Characterization and Quantification of Atmospheric Mercury Sources Using Passive Air Samplers

The Minamata Convention on Mercury (Hg) requires improved atmospheric Hg monitoring and characterization of Hg sources. Here we demonstrate how a network of passive air samplers (PASs) can be used cost effectively to determine the spatial distribution of gaseous Hg and estimate atmospheric Hg emissions at contaminated sites. Gaseous Hg concentrations were mapped around a former Hg mine in the Monte Amiata district in Italy using simultaneous deployments of PASs across local and regional spatial scale grids. The concentration maps help visualize with great detail and precision the dispersal of gaseous Hg from a contaminated site, revealing even subtle effects of wind, season, and minor sources. Emissions estimated from the empirical data (8040 and 15075kg/year for October and July, respectively) were robust to changes in the most uncertain parameters (excess Hg in the air above the mine and advection rate) and compared well to previous estimates for this and other closed Hg mines. This PAS-based approach has a number of advantages: (i) concurrent deployments of multiple samplers constrain concentration changes to spatial variability only, (ii) time-averaged data over longer periods negate biases related to short-term, infrequent measurements, (iii) more spatially representative estimates of Hg distributions and emissions can be made at a fraction of the cost, and (iv) use is easy, especially in difficult terrain. Time-averaged data across a broad area are also most pertinent for assessing chronic human exposure, especially in terms of the inhalation of Hg by workers and residents living close to contaminated sites.