1University of California, Irvine, 531 Rowland Hall, Irvine, 92697 CA, USA
2University of Miami, RSMAS/MAC, 4600 Rickenbacker Causeway, Miami, 33149 FL, USA
3NASA Langley Research Center, Hampton, 23681 VA, USA
4Max Plank Institute, Atmospheric Chemistry Department, Johannes-Joachim-Becherweg 27, 55128 Mainz, Germany
5Florida State University, Department of Meteorology, Tallahassee Florida 32306-4520, USA
6NCAR, 1850 Table Mesa Drive, Boulder, 80305 CO, USA
Abstract. We present results from the Intercontinental Chemical Transport Experiment – Phase B (INTEX-B) aircraft mission conducted in spring 2006. 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 focused on characterizing the VOC composition of these different pollution plumes. 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 HCFC-134a.
Although elevated mixing ratios of Halon-1211 were measured in some of the Chinese plumes, several measurements at background levels were also observed. After analyzing the VOC distribution in the Chinese pollution plumes and the correlations among selected compounds, we suggest the use of a suite of species, rather than the use of a single gas, to be used as specific tracers of Chinese air masses (namely OCS, CH3Cl, 1,2-dichloroethane, and Halon-1211). In an era of constantly changing halocarbon usage patterns, this suite of gases best reflects new emission characteristics from China.