Five-Year Records of Mercury Concentrations Observed at Ground-Based Monitoring Sites in the Framework of the GMOS Global Network

Long-term monitoring data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad hoc oceanographic cruises and measurement flights in the troposphere and lower stratosphere. To date, more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide, analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted a clear gradient of atmospheric Hg concentrations between the Northern and Southern Hemispheres, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both. In order to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were also collected at 17 selected GMOS monitoring sites providing new insight into baseline concentrations of THg concentrations in precipitation particularly in regions, such as the Southern Hemisphere and Tropical areas where wet deposition were never investigated before, opening the way for additional measurements across the GMOS network and new findings in future modeling studies highlighting the need of integrated measurements in ambient air and rainwater samples to improve our understanding of deposition processes and oxidation mechanisms. These new observations in fact, give scientists and modelers some insight into baseline concentrations of Hg concentrations in air and precipitation with the overarching benefit which clearly consists in the advancement of knowledge about Hg processes on global scale.
Authors:
CARLO BARBANTE
MARIANTONIA BENCARDINO
WARREN RAYMOND LEE CAIRNS
SERGIO CINNIRELLA
FRANCESCO D'AMORE
NICOLA PIRRONE
FRANCESCA SPROVIERI
MASSIMILIANO VARDE'