Geochemical study of arsenic and other trace elements in groundwater and sediments of the Old Brahmaputra River Plain, Bangladesh
Geochemical study of arsenic and other trace elements in groundwater and sediments of the Old Brahmaputra River Plain, Bangladesh
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DOI：
10.1007/s12665-009-0270-7
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发表时间：
2010-05
影响因子：
2.8
通讯作者：
F. Ahmed;M. Bibi;H. Ishiga;T. Fukushima;T. Maruoka
中科院分区：
文献类型：
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作者：
F. Ahmed;M. Bibi;H. Ishiga;T. Fukushima;T. Maruoka
对孟加拉国旧雅鲁藏布江平原地下水和岩心沉积物进行了地球化学研究，探讨了砷及相关微量元素的分布。管井地下水的pH值为6.4 ~ 7.4，溶解氧（DO）为0.8 ~ 1.8 mg/l， Ca含量为5 ~ 50 mg/l， Fe含量为0.2 ~ 12.9 mg/l。砷浓度范围为8 ~ 251 μg/l，平均值为63 μg/l。地下水中砷和铁的浓度呈正相关（r2= 0.802;p= 0.001）。岩心的层序为上部为淡黄色粉质粘土，下部为灰黄色至淡黄色粘土和砂层。岩心沉积物上部3 m和下部（13 ~ 31 m）为氧化层（平均氧化还原电位ORP分别为+170和+220 mV），下部3 ~ 13 m为负（- 35 ~ - 180 mV），表明雅鲁藏布江平原浅层含水层主要处于缺氧状态。年龄测定表明，在海平面变化的海侵期，约2000年和5000年BP （14C年龄）沉积了~10 m深度的粘土层。泥沙和粘土中砷、铅、锌、铜、镍、铬和钒的浓度升高，可能是由于被粘土颗粒吸附所致。在9至13米深度的黑泥炭和泥炭质沉积物中存在大量砷。沉积物中As与Fe呈较强的正相关，表明As可能吸附在含水层沉积物的铁氧化物上。
The geochemical study of groundwaters and core sediments from the Old Brahmaputra plain of Bangladesh was conducted to investigate the distribution of arsenic and related trace elements. Groundwaters from tube wells are characterized by pH of 6.4–7.4, dissolved oxygen (DO) of 0.8–1.8 mg/l, Ca contents of 5–50 mg/l, and Fe contents of 0.2–12.9 mg/l. Arsenic concentrations ranged from 8 to 251 μg/l, with an average value of 63 μg/l. A strong positive correlation exists between As and Fe (r2= 0.802;p= 0.001) concentrations in groundwater. The stratigraphic sequences in the cores consist of yellowish silty clays at top, passing downward into grayish to yellowish clays and sands. The uppermost 3 m and lower parts (from 13 to 31 m) of the core sediments are oxidized (average oxidation reduction potential (ORP) +170 and +220 mV, respectively), and the ORP values gradually become negative from 3 to 13 m depths (−35 to −180 mV), indicating that anoxic conditions prevail in the shallow aquifers of the Brahmaputra plain. Age determinations suggest that clay horizons at ~10 m depth were deposited at around 2,000 and 5,000 years BP (14C ages) during the transgressive phase of sea-level change. Elevated concentrations of As, Pb, Zn, Cu, Ni, Cr, and V are present in the silts and clays, probably due to adsorption onto clay particles. Significant concentrations of As occur in black peat and peaty sediments at depths between 9 and 13 m. A strong positive correlation between As and Fe was found in the sediments, indicating As may be adsorbed onto Fe oxides in aquifer sediments.