13 research outputs found
Response of the Aerodyne Aerosol Mass Spectrometer to Inorganic Sulfates and Organosulfur Compounds: Applications in Field and Laboratory Measurements
Organosulfur compounds are important components of secondary organic aerosols (SOA). While the Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) has been extensively used in aerosol studies, the response of the AMS to organosulfur compounds is not well-understood. Here, we investigated the fragmentation patterns of organosulfurs and inorganic sulfates in the AMS, developed a method to deconvolve total sulfate into components of inorganic and organic origins, and applied this method in both laboratory and field measurements. Apportionment results from laboratory isoprene photooxidation experiment showed that with inorganic sulfate seed, sulfate functionality of organic origins can contribute ∼7% of SOA mass at peak growth. Results from measurements in the Southeastern U.S. showed that 4% of measured sulfate is from organosulfur compounds. Methanesulfonic acid was estimated for measurements in the coastal and remote marine boundary layer. We explored the application of this method to unit mass-resolution data, where it performed less well due to interferences. Our apportionment results demonstrate that organosulfur compounds could be a non-negligible source of sulfate fragments in AMS laboratory and field data sets. A reevaluation of previous AMS measurements over the full range of atmospheric conditions using this method could provide a global estimate/constraint on the contribution of organosulfur compounds
Response of the Aerodyne Aerosol Mass Spectrometer to Inorganic Sulfates and Organosulfur Compounds: Applications in Field and Laboratory Measurements
Organosulfur compounds are important components of secondary organic aerosols (SOA). While the Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) has been extensively used in aerosol studies, the response of the AMS to organosulfur compounds is not well-understood. Here, we investigated the fragmentation patterns of organosulfurs and inorganic sulfates in the AMS, developed a method to deconvolve total sulfate into components of inorganic and organic origins, and applied this method in both laboratory and field measurements. Apportionment results from laboratory isoprene photooxidation experiment showed that with inorganic sulfate seed, sulfate functionality of organic origins can contribute ∼7% of SOA mass at peak growth. Results from measurements in the Southeastern U.S. showed that 4% of measured sulfate is from organosulfur compounds. Methanesulfonic acid was estimated for measurements in the coastal and remote marine boundary layer. We explored the application of this method to unit mass-resolution data, where it performed less well due to interferences. Our apportionment results demonstrate that organosulfur compounds could be a non-negligible source of sulfate fragments in AMS laboratory and field data sets. A reevaluation of previous AMS measurements over the full range of atmospheric conditions using this method could provide a global estimate/constraint on the contribution of organosulfur compounds
Influence of Marine Aerosols on Cloud Droplet Number Concentration over the North‐East Atlantic
Marine aerosols and iodine emissions - Reply
O'Dowd et al. reply - McFiggans raises some interesting, but partly speculative, issues about the possibility of additional condensable-iodine-vapour (CIV) precursors being involved in marine aerosol formation from biogenic iodine emissions, and about the relative roles of iodine oxide and sulphuric acid in the marine new-particle formation process
Air quality—climate forcing double whammy from domestic firelighters
Abstract Renewable biomass plays a crucial role in transitioning toward climate-friendly heating sources; however, not without its collateral damage in terms of the disproportionately high effects on local air quality. The associated proliferation of residential heating appliances around the world, including developed regions like Europe, where an estimated 70 million are housed, does not appear to be abating. Here, we identify super self-concentrating ambient pollution events whereby solid-fuel residential heating haze is infused with a hitherto unaccounted for firelighter smoke that contributes additional adsorbing black carbon. This black carbon-organic aerosol combination results in a strong positive radiative forcing (up to 149 W m−2) and alters the boundary layer thermodynamics sufficiently so as to further suppress pollutant dilution and dispersion leading to extraordinary high submicron particulate matter (PM1: 166 µg m−3). Unfortunately, there is no silver lining in this cloud until the promotion of solid biomass fires with firelighters for ignition is replaced by a co-benefit policy
Severe Pollution in China Amplified by Atmospheric Moisture
Abstract In recent years, severe haze events often occurred in China, causing serious environmental problems. The mechanisms responsible for the haze formation, however, are still not well understood, hindering the forecast and mitigation of haze pollution. Our study of the 2012–13 winter haze events in Beijing shows that atmospheric water vapour plays a critical role in enhancing the heavy haze events. Under weak solar radiation and stagnant moist meteorological conditions in winter, air pollutants and water vapour accumulate in a shallow planetary boundary layer (PBL). A positive feedback cycle is triggered resulting in the formation of heavy haze: (1) the dispersal of water vapour is constrained by the shallow PBL, leading to an increase in relative humidity (RH); (2) the high RH induces an increase of aerosol particle size by enhanced hygroscopic growth and multiphase reactions to increase particle size and mass, which results in (3) further dimming and decrease of PBL height, and thus further depressing of aerosol and water vapour in a very shallow PBL. This positive feedback constitutes a self-amplification mechanism in which water vapour leads to a trapping and massive increase of particulate matter in the near-surface air to which people are exposed with severe health hazards
Coastal Iodine Emissions: Part 2. Chamber Experiments of Particle Formation from <i>Laminaria digitata</i>-Derived and Laboratory-Generated I<sub>2</sub>
Laboratory studies into particle formation from <i>Laminaria
digitata</i> macroalgae were undertaken to elucidate aerosol
formation for a range of I<sub>2</sub> (0.3–76 ppb<sub>v</sub>) and O<sub>3</sub> (<3–96 ppb<sub>v</sub>) mixing ratios
and light levels (<i>E</i><sub>PAR</sub> = 15, 100, and
235 μmol photons m<sup>–2</sup> s<sup>–1</sup>). No clear pattern was observed for I<sub>2</sub> or aerosol parameters
as a function of light levels. Aerosol mass fluxes and particle number
concentrations, were, however, correlated with I<sub>2</sub> mixing
ratios for low O<sub>3</sub> mixing ratios of <3 ppb<sub>v</sub> (<i>R</i><sup>2</sup> = 0.7 and 0.83, respectively for
low light levels, and <i>R</i><sup>2</sup> = 0.95 and 0.98,
respectively for medium light levels). Additional experiments into
particle production as a function of laboratory-generated I<sub>2</sub>, over a mixing ratio range of 1–8 ppb<sub>v</sub>, were conducted
under moderate O<sub>3</sub> mixing ratios (∼24 ppb<sub>v</sub>) where a clear, 100-fold or greater, increase in the aerosol number
concentrations and mass fluxes was observed compared to the low O<sub>3</sub> experiments. A linear relationship between particle concentration
and I<sub>2</sub> was found, in reasonable agreement with previous
studies. Scaling the laboratory relationship to aerosol concentrations
typical of the coastal boundary layer suggests a I<sub>2</sub> mixing
ratio range of 6–93 ppt<sub>v</sub> can account for the observed
particle production events. Aerosol number concentration produced
from I<sub>2</sub> is more than a factor of 10 higher than that produced
from CH<sub>2</sub>I<sub>2</sub> for the same mixing ratios