Role of Interfacial Water in the Heterogeneous Uptake of Glyoxal by Mixed Glycine and Ammonium Sulfate Aerosols

Abstract

This study focuses on the heterogeneous reactions of gas phase glyoxal with aerosols of glycine, the most abundant amino acid in atmospheric aerosols, as well as with a mixture of glycine and ammonium sulfate (AS) at a molar ratio of 1:100 (glycine-AS 1:100). Aerosols were exposed to varying relative humidity (RH) conditions in the presence of gas phase glyoxal for ∼1 h, followed by drying and efflorescence. The changes in size, chemical composition, and optical properties were consequently measured. The reactions occur over a wide range of relative humidities, from ∼30% up to 90% RH, covering values that are substantially lower as well as above the deliquescence point of the investigated aerosols. The product aerosols exhibit a trend of increasing growth in size, in optical extinction cross sections, and in extinction efficiencies (at λ = 355 nm) with decreasing seed aerosol size, and with decreasing RH values from 90% to ∼50%. For glycine-AS 1:100 particles, the ratio of the geometric cross section of the product aerosol to the original seed aerosol reached a value of ∼3, the optical extinction cross section ratio was up to ∼25, and the Q(ext) ratio was up to ∼8, exceeding those of both AS and glycine separately, suggesting a synergistic effect. Aerosol mass spectrometer analyses show that the main products of all the studied reactions are glyoxal oligomers (light scattering compounds), with a minor contribution from imidazoles (absorbing compounds at λ = 355 nm). These findings imply that the changes in the optical properties are likely due to enhanced scattering by the reaction products. The fraction of absorbing substances in the reacted aerosol increases with increasing RH, suggesting that the absorption component may become more substantial after longer reaction times, possibly in cloud or fog droplets. The results suggest that these reactions are possibly important in low RH regions, plausibly due to the reaction occurring in a few interfacial monolayers of water well before deliquescence.

An Approach for Faster Retrieval of Aerosols’ Complex Refractive Index Using Cavity Ring-Down Spectroscopy

“…Figure 1 shows the distribution of the real parts of biomass burning (Westphal et al 1991;Yamasoe et al 1998;von Hoyningen-Huene et al 1999;Guyon et al 2003;Procopio et al 2003;Colarco 2004;Schkolnik et al 2007;Hungershoefer et al 2008;Levin et al 2010), and organic (Schnaiter et al 2003;Pettersson et al 2004;Lack et al 2006;Abo Riziq et al 2007;Barkey et al 2007;Yu et al 2008;LangYona et al 2009;Wex et al 2009;Lang-Yona et al 2010b;Nakayama et al 2010b;Trainic et al 2011;Flores et al 2012;Trainic et al 2012) and inorganic (Abo Riziq et al 2007;LangYona et al 2009;Trainic et al 2011) aerosols found in the literature. In this study, we exclude soot particles due to their complex aggregated structure.…”

“…To choose the appropriate range for size parameters, we investigated the Q ext standard deviations (SDs) from measurements done in this study and from studies found in the literature (Pettersson et al 2004;Lack et al 2006;Abo Riziq et al 2007;Dinar et al 2008;Butler et al 2009;Lang-Yona et al 2009Miles et al 2010a, b;Nakayama et al 2010a;Trainic et al 2011;Flores et al 2012;Trainic et al 2012). The average Q ext SD in all datasets did not exceed 0.075.…”

Electrospray surface-enhanced Raman spectroscopy (ES-SERS) for probing surface chemical compositions of atmospherically relevant particles

“…Earlier work has reported the formation of a monolayer of adsorbed water on the surface of solid AS at 60 % relative humidity (RH) (Romakkaniemi et al, 2001). Surface-adsorbed water plays a potential role in facilitating the heterogeneous chemistry of atmospheric aerosols (Trainic et al, 2012;Chu and Chan, 2017). Yet the relative role of surface chemistry and bulk processes is poorly understood due to the lack of surface-sensitive techniques available for studying individual atmospheric particles (Ault et al, 2013).…”

A Calibration Technique for Improving Refractive Index Retrieval from Aerosol Cavity Ring-Down Spectroscopy

“…Recently, several groups have used Aerosol CRDS (A-CRDS) to probe internal and external particle mixing Freedman et al 2009;Khalizov et al 2009;Lack et al 2009;Radney et al 2009;Attwood and Greenslade, 2012), effects of relative humidity (Beaver et al 2008;Attwood and Greenslade, 2012;Brem et al 2012;Trainic et al 2012) and particle reactivity (Lu et al 2011;Zarzana et al 2012). Agreement between extinction cross section measurements and those calculated with Mie theory is often promising, typically on the order of 2-12 % (Pettersson et al 2004;Baynard et al 2007;Riziq et al 2007;Freedman et al 2009;Lang-Yona et al 2009;Radney et al 2009;Miles et al 2010b;Li et al 2011;Mellon et al 2011).…”