Competition of Partitioning and Reaction Controls Brown Carbon Formation from Butenedial in Particles

Abstract

Organic reactions in atmospheric particles impact human health and climate, such as by the production of brown carbon. Previous work suggests that reactions are faster in particles than in bulk solutions because of higher reactant concentrations and pronounced surface-mediated processes. Additionally, dialdehydes may have accelerated reactions in particles, as has been shown for the glyoxal reaction with ammonium sulfate (AS). Here, we examine the competition between evaporation and reaction of butenedial, a semivolatile dialdehyde, and reduced nitrogen (NHX) in bulk solutions and levitated particles with mass spectrometry (MS). Pyrrolinone is the major product of butenedial/AS bulk solutions, indicating brown carbon formation via accretion reactions. By contrast, pyrrolinone is completely absent in all MS measurements of comparable levitated particles suspended in a pure N2 stream. Pyrrolinone is only produced in levitated butenedial particles exposed to gas-phase ammonia, without enhanced reaction kinetics previously observed for glyoxal and other systems. Despite butenedial’s large Henry’s law constant and fast reaction with NHX compared to glyoxal, the brown carbon pathway competes with evaporation only in polluted regions with extreme NHX. Therefore, accurate knowledge of effective volatilities or Henry’s law constants for complex aerosol matrices is required when chemistry studied in bulk solutions is extrapolated to atmospheric particles.

Radical-Initiated Brown Carbon Formation in Sunlit Carbonyl–Amine–Ammonium Sulfate Mixtures and Aqueous Aerosol Particles

“…Carbonyl + Amine + AS Aerosol Particles. Since absorption spectra 51 and browning chemistry can differ in suspended aerosol particles from that in bulk solutions, 33,70 aqueous aerosol particles were generated in Tedlar bags and exposed to either full-spectrum sunlight or ambient indoor light while suspended in air, before filtration and extraction. The mass absorption coefficients (MAC) of filter extracts from suspended aerosol experiments are summarized in Figure 4.…”

Oxidation pathways of linoleic acid revisited with electrodynamic balance–mass spectrometry

“…This technique has been used to monitor the evaporation of semi-volatile compounds, [25][26][27][28] for quantitative measurements of compounds in droplet mixtures, 29,30 and to study chemical reactions in droplets. [31][32][33][34][35] In our setup, an evaporation unit is used to transfer the compounds into the gas phase and ionise those in a cold plasma ion source before MS analysis. A detailed description of the instrumentation and the typical experimental procedure can be found elsewhere.…”

Electrodynamic balance–mass spectrometry reveals impact of oxidant concentration on product composition in the ozonolysis of oleic acid

“…An emerging tool for the detailed study of aerosol processes is the combination of an EDB with MS. [23][24][25][26][27][28][29][30][31] Trapping droplets in an EDB allows the contactless storage and examination of particles over hours and days under well-defined experimental conditions. 32 Transfer of the stored droplets to an MS unit allows to infer the particle composition at the time of ejection.…”