| Literature DB >> 30037992 |
Viral Shah1, Lyatt Jaeglé2, Joel A Thornton2, Felipe D Lopez-Hilfiker2, Ben H Lee2, Jason C Schroder3,4, Pedro Campuzano-Jost3,4, Jose L Jimenez3,4, Hongyu Guo5, Amy P Sullivan6, Rodney J Weber5, Jaime R Green7, Marc N Fiddler8, Solomon Bililign8,9, Teresa L Campos10,11, Meghan Stell11, Andrew J Weinheimer10, Denise D Montzka10, Steven S Brown3,12.
Abstract
Sulfate ([Formula: see text]) and nitrate ([Formula: see text]) account for half of the fine particulate matter mass over the eastern United States. Their wintertime concentrations have changed little in the past decade despite considerable precursor emissions reductions. The reasons for this have remained unclear because detailed observations to constrain the wintertime gas-particle chemical system have been lacking. We use extensive airborne observations over the eastern United States from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) campaign; ground-based observations; and the GEOS-Chem chemical transport model to determine the controls on winter [Formula: see text] and [Formula: see text] GEOS-Chem reproduces observed [Formula: see text]-[Formula: see text]-[Formula: see text] particulate concentrations (2.45 μg [Formula: see text]) and composition ([Formula: see text]: 47%; [Formula: see text]: 32%; [Formula: see text]: 21%) during WINTER. Only 18% of [Formula: see text] emissions were regionally oxidized to [Formula: see text] during WINTER, limited by low [H2O2] and [OH]. Relatively acidic fine particulates (pH∼1.3) allow 45% of nitrate to partition to the particle phase. Using GEOS-Chem, we examine the impact of the 58% decrease in winter [Formula: see text] emissions from 2007 to 2015 and find that the H2O2 limitation on [Formula: see text] oxidation weakened, which increased the fraction of [Formula: see text] emissions oxidizing to [Formula: see text] Simultaneously, NOx emissions decreased by 35%, but the modeled [Formula: see text] particle fraction increased as fine particle acidity decreased. These feedbacks resulted in a 40% decrease of modeled [[Formula: see text]] and no change in [[Formula: see text]], as observed. Wintertime [[Formula: see text]] and [[Formula: see text]] are expected to change slowly between 2015 and 2023, unless [Formula: see text] and NOx emissions decrease faster in the future than in the recent past.Entities:
Keywords: PM2.5; anthropogenic emissions; nitrate; sulfate; winter
Year: 2018 PMID： 30037992 PMCID： PMC6094106 DOI： 10.1073/pnas.1803295115
Source DB: PubMed Journal: Proc Natl Acad Sci U S A ISSN： 0027-8424 Impact factor: 11.205