Diurnal fluxes of gaseous elemental mercury from the water-air interface in coastal environments of the northern Adriatic Sea

Federico Floreani; Alessandro Acquavita; Elisa Petranich; Stefano Covelli

doi:10.1016/j.scitotenv.2019.03.012

Diurnal fluxes of gaseous elemental mercury from the water-air interface in coastal environments of the northern Adriatic Sea

Sci Total Environ. 2019 Jun 10:668:925-935. doi: 10.1016/j.scitotenv.2019.03.012. Epub 2019 Mar 3.

Authors

Federico Floreani¹, Alessandro Acquavita², Elisa Petranich¹, Stefano Covelli³

Affiliations

¹ Dipartimento di Matematica e Geoscienze, Università degli Studi di Trieste, Via Weiss 2, 34128 Trieste, Italy.
² Agenzia Regionale per la Protezione Ambientale del Friuli Venezia Giulia, ARPA FVG, Via Cairoli 14, 33057 Palmanova, Udine, Italy.
³ Dipartimento di Matematica e Geoscienze, Università degli Studi di Trieste, Via Weiss 2, 34128 Trieste, Italy; CoN.I.S.Ma. Consorzio Nazionale Interuniversitario per le Scienze del Mare, Piazzale Flaminio 9, 00196 Rome, Italy. Electronic address: covelli@units.it.

PMID: 30870758
DOI: 10.1016/j.scitotenv.2019.03.012

Abstract

A crucial step towards developing a more complete understanding of mercury (Hg) biogeochemical cycling in coastal environments is the measurement of the fluxes of gaseous elemental mercury (GEM), at the water-air interface (W-A interface). A floating flux chamber coupled with a real-time atomic adsorption spectrometer (Lumex-RA 915M) was applied to measure GEM concentrations, and to estimate the diurnal evasion flux at the W-A interface during three seasonal campaigns at four selected sites: two in a lagoon-based fish farm, one in an open lagoon environment highly impacted by long-term activities from the Idrija mercury mine (Slovenia), and an uncontaminated area of the Gulf of Trieste, the Bay of Piran (Slovenia). In this study, the regional background concentration measured at the uncontaminated site of atmospheric GEM (from 1.60 ± 0.95 to 2.87 ± 1.52 ng m^-3) was determined. GEM fluxes at the W-A interface were found to be significantly higher during the summer (from 51.2 ± 8.8 ng m^-2 h^-1 to 79.9 ± 11.4 ng m^-2 h^-1) and correlated to incident solar radiation and water temperature. This finding confirms the importance of these two parameters in the photoreduction and biotic reduction of Hg²⁺ to dissolved gaseous mercury (DGM), which is volatile and easily released to the atmosphere in the form of GEM. These new insights will be of help for future estimates of Hg mass balance in one of the most contaminated areas in the Adriatic Sea.

Keywords: Gaseous elemental mercury; Idrija mercury mine; Mercury evasion; Northern Adriatic Sea; Water-air exchange.