Gaseous Mercury Exchange from Water–Air Interface in Differently Impacted Freshwater Environments

Federico Floreani, Alessandro Acquavita, Nicolò Barago, Katja Klun, Jadran Faganeli and Stefano Covelli
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Federico Floreani: Department of Mathematics & Geosciences, University of Trieste, Via Weiss 2, 34128 Trieste, Italy
Alessandro Acquavita: ARPA FVG Regional Agency for Environmental Protection of Friuli Venezia Giulia, Via Cairoli 14, 33057 Palmanova, Italy
Nicolò Barago: Department of Mathematics & Geosciences, University of Trieste, Via Weiss 2, 34128 Trieste, Italy
Katja Klun: Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia
Jadran Faganeli: Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia
Stefano Covelli: Department of Mathematics & Geosciences, University of Trieste, Via Weiss 2, 34128 Trieste, Italy

IJERPH, 2022, vol. 19, issue 13, 1-19

Abstract: Gaseous exchanges of mercury (Hg) at the water–air interface in contaminated sites strongly influence its fate in the environment. In this study, diurnal gaseous Hg exchanges were seasonally evaluated by means of a floating flux chamber in two freshwater environments impacted by anthropogenic sources of Hg, specifically historical mining activity (Solkan Reservoir, Slovenia) and the chlor-alkali industry (Torviscosa dockyard, Italy), and in a pristine site, Cavazzo Lake (Italy). The highest fluxes (21.88 ± 11.55 ng m −2 h −1 ) were observed at Solkan, coupled with high dissolved gaseous mercury (DGM) and dissolved Hg (THg D ) concentrations. Conversely, low vertical mixing and saltwater intrusion at Torviscosa limited Hg mobility through the water column, with higher Hg concentrations in the deep layer near the contaminated sediments. Consequently, both DGM and THg D in surface water were generally lower at Torviscosa than at Solkan, resulting in lower fluxes (19.01 ± 12.65 ng m −2 h −1 ). However, at this site, evasion may also be limited by high atmospheric Hg levels related to dispersion of emissions from the nearby chlor-alkali plant. Surprisingly, comparable fluxes (15.56 ± 12.78 ng m −2 h −1 ) and Hg levels in water were observed at Cavazzo, suggesting a previously unidentified Hg input (atmospheric depositions or local geology). Overall, at all sites the fluxes were higher in the summer and correlated to incident UV radiation and water temperature due to enhanced photo production and diffusivity of DGM, the concentrations of which roughly followed the same seasonal trend.

Keywords: Idrija mercury mine; chlor-alkali plant; mercury evasion; dissolved gaseous mercury; flux chamber; water-air exchange (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
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