Multilevel hydrogeochemical monitoring of spatial distribution of arsenic: A case study at Datong Basin, northern China

被引:15
|
作者
Pi, Kunfu
Wang, Yanxin [1 ]
Xie, Xianjun
Liu, Yaqing
Ma, Teng
Su, Chunli
机构
[1] China Univ Geosci, State Key Lab Biogeol & Environm Geol, Wuhan 430074, Peoples R China
基金
中国国家自然科学基金;
关键词
Arsenic mobilization; Redox processes; Hydrochemical monitoring; Groundwater; WEST-BENGAL; COMPETITIVE ADSORPTION; GEOCHEMICAL PROCESSES; SULFATE REDUCTION; IRON-OXIDES; GROUNDWATER; MOBILIZATION; SPECIATION; TRANSPORT; SEDIMENTS;
D O I
10.1016/j.gexplo.2015.09.002
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
To elaborate primary geochemical factors controlling the enrichment and spatial distribution of arsenic (As) species in groundwater systems, multilevel hydrogeochemical monitoring was conducted at an As-contaminated site in central part of Datong Basin, northern China. Aqueous As concentration was highly variable, ranging from 5.47 to 2690 mu g/L. High As groundwater was characterized by elevated HCO3-, Fe(II), HS-, NH4+ and dominated by As(III) species. The positive correlation between As and Fe contents was observed in easily-reducible Fe pool, indicating that poorly crystalline Fe minerals served as an important As sink via chemical adsorption and/or co-precipitation. Under moderately reducing and weakly alkaline conditions (Eh >= 100 mV and pH between 7.69 and 8.04), As mobilization could be controlled by pH-dependent desorption process. The relationships of aqueous As(V) and As(III) versus Fe(II) concentration confirm that reductive dissolution of As-bearing Fe oxides/hydroxides and reductive desorption of As(V) could be responsible for As enrichment and As(III) predominance in groundwater under more reducing conditions (Eh <= 100 mV). The co-presence of elevated As(III) and sulfide indicates that microbial sulfate reduction may promote As(V) transformation into thioarsenate and/or thioarsenite and further into As(III). However, the correlations of As(V) and As(III) concentration versus saturation indices of mackinawite suggest that decrease in aqueous As concentration may be due to re-sequestration of both As(V) and As(III) by Fe(II)-sulfide precipitates. (C) 2015 Published by Elsevier B.V.
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页码:16 / 26
页数:11
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