An overview of reactive chlorine measurements during the WINTER C-130 aircraft campaign
Wednesday, 16 December 2015: 16:45
3010 (Moscone West)
As part of the Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) campaign, the University of Washington Iodide-adduct high resolution time of flight chemical ionization mass spectrometer (HRToF-CIMS) was deployed aboard the NSF/NCAR C-130 aircraft. Calibrated measurements of ClNO2, Cl2, HCl, N2O5, HNO3, HONO, among several other compounds, were made at 2Hz on all 13 research flights. ClNO2 and HCl were often the dominant forms of reactive gas-phase chlorine compounds, with ClNO2 routinely reaching >1.5 ppb in the polluted outflow of the eastern U.S. urban corridor. ClNO2 often becomes a substantial fraction (~30%) of NOz (NOz = NOy – NOx) in these plumes at night. Preliminary analyses suggests that ClNO2 production is most efficient in the polluted marine boundary layer, with yields approaching unity and the evolution of nighttime ClNO2 highly correlated with that of HNO3 and particulate nitrate. However, ClNO2 production was observed throughout the region and a significant source of reactive chlorine from coal-fired power plants was directly confirmed with measurements of HCl strongly correlated with SO2. In addition, there is some evidence that biomass or biofuel combustion is a source of reactive chlorine that can lead to ClNO2 production. Examples of the nocturnal and diel evolution of reactive chlorine species are given, and we show to our knowledge the first measurements of chlorine nitrate (ClONO2) in the polluted mid-latitude marine boundary layer.