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Study on drainage behaviors of toxic substances from mud sediments at excavation engineering

基坑工程泥浆沉积物有毒物质排出行为研究

基本信息

批准号：
18560782
负责人：
OHTA Takehiro
金额：
$ 2.48万
依托单位：
Railway Technical Research Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18560782/
关键词：
System of civil engineering environment Geochemistry Engineering Geology

项目摘要

The pollution of surface and/or ground water caused by the inflow of drainage water from mudstone excavation sites is a serious issue in Japan. It has been recognized that this issue results from the discharge of sulfate generated by the decomposition of pyrite contained in the mudstone. In general, marine mudstone includes the primary framboidal-type pyrite formed during sedimentation and diagenesis. The pyrite in mudstone discharges acid water into the environment by decomposition during the weathering process. Because the pyrite contains inorganic toxic substances such as arsenic and selenium as minor elements, the acid water from mudstone includes these toxic substances. Therefore, it is afraid that the surface water will be polluted by the acid water drainage containing toxic substances from rock muck disposal site where mudstone are disposed. The drainage water from mudstone-muck disposal site contains inorganic toxic substances in actually, and the concentrations of these substances decrease with time. To understand the behaviours of toxic substances in drainage water, mudstone samples are tested by batch-leaching test and column-leaching test. In the leachate at batch-leaching test, the pH is reduced and the electric conductivity(EC) increases with time. Oppositely, in the drainage water at column-leaching test the pH increases and the EC decreases. These leaching tests are modelled and analyzed by PHREEQC. The results of leaching tests are simulated under the condition, that pyrite, calcite and anorthite are dissolved and gypsum is crystallized in kinetic theory. Therefore, it is possible to presume the water qualities of drainage water from mudstone rock muck by numerical study. From these results, we can evaluate the chemical hazard of drainage water from mudstone rock muck disposal sites based on the geochemical characteristics and leaching features of mudstone and the numerical study for drainage water of rock muck disposal sites.

在日本，泥岩挖掘场排水流入造成的地表水和/或地下水污染是一个严重的问题。人们已经认识到这个问题是由于泥岩中所含的黄铁矿分解产生的硫酸盐的排放造成的。一般来说，海相泥岩包括沉积和成岩过程中形成的原生草莓型黄铁矿。泥岩中的黄铁矿在风化过程中通过分解向环境中排放酸性水。由于黄铁矿中含有微量元素砷、硒等无机有毒物质，泥岩中的酸性水就含有这些有毒物质。因此，处置泥岩的石渣处置场排出的含有有毒物质的酸性废水可能会污染地表水。泥石渣处置场排出的废水中实际上含有无机有毒物质，且这些物质的浓度随着时间的推移而降低。为了了解废水中有毒物质的行为，对泥岩样品进行了批浸试验和柱浸试验。在批量浸出试验中，浸出液的pH随着时间的推移而降低，电导率（EC）增加。相反，在柱浸试验的排水中，pH 值升高，EC 降低。这些浸出测试由 PHREEQC 进行建模和分析。用动力学理论模拟了黄铁矿、方解石、钙长石溶解、石膏结晶条件下的浸出试验结果。因此，可以通过数值研究来推测泥岩岩渣排出水的水质。根据这些结果，可以根据泥岩地球化学特征、淋滤特征以及岩渣处置场排水数值研究，评价泥岩岩渣处置场排水的化学危害性。