Long-range atmospheric transport of volatile monocarboxylic acids with Asian dust over a high mountain snow site, central Japan

Abstract

Abstract. To understand the long-range transport of monocarboxylic acids from the Asian continent to the Japanese islands, we collected snowpack samples from a pit sequence (depth ca. 6 m) at the Murodo-Daira snowfield near the summit of Mt. Tateyama, central Japan, in 2009 and 2011. Snow samples (n = 16) were analyzed for normal (C 1 -C 10 ), branched chain (iC 4 -iC 6 ), aromatic (benzoic and toluic acid isomers), and hydroxyl (glycolic and lactic) monocarboxylic acids, together with inorganic ions and dissolved organic carbon (DOC). Acetic acid (C 2 ) was found to be a dominant species (average 125 ng g −1 ), followed by formic acid (C 1 ) (85.7 ng g −1 ) and isopentanoic acid (iC 5 ) (20.0 ng g −1 ). We found a strong correlation (r = 0.88) between formic plus acetic acids and non-sea-salt Ca 2+ that is a proxy of Asian dust. Contributions of total monocarboxylic acids to DOC in 2009 (21.2 ± 11.6 %) were higher than that in 2011 (3.75 ± 2.62 %), being consistent with higher intensity of Asian dust in 2009 than in 2011. Formic plus acetic acids also showed a positive correlation (r = 0.90) with benzoic acid that is a tracer of automobile exhaust, indicating that monocarboxylic acids and their precursors are largely emitted from anthropogenic sources in China and/or secondarily produced in the atmosphere by photochemical processing. In addition, the ratio of formic plus acetic acids to nss-Ca 2+ (0.27) was significantly higher than those (0.00036-0.0018) obtained for reference dust materials of Chinese loess deposits from the Tengger and Gobi deserts. This result suggests that volatile and semi-volatile organic acids are adsorbed on the alkaline dust particles during long-range atmospheric transport. Entrainment of organic acids by dusts is supported by a good correlation (r = 0.87) between formic plus acetic acids and pH of melt snow samples. Our study suggests that Asian alkaline dusts may be a carrier of volatile monocarboxylic acids.

Enhanced levels of atmospheric low-molecular weight monocarboxylic acids in gas and particulates over Mt. Tai, North China, during field burning of agricultural wastes

“…We found a strong positive correlation between lactic and isopentanoic acids in both gas (r = 0.91) and particle (r = 0.93) phases ( Figure 10). This result is similar to that obtained for snow pit samples from high mountain site in central Japan, although the snow samples are influenced by the outflow of Asian dust (Mochizuki et al, 2016). We suggest that major portion of lactic and isopentanoic acids were directly derived from the terrestrial ecosystem.…”

“…To our knowledge, this is the first observation on the abundances of branched chain monoacids in atmospheric aerosols. In previous studies, hydroxy monoacids such as lactic acid and branched chain monoacids such as isopentanoic acid are scarcely reported (Kawamura et al, 2012;Miyazaki et al, 2014;Mochizuki et al, 2016) We propose that measurements of biogenic hydroxy and branched chain monoacids are important to evaluate the source of organic aerosols and their atmospheric chemical processing.…”

Distributions and sources of low-molecular-weight monocarboxylic acids in gas and particles from a deciduous broadleaf forest in northern Japan

“…In our previous study, normal (C 1 -C 10 ), branched (iC 4 -iC 6 ) and hydroxy (glycolic and lactic) monoacids were detected in gas, aerosol and snow pit samples (Kawamura et al, 2000;Mochizuki et al, 2016Mochizuki et al, , 2017. In particular, branched (iC 5 ) and hydroxy (lactic) monoacids were abundantly detected in aerosol samples from northeast China .…”

“…LMW monoacids were determined as p-bromophenacyl esters using a capillary gas chromatograph equipped with a flame ionization detector (GC-FID) and a GC with a mass spectrometer (GC-MS) (Kawamura and Kaplan, 1984;Mochizuki et al, 2017). Briefly, an aliquot of filter (4.3 cm 2 ) was extracted for water-soluble organic compounds with organic-free ultrapure water (resistivity of > 18.2 M cm) under ultrasonication.…”

Distributions and sources of gaseous and particulate low molecular weight monocarboxylic acids in a deciduous broadleaf forest from northern Japan

“…In our previous study on organic acids, normal (C1-C10), branched chain (iC4-iC6), and hydroxy (lactic and glycolic) monoacids were detected in gas, aerosol and snow pit samples (Kawamura et al, 2000;Mochizuki et al, 2016;2017a). In particular, branched chain (iC5) and hydroxy (lactic) monoacids were abundantly detected in aerosol samples from North East China (Mochizuki et al, 2017a).…”