Mercury speciation driven by seasonal changes in a contaminated estuarine environment

• Published in: Environmental research 2013-08, Vol.125, p.171-178
• Main Authors: Bratkič, Arne, Ogrinc, Nives, Kotnik, Jože, Faganeli, Jadran, Žagar, Dušan, Yano, Shinichiro, Tada, Akihide, Horvat, Milena
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; ADRIATIC SEA; CARBON; Carbon - analysis; CORRELATIONS; Environmental Monitoring - methods; Environmental Monitoring - statistics & numerical data; ESTUARIES; Gulf of Trieste; Mediterranean Sea; MERCURY; Mercury - analysis; Mercury - chemistry; METHYLMERCURY; Methylmercury Compounds - metabolism; Nitrogen - analysis; NUTRIENTS; ORGANIC MATTER; PARTICLE RESUSPENSION; REDOX POTENTIAL; RIVERS; SALINITY; SAMPLING; Seasonality; Seasons; SEDIMENTS; Slovenia; Soča/Isonzo River estuary; Spectrometry, Fluorescence; SULFIDES; WATER; Water Movements; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2013.01.004

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. ► Water, sediment and pore water mercury species in front of Soča River estuary were measured. ► Seasonally variable hydrological conditions were shown to influence water column Hg speciation. ► Fluxes for total Hg and MeHg from sediment to water were calculated. ► Sediment is a source of total Hg and MeHg to the water column. ► Correlation of MeHg with organic carbon of marine origin suggests in situ formation.