Field, laboratory, and modeling study of reactive transport of groundwater arsenic in a coastal aquifer.
A field, laboratory, and modeling study of As in groundwater discharging to Waquoit Bay, MA, shed light on coupled control of chemistry and hydrology on reactive transport of As in a coastal aquifer. Dissolved Fe(III) and As(III) in a reducing groundwater plume bracketed by an upper and a lower redox interface are oxidized as water flows toward the bay. This results in precipitation of Fe(III) oxides, along with oxidation and adsorption of As to sediment at the redox interfaces where concentrations of sedimentary HCl-leachable Fe (80-90% Fe(III)) are 734 +/- 232 mg kg(-1) and sedimentary phosphate-extractable As (90-100% As(VI) are 316 +/- 111 microg kg(-1) and are linearly correlated. Batch adsorption of As(III) onto orange, brown, and gray sediments follows Langmuir isotherms and can be fitted by a surface complexation model (SCM) assuming a diffuse layer for ferrihydrite. The sorption capacity and distribution coefficient for As increase with decreasing sediment Fe(II)/Fe. To allow accumulation of the amount of sediment As, similar hydrogeochemical conditions would have been operating for thousands of years at Waquoit Bay. The SCM simulated the observed dissolved As concentration better than a parametric approach based on Kd. Site-specific isotherms should be established for Kd- or SCM-based models.
Jung
Hun Bok
HB
School of Earth and Environmental Sciences, Queens College, The City University of New York, Flushing, New York 11367, USA.
Charette
Matthew A
MA
Zheng
Yan
Y
D000327:Adsorption; D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D005290:Ferric Compounds / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry; D008404:Massachusetts; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D054712:Salinity; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D001151:Arsenic
J Contam Hydrol. 2006 Nov 20;88(1-2):36-54
16945450
Nature. 2005 Aug 25;436(7054):1145-8
16121178
Water Res. 2006 Jun;40(11):2168-80
16725174
Environ Sci Technol. 2008 Apr 1;42(7):2283-8
18504954
Geochem Trans. 2004 Apr 28;5(1):1
35412763
Environ Sci Technol. 2006 May 15;40(10):3273-8
16749693
Science. 1967 Aug 11;157(3789):687-92
17792852
Ground Water. 2003 Mar-Apr;41(2):247-57
12656291