Influence of trans-Pacific pollution transport on acyl peroxy nitrate abundances and speciation at Mount Bachelor Observatory during INTEX-B

[摘要] We present month-long observations of speciated acyl peroxy nitrates (APNs),including PAN, PPN, MPAN, APAN, and the sum of PiBN and PnBN, measured atthe Mount Bachelor Observatory (MBO) as part of the INTEX-B collaborativefield campaign during spring 2006. APN abundances, measured by thermaldissociation-chemical ionization mass spectrometry (TD-CIMS), are discussedin terms of differing contributions from the boundary layer (BL) and thefree troposphere (FT) and in the context of previous APN measurements in theNE Pacific region. PAN mixing ratios range from 11 to 3955 pptv, with a meanvalue of 334 pptv for the full measurement period. PPN is linearlycorrelated with PAN (r²=0.96), with an average abundance of 6.5%relative to PAN; other APNs are generally <1% of PAN. Diurnal cyclesand relationships of APNs with ozone reveal a gradient in hydrocarbonchemistry between the BL and the FT. On average, levels of APNs, ozone andPPN/PAN are substantially higher in FT air relative to BL air, suggestingthat this site is strongly influenced by distant pollution sources. Toestimate the impact of long-range transport of Asian pollution onatmospheric composition at MBO, we perform a detailed analysis utilizingHYSPLIT back trajectories. This analysis suggests that trans-Pacifictransport of Asian pollution leads to substantial increases in APN and ozonemixing ratios at MBO, especially when transport occurs via the freetroposphere. The ensemble of trajectories indicate that Asian-influencedfree tropospheric air was sampled in ~16% of our data and containeda median PAN mixing ratio double that of the full dataset.

[学科分类] 大气科学