粉煤灰复垦土壤中重金属元素的淋溶实验研究

发布时间：2018-07-16 15:29

【摘要】：近年来,随着我国工业化和城市化发展进程的加快促使能源在中国的需求越来越大,燃煤发电是中国电力能源的主要来源,中国是世界上最大的煤炭消费国,也是世界上粉煤灰排弃量最多的国家。由于粉煤灰具有低堆密度、高持水量、适宜的pH值等特点,可以提高土壤的耐久性、刚度和强度,利用粉煤灰作为土壤的充填物料,恢复土壤原有的利用方式,能够提高土壤培肥效果,缩短复垦周期,具有矿区废弃物的回收利用和土壤复垦的双重功效,目前粉煤灰已经成功应用于土壤修复、矿山复垦等方面。然而,在自然降水的条件下,降水的流动性将导致粉煤灰浸出液中的某些重金属元素通过周围的土壤或者岩石的间隙扩散到更深的地下间隙或者更远处,当降水产生的间隙流动的输送性增强,粉煤灰复垦土壤中的某些重金属元素可能会对水环境造成较大的污染。本文通过逐级化学提取实验研究实验中粉煤灰的元素赋存状态,实验结果表明,砷、铬、铜、锌的水溶态和可交换态的含量比例占总含量的0.2%~5.9%之间,属于较容易被浸出的状态,而残渣态占总量的比例较大,属于比较稳定的状态,较难浸出。在酸性条件下,元素的碳酸盐结合态容易被释放出。通过对粉煤灰复垦的土壤连续淋滤2h、8h、14h,对浸出液进行现场分批采样,采用电感耦合等离子体质谱仪(ICP-MS)对浸出液中的砷、铬、铜、锌、硒和锑元素进行分析测定,研究粉煤灰复垦土壤中重金属含量的时空变异规律,分析其可能的污染。研究结果表明,随着复垦土壤距离的增加,这些元素的浓度呈现规律性变化。在下游土壤中,砷元素与铬元素随着复垦距离的增加,浓度一直在增加,其最大平均浓度分别是水体背景值的三倍和五倍;相反,锌元素的浓度随着复垦距离的增加一直在减少。铜元素和锑元素的浓度随着复垦距离的增加先增加后减少;然而,硒元素的浓度在整个淋滤过程中随着复垦距离的增加先减少后增加。不同的元素在浸出液中有不同程度的富集。另一方面,砷元素和锌元素的淋滤浓度排序均为14 h2 h8 h,铬元素和铜元素的淋滤浓度排序均为2h8 h14 h,硒元素的淋滤浓度排序为14 h8 h2 h,而锑元素的淋滤浓度排序为8 h2 h14 h。研究结果可为粉煤灰在土壤复垦中的农业利用提供有用的信息。
[Abstract]:In recent years, with the acceleration of industrialization and urbanization in China, the demand for energy in China is increasing, and coal-fired power generation is the main source of power energy in China, and China is the largest coal consumer in the world. It is also the country with the largest amount of fly ash disposal in the world. Because the fly ash has the characteristics of low pile density, high water holding capacity and suitable pH value, it can improve the durability, rigidity and strength of the soil. The fly ash is used as the filling material of the soil, and the original utilization mode of the soil can be restored. It can improve the effect of soil fertilization, shorten the period of reclamation, and has the dual effects of recycling and reclamation of mine wastes. At present, fly ash has been successfully used in soil remediation, mine reclamation and so on. However, under natural precipitation conditions, the fluidity of precipitation will cause certain heavy metals in the fly ash leachate to spread through the surrounding soil or rock gaps to deeper underground gaps or further away, When the transport capacity of interstitial flow caused by precipitation is enhanced, some heavy metal elements in the soil reclaimed by fly ash may cause great pollution to the water environment. In this paper, the occurrence state of fly ash elements in the experiment was studied by step chemical extraction experiment. The experimental results show that the water soluble and exchangeable state of arsenic, chromium, copper and zinc account for between 0.2% and 5.9% of the total content, so they are easy to be leached out. The residual state is relatively stable and difficult to be leached because of its large proportion of the total amount. In acidic conditions, the carbonate bound states of elements are easily released. The leaching solution was collected in batches by continuous leaching of fly ash for 2 h or 8 h for 14 h. The elements of arsenic, chromium, copper, zinc, selenium and antimony in the leachate were determined by inductively coupled plasma mass spectrometry (ICP-MS), and the results showed that the content of arsenic, chromium, copper, zinc, selenium and antimony in the leachate was determined by inductively coupled plasma mass spectrometry (ICP-MS). The temporal and spatial variation of heavy metal content in fly ash reclamation soil was studied and its possible pollution was analyzed. The results showed that the concentration of these elements changed regularly with the increase of soil reclamation distance. In the downstream soil, the concentration of arsenic and chromium has been increasing with the increase of reclamation distance, and the maximum average concentration is three times and five times of the background value of water body, respectively. The concentration of zinc decreases with the increase of reclamation distance. The concentration of copper and antimony increased first and then decreased with the increase of reclamation distance, however, the concentration of selenium decreased first and then increased with the increase of reclamation distance in the whole leaching process. Different elements are enriched in the leachate to different degrees. On the other hand, the order of leaching concentration of arsenic and zinc is 14 h 2 h 8 h, that of chromium and copper is 14 h 14 h, that of selenium is 14 h 8 h 2 h, and that of antimony is 8 h 2 h 14 h. The results can provide useful information for the agricultural utilization of fly ash in soil reclamation.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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