【作者】 陈原；

【导师】 王琳；

【作者基本信息】 昆明理工大学 ， 市政工程， 2008， 硕士

【摘要】 铬是煤中常见的有害微量元素之一,主要以六价铬和三价铬两种形态存在。其中六价铬是具有强氧化性,且在环境中的溶解性、迁移性大,高毒性的致癌物:而三价铬迁移性小,毒性低。宣威市是云南省的重要煤炭产地,同时也是全国癌症的高发区。煤及产物中铬对环境和癌症高发的影响不容忽视,在宣威市分布大大小小的堆煤场、贮灰场、矸石山,经过雨水淋溶和冲刷,有害元素铬从煤及产物(煤矸石、粉煤灰)中溶出,向土壤和地下水迁移,对地下水环境造成一定的污染,威胁当地人民的身体健康。本文研究以宣威市来宾镇为研究区域,通过对采集自研究区域的原煤、煤矸石、粉煤灰分析测试,进行室内分批浸出实验和室内淋滤实验后,得出影响煤及产物中铬的淋溶释放影响因素为淋溶液pH值、振荡时间、铬的赋存形式以及铬的含量;并通过淋滤强度的对比,发现粉煤灰中的六价铬较原煤和煤矸石中的易淋出,而总铬的淋滤强度都很低且相差不大,说明从煤及产物中淋出的主要是对环境危害大的六价铬。利用室内淋滤实验获得的参数推导煤及产物中铬的淋溶释放模型,并预测煤及产物中六价铬的年均释放浓度,得出粉煤灰堆淋滤液中六价铬达到0.075mg/L,超过《生活饮用水卫生标准》的限值,对地下水和土壤造成一定威胁。对研究区域采集的包气带土壤进行六价铬的吸附实验和迁移实验,发现在弱碱性环境下包气带土壤对六价铬的吸附量很低,吸附模式符合Henry吸附模型,吸附系数K_d=1.1577;六价铬在包气带中的迁移较保守物质氯离子有一定的迟滞现象。利用HYDRUS-1D软件和对流-弥散方程分别模拟了粉煤灰堆淋滤液中的六价铬在包气带厚度为4米、5米、6米时的迁移变化情况,在粉煤灰堆放0.89年、1.4年和2.01年后,穿透包气带的淋滤液中的六价铬含量超过了0.05mg/L的限值。这对地下水已构成威胁,影响当地人民群众身体健康,建议在粉煤灰的临时和永久堆放场地需采取防渗措施,防止含有六价铬的淋滤液污染地下水和土壤。更多还原

【Abstract】 Being one of common malicious trace elements in coal,chromium mainly takes two forms:chromium（Ⅵ）and chromium（Ⅲ）,each of them displaying striking differences in mobility and toxicity for that the former is highly toxic,soluble and cancerogenic whereas the latter is much less toxic and has a strong affinity for soil particle surfaces.Xuanwei is an important coal producing area in Yunnan and it is also a high-incidence area of cancer in China.The malicious influences chromium has on the local environment can not be neglected for that the poisonous elements of chromium can leach and release from coal and its products（coal gangues and fly ash）,resulting from rainwater’s leaching and scouring of many fields of coal heaps,coal gangues as well as fly ash in Xuanwei.The chromium in leaching solution could transfer into and then pollute the soil and the groundwater, threatening badly the local people’s health.The current research takes Laibin town in Xuanwei as the research area and by analyzing the samples of the coal,coal gangue and fly ash collected from the research area and then by making batch leaching and column leaching experiments,the author gained the data which showed that the pH value of the leaching solution,the shaking time,the existing form as well as the content of chromium were those factors which influenced chromium’s leaching and releasing from coal and its products.By contrasting the leaching intensities of chromium among various samples,the author also found that Cr（Ⅵ）leached easier in fly ash than in coal and coal gangue.The leaching intensities of total Cr,however,were very low and of little difference,showing that Cr（Ⅵ）was the main leaching form from coal and its products.Based on the parameters gained from column leaching experiment,the leaching and releasing model of chromium in coal and its products was deduced and by predicting the annual average releasing concentration of Cr（Ⅵ）in coal and its products,the author found that the concentration of Cr（Ⅵ）in fly ash was 0.075mgL^-1which exceeded the current Chinese drinking water quality standard（GB5749-2006）.The soil and groundwater, therefore,was threatened.In addition,the experiment on the adsorption and transfer of Cr（Ⅵ）in the soil of aeration zone confirmed that the adsorption capacity of Cr（Ⅵ）was very low in alkalescent soil of aeration zone.It also showed that the adsorption mode was Henry adsorption model and the adsorption coefficient was 1.1577.The transfer of Cr（Ⅵ）was somewhat delayed in alkalescent soil comparing to that in conservative matter.By using HYDRUS-1D software and convection-dispersion equation,the author respectively conducted several hypothetical experiments to find out the transferring and changing conditions of Cr（Ⅵ）.The results showed that,when the thickness of the aeration zone was 4m,5m and 6m,the Cr（Ⅵ）concentration of leaching solution would all exceed the limit of 0.05mgL^-1with the fly ash’s deposition time of 0.89a,1.4a and 2.01a.This amount of Cr（Ⅵ）concentration would pollute the groundwater and harm local people’s health.The author,therefore,proposed the suggestion that anti-seepage measure should be adopted in both the temporary and permanent fly ash fields.In so doing,the pollution of Cr（Ⅵ）in the leaching solution towards the groundwater and the soil could be prevented.更多还原