Study of polar organic compounds in airborne particulate matter of a coastal urban city

Abstract

Two classes of polar organic compounds, dicarboxylic acids (DCAs) and sugars/sugar anhydrides (S/SAs), were measured in airborne particulate matter in the area of Thessaloniki, northern Greece. The target compounds were measured simultaneously in two particle fractions PM₁₀ and PM_2.5 during cold and warm periods by employing extraction in an ultrasonic bath with a mixture of MeOH/DCM (1:2 v/v), derivatization with BSTFA-TMCS and GC-MS for analysis. At both fractions, phthalic was the predominant carboxylic acid during cold season and a-ketoglutaric acid in warm season, followed by maleic and malic. Levoglucosan was the dominant sugar anhydride during the cold and arabitol during the warm season. In total, the distribution of DCAs seemed to favor the PM_2.5 particle fraction, probably due to anthropogenic emissions and photochemical formation. The relative contribution of DCAs to PM_2.5 fraction was 0.9–3.2% in cold and 0.9–7.0% in warm period. Regarding S/SAs, levoglucosan was also predominantly distributed in fine particles, with relative contribution to this fraction 0.1–6.3% in cold and <0.65% in warm season, suggesting impact of biomass burning emissions. In contrast, arabitol, fructose, and glucose were mainly found in coarse fraction, possibly due to their biogenic origin. Negative correlation of target compounds with temperature and total solar radiation suggested the contribution of seasonal dependant local sources. Positive relationship with NO and NO₂ oxidants and relative humidity showed secondary formation of polar compounds or enhanced gas-to-particle conversion.

http://ift.tt/2xTT5hT