Atmospheric Processing of Nitrophenols and Nitrocresols From Biomass Burning Emissions

Abstract

We present the analysis of the atmospheric budget of nitrophenols and nitrocresols, a class of nitroaromatics that raise great ecosystem and health concerns due to their phytotoxic and genotoxic properties, during the spring wheat harvest season in Eastern China. Significant quantities with maximum concentrations over 100 pptv and distinct diurnal patterns that peak around midnight and maintain low levels throughout the day were observed, in coincidence with the extensive open crop residue burning activities conducted in the vicinity. An observationally constrained zero-dimension box model was constructed to assess the relative importance of various production and removal pathways at play in determining the measured surface concentrations. The NO 3-initiated dark chemistry, in concert with meteorological variations predominantly dilution and entrainment, exerts major controls over the observed diurnal behaviors of nitrophenols and nitrocresols. Structural isomerism is predicted to have a significant impact on the multiphase partitioning and chemistry of nitrophenol isomers. Furthermore, simulations show that an appreciable amount of nitrophenols is present in the aerosol water, thereby representing an important source of water-soluble brown carbon in atmospheric aerosols under the humid subtropical weather prevailing during the campaign. Sensitivity analysis performed on the model parameterizations of reaction schemes helps to further understand the chemistry underlying the diurnal cycles. Implementing NO-dependent yields of cresols from toluene photooxidation improves the model predictions of nitrocresols at low NO ranges (<1 ppb), thereby underscoring the complexity of the peroxy radical reaction pathways from toluene photooxidation under atmospheric relevant conditions. Plain Language Summary Nitrophenols and nitrocresols represent an important class of nitroaromatics that impact Earth's climate by contributing to the formation of light-absorbing aerosols (brown carbon). Here, through a combination of field observations and model simulations, we examine the atmospheric transformation mechanisms of nitrophenols and nitrocresols present in large quantities from the open crop residue burning during the spring wheat harvest season in Eastern China. We show that the observed distinct diurnal patterns of nitrophenols and nitrocresols are responsive to the complex interplay of meteorological variations, oxidative processes, and multiphase chemistry in the atmosphere. Our analysis affords insights into the atmospheric life cycle of nitrophenols and nitrocresols with respect to chemical transformation, mass transport, and phase transitions. Such information is essential in further understanding the climate and health consequences of nitrophenols and nitrocresols.

Secondary Formation and Impacts of Gaseous Nitro-Phenolic Compounds in the Continental Outflow Observed at a Background Site in South China

“…The NPs in the same category showed a similar temporal pattern and good correlations (SI Figure S6), indicating their similar sources and atmospheric processing. The mean concentrations of NPs measured at Cape D’aguilar in this study were much lower than those measured at urban regions, where significant anthropogenic emissions (e.g., Beijing, Santiago, Milano) or biomass/crop residue burning (e.g., Dezhou, Taizhou) dominated the NPs concentrations. ,,,, However, the NPs measured at this regional background site were higher than that detected in the rural site of Lombardia and in the Horse Pool site at Uintah Basin, , suggesting the potential contribution of photochemical secondary formation and significant influences of continental outflows.…”

“…Moreover, because of the fast generation and photochemical consumption of different NPs, continuous and online measurement is necessary and desirable. Recent studies utilizing high-resolution time-of-flight chemical ionization mass spectrometer (Tof-CIMS) and proton-transfer-reaction time-of-flight mass spectrometer (PTR-Tof-MS) have observed abundant gaseous NPs at Uintah Basin, urban Beijing, , Dezhou, and Taizhou, and indicated the importance of secondary formation of some NPs species from urban and BB emissions. However, a comprehensive understanding of the formation and transformation of NPs away from urban source regions, and their impacts in regional or larger scales remain elusive.…”

Chemical characterization of oxygenated organic compounds in gas-phase and particle-phase using iodide-CIMS with FIGAERO in urban air

“…), methyl nitrophenols ( ) and dinitrophenols ( ) were the most significant components of nitro-aromatics in the gas phase. Despite the fact that nitrated phenols could be formed by photochemical oxidation from their aromatic hydrocarbon precursors (Wang et al, 2020a;Yuan et al, 2016), none of them peaked in the daytime, consistent with photolysis as a dominant chemical loss for these compounds (Chen et al, 2011;Yuan et al, 2016). Nitrophenols and methyl nitrophenols peaked in the evening, suggesting either NO3 oxidation or primary emissions was important sources.…”

A Demonstration of Broadband Cavity-Enhanced Absorption Spectroscopy at Deep-Ultraviolet Wavelengths: Application to Sensitive Real-Time Detection of the Aromatic Pollutants Benzene, Toluene, and Xylene

“… 3 − 5 Oxidation of BTX also produces secondary organic aerosols and ozone, thereby aggravating air pollution and exacerbating impacts on public health. 6 , 7 …”