title: Land-ocean contributions of arsenic through a river-estuary-ria system (SW Europe) under the influence of arsenopyrite deposits in the fluvial basin.
abstract: Water was sampled monthly from September 2005 to August 2006 at 14 stations distributed throughout the coastal system of Anllóns-Laxe, from where 30 surface sediment samples were also taken. After filtration through 0.22 μm polycarbonate filters, dissolved inorganic and total arsenic (UV oxidation) concentration was determined by HG-AFS. After microwave digestion, the arsenic in SPM and sediment was determined by AAS. Ultra-clean procedures were adopted during sampling, handling and analysis and the analytical accuracy was checked using certified reference material. Spatial distribution of As in water (0.2-4.0 μg L(-1)), SPM (21-169 mg kg(-1)) and sediment of the river reservoir was altered by the presence of arsenopyrite deposits in the middle fluvial basin that increases 2.1±0.5 and 1.7±0.5 times the concentrations of inorganic dissolved (DI-As) and particulate (P-As) arsenic, respectively. At the termination fluvial zone As fluxes can be calculated to be: [DI-As]=7.09·Q(-0.69). The Anllóns River exports to its estuary 460 kg a(-1) of dissolved (<7% as organic) arsenic annually. It is higher (i.e. 0.83 kgs(-1) km(-2) of DI-As) than that of most of European rivers. In the estuary reservoir, the influence of arsenopyrite is also evident as the river concentration of DI-As, which was lower than in seawater during the wet season and higher during the dry season. Arsenic has non-conservative behaviour, as in other European estuaries, but the Anllóns shows an ambivalent pattern: as it usually gains DI-As during the wet season and loses it during the dry season, whilst P-As seems to behave contrary to the DI-As. When the fluvial arsenic reaches the ria its concentration varies due to the estuarine processes. In the wet season DI-As increases its concentration by one third whilst in the dry season it decreases by one fifth and the annual contribution to the ria is 10% higher than the fluvial output. In the case of P-As more data are necessary to quantify its behaviour; however, the estuarine sediments are contaminated by arsenic. In the ria reservoir DI-As levels were similar to those of the ocean, DO-As comprises 9-22% of the inorganic, P-As ranges from 3 to 40 mg kg(-1), and As-sedimentary can be classified as uncontaminated (4-18 mg kg(-1)), except in the fishing ports. The ria circulation, reinforced by upwelling favours the exportation of arsenic to the ocean. In the Anllóns-Laxe system as a whole, the freshwater-saline interface processes do not lead to a decrease in the dissolved fluvial arsenic flux to the ocean.
authors.affiliation: Dept. de Química Analítica y Alimentaria, Faculty of Chemistry (UVigo), Campus de Vigo, 36310 Vigo, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Costas
authors.forename: Ricardo
authors.initials: R
authors.lastname: Prego
authors.forename: Ana V
authors.initials: AV
authors.lastname: Filgueiras
authors.forename: Carlos
authors.initials: C
authors.lastname: Bendicho
mesh_terms: D001151:Arsenic / Q000032:analysis* / Q000737:chemistry; D001152:Arsenicals / Q000032:analysis / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry; D058085:Iron Compounds / Q000032:analysis / Q000737:chemistry; D008903:Minerals / Q000032:analysis / Q000737:chemistry; D052638:Particulate Matter / Q000032:analysis*; D045483:Rivers / Q000737:chemistry; D054712:Salinity; D012621:Seasons; D012623:Seawater / Q000737:chemistry; D013030:Spain; D013050:Spectrometry, Fluorescence; D013054:Spectrophotometry, Atomic; D013440:Sulfides / Q000032:analysis / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D001152:Arsenicals; D058085:Iron Compounds; D008903:Minerals; D052638:Particulate Matter; D013440:Sulfides; D014874:Water Pollutants, Chemical; C064510:arsenopyrite; D001151:Arsenic