Publications

Bikkina, P; Kawamura, K; Bikkina, S; Yamaguchi, H (2021). Decadal Variations in Hydroxy Fatty Acids Over Chichijima Island in the North Pacific: Long-Term Seasonal Variability in Plant and Microbial Markers. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 126(21), e2020JD033347.

Abstract
To understand the sources and transport pathways of organic compounds associated with soil microbes and higher plant waxes in the East Asian outflow, we assessed source-specific tracers such as alpha-, beta- and omega-hydroxy fatty acids (FAs) in remote marine aerosols collected at Chichijima Island in the western North Pacific (WNP) during 2001-2003. Molecular distributions of hydroxy FAs are characterized by strong even-carbon numbered predominance, indicating biogenic sources. Hydroxy FAs showed a strong seasonality with higher loadings during winter/spring than summer/autumn. Cluster analysis of backward air mass trajectories, satellite-based fire counts and dust extinction data reveal an impact of the East Asian outflow over the WNP in winter/spring. In the spring, there are larger relative abundances of short-chain beta-hydroxy C-10-C-18 FAs (a proxy for soil microbes), consistent with the higher loadings of non-sea-salt Ca2+ (dust tracer). The molecular distributions of beta-hydroxy FAs in spring are in agreement with those of the reference materials of Chinese loess (CJ-1) and simulated Asian mineral dust (CJ-2), suggesting their probable sources in East Asia. A comparison of relative abundances of short-chain beta-hydroxy C-10-C-18 FAs and long-chain omega-hydroxy C-20-C-32 FAs (a proxy for higher plant metabolites) in Chichijima aerosols between this (2001-2003) and previous (1990-1993) studies have unveiled an increment of 20% and 30%, respectively. Such an increase was likely caused by the changes in source strength on a decadal-scale and warrants further investigation. Furthermore, cluster analysis of trajectories and the overall distributions of hydroxy FAs between both datasets have shown their similar provenance in winter/spring.

DOI:
10.1029/2020JD033347

ISSN:
2169-897X