Source characteristics of oxygenated volatile organic compounds and hydrogen cyanide

Airborne trace gas measurements from TRACE-P, PEM-Tropics B, and INTEX-NA experiments are analyzed to examine the major source factors contributing to the observed variabilities of oxygenated volatile organic compounds and cyanides. Positive matrix factorization (PMF) is applied to coincident measurements of 11 chemicals including CH3OH, CH3COCH3, CH3CHO, C2H2, C2H6, i-C5H12, CO, CH3Cl, and CHBr3. Measurements of HCN and CH3CN are available for TRACE-P and INTEX-NA. We identify major source contributions from the terrestrial biosphere, biomass burning, industry/urban regions, and oceans. Spatial and backtrajectory characteristics of these factors are examined. Based on TRACE-P and PEM-Tropics B data, we find that the terrestrial biogenic factor explains 80-88% of the CH3OH variability, 20-40% of CH3COCH3, 7-35% of CH3CHO, and 41% of HCN. The biogenic contribution to HCN derived from this analysis is much larger than previous global estimates. Cyanogenesis in plants is likely a major emission process for HCN, not fully accounted for previously. Larger contributions than previous global estimations to CH3COCH3 and CH3CHO by biomass burning and industry/urban sources likely reflect significant secondary production from volatile organic compounds (VOC) oxidation. No evidence was found for large emissions of CH3COCH3 from the ocean. The oceanic CH3CHO contribution implies large regional variations.