2015 年 30 巻 3 号 p. 198-206
Abstract Airborne culturable microbial concentration was measured during spring (April-May) and fall-winter (September-December) in 2011, using commercial aerobic count plates (Sanita-kun Aerobic Counts). Mean microbial concentration was significantly lower in spring than in fall and winter. During a 5-day-long dust event, microbial concentration had a correlation (R2＝0.71) with number concentration of coarse particles (＞2 μm). However, the ratio of microbial to particle number concentrations differs in another dust event, and statistical analysis using data throughout the sampling period yielded no significant correlation between them. Appearance of colonies on the count plates suggests that Bacillus was abundant in spring. The difference in microbial concentration between seasons can possibly be attributed to the difference in microbial species. The statistical analysis revealed that, among meteorological elements, temperature (positive), solar insolation (negative), and wind speed (positive) are influential to microbial concentration. The meteorological elements during several hours before the sampling also have significant correlations with microbial concentration. Rainfall apparently has conflicting effects to microbial concentration, thus should be evaluated case by case.
