title: Arsenic removal from contaminated brackish sea water by sorption onto Al hydroxides and Fe phases mobilized by land-use.
abstract: This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Rönnskär smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter.
authors.affiliation: Department of Biology and Environmental Science, Linnaeus University, SE-39182 Kalmar, Sweden. Electronic address: changxun.yu@lnu.se.
authors.forename: Changxun
authors.initials: C
authors.lastname: Yu
authors.affiliation: Department of Biology and Environmental Science, Linnaeus University, SE-39182 Kalmar, Sweden.
authors.forename: Pasi
authors.initials: P
authors.lastname: Peltola
authors.affiliation: Department of Geology, Abo Akademi University, FI-20500 Åbo, Finland.
authors.forename: Miriam I
authors.initials: MI
authors.lastname: Nystrand
authors.affiliation: Geological Survey of Finland (GTK), PO Box 96, FI-02151 Espoo, Finland.
authors.forename: Joonas J
authors.initials: JJ
authors.lastname: Virtasalo
authors.affiliation: Department of Geology, Abo Akademi University, FI-20500 Åbo, Finland.
authors.forename: Peter
authors.initials: P
authors.lastname: Österholm
authors.affiliation: Geological Survey of Finland (GTK), PO Box 96, FI-02151 Espoo, Finland.
authors.forename: Antti E K
authors.initials: AE
authors.lastname: Ojala
authors.affiliation: Department of Earth Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Johan K
authors.initials: JK
authors.lastname: Hogmalm
authors.affiliation: Department of Biology and Environmental Science, Linnaeus University, SE-39182 Kalmar, Sweden.
authors.forename: Mats E
authors.initials: ME
authors.lastname: Åström
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D001151:Arsenic / Q000032:analysis / Q000737:chemistry*; D004784:Environmental Monitoring; D063366:Estuaries; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D012623:Seawater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; D000536:Aluminum Hydroxide; D007501:Iron; D001151:Arsenic
keywords: Acid sulfate soils; Arsenic; Estuarine sediments; Rönnskär smelter; The Bothnian Bay