title: 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.
authors.affiliation: United Graduate School of Agricultural Sciences, Ehime University, Matsuyama, 790-8566, Japan. nmphuong81@yahoo.com
authors.forename: Nguyen Minh
authors.initials: NM
authors.lastname: Phuong
authors.forename: Yumei
authors.initials: Y
authors.lastname: Kang
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Sakurai
authors.forename: Miyuki
authors.initials: M
authors.lastname: Sugihara
authors.forename: Chu Ngoc
authors.initials: CN
authors.lastname: Kien
authors.forename: Nguyen Dinh
authors.initials: ND
authors.lastname: Bang
authors.forename: Ha Minh
authors.initials: HM
authors.lastname: Ngoc
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D045483:Rivers / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D014744:Vietnam; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D008903:Minerals; D012987:Soil; D014874:Water Pollutants, Chemical; D007501:Iron; D001151:Arsenic