Mercury is emitted in the atmosphere as elemental vapour (Hg⁰ or GEM, i.e. gaseous elemental mercury) from different sources, including earth’s surface natural degassing and re-evaporation of previously deposited mercury, and past and present anthropogenic activities. The urban environment is not an exception, being characterized and affected by local-sourced emissions (e.g. related to municipal waste, motor vehicles, urban surfaces, industrial activities, and biomass combustion) and by non-point sources of Hg, which, although extremely difficult to identify, can be relevant. In this context, quantifying the presence of mercury in urban air and investigating and deciphering its behavior under different environmental conditions is pivotal, especially following the provisions of the Minamata Convention on Mercury concerning increased knowledge and inventory of Hg emissions. For this purpose, GEM measurements through a Lumex® RA-915M instrument were for the first time performed in different areas of Florence (central Italy) at selected fixed monitoring points and in combination with the analysis of CO₂ and CH₄. Mercury concentrations ranged from <5 to over 150 ng/m³, the daily averages being characterized by a completely different trend with respect to those of CO₂ and CH₄, implying that their emission source(s) and/or behavior in the atmosphere is/are not the same. Indeed, Hg presented a significant increase in the central hours of the day and showed a direct correlation with temperature and an inverse correlation with relative humidity as a consequence of Hg dependence on solar radiation, which causes photochemical reactions that reduce and mobilize previously deposited Hg²⁺. Nevertheless, vehicular traffic (at its highest during peak hours), i.e. the main factor regulating CO₂ and CH₄ dynamics, likely had a minor influence on Hg too, since the measurement stations were characterized by different concentrations in agreement with the traffic intensity.
Gaseous elemental mercury (GEM) in Florence (central Italy): measurements at point stations and comparison with other gaseous pollutants / Cabassi J., Venturi S., Randazzo A., Santi R., Maioli G., Capecchiacci F., Nisi B., Meloni F., Tassi F., Rappuoli D., Vaselli O.. - ELETTRONICO. - (2024), pp. 0-0. (Intervento presentato al convegno 16th International Conference on Mercury as a Global Pollutant ICMGP).
Gaseous elemental mercury (GEM) in Florence (central Italy): measurements at point stations and comparison with other gaseous pollutants
Venturi S.;Meloni F.;Tassi F.;Vaselli O.
2024
Abstract
Mercury is emitted in the atmosphere as elemental vapour (Hg⁰ or GEM, i.e. gaseous elemental mercury) from different sources, including earth’s surface natural degassing and re-evaporation of previously deposited mercury, and past and present anthropogenic activities. The urban environment is not an exception, being characterized and affected by local-sourced emissions (e.g. related to municipal waste, motor vehicles, urban surfaces, industrial activities, and biomass combustion) and by non-point sources of Hg, which, although extremely difficult to identify, can be relevant. In this context, quantifying the presence of mercury in urban air and investigating and deciphering its behavior under different environmental conditions is pivotal, especially following the provisions of the Minamata Convention on Mercury concerning increased knowledge and inventory of Hg emissions. For this purpose, GEM measurements through a Lumex® RA-915M instrument were for the first time performed in different areas of Florence (central Italy) at selected fixed monitoring points and in combination with the analysis of CO₂ and CH₄. Mercury concentrations ranged from <5 to over 150 ng/m³, the daily averages being characterized by a completely different trend with respect to those of CO₂ and CH₄, implying that their emission source(s) and/or behavior in the atmosphere is/are not the same. Indeed, Hg presented a significant increase in the central hours of the day and showed a direct correlation with temperature and an inverse correlation with relative humidity as a consequence of Hg dependence on solar radiation, which causes photochemical reactions that reduce and mobilize previously deposited Hg²⁺. Nevertheless, vehicular traffic (at its highest during peak hours), i.e. the main factor regulating CO₂ and CH₄ dynamics, likely had a minor influence on Hg too, since the measurement stations were characterized by different concentrations in agreement with the traffic intensity.
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