Chemical feedbacks weaken the wintertime response of particulate sulfate and nitrate to emissions reductions over the eastern United States

Shah, Viral; Jaeglé, Lyatt; Thornton, Joel A.; Lopez‐Hilfiker, Felipe D.; Lee, Ben H.; Schroder, Jason C.; Campuzano‐Jost, P.; Jimenez, José L.; Guo, Hongyu; Sullivan, A.; Weber, R. J.; Green, Jaime R.; Fiddler, Marc N.; Bililign, Solomon; Campos, T.; Stell, Meghan; Weinheimer, A. J.; Montzka, D. D.; Brown, Steven S.

doi:10.1073/pnas.1803295115

Cited by 143 publications

(158 citation statements)

References 35 publications

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“…The photochemical growth of modeled ΔOA/ΔCO and ΔSOA/ΔCO with OH equivalent age is similar to the observations but does display some minor differences due to the model underestimate in the observed variability of CO concentrations (Figures , S3, and S4). A detailed comparison of the GEOS‐Chem simulation for other gas and aerosol species for WINTER showed that the model reproduces the observed ozone (O 3 ), nitrogen oxides (NO x ), total reactive nitrogen (NO y ), and inorganic aerosol species (Jaeglé et al, ; Shah et al, ). In the northeastern United States, in the bottom 1 km of the atmosphere, the GEOS‐Chem model predicts that pollution SOA accounts for 56% of OA and that OA contributes to 25% of the PM 1 mass, as much as SO 4 2− (Figure ).…”

Section: Resultsmentioning

confidence: 97%

Widespread Pollution From Secondary Sources of Organic Aerosols During Winter in the Northeastern United States

Shah

Jaeglé

Jimenez

et al. 2019

Geophysical Research Letters

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Secondary organic aerosol (SOA) from pollution sources is thought to be a minor component of organic aerosol (OA) and fine particulate matter beyond the urban scale. Here we present airborne observations of OA in the northeastern United States, showing that 58% of OA over the region during winter is secondary and originates from pollution sources. We observed a doubling of OA mass from SOA formation in aged emissions, with unexpected similarity to OA growth observed in polluted areas in the summer. A regional model with a simple SOA parameterization based on summer measurements reproduces these winter observations and shows that pollution SOA is widespread, accounting for 14% of submicron particulate matter in near‐surface air. This source of particulate matter is largely unaccounted for in air quality management in the northeastern United States and other polluted areas.

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Section: Resultsmentioning

confidence: 97%

Widespread Pollution From Secondary Sources of Organic Aerosols During Winter in the Northeastern United States

Shah

Jaeglé

Jimenez

et al. 2019

Geophysical Research Letters

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“…It is interesting to note that the NR‐PM 1 aerosol species in winter did not show clear trends although the annual average of PM 2.5 has been continuously decreased during the past 5 years. These results might suggest a weak response of aerosol composition to the reductions of precursors in winter (Shah et al, ).…”

Section: Resultsmentioning

confidence: 99%

Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

et al. 2019

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Air quality has been continuously improved in recent years in Beijing, yet severe haze episodes still frequently occur in winter. Here we deployed an Aerodyne high‐resolution aerosol mass spectrometer in two winter seasons during the same period to investigate the changes in aerosol chemistry from 2014 to 2016 in Beijing. Compared to 2014, submicron aerosol (PM1) species showed ubiquitous increases in mass concentrations by 10–130% in winter 2016, of which nitrate showed the largest increase among all aerosol species leading to a much higher NO3/SO4 ratio in 2016 (1.36 ± 0.90) than 2014 (0.72 ± 0.59). This result highlights an increasing role of nitrate in particulate matter pollution in recent years in Beijing. Aerosol composition and size distributions also changed significantly. Secondary inorganic species showed elevated contributions by ~10% in winter 2016 associated with corresponding decreases in organic aerosol (OA). Positive matrix factorization of OA illustrated the significant changes in both primary emissions and secondary production. While cooking OA decreased substantially from 25% in 2014 to 15% in 2016, the contribution of biomass burning OA slightly increased instead. Although secondary OA contributed similarly to OA in the two winters (49% vs. 53%), we observed ubiquitous increases (~50%) in photochemically related oxygenated OA and oxidized primary OA, and oxygen‐to‐carbon ratios of OA, indicating the enhanced photochemical production in winter 2016. Aqueous‐phase production of secondary OA however was relatively similar in the two winters. Further analysis demonstrated that the changes in aerosol and OA composition varied differently across different pollution and relative humidity levels.

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“…Coincident with seasonal shifts in photochemistry, multiphase chemical processes that occur in aerosol particles and clouds are promoted in winter relative to summer (Shah et al, ). A prime example is dinitrogen pentoxide (N 2 O 5 ), formed from the reaction of NO 2 with O 3 to generate the nitrate radical (NO 3 ), which, subsequently reacts with another NO 2 molecule, (Platt et al, ).…”

Section: Introductionmentioning

confidence: 99%

Anthropogenic Control Over Wintertime Oxidation of Atmospheric Pollutants

Haskins

Lopez‐Hilfiker

Lee

et al. 2019

Geophysical Research Letters

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During winter in the midlatitudes, photochemical oxidation is significantly slower than in summer and the main radical oxidants driving formation of secondary pollutants, such as fine particulate matter and ozone, remain uncertain, owing to a lack of observations in this season. Using airborne observations, we quantify the contribution of various oxidants on a regional basis during winter, enabling improved chemical descriptions of wintertime air pollution transformations. We show that 25-60% of NO x is converted to N 2 O 5 via multiphase reactions between gas-phase nitrogen oxide reservoirs and aerosol particles, with~93% reacting in the marine boundary layer to form >2.5 ppbv ClNO 2 . This results in >70% of the oxidizing capacity of polluted air during winter being controlled by multiphase reactions and emissions of volatile organic compounds, such as HCHO, rather than reaction with OH. These findings highlight the control local anthropogenic emissions have on the oxidizing capacity of the polluted wintertime atmosphere.Plain Language Summary During summer, rapid transformations of primary pollutants, those emitted directly into the atmosphere, into secondary pollutants, such as particulate matter and ozone, are driven by reactions with the hydroxyl radical, formed in the atmosphere when sunlight strikes ozone in the presence of water vapor. During winter, when there is less sunlight and water vapor, production of this radical is lower. Yet the conversion of primary pollutants into secondary pollutants still occurs rapidly, pointing to a misunderstanding in the chemical processes that drive this conversion during winter. Using aircraft data collected across the northeast United States during the winter of 2015, we show that reactions with radicals arising from atypical precursors, such as nitryl chloride, account for more than 70% of the reactions that directly emitted pollutants undergo. We show that during winter, the formation of these radicals is tied to human activities. Our data provide critical constraints for improving the descriptions of chemical processes in air quality models, which will help guide improved air quality policy. Other regions of the world, such as China, Europe, and northern India, also experience this seasonal chemical shift in the atmosphere. Our findings, therefore, have global scale implications for understanding wintertime pollution transformations and transport.

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Chemical feedbacks weaken the wintertime response of particulate sulfate and nitrate to emissions reductions over the eastern United States

Cited by 143 publications

References 35 publications

Widespread Pollution From Secondary Sources of Organic Aerosols During Winter in the Northeastern United States

Widespread Pollution From Secondary Sources of Organic Aerosols During Winter in the Northeastern United States

Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

Anthropogenic Control Over Wintertime Oxidation of Atmospheric Pollutants

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