【摘要】：內(nèi)蒙古地區(qū)的河套盆地高砷地下水已經(jīng)嚴(yán)重威脅居民的健康。還原環(huán)境導(dǎo)致了沉積物中的砷釋放,并將受礦物組分和粒度分布影響。然而,在不同氧化還原環(huán)境中沉積物砷和對(duì)應(yīng)深度地下水砷之間的關(guān)系還鮮為人知。此外,沉積物礦物組分和粒度分布是怎樣影響砷釋放的還不是很清楚。為了探討上述問題,選擇河套盆地為研究區(qū),采了不同深度的沉積物樣品和對(duì)應(yīng)深度地下水樣品,研究了沉積物中不同賦存態(tài)砷的特征及其對(duì)地下水砷富集的影響。得出以下主要認(rèn)識(shí):(1)地下水呈中性-弱堿性,砷濃度范圍為2.26-583μg·L-1。溶解性Fe、As和As(III)隨采樣深度的增加而增加。14 m以上的地下水(弱氧化環(huán)境)普遍要比14 m以下的地下水(還原環(huán)境)Eh高。在淺層(深度14 m)弱氧化環(huán)境的地下水中,砷濃度普遍要比深層(深度14 m)還原環(huán)境中的地下水砷濃度低。(2)分步提取表明,沉積物中Fe、Mn、PO_4~(3-)和TOC對(duì)砷的積累均起到重要作用。沉積物中不同賦存態(tài)砷和總砷分布規(guī)律一致。強(qiáng)結(jié)合態(tài)砷和無定形鐵氫氧化物結(jié)合態(tài)砷占總砷的大部分。粘土和粉質(zhì)粘土中,強(qiáng)結(jié)合態(tài)砷和晶態(tài)鐵氫氧化物結(jié)合態(tài)砷的比例高于粉土和細(xì)砂;而粉土和細(xì)砂中無定形鐵氫氧化物結(jié)合態(tài)砷百分?jǐn)?shù)高于粘土和粉質(zhì)粘土。砷更趨向于富集于化學(xué)風(fēng)化程度高、礦物成熟度高的沉積物中。(3)同深度的溶解態(tài)砷濃度和不同賦存態(tài)砷(S1:弱結(jié)合態(tài)砷,S2:強(qiáng)結(jié)合態(tài)砷,F3:Fe/Mn氧化物結(jié)合態(tài)砷)之間呈正相關(guān)關(guān)系。在還原環(huán)境中,砷趨向于向液相中集中,S2賦存態(tài)砷和溶解態(tài)砷之間的相關(guān)性更好些。在弱氧化環(huán)境中,砷趨向于向固態(tài)中集中,S1賦存態(tài)砷和地下水砷濃度的相關(guān)性更好些。(4)氧化還原交替過程導(dǎo)致了沉積物中砷的釋放,且粒徑小的沉積物釋放的砷更多,沉積物粒徑影響砷的吸附和釋放的速率,同種巖性粒徑小的吸附釋放速率更快。(5)經(jīng)過氧化還原交替實(shí)驗(yàn)后,無論是粘土還是細(xì)砂,非晶態(tài)Fe(OH)3結(jié)合態(tài)As減少,而晶態(tài)Fe(OH)3結(jié)合態(tài)As增加。這說明連續(xù)的氧化還原變化增加了Fe(III)-氫氧化物的結(jié)晶度,從而導(dǎo)致了砷的積累釋放。
[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.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：P641.3

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本文編號(hào)：2198962