Effects of Long Term Hg Contamination on Soil Mercury Speciation and Soil Biological Activities

Abstract

Abstract. The suspended matter discharged by the Isonzo river has carried over, for centuries, heavily contaminated mine spoils from the Idrija mercury mining site (Slovenija). A frequently flooded area at the confluence of the Isonzo and Torre rivers was chosen for a preliminary study on the effects of long term mercury pollution on soil biological activities, Hg speciation and plant bioavailability. Soil mercury contamination reached up to about 80 µg g -1 near the banks of Isonzo river and decreased down to about 0.2 µg g -1 near the Torre river, with the predominance of mercuric sulfide and elemental mercury. Soil microbial biomass was not adversely affected by Hg contamination as most soil biological activities, with the exception of arylsulphatase and acid phosphatase, which showed significant negative trends against total mercury and its fractions. Two plant genres (Arum spp. and Rubus spp.) were collected in four different places: Rubus spp. showed the largest uptake capacity of mercury (about 1 µg g -1 ). Long term mercury contamination does not seem to constitute a stressing factor for soil biological activities but remains nevertheless a concern for its transfer through the food chain.

Spatial and Temporal Trends of Gaseous Elemental Mercury over a Highly Impacted Coastal Environment (Northern Adriatic, Italy)

“…Several pollutants (i.e., trace elements and POPs) represent a concern for the area as highlighted in numerous previous studies [34][35][36][37][38][39][40][41][42][43][44]. However, mercury contamination due to secular inland mining exploitation from Idrija (NW Slovenia) shows a wide diffusion in sediments, waters and soils [32,[45][46][47]. 1).…”

Gaseous mercury evasion from bare and grass-covered soils contaminated by mining and ore roasting (Isonzo River alluvial plain, Northeastern Italy)

“…Leaching and erosion of contaminated soils and sediments, mostly during rain events, favour the mobilization and transport of Hg to the Isonzo River and then finally to the northern Adriatic Sea (Baptista-Salazar et al, 2017;Pavoni et al, 2021). Due to flooding events, Hg has been re-distributed over the entire alluvial plain of the Isonzo River, resulting in high concentrations in soils (up to 76 mg kg − 1 ) which progressively decrease as the distance from the river increases (Acquavita et al, 2022;Cerovac et al, 2018;Piani et al, 2013). Few studies have highlighted the occurrence of Hg 0 atmospheric concentrations which are slightly higher than the natural background, mostly in the coastal sector of the southernmost part of the plain (Barago et al, 2020;Floreani et al, 2020), but a direct evaluation of potential Hg 0 releases at the soil-air interface is still lacking.…”