Separate chemical characterizations of fog water, aerosol, and gas before, during, and after fog events near an industrialized area in Japan

Fog water, aerosol, and gas were separately collected at Mt. Rokko (altitude 931 m) in Kobe, Japan, using a new sampling method at a mountainous site near a highly industrialized area. The fog water was collected by an active string-fog collector and the aerosol and gas by using the filter pack method. Using plural filter packs and controlling or switching the airflow before, during, and after a fog event made it possible to collect the fog water, aerosol, and gas separately. Nitrate species such as NO3−(p) and HNO3(g) were effectively scavenged by fog water, while sulfur species such as SO42−(p) and SO2(g) could not be easily and effectively scavenged because of the poor solubility of SO2(g). This difficulty was experimentally examined through an in situ investigation. Ion species (especially Na+(p) and Ca2+(p)) which form coarse particles were easily and effectively scavenged by fog water. On the other hand, the difficulty of scavenging Mg2+(p) could not be explained by particle size.