71-1.42 ng·L^-1 and 0.90-2.49 ng·L^-1 during dry and wet seasons, respectively, while the MeHg content in water was below the method detection limit. The THg content in water during both seasons could meet the requirement of Class I criterion of national surface water environmental quality standard(GB 3838-2002). The THg contents in sediments were 95.66-172.52 ng·g^-1 and 51.74-90.42 ng·g^-1, while the MeHg contents in the corresponding sediment samples were 0.18-0.39 ng·g^-1 and 0.09-0.26 ng·g^-1 for dry and wet seasons, respectively. The ratios of MeHg/THg in sediment were relatively small in comparison to those in other aqueous systems. This might be attributed to the high dissolved oxygen content of bottom water and low organic carbon content of the sediments. The THg concentrations in pore water of sediments were 5.46-41.04 ng·L^-1 and 4.27-9.49 ng·L^-1, and the MeHg concentrations were 0.07-1.01 ng·L^-1 and 0.09-0.99 ng·L^-1, respectively. The THg concentration was significantly higher than that of the overlying water, indicating the diffusion of Hg from the sediment to the water. The THg concentration in fish muscle tissues varied from 43.47 to 304.98 ng·g^-1, while the MeHg concentration varied from 10.77 to 265.23 ng·g^-1. The MeHg content in fish muscle tissues could meet the requirement of national food safety standards(GB 2762-2012)(Non carnivorous fish 500 ng·g^-1, Carnivorous fish 1000 ng·g^-1). The bioaccumulation factors of THg were 1.3×10⁵ for bighead carp, 9.3×10⁴ for barracuda,4.7×10⁴ for crucian carp, 5.0×10⁴ for sharpbelly, 1.7×10⁵ for yellow catfish, and 3.9×10⁴ for arch fish, respectively.