Laboratory measurement of the dry deposition of sulfur dioxide onto northern Chinese soil samples

We investigated soil surface resistance Rc to dry deposition of sulfur dioxide (SO2) onto different types of soils in laboratory experiments, using samples collected from the arid loess plateau and deserts of northern China. We evaluated the factors that affect Rc, which depends on the physical and chemical interaction between a trace constituent and the deposition surface. We observed that the values of Rc for SO2 decreased with increase of soil weight and increased with SO2 concentration, although surface coverage had little effect on Rc. The SO2 uptake rate by all the northern Chinese soil samples seemed to be, on the whole, dependent on relative humidity (RH). In all of the northern Chinese soil samples, Rc was in the range 0.028–0.65 s mm−1, and was exponentially related to the effective surface area of each soil sample, regardless of RH. Wet chemical analysis of sulfur deposited onto the soil samples showed that oxidation ratio of sulfur(IV) to sulfur(VI) was related to RH, which might be related to complex interactions among the amount of water on the soil sample, the pH, and the metallic ions in the liquid phase.