Aging of atmospheric aerosols and the role of iron in catalyzing brown carbon formation

Abstract

Extensive research has been done on the processes that lead to the formation of secondary organic aerosol (SOA) including atmospheric oxidation of volatile organic compounds (VOCs) from biogenic and anthropogenic...

Hygroscopicity of polycatechol and polyguaiacol secondary organic aerosol in sub- and supersaturated water vapor environments

“…Polycatechol has a higher density of hydroxyl groups that have strong water affinity compared to the methyl groups present in polyguaiacol. 14 This is supported by the work of Rahman and Al-Abadleh 19 which offered evidence, through DRIFTS, of strong water bonding with organic functional groups. Polycatechol was shown to have a higher affinity for water than polyguaiacol.…”

“…Examples of these oxidation pathways include those driven by oxidants such as OH, O 3 , NO 3 , and those catalyzed by transition metals like Iron (Fe). 11,13,14 Fe is an abundant component of mineral dust. 15,16 Combustion sources are increasingly being recognized as major contributors to labile iron deposited on the oceans.…”

“…The role of Fe in condensed phase transformation of phenolic organic compounds in aerosol particles has recently been reviewed 18 where it was shown that Fe can convert catechol and guaiacol into light-absorbing and water-insoluble particles, namely polycatechol and polyguaiacol, respectively. 11,14,[19][20][21] Thus, polycatechol and polyguaiacol could be considered secondary organic aerosol (SOA) that form due to aerosol aging of Fecontaining particles under conditions relevant to cloud droplets and aerosol particles.…”

“…17 Processing of these Fe-containing particles takes place in the atmosphere through reactions with acidic gases, organics, in the dark or under irradiation, changing the hygroscopicity of these particles and increasing the amount of dissolved iron. 14 The processed iron-containing particles can act as a sink for SVOCs and undergo mixing with biomass burning organic aerosol (BBOA) containing derivatives of catechol and guaiacol. The role of Fe in condensed phase transformation of phenolic organic compounds in aerosol particles has recently been reviewed 18 where it was shown that Fe can convert catechol and guaiacol into light-absorbing and water-insoluble particles, namely polycatechol and polyguaiacol, respectively.…”

Sulfur radical formation from the tropospheric irradiation of aqueous sulfate aerosols

“…Organic concentrations also play a role in understanding AS-induced photo-kinetics. Although organic molar concentrations in particle liquid water are not well constrained due to factors such as solubility, molecular size, surface activity, volatility, and phase, they are estimated to be in the millimolar range ( 26 , 27 ). The pseudo first-order decay ( k obs = k org+SO4 × [SO 4 •– ] ss ) for both aromatic and aliphatic systems can be modeled to decrease sharply with increasing organic concentration ( Fig.…”