Intercomparison Study of Numerical Models for Long-range Atmospheric Transport of Mercury
Stage I. Comparison of Chemical Modules for Mercury Transformations
in a Cloud/Fog Environment

MSC-E Technical Report 2/2001

A.Ryaboshapko, I.Ilyin, R.Bullock, R.Ebinghaus, K.Lohman, J.Munthe, G.Petersen, C.Seigneur, I.Wangberg

ABSTRACT

The intercomparison study described in this Technical Note represents a first attempt to synthesize the current knowledge of atmospheric mercury chemistry into model systems which can be generally used to evaluate the atmospheric transport and mercury transboundary fluxes in Europe. At the first stage the comparison of modules for physico-chemical transformations of mercury species in a cloud/fog environment with prescribed initial mercury concentrations in ambient air and other physical and chemical parameters relevant for atmospheric mercury transformations has been realized. Five scientific groups involved in atmospheric mercury modeling have participated in the study: U.S. Environmental Protection Agency (USA), GKSS Scientific Research Center (Germany), Atmospheric and Environmental Research/EPRI (USA), Environmental Research Institute (Sweden), Meteorological Synthesizing Centre-East/EMEP (Russia).

Results of individual modules in terms of temporal evolution of mercury concentrations in cloud droplets for a variety of initial concentrations in ambient air have been intercompared. In general, results obtained by all modules agree within a factor of about two. It is confirmed that the modules are based on an adequate parameterization of main physico-chemical processes such as oxidation of mercury both in the gas and aqueous phase, simultaneously occurring reductive processes in the aqueous phase, and the adsorption of oxidized aqueous mercury on soot particles.