| 摘要 | 汞，俗称水银，是有毒、人体非必需元素。汞矿山的长期开采对周边环境造成的汞污染问题，已经受到了世界各国环境工作者的广泛关注。早在上世纪80年代，汞化合物就已被世界各组织及各国政府列为优先污染物。近年来，由于全球汞污染的严峻形势和对汞毒害作用认识的增加，许多大型汞矿山相继停产、闭坑。但这些废弃汞矿山仍通过遗留尾矿和冶炼废渣等固体废弃物、污水、污染土壤以及废气等向当地周边环境持续排放大量的汞污染物，其中进入河流和排放到大气是汞污染物主要的两种迁移方式。一般情况下，废弃汞矿山向河流排放的汞远高于向大气排放的汞，导致附近河流遭受严重的汞污染。贵州万山汞矿区曾是中国最大的汞矿区，矿区内河流密布，纵横交错，由于各种原因，矿区存在的大量固体废弃物未经妥善处理，大都被直接排放于矿坑口或堆放在附近河谷及河流两岸，在雨水冲刷下，固体废弃物源源不断的释放汞污染物，随河流迁移，进入周边农田，导致农田面源汞污染。目前，对于水体汞污染控制技术，如：物理方法、物理化学方法和生物方法等，无法满足矿山河流汞污染治理需求。特别在我国，也尚未开展汞矿区河流汞污染控制及治理技术的研究。基于前期研究结果和水体汞污染治理技术文献调研，我们选择自然净化技术结合底泥清除技术的手段，在大幅降低治理成本的前提下，通过增强河流生态系统自净能力，以达到控制汞污染物向下游迁移的治理效果。论文以贵州万山岩屋坪汞矿区翁曼河为研究对象，在其上游及中游分别修建围堰，通过对翁曼河河水在流经围堰前后汞浓度及河水流量的长期连续监测，建立围堰汞输入、输出模型，评价工程措施对河流水体汞控制的效果。研究期内河水pH平均为8.75±0.37；河水电导（Cond）为294±15us/cm；溶解颗粒物（TDS）平均为141±7mg/L；围堰修建对河水水质参数无明显影响。研究发现，丰水期河流上游（近炉渣堆）THg浓度非常高，THg浓度在6月下旬达到最高值（785ng/L)。翁曼河上游河水总汞浓度在各个时期都比下游高。上游河水甲基汞浓度在丰水期浓度最高，最高可达8.7ng/L,在平水期次之，枯水期浓度最低，最低浓度为0.14ng/L，全年平均浓度为1.1ng/L。在丰水期，河水流经上游围堰前，THg浓度变化非常大，平均浓度高于200ng/L,最高浓度为785ng/L，而流经上游围堰后，平均浓度降低至100ng/L,且浓度变化也显著变小。而在平水期，河水流经上游围堰前，THg浓度显著降低，平均浓度为77ng/L,河水流经上游围堰后，THg平均浓度降至38ng/L,浓度变化也显著变小。在枯水期，河水汞浓度降至最低水平，在上游围堰处及前后河水，THg平均浓度都低于20ng/L,最高浓度不超过30ng/L。THg浓度总体上明显降低，最高可达82%，平均降低浓度约为37%。上游（近炉渣堆）围堰的修建加强了河流的自净能力，降低了汞的迁移距离，使河水在中游时汞浓度远小于地表水环境质量标准（GB3838-2002）中汞浓度的I级限值（50 ng/L）。丰水期河水甲基汞在上游围堰前后都比较高，输入河水甲基汞平均浓度为3ng/L；围堰处河水甲基汞平均浓度为2.36ng/L；围堰后河水甲基汞平均浓度为2.25ng/L。河水流经上游围堰后，甲基汞浓度显著降低。平水期河水甲基汞浓度较丰水期显著下降，输入河水甲基汞平均浓度为0.89ng/L；围堰处河水甲基汞平均浓度为0.88ng/L；围堰后河水甲基汞平均浓度为0.50ng/L。河水流经围堰后，甲基汞浓度有所下降。枯水期河水甲基汞浓度较丰水期和平水期显著下降，输入河水甲基汞平均浓度为0.31ng/L；围堰处河水甲基汞平均浓度为0.32ng/L；围堰后河水甲基汞平均浓度为0.35ng/L。通过分析颗粒态甲基汞含量与溶解态甲基汞含量可知，甲基汞在高浓度条件下，主要与颗粒态甲基汞形式存在，河水流经围堰后，颗粒态甲基汞浓度的降低导致了总甲基汞浓度的降低。河水流经围堰后，甲基汞浓度基本无变化，略有升高，说明河水在枯水期很少接受矿渣堆淋滤汞的情况，甲基汞浓度已经达到背景水平。监测结果显示，围堰的修建没有导致甲基汞浓度的升高，不会增加汞的生态暴露风险。河水中的甲基汞和THg含量呈显著正相关，均与河水流量呈显著正相关。上游各月份输入通量中，丰水期输入汞通量占全部汞输入通量的93.7%，平水期占4.4%，枯水期占1.9%；而输出通量中，丰水期输出汞通量占全部汞输出通量的93.3%，平水期占4.2%，枯水期占2.5%。这说明他们主要来源于矿渣堆的淋滤液。 说明矿渣堆汞向水体传输主要是在丰水期期间进行的。控制汞的迁移应该主要着力于丰水期。岩屋坪汞矿矿渣堆大约有81276吨，矿渣THg平均浓度为23.13mg/kg，可溶态汞浓度平均为6.94μg/kg。汞绝对含量为1879.9kg，DHg绝对含量为564g。研究期内岩屋坪矿渣堆向翁曼河排汞约292g。上游围堰总汞净通量为112.7g。同时说明围堰的修建阻止了汞向中游的传输。其中，直接减少40%的汞向中游的传输，直接作用和间接作用使河流汞向中游迁移的量减少了252.85g，占输入总量的86.6%。同时，在研究期内，上游围堰的修建，河流汞向围堰的修建能极大的增强河流的自净能力，使汞的迁移距离缩短，迁移时间缩短。 |
| 其他摘要 | Mercury is known as a toxic and non-essential element. Impacts on surrounding environment from long mercury mining activities have been attached to extensive attentions all over the world. Early in 1980s, mercury pollutants have been arranged as priority pollutant by organizations and governments in the world. Many large Hg mines were abandoned for increasing environmental concerns and severe pollution situation. However, these abandoned mercury mines persist in discharging abundant Hg through slag, waste water, soil and gas. Hg transports mainly via discharging into atmosphere and moving with river water when released into river, in which, larger amount Hg transport with water flows, causing severe river polluted locally.Wanshan mercury mining district is ever the largest in China. River ... [ More ] Mercury is known as a toxic and non-essential element. Impacts on surrounding environment from long mercury mining activities have been attached to extensive attentions all over the world. Early in 1980s, mercury pollutants have been arranged as priority pollutant by organizations and governments in the world. Many large Hg mines were abandoned for increasing environmental concerns and severe pollution situation. However, these abandoned mercury mines persist in discharging abundant Hg through slag, waste water, soil and gas. Hg transports mainly via discharging into atmosphere and moving with river water when released into river, in which, larger amount Hg transport with water flows, causing severe river polluted locally.Wanshan mercury mining district is ever the largest in China. River nets in Wanshan exist. For reasons, many solid mining waste around mining districts are stacked near the pithead and river valley without any controlment. When rain washes, These wastes release Hg into river, and the pollutants transport with water, finally go into the farmland, causing Hg farmland non-point source pollution. As the river Hg pollution treatment techniques such as Chemical, physics and biological methods are not able to meet the treatment of river Hg pollution in mercury mining area, new technique to control Hg transportation in mining area is needed in China.Based on the previous research and literature survey on water-body Hg pollution treatment techniques, nature attenuation combination with sediment removal techniques are selected to strengthen the attenuation ability of the river ecosystem under the premise of the decrease of treatment costs. Weirs, as selected devices, are built in the upstream and midstream river of Wengman river. Long term monitoring of water Hg concentrations( including total Hg, dissolved Hg, particle Hg and total methyl Hg, dissolved methyl Hg, particle methyl Hg) for ten months are conducted before, at and after the weirs and then set up Hg input/output model to assess the impacts by the devices.pH of the river water is alkaline with an value of 8.75±0.37; and the conductivity is 294±15us/cm. While the total dissolved solids is 141±7mg/L. Results showed that weir construction has no effects on the water quality parameters.In wet season, mercury concentrations of the water before flowing through the weir is very large and vary much with an average of 200 ng/L and the largest 785ng/L. While when the water flow through the weir, THg concentration decreased with an average 100ng/L and varies less. In normal season, THg concentrations of water before the upstream weir decease significant with an average 77ng/L, while THg of water flowing through the weir reduced with an average 38ng/L. While in dry season, THg of water decrease to the lowest level before, at and after the weir. The average concentration is under 20ng/L and the largest did not exceed 30ng/L. In the study period, the water concentration reduced as high as 82% with an average 37%.THg of the midstream weir water is generally below 50ng/L in different periods (Conform to the law of the People's Republic of surface water environmental quality standards I standard).In wet season , methyl mercury (MeHg) concentrations of river water |
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