磷石膏影响区重金属地球化学特征及其赋存形态研究

发布时间：2018-05-13 19:44

  本文选题：磷石膏 + 重金属　； 参考：《成都理工大学》2015年硕士论文

【摘要】：我国磷矿资源储量大,以海相沉积型为主,富含有高含量的铀、钍和重金属元素。近年来,随着农用磷肥、复合肥需求的递增,其副产物磷石膏数量急剧上升。研究表明,磷矿石中重金属元素大部分积存在磷石膏中。龙门山地区磷矿及相关化工企业众多,磷石膏大量堆积沱江流域两岸,严重危害当地的生态环境。磷石膏影响区中重金属元素的含量和赋存形态特征,尚不清楚。本论文依托国家自然科学基金“富磷水系中铀的赋存形式与分配研究”,通过石亭江流域典型磷石膏堆影响区内的水、土壤、水系沉积物调查与分析,查明区内重金属含量与赋存形态的分布特征;利用地质累积指数法、潜在生态危害指数法等方法,对研究区重金属元素污染现状进行评价,结果表明:(1)磷石膏堆是研究区内重金属元素重要富集源区。宏达磷石膏堆中Cd、U元素含量分别超过当地土壤平均值9倍、6倍,金河磷石膏堆中Cd、U元素含量分别超过当地土壤平均值3倍、6倍,磷石膏堆中的重金属元素含量可能存在随储积时间增加而减少的趋势。(2)石亭江水体中除U元素出现局部高值外,其他重金属元素As、Cr、Cu、Zn、Cd平均含量均未超过国标Ⅲ类水质标准,未见显著污染。受沿岸磷石膏堆影响,石亭江中As、Zn、Cu、U元素含量出现较高值,总体来说,下游的重金属含量分布表现出逐渐升高的趋势。(3)石亭江水系沉积物中Cd的平均含量为0.34mg/kg,超过土壤环境质量二级标准。Cd、Cr、Pb、U元素在宏达磷石膏堆旁出现异常高值,As、Zn元素在蓥峰磷石膏堆旁出现异常高值,磷石膏堆可能是引起附近水系沉积物中重金属元素含量升高的主要原因。(4)磷石膏影响区土壤中Cd污染较重,Cd平均含量为0.77mg/kg,超过土壤环境质量二级标准。受蓥峰磷石膏堆、宏达磷石膏堆影响,土壤中重金属元素含量增加,并随着距磷石膏堆距离的增加而逐渐减小。(5)磷石膏影响区水系沉积物中各重金属元素主要以残渣态为主,酸提取态、可还原态、可氧化态含量较低。蓥峰磷石膏堆、宏达磷石膏堆处,重金属酸提取态、可氧化态显著增加。水系沉积物中Cd、Cu、Ni元素的迁移性相对强于Cr、U、Pb、Zn、As元素。(6)磷石膏影响区土壤中重金属元素主要以残渣态为主,酸提取态、可还原态、可氧化态所占比例较小。受上游硫酸厂影响,附近土壤中重金属元素可氧化态显著增加,残渣态明显减小。土壤中Cd、Zn、Pb元素的迁移性相对强于Cr、Cu、As、Ni、U元素的迁移性。(7)通过地质累积指数法评价,石亭江水系沉积物中As元素污染程度为无-中度污染,Zn、U、Cd、Pb、Cu、Cr、Ni元素总体无污染。通过潜在生态危害指数法评价,Cd元素潜在生态危害为中等生态危害,其它元素的潜在生态危害均为轻微生态危害,磷石膏堆附近沉积物中重金属生态危害较大,潜在生态危害程度由高到低依次为:CdAsCuPbCrZn。
[Abstract]:The phosphate rock resources in China are rich in uranium, thorium and heavy metals with large reserves, mainly marine sedimentary type and rich in high content of uranium, thorium and heavy metals. In recent years, with the increasing demand of agricultural phosphate fertilizer and compound fertilizer, the amount of phosphogypsum, the by-product, increased sharply. The results show that the heavy metals in phosphate rock are mostly accumulated in phosphogypsum. There are many phosphorite and related chemical enterprises in Longmen Mountain area, and phosphogypsum accumulates on both banks of Tuojiang River basin, which seriously endangers the local ecological environment. The content and occurrence of heavy metals in phosphogypsum affected areas are unclear. Based on the National Natural Science Foundation of China, "study on the form and Distribution of uranium in Phosphorus-rich Water system", through the investigation and analysis of the water, soil and water system sediment in the typical phosphorous gypsum heap in Shiting River Basin, To find out the distribution characteristics of heavy metal content and occurrence form in the study area, to evaluate the present situation of heavy metal element pollution in the study area by means of geological accumulation index method and potential ecological hazard index method, etc. The results show that the phosphogypsum stack is an important source of heavy metal enrichment in the study area. The content of CDU in Hongda phosphogypsum is 9 times higher than that in the local soil, and that in Jin He is 3 times or 6 times higher than that in the local soil. The content of heavy metal elements in phosphogypsum heap may decrease with the increase of storage time. (2) except for the local high value of U element, the average content of other heavy metal elements, As-Cr-Cr-CuCuZn-Zn ~ (+) CD, does not exceed the national standard type 鈪，

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