Abstract
We present the first assessment of atmospheric pollution by mercury (Hg) in an industrialized area located in the Ossola Valley (Italian Central Alps), in close proximity to the Toce River. The study area suffers from a level of Hg contamination due to a Hg cell chlor-alkali plant operating from 1915 to the end of 2017. We measured gaseous elemental Hg (GEM) levels by means of a portable Hg analyzer during car surveys between autumn 2018 and summer 2020. Moreover, we assessed the long-term dispersion pattern of atmospheric Hg by analyzing the total Hg concentration in samples of lichens collected in the Ossola Valley. High values of GEM concentrations (1112 ng m−3) up to three orders of magnitude higher than the typical terrestrial background concentration in the northern hemisphere were measured in the proximity of the chlor-alkali plant. Hg concentrations in lichens ranged from 142 ng g−1 at sampling sites located north of the chlor-alkali plant to 624 ng g−1 in lichens collected south of the chlor-alkali plant. A north-south gradient of Hg accumulation in lichens along the Ossola Valley channel was observed, highlighting that the area located south of the chlor-alkali plant is more exposed to the dispersion of Hg emitted into the atmosphere from the industrial site. Long-term studies on Hg emission and dispersion in the Ossola Valley are needed to better assess potential impact on ecosystems and human health.
Highlights
Long-range atmospheric transport of mercury (Hg), its transformation to more toxic methylmercury (CH3 Hg) and its bioaccumulation in the environment have motivated intensive research on the dynamics of Hg cycling over the last decades
It is considered a pollutant of global concern and it is globally transported through the atmosphere as gaseous elemental mercury (GEM)
With the aim of assessing the impact of Hg pollution on air quality in the contaminated area around the chemical plant located along the Toce River, in the present study we investigated spatial and temporal changes in Hg distribution coupling short-term measurements of GEM concentrations in air to the measurement of Hg concentration in epiphytic lichens collected in the Ossola Valley at selected sampling points around the chemical plant
Summary
Long-range atmospheric transport of mercury (Hg), its transformation to more toxic methylmercury (CH3 Hg) and its bioaccumulation in the environment have motivated intensive research on the dynamics of Hg cycling over the last decades. Hg is associated with global human health problems due to high toxicity, persistence and bioaccumulation in the aquatic food chain [2,3,4]. It is considered a pollutant of global concern and it is globally transported through the atmosphere as gaseous elemental mercury (GEM). Hgofconcentration lichens collected (from [45], modified).
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