Simulation of the regional atmospheric transport and fate of mercury using a comprehensive eulerian model

Abstract

This paper describes the development, testing and evaluation of a comprehensive mercury simulation model. The model was developed by starting with an existing model that simulates the sulfur/NO x/VOC system and then substituting modules specific to mercury (e.g. chemistry and scavenging). The transport and fate of mercury emissions in the contiguous United States was simulated with the mercury simulation model. We first tested the model by simulating the sulfur system using emissions from the 1990 U.S. EPA criteria pollutants inventory. This testing provided a measure of the uncertainties in the meteorological input data (e.g. gridded wind, cloud and precipitation fields) and model parameterizations (e.g. transport:) that are common to both the sulfur and mercury systems. The mercury simulation model was then evaluated by comparing model estimates of annual average concentrations and wet deposition amounts of mercury against published measurement data. The mercury evaluation showed that the model captured the range of observed values in most regions where observations were available. Moreover, observed spatial gradients in mercury wet deposition amounts and ambient concentrations were also seen in the model results. For the scenario considered here, the simulation results lead to an annual mercury wet deposition amount that is roughly twice the estimated annual dry deposition amount, for most regions of the modeling domain.