Gaseous Elemental Mercury Level and Distribution in a Heavily Contaminated Site: the Ex-chlor Alkali Plant in Torviscosa (Northern Italy)

Abstract

Mercury (Hg) poses environmental and health risks due to its global distribution and high toxicity exhibited in some of its chemical forms. Although Hg is naturally present in the environment, human activities\ud have increased its cycling among the land, atmosphere and ocean by a factor of three to five comparing the pre-industrial period to the present day. The Torviscosa chlor-alkali plant (CAP), which operated\ud since the beginning of twentieth century, was one of the most important Cl2 production capacity in the Northern Italy and was responsible for an uncontrolled discharge of Hg in the surrounding area. Previous studies reported the high degree of Hg pollution in soils, river sediments and surface waters of the area, but the Hg level in the atmospheric media was never taken into consideration. In this work, an integrated approach was applied with the aim to assess the level, distribution and dispersion of gaseous elemental mercury (GEM) close to the CAP area. GEM levels were monitored by means of four surveys conducted from September 2014 to July 2015, at fixed locations and covering an area of about 10 km2 (including CAP area, Torviscosa village and reclaimed land), accomplished to Hg bioaccumulation measurements in selected lichens. The results indicate that the CAP area currently represents the main source of GEM in the Friuli Venezia Giulia region. The highest levels were found close to the old factory’s buildings (more than 5000 ng m−3), whereas other sites are less impacted. The emission of GEM is not clearly related to the intensity of solar radiation (temperature) at the soil level; however, this latter influences the release\ud from the old buildings employed in the past for the production activities. The most important factor driving the GEM dispersion is the wind, as confirmed by the map of lichens bioaccumulation. In this context, the\ud GEM plume partially affects the nearby village of Torviscosa (about 1 km), but the values found were always well below the international thresholds for residential areas, thus excluding the risk of inhalation for\ud local inhabitants

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

“…As previously mentioned, the pristine environment was chosen for its suitability for comparison with other impacted sites at a considerable distance from Hg-bearing sediments and soils affected by the mining activity of the Idrija Hg mine and from other potential emissions. These sites (BAS and PIR) were previously investigated and showed GEM contents that were on average lower than those found in the other sites (1.02 ± 0.32 and 1.88 ± 1.07 ng m -3 , respectively) [51,52]. It is notable that MON, which is located in an urban area, showed lower values (1.19 ± 0.40 ng m -3 ) considering the hourly average, but the maximum reached up to 17.28 ng m -3 .…”

“…Basic statistics of gaseous elemental mercury (GEM) dataset calculated on raw data (not resampled) and grouped by location. (*) Data published by[52] and ( §)[51].…”

Mercury (Hg) Contaminated Sites in Kazakhstan: Review of Current Cases and Site Remediation Responses

“…However, in general, atmospheric Hg concentrations are rarely above risk-inducing levels, and the major problem with long-range transport of Hg is its deposition and subsequent introduction to the food chain [1]. Hg in ambient air exists mainly in the form of elemental Hg [10,12,13], but there are more Hg compounds in water with varying solubilities: Hg(II) chloride is readily soluble, Hg(I) chloride and HgS are less soluble, and Hg 0 is insoluble in water [14]. Inorganic Hg is then methylated in water by bacterial species (Pseudomonas) in biota, which leads to the formation of very toxic methylmercury (MeHg) that can enter the food chain of the aquatic ecosystem [14].…”

Environmental Partitioning, Spatial Distribution, and Transport of Atmospheric Mercury (Hg) Originating from a Site of Former Chlor-Alkali Plant

“…There are three most critical Hg species in the Atmosphere 2021, 12, 275 2 of 21 troposphere: gaseous elemental mercury (Hg 0 ), reactive gaseous or oxidized mercury, and total particulate mercury [4,5]. Atmospheric Hg emission sources can be natural (water/soil surface evasion, emission from earth's crust, volcanic eruptions, bush and forest fires) or anthropogenic (biomass and coal combustion, metal smelters and incinerators, gold mining, and other industrial processes); however, compared to the pre-industrial levels, anthropogenic activities have increased Hg emissions and cycling in the environment by a factor of three to five [3,6,7].…”

“…During the CAP operation process, Hg is extensively used as a catalyst during brine water electrolysis to produce chlorine and sodium hydroxide and is often discharged with wastewater, solid waste, and atmospheric emissions. This type of plant may continuously release Hg to the surrounding environment (water, soil, and air) not only during the production process but also after its operations are seized [7,14,16,19,20]. Numerous studies have assessed the impact of Hg emissions resulting from the use of the Hg-cell technique in operations of CAPs worldwide [7,14,16,19,20]; some of these studies have focused on atmospheric Hg emissions [21][22][23].…”