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Abstract. The atmospheric multiphase reaction of dinitrogenpentoxide (N2O5) with chloride-containing aerosol particlesproduces nitryl chloride (ClNO2), which has been observed across theglobe. The photolysis of ClNO2 produces chlorine radicals and nitrogendioxide (NO2), which alter pollutant fates and air quality. However,the effects of local meteorology on near-surface ClNO2 production arenot yet well understood, as most observational and modeling studies focus onperiods of clear conditions. During a field campaign in Kalamazoo, Michigan,from January–February 2018, N2O5 and ClNO2 were measuredusing chemical ionization mass spectrometry, with simultaneous measurementsof atmospheric particulate matter and meteorological parameters. We examinethe impacts of atmospheric turbulence, precipitation (snow, rain) and fog,and ground cover (snow-covered and bare ground) on the abundances ofClNO2 and N2O5. N2O5 mole ratios were lowest duringperiods of lower turbulence and were not statistically significantlydifferent between snow-covered and bare ground. In contrast, ClNO2 moleratios were highest, on average, over snow-covered ground, due to salinesnowpack ClNO2 production. Both N2O5 and ClNO2 moleratios were lowest, on average, during rainfall and fog because ofscavenging, with N2O5 scavenging by fog droplets likelycontributing to observed increased particulate nitrate concentrations. Theseobservations, specifically those during active precipitation and withsnow-covered ground, highlight important processes, including N2O5and ClNO2 wet scavenging, fog nitrate production, and snowpackClNO2 production, that govern the variability in observed atmosphericchlorine and nitrogen chemistry and are missed when considering only clearconditions. 

Abstract. Sea salt aerosols play an important role in the radiationbudget and atmospheric composition over the Arctic, where the climate israpidly changing. Previous observational studies have shown that Arctic sea ice leads are an important source of sea salt aerosols, and modeling efforts have also proposed blowing snow sublimation as a source. In this study,size-resolved atmospheric particle number concentrations and chemicalcomposition were measured at the Arctic coastal tundra site ofUtqiaġvik, Alaska, during spring (3 April–7 May 2016). Blowing snow conditions were observed during 25 % of the 5-week study period andwere overpredicted by a commonly used blowing snow parameterization based solely on wind speed and temperature. Throughout the study, open leads werepresent locally. During periods when blowing snow was observed, significantincreases in the number concentrations of 0.01–0.06 µm particles(factor of 6, on average) and 0.06–0.3 µm particles (67 %, on average) and a significant decrease (82 %, on average) in 1–4 µmparticles were observed compared to low wind speed periods. These size distribution changes were likely caused by the generation of ultrafineparticles from leads and/or blowing snow, with scavenging of supermicronparticles by blowing snow. At elevated wind speeds, both submicron andsupermicron sodium and chloride mass concentrations were enhanced,consistent with wind-dependent local sea salt aerosol production. Atmoderate wind speeds below the threshold for blowing snow as well as during observed blowing snow, individual sea spray aerosol particles were measured.These individual salt particles were enriched in calcium relative to sodiumin seawater due to the binding of this divalent cation with organic matter in the sea surface microlayer and subsequent enrichment during seawaterbubble bursting. The chemical composition of the surface snowpack alsoshowed contributions from sea spray aerosol deposition. Overall, theseresults show the contribution of sea spray aerosol production from leads onboth aerosols and the surface snowpack. Therefore, if blowing snowsublimation contributed to the observed sea salt aerosol, the snow beingsublimated would have been impacted by sea spray aerosol deposition rather than upward brine migration through the snowpack. Sea spray aerosol production from leads is expected to increase, with thinning and fracturingof sea ice in the rapidly warming Arctic.