The Gulf of Trieste is one of the most mercury-contaminated areas in the Mediterranean Sea. It is characterized by high mercury inputs from the Isonzo River whose tributary, the Idrijca River, drains the mercury mining area of Idrija in Slovenia where extraction activity has taken place for nearly 500 years. This appears, therefore, to be one of the most suitable sites for studying processes that affect Hg cycling in the marine environment and for determining whether sediments might act as secondary sources of mercury species in the water column. Porewater seasonal distributions of total dissolved Hg (HgT) and methylmercury (MeHg) were investigated. Using in situ benthic chambers it was possible to determine benthic fluxes of HgT and MeHg at the water–sediment interface throughout the year. Benthic fluxes were also compared with diffusive fluxes calculated from porewater profiles. The results indicate that, following hypoxic conditions which occurred in late summer in the sea-bottom layer, highest benthic effluxes and porewater concentrations of Hg and MeHg appeared during autumn and winter. This was probably due to the transition from rapid sulphate reduction in late summer to cooler temperatures, higher oxygenation of the bottom water layer, and lower microbial activity which is well suited for Hg transformation, accumulation and flux. A tentative budget based on benthic flux measurements indicates that 75% of HgT is buried in the sediment whereas 25% of HgT, approximately 23% in methylated form, is annually recycled and released at the water–sediment interface.

Pore water distribution and benthic fluxes measurements of mercury and methylmercury in the Gulf of Trieste (Northern Adriatic Sea)

COVELLI, STEFANO;BRAMBATI, ANTONIO
1999-01-01

Abstract

The Gulf of Trieste is one of the most mercury-contaminated areas in the Mediterranean Sea. It is characterized by high mercury inputs from the Isonzo River whose tributary, the Idrijca River, drains the mercury mining area of Idrija in Slovenia where extraction activity has taken place for nearly 500 years. This appears, therefore, to be one of the most suitable sites for studying processes that affect Hg cycling in the marine environment and for determining whether sediments might act as secondary sources of mercury species in the water column. Porewater seasonal distributions of total dissolved Hg (HgT) and methylmercury (MeHg) were investigated. Using in situ benthic chambers it was possible to determine benthic fluxes of HgT and MeHg at the water–sediment interface throughout the year. Benthic fluxes were also compared with diffusive fluxes calculated from porewater profiles. The results indicate that, following hypoxic conditions which occurred in late summer in the sea-bottom layer, highest benthic effluxes and porewater concentrations of Hg and MeHg appeared during autumn and winter. This was probably due to the transition from rapid sulphate reduction in late summer to cooler temperatures, higher oxygenation of the bottom water layer, and lower microbial activity which is well suited for Hg transformation, accumulation and flux. A tentative budget based on benthic flux measurements indicates that 75% of HgT is buried in the sediment whereas 25% of HgT, approximately 23% in methylated form, is annually recycled and released at the water–sediment interface.
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/1692681
 Avviso

Registrazione in corso di verifica.
La registrazione di questo prodotto non è ancora stata validata in ArTS.

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact