Distribution and partitioning of mercury in a river catchment impacted by former mercury mining activity

Abstract

Mercury distribution and partitioning was studied in the River Idrijca system, draining the area of the former Idrija mercury mine, Slovenia. Mercury dynamics were assessed by speciation analysis of mercury in water and river bed sediment samples during a 2-year study at locations on the River Idrijca and its major tributaries. Simultaneously, the influence of some major physico-chemical parameters that influence the fate of mercury in the aquatic environment was investigated. The distribution of mercury species in the River Idrijca catchment indicated contamination from mine tailings distributed in the town of Idrija and erosion of contaminated soils. The partitioning between dissolved and particulate mercury phases in river water was found to be mostly controlled by the variable content of suspended solids resulting from changing hydrological conditions and complexation with various ligands present in river water, among which dissolved organic carbon (DOC) seems to be the most important. Overall results indicate that mercury is transported downstream from the mining area mainly as finely suspended material including colloids rather than in the dissolved phase. This riverine transport occurs mostly during short, but extreme hydro-meteorological conditions when remobilization of mercury from the river bed sediments occurs. A significant part of the mercury particulate phase in water corresponds to cinnabar particles. During its transport, important Hg transformation mechanisms that increase the risk of mercury uptake by biota take place, evidenced by the increase in the relative contribution of reactive mercury (Hg R ), dissolved gaseous mercury (DGM) and monomethylmercury (MeHg) downstream from the Idrija mine. However, our data revealed relatively low methylation efficiency in this contaminated river system. We attribute this to the site specific physico-chemical conditions responsible for making inorganic mercury unavailable and limiting the capacity of methylating bacteria.

The Challenge and Its Solution When Determining Biogeochemically Reactive Inorganic Mercury (RHg): Getting the Analytical Method Right

“…The Idrijca River in Slovenia drains the area of the Idrija Hg mine, now closed but formerly the world's second largest Hg mine. Five sampling locations were selected along the Idrijca River (Figure 7), representative of different levels of Hg impact as determined by previous studies [15,[35][36][37][38][39]. The first location, above the Belca inflow, is a pristine site with very low Hg contamination, while all the downstream sampling sites are affected by the Hg mine to some extent [36].…”

Probabilistic meta-analysis of risk from the exposure to Hg in artisanal gold mining communities in Colombia

“…The geochemistry of Hg has been extensively investigated (UIIrich et al, 2001;Kocman et al, 2011) and its global biogeochemical cycle is well characterized. The impact of Hg environmental contamination on human health has also attracted much scientific attention, originally directed to large-scale industrial releases or agricultural applications (Gochfeld, 2003;Kobal et al, 2004Kobal et al, , 2008.…”

The Legacy of the Idrija Mine Twenty-Five Years after Closing: Is Mercury in the Water Column of the Gulf of Trieste Still an Environmental Issue?

“…It has been demonstrated that Hg contamination in the Gulf of Trieste mostly originates from riverine inputs of the Isonzo/Soča River e.g., [19,22,23] draining Hg-enriched river banks and floodplain deposits along the river basin hosting the second largest Hg mine worldwide [24][25][26]. Indeed, over 500 years of cinnabar (HgS) extraction activity at the Idrija mining district (western Slovenia, Figure 1) has led to Hg contamination of multiple environmental matrices both in the areas surrounding the mine and far from this primary source [24,25,[27][28][29]. the world-wide natural background (0.03 µg•g −1 ) [15] due to both natural and anthropogenic sources.…”

“…Among the most contaminated areas in Italy, the Venice Lagoon, the Marano and Grado Lagoon and the Gulf of Trieste are located in the northern area of the Adriatic Sea [16][17][18][19][20] where marine sediments showed the highest amount of Hg (0.05-8.63 µg•g −1 , [21]), diminishing towards the central and southern sector of the same basin [21]. It has been demonstrated that Hg contamination in the Gulf of Trieste mostly originates from riverine inputs of the Isonzo/Soča River e.g., [19,22,23] draining Hgenriched river banks and floodplain deposits along the river basin hosting the second largest Hg mine worldwide [24][25][26]. Indeed, over 500 years of cinnabar (HgS) extraction activity at the Idrija mining district (western Slovenia, Figure 1) has led to Hg contamination of multiple environmental matrices both in the areas surrounding the mine and far from this primary source [24,25,[27][28][29].…”