Airborne and ground-based observations of ammonium nitrate
dominated aerosols in a shallow boundary layer during intense winter
pollution episodes in northern Utah

Franchin, Alessandro; Fibiger, D. L.; Goldberger, Lexie; McDuffie, Erin E.; Moravek, Alexander; Womack, Caroline C.; Crosman, Erik T.; Docherty, Kenneth S.; Dubé, W. P.; Hoch, Sebastian W.; Lee, Ho-Chang; Long, Russell; Murphy, J. G.; Brown, Steven S.; Baasandorj, Munkhbayar; Middlebrook, A. M.

doi:10.5194/acp-2018-629

Cited by 7 publications

(16 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Nenes et al (2020) derived a set of thermodynamic equations showing that sensitivities of nitrate and ammonium to precursor emissions are functions of atmospheric pH and liquid water content. In addition, NH 3 emissions can alter the relative fraction of secondary aerosols and their sensitivity to emissions reductions of NO x and NH 3 (Franchin et al, 2018; Sharma et al, 2007). Over China, recent observational studies (e.g., Xu, Wang, et al, 2019) showed that for 2013–2017, wintertime sulfate became less important while nitrate became dominant despite reductions in both SO 2 and NO x (Ding, Xing, et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Wintertime Particulate Matter Decrease Buffered by Unfavorable Chemical Processes Despite Emissions Reductions in China

Leung

Shi

Zhao

et al. 2020

Geophysical Research Letters

View full text Add to dashboard Cite

Extreme and persistent haze events frequently occur during wintertime China. While recent emissions reductions reduced annual mean fine particulate matter (PM2.5) concentrations over eastern China, their effectiveness on wintertime PM2.5 trend remains uncertain. We use observations and model simulations to quantify seasonal differences in PM2.5 trends and investigate the underlying chemical mechanisms driving such differences. We find a much slower decrease in observed wintertime PM2.5 (−3.2% yr−1) since 2014, in contrast to a drastic summertime decrease (−10.3% yr−1). Simulations show two previously underappreciated mechanisms buffering wintertime PM2.5 decrease, including an increase in oxidation capacity due to nitrogen oxides (NOx) reductions under wintertime volatile organic compound (VOC)‐limited chemistry, and an enhanced conversion of nitric acid to nitrate by ammonia due to sulfur dioxide reductions. Our findings suggest that control policies targeting VOC and deep NOx reductions are needed to improve wintertime PM2.5 air quality over China.

show abstract

Section: Introductionmentioning

confidence: 99%

Wintertime Particulate Matter Decrease Buffered by Unfavorable Chemical Processes Despite Emissions Reductions in China

Leung

Shi

Zhao

et al. 2020

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…In the Great Salt Lake Region in northern Utah, the 24-hr U.S. National Ambient Air Quality Standard (NAAQS) for PM2.5 (35 μg m -3 ) is exceeded on average 18 days per winter (Silcox et al, 2012;Whiteman et al, 2014). Previous measurements made in the Salt Lake Valley (Kelly et al, 2013;Kuprov et al, 2014) and recently published analysis of the UWFPS aerosol composition (Franchin et al, 2018) agree that during PCAP periods up to 75% of wintertime PM2.5 is ammonium nitrate.…”

Section: Introductionmentioning

confidence: 90%

“…If we account for the observed underestimation of emission sources in the UDAQ inventory by increasing area source and mobile emissions by a factor 4.5 and 3, respectively, ( Fig. S19) (Franchin et al, 2018). Therefore, the advection of nitrate or NOx may be a significant process for PM2.5 formation in Cache Valley.…”

Section: Inter-valley Exchange Of Nh3 and Impact On Pm Formationmentioning

confidence: 99%

“…The Twin Otter aircraft was equipped with an Aerosol Mass Spectrometer (AMS, Aerodyne Research Inc., MA) to measure the chemical composition of the non-refractory aerosol particles in the 70 to 800 nm range (NR-PM1) (Drewnick et al, 2005;Jayne et al, 2000) . The operation of the AMS during UWFPS is described in detail in Franchin et al (2018). In brief, ambient aerosol particles are focused in an aerodynamic lens, evaporated, ionized with electron-impact ionization and detected by a mass spectrometer.…”

Section: Airborne Measurements Of Other Trace Gases and Aerosolsmentioning

confidence: 99%

“…Discussion started: 21 May 2019 c Author(s) 2019. CC BY 4.0 License.is transported to Salt Lake Valley, its equilibrium with HNO3 produced from oxidation of NOx emitted by mobile and industrial sources may affect the limiting reagent and thus the control strategy for ammonium nitrate PM2.5 formation in Utah's most densely populated region(Franchin et al, 2018). Similarly, NOx enriched air masses transported from Salt Lake Valley may lead to PM2.5 formation in Cache Valley.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Wintertime Spatial Distribution of Ammonia and its Emission Sources in the Great Salt Lake Region

Moravek¹,

Murphy²,

Hrdina³

et al. 2019

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Ammonium-containing aerosols are a major component of winter time air pollution in many densely populated regions around the world. Especially in mountain basins, the formation of persistent cold air pool (PCAP) periods can enhance particulate matter with diameters less than 2.5&#8201;&#956;m (PM2.5) to levels above air quality standards. Under these conditions, PM2.5 in the Great Salt Lake Region of northern Utah has been shown to be primarily composed of ammonium nitrate, however, its formation processes and sources of its precursors are not fully understood. Hence, it is key to understand the emission sources of its gas-phase precursor, ammonia (NH3). To investigate the formation of ammonium nitrate, a suite of trace gases and aerosol composition were sampled from the NOAA Twin Otter aircraft during the Utah Winter Fine Particulate Study (UWFPS) in January and February 2017. NH3 was measured using a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS), while aerosol composition, including particulate ammonium (pNH4), was measured with an aerosol mass spectrometer (AMS). The origin of the sampled air masses was investigated using the Stochastic Time-Inverted Lagrangian Transport (STILT) model and combined with an NH3 emission inventory to obtain model-predicted NHx (=&#8201;NH3&#8201;+&#8201;pNH4) enhancements. Comparison of these NHx enhancements with measured NHx from the Twin Otter shows that modelled values are a factor of 1.6 to 4.4 lower for the three major valleys in the region. Among these, the underestimation is largest for Cache Valley, an area with intensive agricultural activities. We find that one explanation for the underestimation of wintertime emissions may be the seasonality factors applied to NH3 emissions from livestock. An investigation of inter-valley exchange revealed that transport of NH3 between major valleys was limited and PM2.5 in Salt Lake Valley (the most densely populated area in Utah) was not significantly impacted by NH3 from the agricultural areas in Cache Valley. We found that in Salt Lake Valley around two thirds of NHx originated within the valley, while about 30&#8201;% originated from mobile source and 60&#8201;% from area source emissions in the region. For Cache Valley, a large fraction of NOx potentially leading to PM2.5 formation may not be locally emitted but mixed in from other counties.

show abstract

Assessing PM2.5 model performance for the conterminous U.S. with comparison to model performance statistics from 2007-2015

Kelly

Koplitz

Baker

et al. 2019

Atmospheric Environment

View full text Add to dashboard Cite

Previous studies have proposed that model performance statistics from earlier photochemical grid model (PGM) applications can be used to benchmark performance in new PGM applications. A challenge in implementing this approach is that limited information is available on consistently calculated model performance statistics that vary spatially and temporally over the U.S. Here, a consistent set of model performance statistics are calculated by year, season, region, and monitoring network for PM 2.5 and its major components using simulations from versions 4.7.1-5.2.1 of the Community Multiscale Air Quality (CMAQ) model for years 2007-2015. The multiyear set of statistics is then used to provide quantitative context for model performance results from the 2015 simulation. Model performance for PM 2.5 organic carbon in the 2015 simulation ranked high (i.e., favorable performance) in the multi-year dataset, due to factors including recent improvements in biogenic secondary organic aerosol and atmospheric mixing parameterizations in CMAQ. Model performance statistics for the Northwest region in 2015 ranked low (i.e., unfavorable performance) for many species in comparison to the 2007-2015 dataset. This finding motivated additional investigation that suggests a need for improved speciation of wildfire PM 2.5 emissions and modeling of boundary layer dynamics near water bodies. Several limitations were identified in the approach of benchmarking new model performance results with previous results. Since performance statistics vary widely by region and season, a simple set of national

show abstract

Airborne and ground-based observations of ammonium nitrate dominated aerosols in a shallow boundary layer during intense winter pollution episodes in northern Utah

Cited by 7 publications

References 49 publications

Wintertime Particulate Matter Decrease Buffered by Unfavorable Chemical Processes Despite Emissions Reductions in China

Wintertime Particulate Matter Decrease Buffered by Unfavorable Chemical Processes Despite Emissions Reductions in China

Wintertime Spatial Distribution of Ammonia and its Emission Sources in the Great Salt Lake Region

Assessing PM2.5 model performance for the conterminous U.S. with comparison to model performance statistics from 2007-2015

Contact Info

Product

Resources

About