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篇目详细内容 |
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【篇名】 |
Geostatistical analysis of arsenic concentration in the groundwater of Malda district of West Bengal, India |
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【刊名】 |
Frontiers of Earth Science in China |
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【刊名缩写】 |
Front. Earth Sci. China |
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【ISSN】 |
1673-7385 |
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【EISSN】 |
1673-7490 |
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【DOI】 |
10.1007/s11707-008-0023-z |
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【出版社】 |
Higher Education Press and Springer-Verlag |
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【出版年】 |
2008 |
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【卷期】 |
2
卷3期 |
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【页码】 |
292-301
页,共
10
页 |
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【作者】 |
PURKAIT Barendra;
MUKHERJEE Amitava;
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【关键词】 |
Arsenic; Bengal Basin; Deltaic plain; Geostatistical analysis; West Bengal |
【摘要】 |
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The problem of arsenic (As) poisoning in the upper deltaic plain of the Ganga-Bhagirathi river system in the Bengal Basin of West Bengal, India is an alarming issue. Four blocks (Kaliachak-1, 2, 3 and English Bazar) of Malda district, West Bengal were critically studied. Geomorphologically, the area exhibits three terraces: the present Youngest terrace (T0-terrace), the Older Shaugaon Surface (T1-terrace) and the Oldest Baikunthapur Surface (T2-terrace). On the basis of numerous measurements, including As-content, pH, DO, specific conductivity and salinity, it was observed that maximum As-content beyond the permissible limit (0.05 mg/L, Indian standard) occurs within a depth range of 10–30 m with a non-linear distribution pattern. Variance test also found that a block effect was highly significant in an As-distribution pattern. Mean arsenic level of Kaliachak block-1 is 0.2253 mg/L, followed by Kaliachak-2 with arsenic level 0.1923, Kaliachak-3 with arsenic level 0.1755 and English Bazar with arsenic level 0.1324. The arsenious belt lies mainly within the Older terrace (T1). The very recent flood plain deposits of silvery white, fine sands lying very close to the Ganga River margin do not contain significant amounts of As. Elevated As-concentration in the ground water was observed in alluvial sands, grayish white to brownish in color and occurring away from the Ganga margin. The Oldest terrace (T2) further away from the Ganga margin (e.g. English Bazar) and Barind surface contains less arsenic. Barind surface acts as a hard capping with ferruginous sands and lateritic concretions - chocolate, mottled and purple brown in color - occurring northeast of the studied area. Arsenic content of ground water in the same locality within a radius of ∼ 20 m varies within wide limits. Thus, it poses problem to delineate its distribution pattern. Such a patchy occurrence possibly could not be explained satisfactorily solely by geomorphology. Chemical analysis of aquifer clay samples of the cores shows a maximum As-content of up to 3 mg/kg, whereas the bulk samples (sand-clay mixture) of the cores contain a maximum of 17 mg/kg As-value. Therefore, it is not always true that clay contains elevated As-value. |
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