Publication Date:
2017-10-01
Description:
Nitryl Chloride (ClNO 2 ) measurements from the Weybourne Atmospheric Observatory (WAO) are reported from March and April 2013 using a quadruple chemical ionisation mass spectrometer (CIMS) with the I - ionisation scheme. WAO is a rural coastal site with generally low NO x concentrations, a type of location poorly studied for ClNO 2 production. Concentrations of ClNO 2 exceeded that of the limit of detection (0.8 ppt) on each night of the campaign, as did concentrations of N 2 O 5 , which was also measured simultaneously with the Cambridge Broadband Cavity Enhanced Absorption Spectrometer (BBCEAS). A peak concentration of 65 ppt of ClNO 2 is reported here. Vertical profiles of ClNO 2 from early- to mid-morning flights in close proximity to WAO are also reported, showing elevated concentrations at low altitude. The photolysis of observed ClNO 2 and a box model utilising the Master Chemical Mechanism modified to include chlorine chemistry was used to calculate Cl atom concentrations. This model utilised numerous VOCs from the second Tropospheric ORganic CHemistry project (TORCH 2) in 2004, at the same location and time of year. From this the relative importance of the oxidation of three groups of measured VOCs (alkanes, alkenes and alkynes) by OH radicals, Cl atoms and O 3 is compared. Cl atom oxidation was deemed generally insignificant at this time and location for total oxidation due to the much lower concentration of ClNO 2 observed, even following the night of greatest ClNO 2 production.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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