Abstract
Biogeochemical processes involving mercury compounds in aquatic environments are of great importance especially in areas where mercury inputs are particularly high, as in the case in the Gulf of Trieste (northern Adriatic Sea). In this study, stable isotope data were used in order to determine the role of sedimentary organic carbon and total nitrogen in the distribution of Hg species. The results show that the major source of inorganic mercury is the river Isonzo, from which mercury is transported into the Gulf, and adsorbed onto particles, while the major source of methylmercury is the bottom sediment of the Gulf itself. Terrigenous nitrogen seems to be involved in the transformation processes of methylmercury in sediments.
Highlights
During the last two decades, the global biogeochemical cycles of many elements have been investigated in considerable detail
The results show that the major source of inorganic mercury is the river Isonzo, from which mercury is transported into the Gulf, and adsorbed onto particles, while the major source of methylmercury is the bottom sediment of the Gulf itself
Isotopic analysis of organic carbon (OC) in sediment was determined after treatment with 3M HCl, while for nitrogen (TN), bulk powdered samples were analysed. δ13C and δ15N were determined after Dumas combustion of samples at 1800°C using a Europa 20-20 continuous-flow stable isotope analyser with ANCA-SL preparation module
Summary
During the last two decades, the global biogeochemical cycles of many elements have been investigated in considerable detail. Hg toxicity often poses a serious threat to wildlife and the human population The interest in this cycle and others, like those of carbon and nitrogen, has been heightened by problems associated with global, regional and local environmental changes. Estimates of the Hg balance in the Gulf of Trieste have shown that the annual input through the Isonzo discharge is about one and a half tons [9] This area is subjected to summer water temperature stratification and hypoxic conditions in the bottom layer [10]. Such conditions generally favour the microbial transformation of inorganic Hg to more toxic MeHg, leading to elevated Hg values in marine organisms [11].
Sign-in/Register to view highlights & summary 
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call