The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings

Abstract

<p><strong>Abstract.</strong> Atmospheric marine aerosol particles impact Earth's albedo and climate. These particles can be primary or secondary and come from a variety of sources, including sea salt, dissolved organic matter, volatile organic compounds, and sulfur-containing compounds. Dimethylsulfide (DMS) marine emissions contribute greatly to the global biogenic sulfur budget, and its oxidation products can contribute to aerosol mass, specifically as sulfuric acid and methanesulfonic acid (MSA). Further, sulfuric acid is a known nucleating compound, and MSA may be able to participate in nucleation when bases are available. As DMS emissions, and thus MSA and sulfuric acid from DMS oxidation, may have changed since pre-industrial times and may change in a warming climate, it is important to characterize and constrain the climate impacts of both species. Currently, global models that simulate aerosol size distributions include contributions of sulfate and sulfuric acid from DMS oxidation, but to our knowledge, global models typically neglect the impact of MSA on size distributions.</p> <p>In this study, we use the GEOS-Chem-TOMAS (GC-TOMAS) global aerosol microphysics model to determine the impact on aerosol size distributions and subsequent aerosol radiative effects from including MSA in the size-resolved portion of the model. The effective equilibrium vapor pressure of MSA is currently uncertain, and we use the Extended Aerosol Inorganics Model (E-AIM) to build a parameterization for GC-TOMAS of MSA's effective volatility as a function of temperature, relative humidity, and available gas-phase bases, allowing MSA to condense as an ideally nonvolatile or semivolatile species or too volatile to condense. We also present two limiting cases for MSA's volatility, assuming that MSA is always ideally nonvolatile (irreversible condensation) or that MSA is always ideally semivolatile (quasi-equilibrium condensation but still irreversible condensation). We further present simulations in which MSA participates in binary and ternary nucleation with the same efficacy as sulfuric acid whenever MSA is treated as ideally nonvolatile. When using the volatility parameterization described above (both with and without nucleation), including MSA in the model changes the global annual averages at 900 hPa of submicron aerosol mass by 1.2 %, N3 (number concentration of particles greater than 3 nm in diameter) by −3.9 % (non-nucleating) or 112.5 % (nucleating), N80 by 0.8 % (non-nucleating) or 2.1 % (nucleating), the aerosol indirect effect (AIE) by −8.6 mW m<sup>−2</sup> (non-nucleating) or −26 mW m<sup>−2</sup> (nucleating), and the direct radiative effect (DRE) by −15 mW m<sup>−2</sup> (non-nucleating) or −14 mW m<sup>−2</sup> (nucleating). The sulfate and sulfuric acid from DMS oxidation produces 4–6 times more submicron mass than MSA does, leading to ~ 10 times a stronger cooling effect in the DRE. But the changes in N80 are comparable between the contributions from MSA and from DMS-derived sulfate/sulfuric acid, leading to comparable changes in the AIE.</p> <p>Model-measurement comparisons with the Heintzenberg et al. (2000) dataset over the Southern Ocean indicate that the default model has a missing source or sources of ultrafine particles: the cases in which MSA participates in nucleation (thus increasing ultrafine number) most closely match the Heintzenberg distributions, but we cannot conclude nucleation from MSA is the correct reason for improvement. Model-measurement comparisons with particle-phase MSA observed with a customized Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) from the ATom campaign show that cases with the MSA volatility parameterizations (both with and without nucleation) tend to fit the measurements the best (as this is the first use of MSA measurements from ATom, we provide a detailed description of these measurements and their calibration). However, no one model sensitivity case shows the best model-measurement agreement for both Heintzenberg and the ATom campaigns. As there are uncertainties in both MSA's behavior (nucleation and condensation) and the DMS emissions inventory, further studies on both fronts are needed to better constrain MSA's past, current and future impacts upon the global aerosol size distribution and radiative forcing.</p>

Arctic marine secondary organic aerosol contributes significantly to summertime particle size distributions in the Canadian Arctic Archipelago

“…In general, particles with diameters of 50 nm or larger activate in our simulations, although observations from the Canadian Arctic Archipelago indicate that particles as small as 20 nm could activate in clean summertime atmospheric layers above 200 m altitude when low concentrations of larger particles (diameters greater than 100 nm) enable relatively high supersaturations (Leaitch et al, 2016). MSA that is produced by the DMS-OH-addition channel can contribute to condensational growth of existing particles (Chen et al, 2015;Hoffmann et al, 2016;Willis et al, 2016;Hodshire et al, 2019). In our simulations, MSA contributes to particle condensational growth, but not to particle nucleation.…”

“…In our simulations, MSA contributes to particle condensational growth, but not to particle nucleation. In this study, we did not include additional chemistry related to the production of dimethylsulfoxide (DMSO), which could increases the yield of MSA and reduce sulfate concentrations (Breider et al, 2014;Hoffmann et al, 2016). Future studies are needed to quantify the impact of multiphase DMS chemistry.…”

“…For calculation of the direct radiative effect (DRE) attributed to AMSOA, the aerosol optical depth, single-scattering albedo, and asymmetry factor are calculated with Mie code (Bohren and Huffman, 1983) and use refractive indices from the Global Aerosol Dataset (GADS) (Koepke et al, 1997). These optical properties, along with cloud fraction and surface albedo from GEOS-FP assimilated meteorology are input to the Rapid Radiative Transfer Model for Global Climate Models (RRTMG) (Iacono et al, 2008), to determine the change in top-of-the-atmosphere solar flux between two simulations, treating all particles except black carbon as internally mixed and spherical. Kodros et al (2018) found that the Arctic springtime DRE for all aerosol is less negative than the external mixing-state assumption by 0.05 W m −2 when constraining by coating thickness of the mixed particles and by 0.19 W m −2 when constraining by BC-containing particle number fraction.…”

Oxygenated Aromatic Compounds are Important Precursors of Secondary Organic Aerosol in Biomass-Burning Emissions

“…27,67 Several studies have hypothesized that the lack of an enhancement in OA mass in the field could be explained if the photochemistry-driven SOA formation was balanced by dilution-driven POA evaporation. [68][69][70] In this work, based on the available evidence, we assumed that the POA mass concentrations did not vary during the chamber experiment but note that there was very little dilution in our experiments compared to what would be observed in a biomass burning plume. This hypothesis currently remains untested for field data and any hypothesis testing would need to not only model the SOA formation from oxygenated aromatics and heterocyclic compounds but also model the evaporation kinetics of the POA and subsequent oxidation of the evaporated vapors to correctly interpret the field observations.…”

Methanesulfonic Acid-driven New Particle Formation Enhanced by Monoethanolamine: A Computational Study

“…Besides SA, methanesulfonic acid (MSA) has been identified as an important NPF precursor. 29,[33][34][35][36] MSA will play a more important role in NPF after the implementation of stricter regulations on SO2 emission of fossil fuel combustion. 33,37 MSA is mainly derived from the oxidation of organosulfur compounds (OSCs) coming from oceans, agricultural activity, forest cover, and even from human exhalation.…”