Decadal Variations in Hydroxy Fatty Acids Over Chichijima Island in the North Pacific: Long‐Term Seasonal Variability in Plant and Microbial Markers. Issue 21 (27th October 2021)

• Record Type: Journal Article
• Authors: Bikkina, Poonam; Kawamura, Kimitaka; Bikkina, Srinivas; Yamaguchi, Hayato
• Is Part Of: Journal of geophysical research. Volume 126:Issue 21(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-27
• Subjects: hydroxy fatty acids -- decadal variation -- marine aerosols -- remote Pacific Ocean -- plant and microbial markers; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD033347
• Languages: English
• ISSNs: 2169-897X

Abstract

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 α‐, β‐ and ω‐ 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 β‐ hydroxy C10 ‐C18 FAs (a proxy for soil microbes), consistent with the higher loadings of non‐sea‐salt Ca 2+ (dust tracer). The molecular distributions of β‐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 β‐ hydroxy C10 ‐C18 FAs and long‐chain ω‐ hydroxy C20 ‐C32 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. Plain Language Summary: Atmospheric transport is a major source of land‐derived lipid compounds in the deep‐sea sediments. Here, we assessed the source‐specific tracers ( α‐, β‐ and ω‐ hydroxy fatty acids [FAs]) of soil microbes and higher plant waxes in remote marine aerosols collected at Chichijima Island in the western North Pacific during 2001–2003 to understand their sources and transport patterns from East Asia. Molecular distributions of hydroxy FAs revealed characteristic even‐C number predominance, suggesting their origin from plant waxes/soil microbes. Besides, hydroxy FAs showed higher concentrations in winter/spring compared to summer/autumn. High concentrations of short‐chain β‐ (C10 ‐C18 ) hydroxy FAs (tracers of soil‐microbes) coincide with the non‐sea‐salt Ca 2+ loadings (dust tracer) in spring. Similar molecular distributions of β‐ hydroxy FAs in the Chichijima aerosols and 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 β‐ (C10 ‐C18 ) and long‐chain ω‐ (C20 ‐C32 ) hydroxy FAs (tracer of plant lipids) in Chichijima aerosols collected between 2001–2003 and 1990–1993 have unveiled an increment of ∼20% and 30%, respectively. Despite having similar sources in winter/spring between both these datasets, such an increase could only be explained by changes in source strength on decadal‐scale. Key Points: High concentrations of β / ω‐ hydroxy fatty acids (FA) in winter/spring suggest the impact of plant/microbial lipids in the East Asian outflow Distributions of β / ω‐ hydroxy FAs between 1990–93 and 2001‐03 clearly indicate their similar sources in East Asia Significant increases in β‐ (20%) and ω‐ hydroxy FAs (30%) from 1990–93 to 2001–2003 suggest changes in source‐strength of the Asian outflow