三门峡水库水体中不同形态汞的分布特征

为了解三门峡水库水体中不同形态汞的分布特征,在丰水期和枯水期对三门峡水库进行采样,分别采用冷原子荧光光谱法(CVAFS)和蒸馏-乙基化衍生-气相色谱-冷原子荧光法(GC-CVAFS)测定水样中总汞、总甲基汞、溶解态总汞和溶解态甲基汞的浓度.结果表明,三门峡水库水体中总汞、溶解态汞和颗粒态汞浓度范围分别为1.65~9.65、0.80~3.16和0.70~7.81 ng·L~(-1),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;总甲基汞、溶解态甲基汞和颗粒态甲基汞浓度分别为0.05~0.36、0.02~0.14和ND~0.26 ng·L~(-1).三门峡水库水体总汞和甲基汞在季节和空间分布上没有呈现出明显的变化规律.总汞和甲基汞与未受污染的天然水体差别不大,水库未受到明显的汞污染.丰、枯水期沉积物中总汞浓度分别为(92.96±10.65)ng·g~(-1)和(80.06±19.14)ng·g~(-1),甲基汞浓度分别为(0.33±0.14)ng·g~(-1)和(0.50±0.19)ng·g~(-1).较低的甲基汞浓度说明在三门峡水库汞的迁移转化过程中,甲基化作用可能并非主要的过程,这可能与水体底层溶解氧浓度较高以及沉积物中有机质浓度较低有关.

Distribution of Different Mercury Species in the Waterbody at Sanmenxia Reservoir

In order to obtain the distribution of different species of mercury (Hg) in the water in the Sanmenxia Reservoir, cold vapor atomic fluorescence spectrometry (CVAFS) and aqueous phase ethylation derivatization-gas chromatography-atomic fluorescence spectrometry (GC-CVAFS) methods were used for the analysis of total Hg (THg) and methylmercury (MeHg) in water and sediment samples, respectively. It was found that the levels of THg, dissolved mercury, and particulate mercury in the water ranged from 1.65-9.65, 0.80-3.16, and 0.70-7.81 ng·L^-1, respectively. The THg in the water could meet the requirement for the Class I criterion in the national surface water environmental quality standard (GB 3838-2002). The amounts of MeHg, dissolved MeHg, and particulate MeHg in the water samples were 0.05-0.36, 0.02-0.14, and ND-0.26 ng·L^-1, respectively. No evident seasonal or spatial patterns for Hg were observed. The THg and MeHg in the Sanmenxia Reservoir were within the ranges for those in uncontaminated waterbodies worldwide. The amount of THg in the sediments was (92.96±10.65) ng·g^-1 and (80.06±19.14) ng·g^-1, while the amount of MeHg in the corresponding sediment samples was (0.33±0.14) ng·g^-1 and (0.50±0.19) ng·g^-1 for wet and dry seasons, respectively. The ratios of MeHg/THg in the sediment of the Sanmenxia Reservoir were relatively small in comparison to those in other aqueous systems, indicating that methylation might play a minor role in the biogeochemistry of Hg in the Sanmenxia Reservoir. This might be attributed to the high dissolved oxygen levels of the bottom water and low organic carbon content of the sediments.