Evaluation of mercury biogeochemical cycling at the sediment–water interface in anthropogenically modified lagoon environments  

作　　者：Elisa Petranich Stefano Covelli Alessandro Acquavita Jadran Faganeli Milena Horvat Marco Contin 

机构地区：[1]Dipartimento di Matematica e Geoscienze, Universita degli Studi di Trieste, Via Weiss 2, 34128 Trieste, Italy [2]Dipartimento di Scienze della Vita, Universita degli Studi di Trieste, Via Licio Giorgieri 5, 34128 Trieste, Italy [3]CoN.I.S.Ma. Consorzio Nazionale Interuniversitario per le Scienze del Mare, Piazzale Flaminio 9, 00196 Rome, Italy [4]Agenzia Regionale per la Protezione Ambientale del Friuli Venezia Giulia, ARPA FVC, Via Cairoli 14, 33057 Palmanoua (Udine), Italy [5]Marine Biological Station, Fornace 41, 6330 Piran, Slovenia [6]Department of Environmental Sciences, Joker Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia [7]Dipartimento di Scienze Agro-Alimentari, Ambientali e Animali, Universita di Udine, Via delle Scienze 206, 33100 Udine, Italy

出　　处：《Journal of Environmental Sciences》2018年第6期5-23,共19页环境科学学报（英文版）

基　　金：supported by the University of Trieste (Finanziamento di Ateneo per progetti di ricerca scientifica-FRA 2014,ref.Stefano Covelli)

摘　　要：The Marano and Grado Lagoon is well known for being contaminated by mercury（Hg） from the Idrija mine（Slovenia） and the decommissioned chlor-alkali plant of Torviscosa（Italy）.Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments（up to 6.81 μg/g）showed a slight variability with depth, whereas the highest methylmercury（MeHg） values（up to 10 ng/g） were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3 cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally（from 0.1 and 17% of dissolved Hg（DHg）） with the highest concentrations in summer. DHg diffusive effluxes higher（up to 444 ng/m^2/day） than those reported in the open lagoon（~ 95 ng/m^2/day）, whereas DMeHg showed influxes in the fish farm（up to-156 ng/m^2/day）. The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.The Marano and Grado Lagoon is well known for being contaminated by mercury（Hg） from the Idrija mine（Slovenia） and the decommissioned chlor-alkali plant of Torviscosa（Italy）.Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments（up to 6.81 μg/g）showed a slight variability with depth, whereas the highest methylmercury（MeHg） values（up to 10 ng/g） were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3 cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally（from 0.1 and 17% of dissolved Hg（DHg）） with the highest concentrations in summer. DHg diffusive effluxes higher（up to 444 ng/m^2/day） than those reported in the open lagoon（~ 95 ng/m^2/day）, whereas DMeHg showed influxes in the fish farm（up to-156 ng/m^2/day）. The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.

关 键 词：MERCURY Benthic fluxes BIOGEOCHEMISTRY LAGOONS Sediment–water interface 

分 类 号：X52[环境科学与工程—环境工程]