河套盆地含水层沉积物赋存态砷及对地下水砷富集的影响
发布时间：2018-08-23 11:34
【摘要】：内蒙古地区的河套盆地高砷地下水已经严重威胁居民的健康。还原环境导致了沉积物中的砷释放,并将受矿物组分和粒度分布影响。然而,在不同氧化还原环境中沉积物砷和对应深度地下水砷之间的关系还鲜为人知。此外,沉积物矿物组分和粒度分布是怎样影响砷释放的还不是很清楚。为了探讨上述问题,选择河套盆地为研究区,采了不同深度的沉积物样品和对应深度地下水样品,研究了沉积物中不同赋存态砷的特征及其对地下水砷富集的影响。得出以下主要认识:(1)地下水呈中性-弱碱性,砷浓度范围为2.26-583μg·L-1。溶解性Fe、As和As(III)随采样深度的增加而增加。14 m以上的地下水(弱氧化环境)普遍要比14 m以下的地下水(还原环境)Eh高。在浅层(深度14 m)弱氧化环境的地下水中,砷浓度普遍要比深层(深度14 m)还原环境中的地下水砷浓度低。(2)分步提取表明,沉积物中Fe、Mn、PO_4~(3-)和TOC对砷的积累均起到重要作用。沉积物中不同赋存态砷和总砷分布规律一致。强结合态砷和无定形铁氢氧化物结合态砷占总砷的大部分。粘土和粉质粘土中,强结合态砷和晶态铁氢氧化物结合态砷的比例高于粉土和细砂;而粉土和细砂中无定形铁氢氧化物结合态砷百分数高于粘土和粉质粘土。砷更趋向于富集于化学风化程度高、矿物成熟度高的沉积物中。(3)同深度的溶解态砷浓度和不同赋存态砷(S1:弱结合态砷,S2:强结合态砷,F3:Fe/Mn氧化物结合态砷)之间呈正相关关系。在还原环境中,砷趋向于向液相中集中,S2赋存态砷和溶解态砷之间的相关性更好些。在弱氧化环境中,砷趋向于向固态中集中,S1赋存态砷和地下水砷浓度的相关性更好些。(4)氧化还原交替过程导致了沉积物中砷的释放,且粒径小的沉积物释放的砷更多,沉积物粒径影响砷的吸附和释放的速率,同种岩性粒径小的吸附释放速率更快。(5)经过氧化还原交替实验后,无论是粘土还是细砂,非晶态Fe(OH)3结合态As减少,而晶态Fe(OH)3结合态As增加。这说明连续的氧化还原变化增加了Fe(III)-氢氧化物的结晶度,从而导致了砷的积累释放。
[Abstract]:High arsenic groundwater in Hetao Basin in Inner Mongolia has seriously threatened the health of residents. The reduction environment results in the release of arsenic from sediments and will be affected by mineral composition and particle size distribution. However, the relationship between arsenic in sediments and groundwater in different redox environments is still unknown. In addition, it is not clear how mineral composition and particle size distribution affect arsenic release. In order to discuss the above problems, the sediment samples and groundwater samples of different depths were collected from the Hetao Basin as the study area, and the characteristics of the different occurrence of arsenic in the sediments and their effects on the arsenic enrichment in the groundwater were studied. The main results are as follows: (1) groundwater is neutral to weak alkaline, and arsenic concentration ranges from 2.26-583 渭 g / L ~ (-1). With the increase of sampling depth, the dissolved Feas and As (III) are generally higher in the groundwater (weak oxidation environment) than that in the groundwater below 14 m (reduction environment). In shallow (14 m) weakly oxidized groundwater, arsenic concentration is generally lower than that in deep (14 m) reduction environment. (2) step by step extraction shows that both Feimanlun PO4- and TOC play an important role in arsenic accumulation in sediments. The distributions of arsenic and total arsenic in sediments are consistent. Strong bound arsenic and amorphous iron hydroxide bound arsenic account for most of the total arsenic. In clay and silty clay, the ratio of strong bound arsenic and crystalline iron hydroxide bound arsenic is higher than that of silt and fine sand, while the percentage of amorphous iron hydroxide bound arsenic in silt and fine sand is higher than that in clay and silty clay. Arsenic tends to be enriched in sediments with high chemical weathering and high mineral maturity. (3) there is a positive correlation between dissolved arsenic concentration at the same depth and different occurrence of arsenic (S1: weakly bound arsenic S2: strongly bound arsenic F3: Fe / mn oxide bound arsenic). In the reduction environment, arsenic tends to concentrate in liquid phase with a better correlation between the soluble arsenic and the S 2 occurring arsenic. In the weakly oxidized environment, arsenic tends to be concentrated in solid state and has better correlation with groundwater arsenic concentration. (4) the alternating redox process leads to the release of arsenic from sediments, and the sediment with small particle size releases more arsenic. The sediment particle size affects the adsorption and release rate of arsenic, and the adsorption and release rate of the same rock size is faster. (5) after the redox alternating experiment, the amorphous Fe (OH) _ 3 binding state as is decreased, whether clay or fine sand. However, the crystalline Fe (OH) _ 3 binding state as increased. The results show that the continuous redox changes increase the crystallinity of Fe (III)-hydroxide and lead to the accumulation and release of arsenic.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P641.3
本文编号：2198962
[Abstract]:High arsenic groundwater in Hetao Basin in Inner Mongolia has seriously threatened the health of residents. The reduction environment results in the release of arsenic from sediments and will be affected by mineral composition and particle size distribution. However, the relationship between arsenic in sediments and groundwater in different redox environments is still unknown. In addition, it is not clear how mineral composition and particle size distribution affect arsenic release. In order to discuss the above problems, the sediment samples and groundwater samples of different depths were collected from the Hetao Basin as the study area, and the characteristics of the different occurrence of arsenic in the sediments and their effects on the arsenic enrichment in the groundwater were studied. The main results are as follows: (1) groundwater is neutral to weak alkaline, and arsenic concentration ranges from 2.26-583 渭 g / L ~ (-1). With the increase of sampling depth, the dissolved Feas and As (III) are generally higher in the groundwater (weak oxidation environment) than that in the groundwater below 14 m (reduction environment). In shallow (14 m) weakly oxidized groundwater, arsenic concentration is generally lower than that in deep (14 m) reduction environment. (2) step by step extraction shows that both Feimanlun PO4- and TOC play an important role in arsenic accumulation in sediments. The distributions of arsenic and total arsenic in sediments are consistent. Strong bound arsenic and amorphous iron hydroxide bound arsenic account for most of the total arsenic. In clay and silty clay, the ratio of strong bound arsenic and crystalline iron hydroxide bound arsenic is higher than that of silt and fine sand, while the percentage of amorphous iron hydroxide bound arsenic in silt and fine sand is higher than that in clay and silty clay. Arsenic tends to be enriched in sediments with high chemical weathering and high mineral maturity. (3) there is a positive correlation between dissolved arsenic concentration at the same depth and different occurrence of arsenic (S1: weakly bound arsenic S2: strongly bound arsenic F3: Fe / mn oxide bound arsenic). In the reduction environment, arsenic tends to concentrate in liquid phase with a better correlation between the soluble arsenic and the S 2 occurring arsenic. In the weakly oxidized environment, arsenic tends to be concentrated in solid state and has better correlation with groundwater arsenic concentration. (4) the alternating redox process leads to the release of arsenic from sediments, and the sediment with small particle size releases more arsenic. The sediment particle size affects the adsorption and release rate of arsenic, and the adsorption and release rate of the same rock size is faster. (5) after the redox alternating experiment, the amorphous Fe (OH) _ 3 binding state as is decreased, whether clay or fine sand. However, the crystalline Fe (OH) _ 3 binding state as increased. The results show that the continuous redox changes increase the crystallinity of Fe (III)-hydroxide and lead to the accumulation and release of arsenic.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P641.3
【参考文献】
相关期刊论文 前2条
1 汤洁，，林年丰，卞建民，刘五洲，张振林;内蒙河套平原砷中毒病区砷的环境地球化学研究[J];水文地质工程地质;1996年01期
2 葛肖虹;;华北板内造山带的形成史[J];地质论评;1989年03期
本文编号：2198962
本文链接：https://www.wllwen.com/kejilunwen/diqiudizhi/2198962.html
