Sulfur dioxide dry deposition on the loess surface–surface reaction concept for measuring dry deposition flux

As an effort to obtain more extensive data on sulfur dioxide dry deposition in northern China, experiments were carried out in Beijing by trying a new approach to the deposition flux determination. In this approach we determined the flux by a traditional concentration gradient method in the cases where the wind velocity profile conformed to the logarithmic law. In the cases outside the efficacy of the logarithmic law, in which considerable difficulty had been experienced in the traditional method, we resorted to a new concept of regarding the deposition as a reaction between sulfur dioxide and the ground surface. We introduced a mathematical model for the surface reaction, and, determining the reaction parameters on the basis of the logarithmic wind profile data, used the model to evaluate the flux in the non-logarithmic law cases. This method should enable us to obtain the dry deposition data for much more situations, including those which are difficult to be dealt with by the traditional method.