原位掩蔽对底泥汞释放的抑制效果及中试评估

为解决贵州省百花湖底泥中的汞污染问题,研究了原位掩蔽对底泥中汞释放的抑制效果. 选择沸石、高岭土和赤铁矿为掩蔽材料,通过模拟试验,确定原位掩蔽的最佳覆盖厚度为2.0 cm,此时沸石、高岭土和赤铁矿对底泥汞释放的控制率分别为47.1%、64.9%和62.3%,说明最佳掩蔽材料为高岭土. 以高岭土为掩蔽材料的情况下,试验实施7 d后,水体扰动对控制率的影响不足6.7%. 中试区位于百花湖重度污染区,面积约为22 000 m2,采用驳船少量多次撒布高岭土原位掩蔽汞污染底泥,控制覆盖厚度为2.0~3.0 cm,按月连续监测6次. 结果显示,高岭土对汞污染底泥的控制率达到47.1%. 模拟试验及中试效果显示,高岭土原位掩蔽可有效抑制底泥中汞的释放,并且较薄的覆盖厚度可降低工程成本和对湖底生态系统的影响. 

Effects of Mercury Release Control by Sediment Capping and its Pilot Evaluation

Abstract: In the present study, the effects of mercury release control by sediment capping were investigated to solve the serious mercury pollution problem in the sediments of Lake Baihua in Guizhou province. The inhibition effect on the release of mercury of three different materials of zeolite, hematite and kaoline were studied after being capped onto sediments. Laboratory-scale simulation experiments showed the optimal capping thickness of 2.0 cm for mercury release control, and kaoline was the optimal material, since the inhibition rates were determined to be 47.1%, 64.9% and 62.3% for zeolite, hematite and kaoline, respectively. Water disturbance showed little effect (<6.7%) on sediment capping, as indicated from the slight variation in mercury concentrations in overlying water during the first 7 days after the sediment was capped with kaoline. Moreover, 22,0 m² area in Baihua reservoir, which was severely contaminated with mercury, was isolated with tarpaulins for pilot-scale investigation. Powdered kaoline was carefully spread three times by barges to achieve the capping thickness of 2.0-3.0 cm, and after being settled and stabilized, mercury concentrations in the overlying water and pore water were monitored once a month over the next 6 months. The pilot-scale results demonstrated the significant inhibition efficiency of kaoline capping on the control of mercury release from sediments with a flux decrease ratio as high as 47.1%. The results showed that the mercury release could be effectively inhibited by the capping of kaoline, and 2 cm thickness of the kaoline capping could reduce the engineering cost as well as the ecological impact.