TOTAL GASEOUS MERCURY (TGM) AND OZONE (O3) OVER SPRING - SUMMER 2018 AND WINTER 2019 AT THE COL MARGHERITA ATMOSPHERIC OBSERVATORY (2543 M A.S.L.)

Measurements of Hg and O3 in alpine environments are pivotal when evaluating air quality in natural ecosystems as well as when trying to understand regional and synoptic atmospheric transport regimes and advection of air pollutant to the Alps. This study is crucial for the evaluation of Hg exchange processes between soil and atmosphere in a high-altitude alpine environment, where increasing Hg snowpack concentrations occur during winter time, followed by Hg release to the overlying atmosphere during spring and summer time snowmelt. In this context, evaluating the gas phase reaction between elemental mercury and ozone is essential. All the experimental activities were performed at the CNR-IDPA atmospheric observatory at Col Margherita (CMA) that located in the Italian South Eastern Alps, a UNESCO protected region far from anthropogenic and natural sources of air pollutants (altitude 2543 m a.s.l., 46°22'0.6" N, 11°47'30.9" E). Local meteorological conditions, ozone and Total Gaseous Mercury (TGM) has been measured from March 2018 to present. The TGM was monitored using a Tekran 2537B (Tekran Inc.) using the same protocols as used for the GMOS project. Near-surface O3 measurements were taken with a Thermo 49c UV photometric analyzer (Thermo Corp.), following WMO/GAW guidelines. In the present study, daily and monthly levels of hourly Hg and O3 concentrations were assessed and compared the meteorological parameters (i.e. T, RH, P, WS, WD, Solar Radiation, Snowpack). These mercury results obtained during the iGOSP ERA-Planet project were then compared with data taken during GMOS covering the same periods in 2014 and 2015. Notable events were investigated by performing back trajectory atmospheric reanalysis using HYSPLIT. The results showed that Hg concentrations increase, on average, from spring to summer, with some episodes of rapid daytime increase or decrease of atmospheric Hg that could be related to both the O3 variability and specific weather conditions. Another confounder is the presumed release of Hg from freshly deposited snow in the winter months resulting in a large local variability.