Bioaccumulation and Translocation of Arsenic in the Ecosystem of the Guandu Wetland, Taiwan

High arsenic (As) levels occur naturally in geothermal areas, potentially polluting downstream wetland ecosystems. The study was to determine the distribution of As among aqueous, solid, and plant phases in the Guandu Wetland of Taiwan. Chemical compounds (As, Fe, Mn, TOC, SO42-, and FeS2) and isotopic compositions (δ34S) in water and soil samples were analyzed to characterize the As distribution. The sequential extraction of As and total As in plant samples wasanalyzed to estimate the bioconcentration factor (BCF) and translocation factor (TF; defined as the ratio of metal concentration in the shoots to those in the roots) of As in Kandelia obovata in aqueous and solid phases. The As concentrations in plants (23.69 mg/kg) were higher than in the surrounding water (0.0018 mg/L) and soils (17.24 mg/kg). Kandelia obovata have high As bioavailability and low TF, causing easy adaptation to grow in As-contaminated wetland ecosystems. BCFplants/water (13657.92) was higher than BCFplants/soil (1.38). The uptake and bioaccumulation of As in Kandelia obovata are significant; therefore, Kandelia obovata is an As accumulator. The uptake As by the Kandelia obovata plant might depend on the oxidation of As-contained FeS2 in the aerial roots and/or adsorption of As on root surface.