Portable X-ray fluorescence (pXRF) is one of the main geochemical techniques employed in multi-elemental analysis screening for contaminated sites management. As the confidence of pXRF analyses are matrix-specific, efforts are made to provide studies of pXRF quality on different geochemical datasets, focusing on less investigated elements such as mercury (Hg) and antimony (Sb), to help both new and experienced users. The analysis of environmental solid samples from two decommissioned mining sites in NE Italy, characterised by Pb-Zn and (Hg-rich) Cu-Sb ore deposits, were prepared with two different protocols and compared with traditional destructive analyses. Sample composition was found strictly dependent to the occurrence of false positives and overestimation at low concentrations. In contrast, milling the sample did not produce major variations in the overall quality. Lead (Pb), Sb, and Zn reached the definitive data quality in at least one of the two datasets. Consequently, as far as a thorough QA/QC protocol is followed, pXRF can rapidly produce chemical data that is as accurate as that produced by destructive standard laboratory techniques, thus allowing to identify potential sources of contamination that could be reprocessed for the extraction of valuable elements and mitigating the dispersion of contaminants and ecological or health risks.

Mercury (Hg) is a global pollutant, being highly persistent in the atmosphere, in particular gaseous elemental mercury (GEM), which can easily be emitted and then transported over long distances. In the Gulf of Trieste (northern Adriatic Sea, Italy), contamination by Hg is well characterised but little is known regarding the concentrations, sources and fate of GEM in the atmosphere. In this work, discrete measurements of GEM were recorded from several sites at different times of the year. The database is consistent with temporal night-day variations monitored using a continuous real-time device. The meteorological conditions were collected as ancillary parameters. GEM levels varied from <LOD (2.0 ng m⁻³) to 48.5 ng m⁻³ (mean 2.7 ng m⁻³), with no significant differences found among sites. A clear daily pattern emerged, with maximum values reached just after sunset. Air temperature, relative humidity, wind speed and direction were identified as the main micrometeorological factors influencing both the spatial and temporal variation of GEM. Our results show that average atmospheric GEM values are higher than the natural background of the Northern Hemisphere and will be useful in future selection regarding the most suitable sites to monitor atmospheric Hg depositions and fluxes from soil and water.

The Marano and Grado Lagoon (Northern Adriatic Sea) has been affected by mercury (Hg) contamination coming from two sources, mining activity and discharges from a chlor-alkali plant (CAP). Sediments and water contamination have been previously well characterised, but little is known about the atmospheric compartment, where Hg is easily emitted and can persist for a long time as gaseous elemental mercury (GEM). In this work, atmospheric GEM levels and its spatial distribution over the lagoon were monitored at several sites by means of both continuous discrete instrumental measurements over several months and the determination of Hg bioaccumulated in lichens (Xanthoria parietina L.). Average GEM levels varied from 1.80 ± 0.74 to 3.04 ± 0.66 ng m⁻³, whereas Hg in lichens ranged between 0.06 to 0.40 mg kg⁻¹. In both cases, the highest values were found downwind of the CAP, but excluding this point, spatial patterns of Hg in the atmosphere and lichens reflected the concentration of this metal in the sediments of the lagoon, showing a decrease moving westward. These results could indicate that the lagoon acts as a secondary source of Hg into the atmosphere: future work is needed to characterise the quantity of releases and depositions at different environments inside the lagoon.

Considerable amounts of gaseous elemental mercury (Hg⁰) can be released into the atmosphere from Hg-enriched substrates, such as those from former mining areas, posing a potential environmental threat. In this work, Hg⁰ fluxes at the soil–air interface under natural vegetation covers were measured in various locations within the Idrija Hg mining area (Slovenia) and its surroundings. Sites were selected in order to compare Hg⁰ fluxes from both forest soils heavily impacted by historical ore roasting and urban soils characterised by a different degree of Hg enrichment due to the natural occurrence of Hg in rocks or recent mining and roasting processes. Replicate measurements at each site were conducted using a non-steady state flux chamber coupled with a real-time Hg⁰ analyser (Lumex RA-915M). Moreover, topsoil samples (0–2 cm) were analysed for Hg total concentration and speciation. Cinnabar was the predominant Hg form in almost all the sites. Despite Hg⁰ being undetectable in soils using thermo-desorption, substantial emissions were observed (70.7–701.8 ng m⁻² h⁻¹). Urban soils in a naturally enriched area showed on average the highest Hg⁰ fluxes, whereas relatively low emissions were found at the historical roasting site, which is currently forested, despite the significantly high total Hg content in soils (up to 219.0 and 10,400 mg kg⁻¹, respectively). Overall, our findings confirm that shading by trees or litter may effectively limit the amount of Hg⁰ released into the atmosphere even from extremely enriched soils, thus acting as a natural mitigation.