Sub-decadal increase of glyoxal and methylglyoxal in atmospheric total suspended particles in East Asia

Abstract:

Glyoxal and methylglyoxal are good tracers to evaluate the chemistry of volatile organic compounds (VOCs) in the atmosphere and are important precursors for the production of secondary organic aerosols (SOA) in aqueous phase. Here we report seasonal and interannual variations of aerosol-phase glyoxal and methylglyoxal over sub-decadal scale (2001-2008) in ambient aerosols collected at Gosan, Jeju Island in the East China Sea. Glyoxal concentrations ranged from 0.06 to 106 ng m^-3, with a peak in January. Concentrations of methylglyoxal ranged from 0.05 to 110 ng m^-3 with a peak in April. The glyoxal peak is related with carbon monoxide and levoglucosan whereas methylglyoxal peak aligns with ozone. These results suggest an elevated combustion sources of glyoxal in January and secondary sources of methylglyoxal in April. A pronounced seasonal variation was observed for methylglyoxal to glyoxal ratios with maximum in summer followed by spring, autumn and winter, suggesting methyglyoxal to glyoxal ratio is an effective proxy to evaluate the strength of biogenic versus anthropogenic sources of organic aerosol in East Asia. Overall, concentrations of glyoxal from 2001 to 2008 increased by at least 29% per year in winter and 83% per year in spring, being consistent with the increase of ozone, carbon monoxide, and biogenic and anthropogenic VOCs in East Asia. We propose that the increased glyoxal and methylglyoxal could be related to an enhanced SOA production by their reactive uptake in aqueous phase over East Asia.