Mode calculations) or from the measured gas–particle partitioning of Predictions of aerosol pH come from aerosol thermodynamic equilibrium modelsĬonstrained by both aerosol- and gas-phase measurements (i.e., forward (dissociated H + and undissociated H + bound to weak acids) Such as aerosol strong acidity ( H + contributed by strong acids thatĭissociated completely at any pH level) or aerosol total acidity Solutions, often has no direct correlation with proxy measurement methods PH, the parameter serving to define and describe the acidity of aqueous Populations therein either directly (Gwynn et al., 2000 Peters et al.,ġ996 Schindler, 1988 Spengler et al., 1996 Fang et al., 2017 Johnson etĪl., 2008) or by their effects on nutrient deposition (MyriokefalitakisĮt al., 2016, 2018 Kanakidou et al., 2016 Nenes InĪddition to the physicochemical effects within particles, their bulk acidityĬan affect the health of both environmental ecosystems and the human ( NH 4HSO 4), contribute to particle acidity and water content, withĮffects on aerosol radiative forcing (Seinfeld and Pandis, 2016).
Sulfate ( (NH 4) 2SO 4) and ammonium bisulfate Inorganic salt constituents in atmospheric particles, such as ammonium (Ahrens et al., 2012 Keene et al., 2004) and enhancements to secondary Sulfates (Chameides, 1984) the oxidation of volatile organicĬompounds (VOCs) and ozone formation in marine environments (Keene etĪl., 1998) the gas–particle partitioning of many semivolatile species Some of these processes include sulfur oxidationĪnd halogen chemistry, with important implications for the formation of The acidity of atmospheric particles plays a critical role in many Inorganic constituents alone under conditions where liquid–liquid phase Of these effects suggests that aerosol pH is sufficiently constrained by the At 90 % RH, WSOC alteredĪerosol pH by up to ∼0.2 pH units, though the effect was up Run at 70 %, 80 %, and 90 % relative humidity (RH) levels and theĮffect of WSOC was inversely related to RH. Unrealistic organic acid levels (aerosol organic acid concentrations The inorganic-only pH was above the p K a value of all three organicĪcids investigated, pH changes in excess of 1 pH unit were only observed at Other, giving pH changes of malonic acid > glutaric acid). (inorganic-only pH ∼1), these effects mostly offset each Under the highly acidic conditions typical of the eastern US Organic species concurrently increases γ H + and aerosol liquid We find that addition of organic acids and nonacid Mixtures Functional groups Activity Coefficient) to evaluate theĮffects of WSOC on the H + ion activity coefficients ( γ H + )Īnd activity (pH). In combination with activity coefficient model AIOMFAC (Aerosol Inorganic–Organic Particles and thermodynamically analyzed by the Extended Aerosol Inorganics Model (E-AIM) and ISORROPIA models Then used to construct mixed inorganic–organic single-phase aqueous Weakly acidic conditions characteristic of Beijing, China. Studying submicron aerosols that represent the two extremes in acidity levelsįound in the atmosphere: strongly acidic aerosol from Baltimore, MD, and Despite advances in aerosol thermodynamicĮquilibrium models, there is limited understanding on the comprehensive Water-soluble organic carbon (WSOC) is a ubiquitous and significant fraction
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