Contributions of biogenic volatile organic compounds to the formation of secondary organic aerosols over Mt Tai, Central East China

To better understand the contribution of biogenic volatile organic compounds to the formation of secondary organic aerosol (SOA) in high mountain regions ambient aerosols were collected at the summit of Mt Tai (1534 m a s l) Central East China (CEC) during the Mount Tai Experiment 2006 campaign (MTX2006) in early summer Biogenic SOA tracers for the oxidation of isoprene alpha/beta-pinene and beta-caryophyllene were measured using gas chromatography/mass spectrometry Most of the biogenic SOA tracers did not show clear diurnal variations suggesting that they are formed during long-range atmospheric transport or over relatively long time scales Although isoprene- and alpha/beta-pinene-derived SOA tracers did not correlate with levoglucosan (a biomass burning tracer) beta-caryophyllinic acid showed a good correlation with levoglucosan indicating that crop residue burning may be a source for this acid Total concentrations of isoprene oxidation products are much higher than those of alpha/beta-pinene and beta-caryophyllene oxidation products The averaged ratio of isoprene to alpha/beta-pinene oxidation products (R-iso/pine) was 49 and 67 for the daytime and nighttime samples respectively These values are among the highest in the aerosols reported in different geographical regions which may be due to the large isoprene fluxes and relatively high levels of oxidants such as OH in CEC Using a tracer-based method we estimated the concentrations of secondary organic carbon (SOC) derived from isoprene alpha/beta-pinene and beta-caryophyllene to be 0 42-3 1 mu gC m(-3) (average 1 6 mu gC m(-3)) during the daytime and 0 11-4 2 mu gC m(-3) (1 7 mu gC m(-3)) during the nighttime These values correspond to 2 9-23%(10%) and 3 2-28% (9 8%) of the total OC concentrations in which isoprene-derived SOC accounts for 58% and 63% of total SOC during the daytime and nighttime respectively This study suggests that isoprene is a more significant precursor for biogenic SOA than alpha/beta-pinene and beta-caryophyllene at high altitudes in CEC (C) 2010 Elsevier Ltd All rights reserved