Browsing by Subject "TOTAL OH REACTIVITY"

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  • Novelli, Anna; Hens, Korbinian; Ernest, Cheryl Tatum; Martinez, Monica; Noelscher, Anke C.; Sinha, Vinayak; Paasonen, Pauli; Petäjä, Tuukka; Sipilä, Mikko; Elste, Thomas; Plass-Duelmer, Christian; Phillips, Gavin J.; Kubistin, Dagmar; Williams, Jonathan; Vereecken, Luc; Lelieveld, Jos; Harder, Hartwig (2017)
    We analysed the extensive dataset from the HUMPPA-COPEC 2010 and the HOPE 2012 field campaigns in the boreal forest and rural environments of Finland and Germany, respectively, and estimated the abundance of stabilised Criegee intermediates (SCIs) in the lower troposphere. Based on laboratory tests, we propose that the background OH signal observed in our IPI-LIF-FAGE instrument during the aforementioned campaigns is caused at least partially by SCIs. This hypothesis is based on observed correlations with temperature and with concentrations of unsaturated volatile organic compounds and ozone. Just like SCIs, the background OH concentration can be removed through the addition of sulfur dioxide. SCIs also add to the previously underestimated production rate of sulfuric acid. An average estimate of the SCI concentration of similar to 5.0 x 10(4) molecules cm(-3) (with an order of magnitude uncertainty) is calculated for the two environments. This implies a very low ambient concentration of SCIs, though, over the boreal forest, significant for the conversion of SO2 into H2SO4. The large uncertainties in these calculations, owing to the many unknowns in the chemistry of Criegee intermediates, emphasise the need to better understand these processes and their potential effect on the self-cleaning capacity of the atmosphere.
  • Yang, Yuan; Wang, Yonghong; Yao, Dan; Zhao, Shuman; Yang, Shuanghong; Ji, Dongsheng; Sun, Jie; Wang, Yinghong; Liu, Zirui; Hu, Bo; Zhang, Renjian; Wang, Yuesi (2020)
    To what extent anthropogenic emissions could influence volatile organic compound (VOCs) concentrations and related atmospheric reactivity is still poorly understood. China's 70th National Day holidays, during which anthropogenic emissions were significantly reduced to ensure good air quality on Anniversary Day, provides a unique opportunity to investigate these processes. Atmospheric oxidation capacity (AOC), OH reactivity, secondary transformation, O-3 formation and VOCs-PM2.5 sensitivity are evaluated based on parameterization methods and simultaneous measurements of VOCs, O-3, NOx, CO, SO2, PM2.5, JO(1)D, JNO(2), JNO(3) carried out at a suburban site between Beijing and Tianjin before, during, and after the National Day holiday 2019. During the National Day holidays, the AOC, OH reactivity, O-3 formation potential (OFP) and secondary organic aerosol formation potential (SOAP) were 1.6 x 10(7) molecules cm(-3) s(-1), 41.8 s(-1), 299.2 mg cm(-3) and 1471.8 mg cm(-3), respectively, which were 42%, 29%, 47% and 42% lower than pre-National Day values and -12%, 42%, 36% and 42% lower than post-National Day values, respectively. Reactions involving OH radicals dominated the AOC during the day, but OH radicals and O-3 reactions at night. Alkanes (the degree of unsaturation = 0, (D, Equation (1)) accounted for the largest contributions to the total VOCs concentration, oxygenated VOCs (OVOCs; D