百花湖含汞底泥的原位掩蔽治理技术研究及工程效益评估

发布时间：2018-08-06 13:30

【摘要】：汞污染问题已成为国际社会各界关注的热点,随着汞公约的履行,我国对汞污染控制与治理力度逐渐加大。贵州省具有600多年汞冶炼历史,目前涉汞行业达14个,汞污染源类型繁多、排放量大,是我国最典型的汞污染区域之一。百花湖位于贵州省中部,距离贵阳市区16 km,是贵阳市的重要饮用水源地,早期受贵州省有机化工厂含汞废水污染,湖泊中汞含量超标,尤其是底泥中汞含量达0.26~38.9 mg kg-1,平均为6.5 mg kg-1,明显超出贵州土壤汞本底值(0.26 mg kg-1)。随着该厂涉汞工艺的关停,底泥释放成为百花湖水体中汞污染的重要来源。因此,本研究采用原位掩蔽治理技术,探讨底泥中汞释放的抑制效果,从而降低百花湖水体汞污染风险,保障贵阳市饮用水安全。具体研究内容如下:(1)通过调查研究,选取百花湖入口处具有代表性的点位,研究百花湖沉积物和孔隙水汞污染程度和空间分布,揭示其对下游入湖口处沉积物及孔隙水汞含量造成的影响。研究结果表明:百花湖入口处沉积物平均含汞量为6.084 mg kg-1,超过土壤背景值22.2倍,孔隙水溶解态汞平均含量为23.7 ng L-1。从水平方向上看,相近水文条件下,下游的沉积物明显比上游的汞污染程度底;不同水文条件下,回流湾处沉积物内汞含量较高。从沉积物剖面看,自污染后到2008年沉积物内整体汞含量呈下降趋势,但上游2008年的疏浚清淤后,百花湖入口处沉积物及孔隙水内汞含量有一定程度的上升,但幅度较小,基本不会对水质和生态系统造成太大影响。(2)针对百花湖底泥中汞污染严重的实情,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,通过模拟实验研究,确定了原位掩蔽最佳厚度为2 cm,覆盖厚度为2 cm时沸石、高岭土和赤铁矿对底泥汞释放控制率分别为47.1%、64.9%和62.3%,确定最佳掩蔽材料为高岭土,并分析了水体扰动对掩蔽效果的影响,发现掩蔽实施7 d后,扰动对掩蔽效果的影响不明显。(3)在百花湖重度污染区域搭建了封闭式中试实验区,约为22000 m2。确定最佳工程覆盖材料为高岭土,覆盖厚度控制在2~3 cm,采用驳船少量多次撒布材料原位掩蔽汞污染底泥,控制每次的撒布厚度为0.5 cm。长期监测结果表明,高岭土原位掩蔽对底泥中汞释放的抑制具有较好的效果,控制率可达47.1%±17.1%;且较薄的掩蔽厚度既可降低成本,又可减少掩蔽对湖底生态系统的影响。
[Abstract]:Mercury pollution has become the focus of attention in the international community. With the implementation of the mercury convention, the control and control of mercury pollution in China has gradually increased. Guizhou Province has a history of more than 600 years of mercury smelting. At present, there are 14 mercury-related industries in Guizhou Province. There are many types of mercury pollution sources and large emissions, so it is one of the most typical mercury pollution areas in China. Baihua Lake is located in the central part of Guizhou Province, 16 km from Guiyang City. It is an important drinking water source in Guiyang City. It was polluted by mercury wastewater from organic chemical plants in Guizhou Province in the early stage, and the mercury content in the lake exceeded the standard. In particular, the content of mercury in the sediment was 0.26 ~ 38.9 mg 路kg ~ (-1), with an average of 6.5 mg 路kg ~ (-1), which was significantly higher than the background value of mercury (0.26 mg kg-1) in Guizhou soil. With the closure of mercury process, sediment release has become an important source of mercury pollution in Baihua Lake. Therefore, in order to reduce the risk of mercury pollution in Baihua Lake and ensure the safety of drinking water in Guiyang City, the inhibition effect of mercury release from sediment was discussed by in-situ masking and treatment technology. The specific contents of the study are as follows: (1) through investigation and study, select representative points at the entrance of Baihua Lake, study the mercury pollution degree and spatial distribution of sediment and pore water in Baihua Lake. The effect of mercury content on sediment and pore water in the lower reaches of the lake was revealed. The results showed that the average mercury content at the entrance of Baihua Lake was 6.084 mg 路kg ~ (-1), which exceeded the soil background value by 22.2 times, and the average dissolved mercury content in pore water was 23.7 ng / L ~ (-1). In the horizontal direction, the sediment in the lower reaches is obviously lower than the bottom of the mercury pollution in the upper reaches under the similar hydrological conditions, and the mercury content in the sediments at the return bay is higher under different hydrological conditions. From the sediment profile, the overall mercury content in sediment decreased from the pollution to 2008, but after dredging and silting in the upstream in 2008, the mercury content in sediment and pore water at the entrance of Baihua Lake increased to a certain extent, but the extent was relatively small. (2) aiming at the serious mercury pollution in bottom mud of Baihua Lake, the inhibition effect of in-situ masking on mercury release from sediment was studied. Zeolite, kaolin and hematite were selected as masking materials. The optimum thickness of in-situ masking was 2 cm and the cover thickness was 2 cm. The control rates of mercury release from bottom mud by kaolin and hematite were 47.9% and 62.3%, respectively. The optimum masking material was determined as kaolin, and the influence of water disturbance on the masking effect was analyzed. It was found that the masking was carried out 7 days later. The effect of disturbance on masking effect is not obvious. (3) A closed pilot-scale experimental area is built in the heavily polluted area of Baihua Lake, which is about 22000 m2. It is determined that the best engineering covering material is kaolin, the thickness of covering is controlled at 2 ~ 3 cm, the mercury contaminated sediment is masked in situ by a small amount of barge distributing materials, and the thickness of each dispersal is controlled to be 0.5 cm. The results of long-term monitoring show that kaolin in-situ masking has a good effect on the inhibition of mercury release from sediment, and the control rate is up to 47.1% 卤17.1.The thinner masking thickness can not only reduce the cost, but also reduce the effect of masking on the lake bottom ecosystem.
【学位授予单位】：浙江农林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X524

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