MODELING OF THE MERCURY CYCLE IN THE ATMOSPHERE

摘要

The modeling of the mercury processes has similarities with conventional air pollution modeling to a high degree. The processes involved and especially the aqueous phase chemistry and Gas-to-Particle conversion are very complicated and need special treatment. The model development performed so far gave encouraging results, which need further analysis. The processes included so far seem to work quite satisfactorily but a systematic model evaluation is difficult unless some other controlling factors, like emission inventories and observation quality, are not improved significantly. The present status of the emission inventories is not considered as satisfactory (the order of magnitude of the approximation is still unknown). Also, the accuracy provided by the various measurement techniques certainly needs significant improvement. Several other processes like fluxes of mercury species from/to water bodies or soil are poorly understood so far but play a very important role in the system. In addition, re-emission processes are considered as very important but there is lack of knowledge to a certain degree. Modeling attempts are not only constrained by adequate knowledge but also from available computer resources, despite the fact that the computer power available today is cheap. From our modeling experience with both models, the mercury processes require at least an order of magnitude more the computer power needed for the atmospheric processes, even with the cloud microphysical processes on. Although significant modeling effort is devoted so far, there is still need for further development. There is a need for a better representation of the gas-phase chemistry, which is poorly represented in the current version of the models. A more systematic way for measurements of the various mercury species and a better understanding of the air-water interactions is absolutely necessary.