Investigating Hg species bioavailability in the mine-impacted Gulf of Trieste (Northern Adriatic)

Research output: Unpublished contribution to conferencePoster


Bioaccumulation of sea-borne mercury species results in their biomagnification
in marine food webs, often with detrimental effects to local
ecosystems and increased exposure to humans. Gulf of Triste has been
under continuous 500 year-long Hg stress due to Hg mining in Idrija,
Slovenia. 1.5 tons of Hg are annually still transported into the Gulf, deposited
onto the sediment or distributed further towards Adriatic. Hg
is prone to microbial methylation to monomethyl mercury (MeHg) in
anoxic marine sediments during sulphate and metal reduction processes.
The existence of its bioavailable species is a result of a complex biogeochemical
transformations, as well as specifics of sources and sinks.
To assess the lability and therefore bioavailability of Hg species, we
applied for the first time Diffusive Gradients in Thin-films (DGT) technique
in the water column and sediment in the Gulf of Trieste. Ratios
of MeHg/THg in the water column and sediment porewaters ranged
10-75% and were much higher than previously observed values. Comparing
our results with previously published labile Hg assessments (filtration
and SnCl2 reduction) revealed that labile THg values coincided
more for water column and less for sediment porewater. On the contrary,
labile MeHg values assessed with these techniques were more
similar in porewater than seawater.
In sediment porewater, labile THg and MeHg concentrations varied
with depth (1-7 ng/L and 0.3-2.3 ng/L for THg and MeHg, respectively).
MeHg concentrations were higher at previously determined depths
of sulphate reduction. Variability in THg concentration were probably
due to fractionation between solid and dissolved phase. Sediments appear
to be a source of labile Hg species (1.13 ng/L and 0.78 ng/L for
THg and MeHg, respectively) to the water column, facilitating complexation
and transport with organic matter and/or uptake into the lower
food web. These species are only a small fraction of their total environmental
amount yet may play one of the most important roles in the
interaction with biota.
This work also shows that DGTs can provide valuable data on spatial
and temporal variation in Hg bioavailability caused by global
change-driven transitions of coastal areas. Such information will be key
to support successful mitigation strategies to Hg toxicity in the future.
Original languageEnglish
Number of pages1
Publication statusPublished - 11 Sep 2019
EventInternational Conference on Mercury as a Global Pollutant 2019 -
Duration: 8 Sep 201913 Sep 2019
Conference number: 14


ConferenceInternational Conference on Mercury as a Global Pollutant 2019
Abbreviated titleICMGP 2019
Internet address


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