Article

Occurrence of Arsenic in Ground Water in the Choushui River Alluvial Fan, Taiwan

National Chung Cheng University, Chia-i-hsien, Taiwan, Taiwan
Journal of Environmental Quality (Impact Factor: 2.65). 01/2006; 35(1):68-75. DOI: 10.2134/jeq2005.0129
Source: PubMed

ABSTRACT

An investigation of shallow ground water quality revealed that high arsenic (As) concentrations were found in both aquifers and aquitards in the southern Choushui River alluvial fan of Taiwan. A total of 655 geological core samples from 13 drilling wells were collected and analyzed. High As contents were found primarily in aquitards, to a maximum of 590 mg/kg. The contents were correlated with the locations of the marine sequences. Additionally, strong correlations among the As concentrations of core samples, the clay, and the geological age of the Holocene transgression were identified. Most of the As in ground water originated from the aquitard of the marine sequence. The high As content in marine formations with high clay contents may be attributable to the bioaccumulation of As in the sea organisms, which accrued and were deposited in the formation. A preliminary geogenic model of the origin of the high As concentration in the shallow sedimentary basin of the Choushui River alluvial fan of Taiwan is proposed.

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    • "Subsurface hydrogeological analyses of approximately 300 m in depth partitioned the alluvial fan deposits into four marine units and four nonmarine units in the distal-fan and mid-fan areas (Taiwan Central Geological Survey (CGS), 1999) (the hydrogeological map shown in Chen et al. (2013)). Nonmarine units ranging from medium sand to gravel with high permeability (hydraulic conductivity (K) of more than 0.4 m/day) comprised aquifers, and marine units ranging from clay to fine sand with low permeability (K of less than 0.001 m/day) served as aquitards (Liu et al., 2006). Aquitards were primarily present in the distal-fan and mid-fan regions, but were absent in the proximal-fan region. "
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    • "Arsenic concentration in southern and northern areas of Taiwan from previous studies is collected and classified into different locations and arsenic levels from lowest (0.12 mg/L) to highest (3.59 mg/L) (Liu et al., 2006; Huang et al., 2007; Wang et al., 2007; Tseng et al., 2005; Chiou et al., 2001b; Lamm et al., 2006b) (Table 1). "
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    • "). Liu et al. (2006) indicated over-pumping groundwater induces dissolved oxygen and increases As mobility in water and the relatively high As content has accumulated and been deposited in the marine sequences with fine sediments. "
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