Application of polymeric water absorbent film to the study of drop size-resolved fog samples

In order to propose a new method for the collection of size-classified fog droplets using polymeric water absorbent film, both laboratory and field experiments were carried out. The starch-polyacrylic acid sodium (S-PAAS) polymeric water absorbent film (PWAF) with 100±10 μm thickness formed on Nuclepore filter was successfully made. The applicability of particle-induced X-ray emission (PIXE) method to the chemical analysis of size-segregated fog droplets was examined. Field measurements were performed at mountain sites in Kyoto, Japan from the end of February to the end of March 2000. The application of PIXE method to the chemical analysis of fog droplets collected on PWAF was successfully performed without any concern of filter rupture and blank concentration of PWAF. As might be expected, the droplet size dependence of elemental concentration and liquid water content (LWC) of fog samples collected at field measurement was obviously found. Though drop size dependence of LWC cannot be discussed in the whole range of fog droplet size, it shows a continuous increase between 1.4 and 20 μm drop diameter. On the other hand, elemental concentrations varies as a function of droplet diameter, showing monomodal maximum values in 6–10 μm drop size.