Arsenic contamination in groundwater and its possible sources in Hanam, Vietnam

Abstract

This study investigated the arsenic (As) level in groundwater, and the characteristics of aquifer sediment as related to the occurrence of As in groundwater in Hanam, Vietnam. The deposition and transport of As-containing substances through rivers were also examined. Arsenic concentrations in 88% of the groundwater samples exceeded the As limit for drinking water based on the WHO standards. The dominating form of arsenic was As(III). The maximum total As content in bore core sediment was found in a peat horizon of the profiles and generally, elevated levels of As were also found in other organic matter-rich horizons. Total As contents of the bore core sediments were significantly correlated with crystalline iron oxide, silt and clay contents, suggesting that As in aquifer sediment was mainly associated with iron (hydr)oxides and clay mineral. In the groundwater, As concentration showed significant correlations with the total concentrations of Fe and HCO (3)(-). Significant correlations between HCl-extractable As and non-crystalline Fe oxide, total C, N, and S were also observed in the profiles. The results support the hypothesis that under favorable reductive conditions established by the degradation of organic matter, the dissolution of iron (hydr)oxides releases adsorbed As into the groundwater. The deposition of As in the sediments from the Red River were significantly higher than that in the Chau Giang River, suggesting that the Red River is the main source of As-containing substances deposited in the study area.

Reactivity and speciation of mineral-associated arsenic in seasonal and permanent wetlands of the Mekong Delta

“…4). The reducible Fe ranges from 1.3 x 10 4 -1.9 x 10 4 mg Fe/kg -similar to levels found in Red River delta sediments (Phuong et al, 2012) -constituting 27 -44 % of the total Fe.…”

“…Linking As reactivity and speciation to the identity, relative quantity, and reactivity of Fe-bearing minerals in the river basins of South and Southeast Asia is needed to understand the distribution and transport of As. Moreover, efforts to this end have concentrated in the Bengal Basin (Akai et al, 2004;Datta et al, 2009;Ghosh et al, 2006;Hasan et al, 2009;Itai et al, 2010;Polizzotto et al, 2006;Polizzotto et al, 2005;Seddique et al, 2008;Seddique et al, 2011;Swartz et al, 2004;Uddin et al, 2011), and to a lesser extent in the Red River Delta (Vietnam) (Phuong et al, 2012;Postma et al, 2010;Postma et al, 2007) and Datong Basin (China) (Xie et al, 2009a;Xie et al, 2009b;Xie et al, 2011;Xie et al, 2008). Little is known about mineralogical aspects of the Mekong Delta influencing dissolved As concentrations (Kocar et al, 2008;Rowland et al, 2008).…”

The distribution of arsenic in shallow alluvial groundwater under agricultural land in central Portugal: Insights from multivariate geostatistical modeling

“…Similar relations are found in other studies (e.g. Phuong et al, 2012;Selim Reza et al, 2010;Kim et al, 2009). According to these authors, this points towards the reductive dissolution of Fe (hydr)oxides as the essential mechanism of As release, a natural origin of As.…”

“…5b) suggest that dissolved As does not result from the oxidation of As-rich sulfide minerals. Phuong et al (2012) reached similar conclusions in their case study based on low SO 4 2 − concentrations and high correlations between…”

Principal component analysis and hierarchical cluster analyses of arsenic groundwater geochemistry in the Hetao basin, Inner Mongolia

“…2, and Table 3). Effects of reducing conditions have been studied and the similar relations are found (Andrade and Stigter, 2013;Kim et al, 2009;Phuong et al, 2012;Smedley and Kinniburgh, 2002). Surface geology has been considered as an important effect on As concentration in alluvial groundwater (Kim et al, 2009).…”