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要旨:
Biogenic volatile organic compounds (BVOCs) are to a great extent oxidized by NO3 radicals at night leading to the formation of organic nitrates and secondary organic aerosols (SOA), which have an impact on human health and air quality. One of the focus points of the ACROSS (Atmospheric ChemistRy Of the Suburban forest) campaign, which took place in a temperate forest influenced by emissions from Paris over a period of 6 weeks during the Summer of 2022, was nighttime chemistry between NO3 radicals and BVOCs and its relative importance to daytime chemistry for organic nitrate formation.
Measurements of total alkyl and peroxy nitrates and NO2 mixing ratios were performed using multi-channel cavity-ring-down spectroscopy (CRDS) with thermal dissociation inlets operated at different temperatures to distinguish between alkyl nitrates and peroxy-nitrates.
NO2 were on average 1500 pptv across the entire campaign with an average diel maximum of 2200 pptv at nighttime and minimum of 800 pptv in the afternoon. Both total alkyl and peroxy nitrates showed a diel profile with average daytime maxima of 250 and 450 pptv, respectively, and average nighttime minima of 150 and 250 pptv, respectively.
The relative contributions of day- and nighttime chemistry for generation of ANs will be assessed as will the lifetime of ANs in this environment and the efficiency of NOx conversion into organic nitrates.
