Geological and geochemical examination of arsenic contamination in groundwater in the Holocene Terai Basin, Nepal

Gurung, Jaya K.; Ishiga, Hiroaki; Khadka, Mohan Singh

doi:10.1007/s00254-005-0063-6

Cited by 91 publications

(41 citation statements)

References 15 publications

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“…Groundwater quality is generally good, with little saline groundwater at any depth in the aquifer typology, but elevated As concentrations (>10 μg/L) exist within some parts of the typology (Shrestha et al 2004;Gurung et al 2005;Pokhre et al 2009). The controls of this arsenic contamination are thought to relate to the sediment provenance and the sediment size (relating to the depositional processes) as well as redox conditions.…”

Section: A: Main Piedmont Marginmentioning

confidence: 99%

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

et al. 2017

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The Indo-Gangetic aquifer is one of the world's most important transboundary water resources, and the most heavily exploited aquifer in the world. To better understand the aquifer system, typologies have been characterized for the aquifer, which integrate existing datasets across the IndoGangetic catchment basin at a transboundary scale for the first time, and provide an alternative conceptualization of this aquifer system. Traditionally considered and mapped as a single homogenous aquifer of comparable aquifer properties and groundwater resource at a transboundary scale, the typologies illuminate significant spatial differences in recharge, permeability, storage, and groundwater chemistry across the aquifer system at this transboundary scale. These changes are shown to be systematic, concurrent with large-scale changes in sedimentology of the Pleistocene and Holocene alluvial aquifer, climate, and recent irrigation practices. Seven typologies of the aquifer are presented, each having a distinct set of challenges and opportunities for groundwater development and a different resilience to abstraction and climate change. The seven typologies are: (1) the piedmont margin, (2) the Upper Indus and Upper-Mid Ganges, (3) the Lower Ganges and Mid Brahmaputra, (4) the fluvially influenced deltaic area of the Bengal Basin, (5) the Middle Indus and Upper Ganges, (6) the Lower Indus, and (7) the marine-influenced deltaic areas.

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Section: A: Main Piedmont Marginmentioning

confidence: 99%

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

et al. 2017

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“…The sources of arsenic in the groundwater are geogenic. The dissolution of arsenic-bearing rocks, sediments and minerals contribute arsenic to the groundwater [33,34]. Hydrogeochemical analysis of Terai groundwater results suggested high HCO 3 − and low SO 4 2− concentrations, indicating possible oxidation of organic matter and reduction of sulfate.…”

Section: Sources Of Arsenicmentioning

confidence: 98%

Arsenic Contamination of Groundwater in Nepal—An Overview

Thakur

Ramanathan

et al. 2010

Water

127

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In Nepal, arsenic (As) contamination is a major issue of current drinking water supply systems using groundwater and has recently been one of the major environmental health management issues especially in the plain region, i.e., in the Terai districts, where the population density is very high. The Terai inhabitants still use hand tube and dug wells (with hand held pumps that are bored at shallow to medium depth) for their daily water requirements, including drinking water. The National Sanitation Steering Committee (NSSC), with the help of many other organizations, has completed arsenic blanket test in 25 districts of Nepal by analysing 737,009 groundwater samples. Several organizations, including academic institutions, made an effort to determine the levels of arsenic concentrations in groundwater and their consequences in Nepal. The results of the analyses on 25,058 samples tested in 20 districts, published in the status report of arsenic in Nepal (2003), demonstrated that the 23% of the samples were containing 10-50 µg/L of As, and the 8% of the samples were containing more than 50 µg/L of As. Recent status of over 737,009 samples tested, the 7.9% and 2.3% were contaminated by 10-50 µg/L and OPEN ACCESSWater 2011, 3 2 >50 µg/L, respectively of As. The present paper examines the various techniques available for the reduction of arsenic concentrations in Nepal in combination with the main results achieved, the socio-economic status and the strategies. This paper aims to comprehensively compile all existing data sets and analyze them scientifically, by trying to suggest a common sustainable approach for identifying the As contamination in the nation, that can be easily adopted by local communities for developing a sustainable society. The paper aims also to find probable solutions to quantify and mitigate As problem without any external support. The outcome of this paper will ultimately help to identify various ways for: identify risk areas; develop awareness; adopt the World Health Organization (WHO) guideline; identify alternative safe water sources and assess their sustainability; give priorities to water supply and simple eco-friendly treatment techniques; investigate impacts of arsenic on health and agriculture; strengthen the capability of government, public, Non-governmental Organization (NGO) and research institutions.

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“…Hydrochemical data from shallow wells ranging in depth from 7 to 55 m in the southwestern part of Nawalparasi district in the Terai belt suggest a predominant reducing character with high HCO 3 − and low SO 4 2 − and NO 3 − concentrations [157,159,160]. Elevated HCO 3 − levels primarily are a result of the oxidation of organic matter associated with the sediments.…”

Section: Nepalmentioning

confidence: 99%

“…The redox levels (Eh < − 0.2 V) measured at the well heads are low, triggering the reduction of Fe(III) and Mn(IV) oxides in the aquifer sediments of the region. The sequence of redox reactions or terminal electronaccepting processes prevalent in the TAP aquifers plays a critical role in mobilizing As through the natural interaction between the aqueous phases and the aquifer sediments under anoxic conditions in the groundwater environment of the Terai aquifers [156][157][158][159][160].…”

Section: Nepalmentioning

confidence: 99%

Natural Arsenic in Global Groundwaters: Distribution and Geochemical Triggers for Mobilization

et al. 2016

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The elevated concentration of arsenic (As) in the groundwaters of many countries worldwide has received much attention during recent decades. This article presents an overview of the natural geochemical processes that mobilize As from aquifer sediments into groundwater and provides a concise description of the distribution of As in different global groundwater systems, with an emphasis on the highly vulnerable regions of Southeast Asia, the USA, Latin America, and Europe. Natural biogeochemical processes and anthropogenic activities may lead to the contamination of groundwaters by increased As concentrations. The primary source of As in groundwater is predominantly natural (geogenic) and mobilized through complex biogeochemical interactions within various aquifer solids and water. Sulfide minerals such as arsenopyrite and As-substituted pyrite, as well as other sulfide minerals, are susceptible to oxidation in the near-surface environment and quantitatively release significant quantities of As in the sediments. The geochemistry of As generally is a function of its multiple oxidation states, speciation, and redox transformation. The reductive dissolution of As-bearing Fe(III) oxides and sulfide oxidation are the most common and significant geochemical triggers that release As from aquifer sediments into groundwaters. The mobilization of As in groundwater is controlled by adsorption onto metal oxyhydroxides and clay minerals. According to recent estimates, more than 130 million people worldwide potentially are exposed to As in drinking water at levels above the World Health Organization's (WHO's) guideline value of 10 μg/L. Hence, community education to strengthen public awareness, the involvement and capacity building of local stakeholders in targeting As-safe aquifers, and direct action and implementation of best practices in identifying safe groundwater sources for the installation of safe drinking water wells through action and enforcement by local governments and international water sector professionals are urgent necessities for sustainable As mitigation on a global scale.

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Geological and geochemical examination of arsenic contamination in groundwater in the Holocene Terai Basin, Nepal

Cited by 91 publications

References 15 publications

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

Arsenic Contamination of Groundwater in Nepal—An Overview

Natural Arsenic in Global Groundwaters: Distribution and Geochemical Triggers for Mobilization

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