Estimation of sulphate concentration in high elevation fog in Northeastern North America

Alternate approaches for estimating deposition of acidifying compounds by fog are needed. This paper presents empirical models for estimating concentration of SO42− in fog at high elevation locations in eastern North America. They are based upon meteorological predictors, pollutant emissions data and ambient ozone measurements and were developed using fog measurements from the chemistry of high elevation fog (CHEF) and the mountain cloud chemistry program (MCCP). Optimum models have a relative error (RE) of 0.37, indicating that the variance in the fog SO42− observations could be reduced by 63%. In addition to meteorological observations from nearby airports, the best models also utilized information on air mass history determined from back-trajectories. Ozone, measured at the fog collection site, was also found to be a potentially useful predictor of SO42− in fog. The best models performed as well as models developed from on-site meteorological measurements, indicating that it is possible to estimate fog SO42− from readily available meteorological data.