Seasonal variations of monosaccharide anhydrides in PM1 and PM2.5 aerosol in urban areas

摘要

The concentrations of monosaccharide anhydrides (levoglucosan, mannosan, galactosan) in PM1 and PM2.5 aerosol samples were measured in Brno and Slapanice in the Czech Republic in winter and summer 2009. 56 aerosol samples were collected together at both sites to investigate the different sources that contribute to aerosol composition in studied localities. Daily PM1 and PM2.5 aerosol samples were collected on pre-fired quartz fibre filters. The sum of average atmospheric concentration of levoglucosan, mannosan and galactosan in PM1 aerosol in Slapanice and Brno during winter was 513 and 273 ng m~(-3), while in summer the sum of average atmospheric concentration of monosaccharide anhydrides (MAs) was 42 and 38ngm~(-3), respectively. The sum of average atmospheric concentration of MAs in PM1 aerosol formed 71 and 63% of the sum of MA concentration in PM2.5 aerosol collected in winter in Slapanice and Brno, whereas in summer the sum of average atmospheric concentration of MAs in PM1 aerosol formed 45 and 43% of the sum of MA concentration in PM2.5 aerosol in Slapanice and Brno, respectively. In winter, the sum of MAs contributed significantly to PM1 mass ranging between 1.37% and 2.67% of PM1 mass (Brno - Slapanice), while in summer the contribution of the sum of MAs was smaller (0.28 -0.32%). Contribution of the sum of MAs to PM2.5 mass is similar both in winter (1.37-2.71%) and summer (0.44-0.55%). The higher concentrations of monosaccharide anhydrides in aerosols in Slapanice indicate higher biomass combustion in this location than in Brno during winter season. The comparison of levoglucosan concentration in PM1 and PM2.5 aerosol shows prevailing presence of levoglucosan in PM1 aerosol both in winter (72% on average) and summer (60% on average). The aerosol samples collected in Slapanice and Brno in winter and summer show comparable contributions of levoglucosan, mannosan and galactosan to the total amount of monosaccharide anhydrides in both aerosol size fractions. Levoglucosan was the most abundant monosaccharide anhydride with a relative average contribution to the total amount of MAs in the range of 71-82% for PM1 aerosols and 52-79% for PM2.5 aerosols.