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水库汞的活化效应及硒对汞污染的影响
勒立军
Subtype博士
Thesis Advisor刘建康 ; 徐小清
1996
Degree Grantor中国科学院水生生物研究所
Place of Conferral中国科学院水生生物研究所
Degree Discipline水生生物学
Keyword水库 汞的活化效应 汞污染 相互作用 预测模型
Abstract近十年来,世界范围内汞污染加剧,再度引起国际上的重视,许多国际组织将汞列为全球污染物的重要研究内容。其中大坝蓄水引起的鱼体汞积累的加剧,便是这些重要的研究内容之一。去年SCOPE(Scientific Committee on the Problem of Environment)组织在俄罗斯还为此召开了专门的国际会议讨论全球汞污染问题。本文作者在前人研究三峡工程对生态与环境影响及其对策的基础上,较详细地研究了水库汞的活化效应,探讨了硒对汞污染的影响,以寻找减轻水库的活化效应的措施。三峡库区泵污染的分布表明,武隆、涪陵和重庆燃煤汞含量高达1毫克/公斤左右,燃煤释放的汞占三峡江段年输送汞量的6.7%。除巫山、巴东和秭归以外,三峡库区各地土壤汞含量均高于四川省土壤背景值。其中以库尾的重庆、涪陵、武隆以及库区中部的万县市最高。经相关分析发现,土壤汞含量与燃煤汞含量呈较好的线性关系。高汞背景土壤的流失是造成库区沉积物汞含量高的主要原因之一。水库沉积物的总汞含量以及生物可利用态汞的含量均高于入库河流沉积物。三峡库区江水中甲基汞含量的平均值为0.24ng/l。库区江段采集的四种鱼类肌肉甲基汞含量占总汞含量的60-77%,占有机汞含量的72-87%;各组织器官中的甲基汞含量与其有机汞含量和总汞含量和总汞含量呈很好的线性关系,因此,根据鲤鱼肌肉中的总汞和有机汞含量,可以比较准确地估计出其甲基汞含量。此外,鱼体甲基汞含量与其生长之间呈显著的幂函数关系。水库汞的活化效应研究表明,水库沉积物的汞活性比入库河流沉积物的高。水库蓄水淹没土地,增加了具有高汞活性的底泥的表面积。同时形成新的湿地,增加了来自陆地集水区的外源甲基汞的输入量。有机质的大量输入和沉积作用提高了甲基化微生物的活性。大量有机质分解以及复氧能力降低又造成了水体溶解氧下降、pH降低,从而提高了汞甲基化的速率,降低了挥发性汞(二甲基汞)的损失。这些作用增加了水库中总无机汞以及生物可利用态汞的量,促进了甲基汞的产生。在前人和以上工作的基础上,将水库鱼体对入库河流同一种鱼体汞含量(有机汞、无机汞和总汞)的比值F与各水文参数进行了相关分析和逐步回归,证实F值与径流深的倒数成线性关系的正确性,并改进了二元预测方程的精度。预测方程表明径流深的倒数(A/Q,a/m)是影响水库汞活性的关键性因子,其次是淹没耕地面积与死库容的水库面积的比值、以及水库面积的倒数。硒对汞在鱼体内积累的影响研究表明,硒含量高的铒料(2mg/kg)使鱼体汞含量增加,与对照组相比,达到50%和95%稳态汞含量所需时间延长了4.2和18.5天,汞的吸收速率和排除常数分别降低了14.7%和33.7%,说明高硒饵料有效地降低了鱼体汞的排除常数,使得鱼体总汞的稳态含量增大。这个结果从一个侧面解释了自然条件下鲤鱼肌肉中汞与硒含量呈正相关的现象。硒对汞在不同条件下甲基化作用的影响研究表明,在间歇性通空气和通氮气的条件下,加硒于底泥中能够显著抑制汞的甲基化作用。且随硒含量的增加,抑制作用增强;厌氧条件下,低浓度的硒(0.25μ g/g)促进汞的甲基化作用,而高浓度的硒则抑制汞的甲基化作用。这说明向底泥中加入亚硒酸钠降低了底泥中汞的甲基化速率,使得甲基汞浓度降低,由此引起鱼体汞含量的减少。此外,研究表明,适度高温有利于汞的甲基化,并导致甲基汞含量最高值出现的时间提前。在未加入硒的情况下,富营养化底泥在间歇性通空气的条件下甲基化速率高于厌氧条件。根据以上研究结果和预测方程,预测三峡大坝修建后水库鱼体汞含量将增加0.43-1.86倍,汞污染问题最严重的将是库区南岸乌江下游水域。针对这些问题,探讨了网箱养殖鱼体汞积累的预防方法,以及甲基汞污染危害的生态防治措施。
Other AbstractIn recent decade, worldwide mercury contamination aggravated. One of the causes of such aggravation was dam construction and irrigation projects, and many international organizations concentrated on its study. In 1995, SCOPE convened an international conference on this problem in Russia. The present study was therefore designed to study the activation effect of mercury in reservoirs, and the effect on selenium on mercury contamination in order to explore ways of alleviating mercury activation effect. Distribution of mercury in the Three-gorge Reservoir area was studied. Mercury content of coal from Wulong, Fuling and Chongqing was the highest (about 1 mg/kg), and mercury released from coal constituted about 6.7% of total mercury transported in this area. Except of Wushan, Badong and Zigui, mercury content of soils was all higher than mercury background values in Sichuan province, while the highest was the soil of Chongqing, Fuling, Wulong and Wanxian. Erosion of soil of high mercury background values resulted in the high mercury content in sediments. Regression analysis showed there was good correlation between mercury content of soil and coal. Total mercury and biologically available mercury content in sediment of reservoirs was higher than that of rivers. The average methyl-mercury (MeHg) concentration in river water was 0.24ng/l. MeHg content in muscle of fish was 60-77% of total mercury content, and there were good correlations among MeHg, organic mercury and total mercury contents in various tissues and organs. Therefore, we could predict MeHg content in muscle of fish according to the total or organic content. MeHg content in muscle of fish was significantly related to fish growth. Study of activation effect of mercury in reservoirs revealed that, flooding of land increased the area of surface sediment where the methylation rate was the highest, and produced new saturated organic soils which were important sources of MeHg to downstream reservoirs. Nutrients, especially labile organic substances introduced into the aquatic environment from recently submerged soil and vegetation, stimulated microbial methylation of mercury in sediment. Decomposition of organic matters and reduction of oxygenation capacity resulted in decrease of dissolved oxygen and pH, settlement of rich mercury suspended substances and release of mercury into the aquatic ecosystem from scattered low-level sources in flooded land increased total mercury, which were all important for the production of mono-MeHg. Correlation analysis and stepwise regression of F(ratio of mercury content in fish from reservoirs and that from rivers of the same water system) and various hydrologic parameters demonstrated that the ratio of catchment area and runoff was the crucial limiting factor. Other limiting factors were the ratio of flooding area of land and reservoir area of dead storage capacity, and the reciprocal of reservoir area. On this basis, I obtained the prediction equations of mercury accumulation in fish after reservoir construction, with one and two unknown quantity respectively, and the equations were proved to be of high precision.
Pages131
Language中文
Document Type学位论文
Identifierhttp://ir.ihb.ac.cn/handle/342005/12502
Collection学位论文
Recommended Citation
GB/T 7714
勒立军. 水库汞的活化效应及硒对汞污染的影响[D]. 中国科学院水生生物研究所. 中国科学院水生生物研究所,1996.
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