title: Mercury speciation driven by seasonal changes in a contaminated estuarine environment.
abstract: In this study, seasonal changes of mercury (Hg) species in the highly variable estuary of Soča/Isonzo River (northern Adriatic Sea) were investigated. Samplings were performed on a seasonal basis (September 2009, May, August and October 2010) and Hg species (total Hg, methylmercury (MeHg), dissolved gaseous Hg (DGM)) in waters, sediments and pore waters were determined. In addition, a range of ancillary parameters were measured (salinity, nutrients, organic carbon (OC), nitrogen species). Hg values were interpreted using these parameters and hydrological conditions (river flow, wave height) around the time of sampling. There were no significant changes in Hg load from river to the gulf, compared to previous studies. The load was temporarily higher in May 2010 due to higher river flow. Wave height, through changing hydrostatic pressure, was most likely to cause resuspension of already deposited Hg from the bottom (August 2010). The estuary is a net source of DGM to the atmosphere as suggested by DGM profiles, with salinity, redox potential and organic matter as the most probable controls over its production. MeHg is produced in situ in sediment or in water column, rather than transported by river, as indicated by its correlation with OC of the marine origin. Calculated fluxes for THg and MeHg showed sediment as a source for both the water column. In pore waters, OC in part affects partitioning of both THg and MeHg; however other factors (e.g. sulphide and/or oxyhydroxides precipitation and dissolution) are also probably important.
authors.affiliation: Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia. arne.bratkic@ijs.si
authors.forename: Arne
authors.initials: A
authors.lastname: Bratkič
authors.forename: Nives
authors.initials: N
authors.lastname: Ogrinc
authors.forename: Jože
authors.initials: J
authors.lastname: Kotnik
authors.forename: Jadran
authors.initials: J
authors.lastname: Faganeli
authors.forename: Dušan
authors.initials: D
authors.lastname: Žagar
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Yano
authors.forename: Akihide
authors.initials: A
authors.lastname: Tada
authors.forename: Milena
authors.initials: M
authors.lastname: Horvat
mesh_terms: D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D063366:Estuaries; D008522:Mediterranean Sea; D008628:Mercury / Q000032:analysis / Q000737:chemistry*; D008767:Methylmercury Compounds / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis; D054712:Salinity; D012621:Seasons; D017524:Slovenia; D013050:Spectrometry, Fluorescence; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D002244:Carbon; D008628:Mercury; D009584:Nitrogen
keywords: Gulf of Trieste; Seasonality; Soča/Isonzo River estuary