Pubblicazione:
Gaseous mercury evasion from the water-air interface at freshwater environments impacted by different anthropogenic sources
Gaseous mercury evasion from the water-air interface at freshwater environments impacted by different anthropogenic sources
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Data
2021
Autori
Floreani F.
Acquavita A.
Barago N.
Petranich E.
Faganeli J.
Covelli S.
Titolo del Periodico
ISSN Periodico
Titolo volume
Editore
Società Geologica Italiana
Progetti di ricerca
Strutture
Fascicolo Periodico
Abstract
The gaseous exchange of mercury (Hg) at the water-air interface represents an important aspect of
the biogeochemical cycle of this element in the environment. Particularly at sites impacted by Hg due to
anthropogenic activities, evasion can contribute to reduce the amount of this metal in the water column, but
also to widen its spreading in the environment due to the long-range atmospheric transport of the element
(Driscoll et al., 2013). However, dynamics of gaseous elemental Hg emissions from the water-air interface
at Hg contaminated sites are still poorly characterised. In this work, Hg evasion fluxes were monitored by
means of a flux chamber coupled with a real-time gaseous Hg analyzer (Lumex RA915M) in 3 freshwater
environments characterized by different contamination legacy: the artificial reservoir of Solkan (SK-Slovenia)
along the Isonzo River, where Hg contaminated sediments due to cinnabar extraction activities at the Idrija
Hg mine have been accumulated since 1984, date of the dam construction; the dock near a chlor-alkali plant
at Torviscosa (TR-Italy); the Cavazzo Lake (CV-Italy), chosen as pristine environment with no known Hg
sources. At each site, 6 distinct sets of flux measurements were performed at regular time intervals during
the diurnal period in 3 different seasons (spring, summer, and autumn). Moreover, the concentrations of
dissolved gaseous mercury (DGM) were monitored during the sampling period together with total dissolved
Hg, incoming UV radiation and main water physico-chemical parameters. As expected, at all sites the highest
Hg fluxes were found in summer, due to higher irradiation, which favours the formation of volatile DGM
through photoreduction, and higher water temperatures, which decrease the solubility of Hg. On average, Hg
evasion fluxes found in this study were higher than those reported in literature for other background freshwater
environments. Surprisingly, Hg fluxes at CV site were comparable to those of the other sites, likely due to reemission
of Hg of atmospheric origin, but further research is needed to confirm this hypothesis. The widest
diurnal variability of Hg fluxes was observed at TR site, located inside an industrial complex, and likely
related to irregular supplies of Hg through atmospheric depositions and water circulation. Conversely, SK and
CV showed a more regular trend, confirming that Hg fluxes are strongly influenced by local conditions and
site-specific interaction of different factors. Based on these results, the investigated sites can be considered
as secondary sources of Hg for the atmosphere, underlining the importance of direct Hg fluxes monitoring to
understand its fate in the environment.
Driscoll C.T., Mason R.P. Chan H.M., Jacob D.J. & Pirrone N. (2013) - Mercury as a Global Pollutant: Sources, Pathways,
and Effect. Environ. Sci. Technol., 47, 4967-4983.
Descrizione
Parole chiavi
Mercury,
contamination,
flux chamber,
water-air exchange,
evasion