Characterization of volatile organic compounds (VOCs) in Asian and north American pollution plumes during INTEX-B: Identification of specific Chinese air mass tracers

By analyzing the mixing ratios of volatile organic compounds (VOCs) measured during the second part of the field campaign, together with kinematic back trajectories, we were able to identify five plumes originating from China, four plumes from other Asian regions, and three plumes from the United States.

To identify specific tracers for the different air masses we characterized their VOC composition and we compared their background levels with those obtained during the 2004 INTEX-A mission. The Chinese and other Asian air masses were significantly enhanced in carbonyl sulfide (OCS) and methyl chloride (CH₃Cl), while all CFC replacement compounds were elevated in US plumes, particularly HFC-134a. Although elevated mixing ratios of Halon-1211 were measured in some Chinese plume samples, several measurements at background levels were also observed.