Hydroxy Fatty Acids In Rainwater And Aerosols From Suburban Tokyo In Central Japan: The Impact Of Long-Range Transport Of Soil Microbes And Plant Waxes

We characterize here the airborne lipids (beta/omega-hydroxy fatty acids: FAs) specific to soil microbes and plant waxes over suburban Tokyo in simultaneously collected aerosols and rainwater from spring and autumn seasons. Air mass trajectories in spring revealed transport mostly from the North Pacific but with a lesser contribution from East Asia and vice versa in autumn. Low-molecular-weight (<= C-20) beta-hydroxy FAs are more abundant, suggesting their contribution from soil/marine microbial organic matter. The occurrence of high-molecular-weight (>C-20; the subscript denotes carbon chain length) compounds and, in particular, high concentrations of even-C homologs in C-9-C-30 omega-hydroxy FAs revealed their origin from higher plant waxes. Besides, a gradual decrease in beta/omega-hydroxy FA loadings in spring suggests their particle bound nature and efficient removal by wet-scavenging. However, this pattern was not obvious for autumn rains likely because of lateral advection of air parcels. Estimated endotoxin levels of ambient Gram-negative bacteria based on C-10-C-18 beta-hydroxy FAs for the autumn season (median: 14 ng m(-3)) were higher than the inhalable human exposure limit set by the Dutch committee (9 ng m(-3)). These results have implications for understanding endotoxin exposure on human health in Japanese cities during early winter.