Dicarboxylic acids, ketocarboxylic acids and dicarbonyls in the urban roadside area of Hong Kong

Abstract

Homologous dicarboxylic acids (C 2 -C 12 ), ketocarboxylic acids (ωC 2 -ωC 9 , pyruvic acid) and dicarbonyls (glyoxal and methylglyoxal) have been studied in the urban aerosol samples (PM 2.5 ) collected from the Hong Kong roadside atmosphere during winter and summer of 2003 using a capillary GC and GC-MS method. The concentrations of total dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls were higher in winter than in summer (except for some species like phthalic acid, Ph).Oxalic (C 2 ) acid was found as the most abundant species in summer, followed by Ph.Oxalic (C 2 ) acid was also found as the most abundant species in winter, but followed by malonic (C 3 ) acid. The C 2 diacid comprised 28-66 % of the total diacid concentrations. The diacids with higher carbon numbers were less abundant, although C 9 diacid was relatively abundant (2 %). Glyoxylic acid (ωC 2 ) and methylglyoxal were found as the most abundant ketocarboxylic acid and dicarbonyl in both seasons, * Corresponding author. Tel.: +86-852-27666011; fax: +86-852-23346389. E-mail address: ceslee@polyu.edu.hk (S.C. Lee).2 respectively. The concentrations of the total diacids, total ketoacids and total dicarbonyls ranged from 224 to 1381 ng m -3 , 10 to 89 ng m -3 and 5 to 21 ng m -3 , respectively. Their relative abundances in PM 2.5 mass were 1.18 %, 0.06 % and 0.02 %, respectively. High concentrations of toluene (winter: 33.8 µg m -3 ; summer: 41.3 µg m -3 ) and naphthalenes (winter: 1.2 µg m -3 ; summer: 1.9 µg m -3 ) observed were one possible source for the abundant phthalic and also methylmaleic acids detected.

Chemical Characterization of Water-Soluble Organic Acids in Size-Segregated Particles at a Suburban Site in Saitama, Japan

“…Good correlation was observed between OA and oxidants (r= =0.87 in Table 3, n= =12, p⁄0.001), especially in warm period (spring and summer) (r= =0.92, n= =7, p⁄0.005). The increase of the correlation was found to depend on carbon chain length and on the structure of the acid species, which is consistent with results reported in previous studies (Ho et al, 2006;Kawamura and Yasuib., 2005). In particular, C 2 had the strongest correlation with oxidants (r= =0.90, n= =12, p⁄0.001; Fig.…”

“…Glyoxylic acid (WC 2 ) was an abundant species in all target compounds, and its predominance in ketocarboxylic acids detected in urban atmospheres has been reported (Ho et al, 2006;Kawamura and Yasuib, 2005). Glyoxal (Gly) and methylglyoxal (MeGly) were detected at abundant concentrations in SPM, and MeGly was the most abundant dicarbonyl observed in the particles, most likely because Gly is largely present in the gas phase (Oritz et al, 2006).…”

“…Good correlation was also observed between Ph and C 6 (r= =0.91 in Table 3, n= =12, p⁄0.001); these two dicarboxylic acids were well correlated with EC (r¤0.53 in Table 3, n= =12, p⁄0.07), suggesting that the source of Ph and C 6 was related to incomplete combustion to a certain extent. Ph, an important aromatic acid, can be directly emitted from combustion sources and also can be generated by atmospheric degradation of aro- matic hydrocarbons such as naphthalene (Ho et al, 2006;Kawamura and Ikushima, 1993b). Laboratory experiments have shown that C 6 is produced by photochemical oxidation of cyclic alkenes, which are present in the atmosphere as a result of atmospheric emissions from internal combustion engines (Hatakeyama et al, 1987).…”

Seasonal variations of water-soluble organic carbon, dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls in Central Himalayan aerosols

“…Similarly, the mass ratios of total α−dicarbonyls to TSPM were remarkably higher for summer (almost 3 times). The summertime high concentrations seem to be associated with increased solar radiation (Ho et al, 2006). The daytime concentrations were slightly higher (by˜10 %) than nighttime concentrations for both the seasons.…”

Hydroxyl radical-induced photochemical formation of dicarboxylic acids from unsaturated fatty acid (oleic acid) in aqueous solution

“…Low molecular weight (LMW) dicarboxylic acids and related compounds (C 2 -C 9 ) (DCAs) are ubiquitous water soluble organic compounds that have been detected in a variety of environmental samples including atmospheric aerosols [1], rain waters [2], ice cores [3], marine sediments [4], fresh waters [5] and seawater [6]. Because of their hygroscopic properties, DCAs can act as cloud condensation nuclei and have an impact on the radiative forcing at the Earth's surface [7].…”