A086-0013
Exploring the Reactive Chlorine Budget in the Polluted Marine Boundary Layer During the Halifax Fog and Air Quality Study (HaliFAQS) Field Campaign

Thursday, 10 December 2020
Poster
Teles Furlani1, Alexander Moravek2, Cameron Nicholas Eugene Power3, Aldona Wiacek4, Rachel Chang5, Trevor C VandenBoer6 and Cora Young6, (1)York University, Toronto, ON, Canada, (2)York University, Toronto, Canada, (3)Saint Mary's University, Astronomy & Physics, Halifax, Canada, (4)Saint Mary's University, Environmental Science, Astronomy & Physics, Halifax, NS, Canada, (5)Dalhousie University, Physics & Atmospheric Science, Halifax, NS, Canada, (6)York University, Chemistry, Toronto, ON, Canada
Abstract:
Elevated levels of chlorine atoms (Cl) can impact the oxidative capacity of the troposphere, but the extent to which this occurs is currently unknown. Early morning oxidation in the troposphere is thought to be influenced by chlorine atoms released by photolabile chlorine species (Osthoff et al., 2008; Young et al., 2014). Here we monitor the formation of hydrogen chloride (HCl) using a high-time resolution cavity ring-down spectrometer during the Halifax Fog and Air Quality Study (HaliFAQS). HCl that can be formed from hydrogen abstraction reactions involving Cl, as well as acid displacement reactions. The HaliFAQS campaign occurred in May and June in 2019 in the marine boundary layer of Halifax, Canada. We combine HCl measurements with co-located irradiance, NOx, O3, and size-resolved aerosol composition to estimate the contribution of Cl production from the early morning photolysis of chlorine radical precursors. We correlate the estimated loss for precursor compounds to the late morning rise in HCl observed on high irradiance days to determine the efficacy of using HCl as an Cl production tracer. We explore in the integral role HCl has on the fate of Cl in the troposphere and discuss the implications on early morning oxidative capacity.

References

Osthoff, H. D., Roberts, J. M., Ravishankara, A. R., Williams, E. J., Lerner, B. M., Sommariva, R., Bates, T. S., Coffman, D., Quinn, P. K., Dibb, J. E., Stark, H., Burkholder, J. B., Talukdar, R. K., Meagher, J., Fehsenfeld, F. C. and Brown, S. S.: High levels of nitryl chloride in the polluted subtropical marine boundary layer, Nat. Geosci, 1(5), 324–328, 2008.

Young, C. J., Washenfelder, R. A., Edwards, P. M., Parrish, D. D., Gilman, J. B., Kuster, W. C., Mielke, L. H., Osthoff, H. D., Tsai, C., Pikelnaya, O., Stutz, J., Veres, P. R., Roberts, J. M., Griffith, S., Dusanter, S., Stevens, P. S., Flynn, J., Grossberg, N., Lefer, B., Holloway, J. S., Peischl, J., Ryerson, T. B., Atlas, E. L., Blake, D. R. and Brown, S. S.: Chlorine as a primary radical: Evaluation of methods to understand its role in initiation of oxidative cycles, Atmos. Chem. Phys., 14(7), 3427–3440, doi:10.5194/acp-14-3427-2014, 2014.

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