Sun Song, Li Chu-Xian, Zhang Cheng, Wang Yong-Min, Wang Ding-Yong
College of Resources and Environment, Southwest University, Chongqing 400715, China.
Chongqing Engineering Research Center for Agricultural Non-point Source Pollution Control in the Three Gorges Reservoir Area, Chongqing 400716, China.
Huan Jing Ke Xue. 2017 Apr 8;38(4):1689-1696. doi: 10.13227/j.hjkx.201609006.
Mercury (Hg) in the aquatic environment is easy to accumulate in fish. In order to study the effect of the sediments on Hg accumulation in fish in the water-level-fluctuation zone of the Three Gorges Reservoir, we conducted a 90-days simulated flooding experiment by using the sediments with different concentrations of Hg. Our study showed that the concentrations of the total mercury (THg) and methyl mercury (MeHg) in the overlying water increased after flooding, and the concentrations in the muscle of fish kept increasing in the period of experiment, the concentrations in the viscera and head increased in the earlier period but seemingly decreased in the later period. The bioaccumulated Hg content in the fresh was higher than that in the viscera and head, between which there was no significant difference. Compared with the control group (no sediment), the presence of sediments obviously increased the content of Hg bioaccumulated in fish, and the bioaccumulated Hg level increased with the Hg concentrations in sediment. The THg and MeHg in different fish parts presented a similar variation trend with the BCF ranging 1.93×10-8.89×10 for MeHg and 1.3×10-12.8×10 for inorganic mercury, indicating that MeHg was more prone to accumulate in fish. The MeHg in fish was significantly related with THg, and accumulated MeHg occupied about 80.1% (muscle), 79.3% (visceral) and 66.7% (head) of increased THg. After the reflooding of the sediment in the water-level-fluctuating zone, net methylation could occur with MeHg as the product, and then MeHg would diffuse to overlay water, further increasing the Hg bioaccumulation in fish. Therefore, the potential pollution risk of Hg in the water-level-fluctuationg zone with large area of the Three Gorges Reservoir cannot be ignored.
水环境中的汞（Hg）易于在鱼类体内蓄积。为研究三峡水库消落带沉积物对鱼类汞蓄积的影响，我们利用不同汞浓度的沉积物进行了为期90天的模拟水淹实验。研究表明，水淹后上覆水中总汞（THg）和甲基汞（MeHg）浓度升高，实验期间鱼肌肉中的汞浓度持续上升，内脏和头部的汞浓度前期升高但后期似乎下降。鱼肉中生物累积的汞含量高于内脏和头部，二者之间无显著差异。与对照组（无沉积物）相比，沉积物的存在明显增加了鱼体中生物累积的汞含量，且生物累积的汞水平随沉积物中汞浓度的增加而升高。不同鱼体部位的THg和MeHg呈现相似的变化趋势，甲基汞的生物富集系数范围为1.93×10 - 8.89×10，无机汞的生物富集系数范围为1.3×10 - 12.8×10，表明甲基汞更易在鱼体中蓄积。鱼体中的甲基汞与总汞显著相关，累积的甲基汞约占总汞增加量的80.1%（肌肉）、79.3%（内脏）和66.7%（头部）。三峡水库大面积消落带沉积物再淹没后，会发生以甲基汞为产物的净甲基化作用，然后甲基汞会扩散到上覆水中，进一步增加鱼体中的汞生物累积。因此，三峡水库大面积消落带汞的潜在污染风险不容忽视。
