Multilevel hydrogeochemical monitoring of spatial distribution of arsenic: A case study at Datong Basin, northern China
| Autor: | Teng Ma, Chunli Su, Kunfu Pi, Yaqing Liu, Yanxin Wang, Xianjun Xie |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
chemistry.chemical_classification
Thioarsenite Aqueous solution 010504 meteorology & atmospheric sciences Sulfide chemistry.chemical_element 010501 environmental sciences engineering.material 01 natural sciences chemistry.chemical_compound chemistry Mackinawite Geochemistry and Petrology Environmental chemistry Desorption engineering Economic Geology Sulfate Dissolution Arsenic Geology 0105 earth and related environmental sciences |
| Zdroj: | Journal of Geochemical Exploration. 161:16-26 |
| ISSN: | 0375-6742 |
| Popis: | 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 μg/L. High As groundwater was characterized by elevated HCO 3 − , Fe(II), HS − , NH 4 + 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. |
| Databáze: | OpenAIRE |
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