Effects of NO_xon the Volatility of Secondary Organic Aerosol from Isoprene Photooxidation

Abstract

The effects of NOx on the volatility of the secondary organic aerosol (SOA) formed from isoprene photooxidation are investigated in environmental chamber experiments. Two types of experiments are performed. In HO2-dominant experiments, organic peroxy radicals (RO2) primarily react with HO2. In mixed experiments, RO2 reacts through multiple pathways, including with NO, NO2, and HO2. The volatility and oxidation state of isoprene SOA are sensitive to and exhibit a nonlinear dependence on NOx levels. Depending on the NOx levels, the SOA formed in mixed experiments can be of similar or lower volatility compared to that formed in HO2-dominant experiments. The dependence of SOA yield, volatility, and oxidation state on the NOx level likely arises from gas-phase RO2 chemistry and succeeding particle-phase oligomerization reactions. The NOx level also plays a strong role in SOA aging. While the volatility of SOA in mixed experiments does not change substantially over time, SOA becomes less volatile and more oxidized as oxidation progresses in HO2-dominant experiments.

Inflammatory responses to secondary organic aerosols (SOA) generated from biogenic and anthropogenic precursors

“…Furthermore, isoprene SOA generated from different pathways (i.e., photooxidation under different RO 2 fates and reactive uptake of IEPOX; Surratt et al, 2010;Xu et al, 2014; produced similar responses for each inflammatory endpoint. These results suggest that different isoprene SOA products Xu et al, 2014; may induce similarly low inflammatory responses and are consistent with the intrinsic OP WS-DTT obtained for these SOA samples, where isoprene SOA generated the lowest OP WS-DTT of all SOA systems studied and the OP WS-DTT was similar for all SOA formation conditions explored (Tuet et al, 2017). This finding is in contrast to a previous study by Lin et al (2016), where methacrylic acid epoxide (MAE)-derived SOA was found to be substantially more potent than IEPOX-derived SOA.…”

Dithiothreitol activity by particulate oxidizers of SOA produced from photooxidation of hydrocarbons under varied NO<sub><i>x</i></sub> levels

“…Alkenes substituted with an electron-withdrawing group (e.g., conjugated carbonyls) are commonly found in ring-opening products from the photooxidation of aromatic HCs (e.g., toluene; Jang and Kamens, 2001;Saunders et al, 2003Saunders et al, , 1997Wyche et al, 2009). The contributions of all three groups of SOA products to DTT activity can be influenced by the type of precursor HC (aromatics vs. biogenics) and by NO x (NO + NO 2 ) levels (HC / NO x ratios; Eddingsaas et al, 2012b;Jang and Kamens, 2001;Wyche et al, 2009;Xu et al, 2014).…”

Effect of treatment with tartaric acid on carbon as a catalyst in the absorption of NO into the hexamminecobalt(II) solution

“…Furthermore, high concentrations of these undesirable contaminants in air pose serious health threats to human beings. In particular, these pollutants highly contribute to the formation of secondary organic aerosols (SOAs), which exert an impact on the climate as well [1,2]. The adverse effects on environmental and health have catalyzed research and development on the control of SOx and NOx.…”

“…Indeed, various methods and technologies have been put forward to curtail the emission of these pollutants. The technologies, such as wet flue gas desulfurization (WFGD) combined with selective catalytic reduction (SCR), or/and with selective noncatalytic reduction (SNCR), have been applied to remove NOx and SO 2 .…”

“…The low solubility of NO is the main obstacle for aqueous absorption of NOx because NO generally occupies 95% NOx in flue gas. As a result, the uses of aqueous solutions of H 2 O 2 , NaClO 2 , KMnO 4 , sodium persulfate, and sonochemical oxidation processes to turn NO into soluble NO 2 , are the subjects of many studies [3][4][5][6][7][8][9][10][11][12][13][14]. However, none of these methods have been put into commercial application.…”