scholarly journals The role of coarse aerosol particles as a sink of HNO<sub>3</sub> in wintertime pollution events in the Salt Lake Valley

2021 ◽  
Vol 21 (10) ◽  
pp. 8111-8126
Author(s):  
Amy Hrdina ◽  
Jennifer G. Murphy ◽  
Anna Gannet Hallar ◽  
John C. Lin ◽  
Alexander Moravek ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Gas Phase ◽  
Salt Lake ◽  
Fine Particulate Matter ◽  
The United States ◽  
Water Soluble ◽  
Salt Lake Valley ◽  
Fine Particulate ◽  
Coarse Mode ◽  
Pollution Events

Abstract. Wintertime ammonium nitrate (NH4NO3) pollution events burden urban mountain basins around the globe. In the Salt Lake Valley of Utah in the United States, such pollution events are often driven by the formation of persistent cold-air pools (PCAPs) that trap emissions near the surface for several consecutive days. As a result, secondary pollutants including fine particulate matter less than 2.5 µm in diameter (PM2.5), largely in the form of NH4NO3, build up during these events and lead to severe haze. As part of an extensive measurement campaign to understand the chemical processes underlying PM2.5 formation, the 2017 Utah Winter Fine Particulate Study, water-soluble trace gases and PM2.5 constituents were continuously monitored using the ambient ion monitoring ion chromatograph (AIM-IC) system at the University of Utah campus. Gas-phase NH3, HNO3, HCl, and SO2 along with particulate NH4+, Na+, K+, Mg2+, Ca2+, NO3-, Cl−, and SO42- were measured from 21 January to 21 February 2017. During the two PCAP events captured, the fine particulate matter was dominated by secondary NH4NO3. The comparison of total nitrate (HNO3 + PM2.5 NO3-) and total NHx (NH3 + PM2.5 NH4+) showed NHx was in excess during both pollution events. However, chemical composition analysis of the snowpack during the first PCAP event revealed that the total concentration of deposited NO3- was nearly 3 times greater than that of deposited NH4+. Daily snow composition measurements showed a strong correlation between NO3- and Ca2+ in the snowpack. The presence of non-volatile salts (Na+, Ca2+, and Mg2+), which are frequently associated with coarse-mode dust, was also detected in PM2.5 by the AIM-IC during the two PCAP events, accounting for roughly 5 % of total mass loading. The presence of a significant particle mass and surface area in the coarse mode during the first PCAP event was indicated by size-resolved particle measurements from an aerodynamic particle sizer. Taken together, these observations imply that atmospheric measurements of the gas-phase and fine-mode particle nitrate may not represent the total burden of nitrate in the atmosphere, implying a potentially significant role for uptake by coarse-mode dust. Using the NO3- : NH4+ ratio observed in the snowpack to estimate the proportion of atmospheric nitrate present in the coarse mode, we estimate that the amount of secondary NH4NO3 could double in the absence of the coarse-mode sink. The underestimation of total nitrate indicates an incomplete account of the total oxidant production during PCAP events. The ability of coarse particles to permanently remove HNO3 and influence PM2.5 formation is discussed using information about particle composition and size distribution.

scholarly journals The Role of Coarse Aerosol Particles as a Sink of HNO<sub>3</sub> in Wintertime Pollution Events in the Salt Lake Valley

2020 ◽  
Author(s):  
Amy Hrdina ◽  
Jennifer G. Murphy ◽  
Anna Gannet Hallar ◽  
John C. Lin ◽  
Alexander Moravek ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Gas Phase ◽  
Salt Lake ◽  
Fine Particulate Matter ◽  
The United States ◽  
Water Soluble ◽  
Salt Lake Valley ◽  
Fine Particulate ◽  
Coarse Mode ◽  
Pollution Events

Abstract. Wintertime ammonium nitrate (NH4NO3) pollution events burden urban mountain basins around the globe. In the Salt Lake Valley of Utah in the United States, such pollution events are often driven by the formation of persistent cold air pools (PCAP) that trap emissions near the surface for several consecutive days. As a result, secondary pollutants including fine particulate matter less than 2.5 μm in diameter (PM2.5), largely in the form of NH4NO3, build up during these events and lead to severe haze. As part of an extensive measurement campaign to understand the chemical processes underlying PM2.5 formation, the 2017 Utah Winter Fine Particulate Study, water-soluble trace gases and PM2.5 constituents were continuously monitored using the Ambient Ion Monitoring Ion Chromatograph system (AIM-IC) at the University of Utah campus. Gas phase NH3, HNO3, HCl and SO2 along with particulate NH4+, Na+, K+, Mg2+, Ca2+, NO3−, Cl−, and SO42− were measured from January 21 to February 21, 2017. During the two PCAP events captured, the fine particulate matter was dominated by secondary NH4NO3. The comparison of total nitrate (HNO3 + PM2.5 NO3−) and total NHx (NH3 + PM2.5 NH4+) showed NHx was in excess during both pollution events. However, chemical composition analysis of the snowpack during the first PCAP event revealed that the total concentration of deposited NO3− was nearly three times greater than that of deposited NH4+. Daily snow composition measurements showed a strong correlation between NO3− and Ca2+ in the snowpack. The presence of non-volatile salts (Na+, Ca2+, and Mg2+), which are frequently associated with coarse mode dust, was also detected in PM2.5 by the AIM-IC during the two PCAP events, accounting for roughly 5 % of total mass loading. The presence of a significant particle mass and surface area in the coarse mode during the first PCAP event was indicated by size-resolved particle measurements from an Aerodynamic Particle Sizer. Taken together, these observations imply that atmospheric measurements of the gas phase and fine mode particle nitrate may not represent the total burden of nitrate in the atmosphere, implying a potentially significant role for uptake by coarse mode dust. Using the NO3− : NH4+ ratio observed in the snowpack to estimate the proportion of atmospheric nitrate present in the coarse mode, we estimate that the amount of secondary NH4NO3 could double in the absence of the coarse mode sink. The underestimation of total nitrate indicates an incomplete account of the total oxidant production during PCAP events. The ability of coarse particles to permanently remove HNO3 and influence PM2.5 formation is discussed using information about particle composition and size distribution.

scholarly journals On the contribution of nocturnal heterogeneous reactive nitrogen chemistry to particulate matter formation during wintertime pollution events in Northern Utah

2019 ◽  
Vol 19 (14) ◽  
pp. 9287-9308 ◽  
Author(s):  
Erin E. McDuffie ◽  
Caroline C. Womack ◽  
Dorothy L. Fibiger ◽  
William P. Dube ◽  
Alessandro Franchin ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Salt Lake ◽  
Fine Particulate Matter ◽  
Ambient Air ◽  
Atmospheric Conditions ◽  
Mixing Processes ◽  
Salt Lake Valley ◽  
Fine Particulate ◽  
Northern Utah ◽  
Pollution Events

Abstract. Mountain basins in Northern Utah, including the Salt Lake Valley (SLV), suffer from wintertime air pollution events associated with stagnant atmospheric conditions. During these events, fine particulate matter concentrations (PM2.5) can exceed national ambient air quality standards. Previous studies in the SLV have found that PM2.5 is primarily composed of ammonium nitrate (NH4NO3), formed from the condensation of gas-phase ammonia (NH3) and nitric acid (HNO3). Additional studies in several western basins, including the SLV, have suggested that production of HNO3 from nocturnal heterogeneous N2O5 uptake is the dominant source of NH4NO3 during winter. The rate of this process, however, remains poorly quantified, in part due to limited vertical measurements above the surface, where this chemistry is most active. The 2017 Utah Winter Fine Particulate Study (UWFPS) provided the first aircraft measurements of detailed chemical composition during wintertime pollution events in the SLV. Coupled with ground-based observations, analyses of day- and nighttime research flights confirm that PM2.5 during wintertime pollution events is principally composed of NH4NO3, limited by HNO3. Here, observations and box model analyses assess the contribution of N2O5 uptake to nitrate aerosol during pollution events using the NO3- production rate, N2O5 heterogeneous uptake coefficient (γ(N2O5)), and production yield of ClNO2 (φ(ClNO2)), which had medians of 1.6 µg m−3 h−1, 0.076, and 0.220, respectively. While fit values of γ(N2O5) may be biased high by a potential under-measurement in aerosol surface area, other fit quantities are unaffected. Lastly, additional model simulations suggest nocturnal N2O5 uptake produces between 2.4 and 3.9 µg m−3 of nitrate per day when considering the possible effects of dilution. This nocturnal production is sufficient to account for 52 %–85 % of the daily observed surface-level buildup of aerosol nitrate, though accurate quantification is dependent on modeled dilution, mixing processes, and photochemistry.

scholarly journals On the contribution of nocturnal heterogeneous reactive nitrogen chemistry to particulate matter formation during wintertime pollution events in Northern Utah

2019 ◽  
Author(s):  
Erin E. McDuffie ◽  
Caroline Womack ◽  
Dorothy L. Fibiger ◽  
William P. Dube ◽  
Alessandro Franchin ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Salt Lake ◽  
Fine Particulate Matter ◽  
Ambient Air ◽  
Atmospheric Conditions ◽  
Mixing Processes ◽  
Salt Lake Valley ◽  
Fine Particulate ◽  
Northern Utah ◽  
Pollution Events

Abstract. Mountain basins in Northern Utah, including Salt Lake Valley (SLV), suffer from wintertime air pollution events associated with stagnant atmospheric conditions. During these events, fine particulate matter concentrations (PM2.5) can exceed national ambient air quality standards. Previous studies in SLV have found PM2.5 is primarily composed of ammonium nitrate (NH4NO3), formed from the condensation of gas-phase ammonia (NH3) and nitric acid (HNO3). Additional studies in several western basins, including SLV, have suggested that production of HNO3 from nocturnal heterogeneous N2O5 uptake is the dominant source of NH4NO3 during winter. The rate of this process, however, remains poorly quantified, in part due to limited vertical measurements above the surface, where this chemistry is most active. The 2017 Utah Winter Fine Particulate Study (UWFPS) provided the first aircraft measurements of detailed chemical composition during SLV wintertime pollution events. Coupled with ground-based observations, analysis of day and nighttime research flights confirm that PM2.5 during wintertime pollution events is principally composed of NH4NO3, limited by HNO3. Here, observations and box-model analyses assess the contribution of N2O5 uptake to nitrate aerosol during pollution events using the NO3− production rate, N2O5 heterogeneous uptake coefficient (γ(N2O5)), and production yield of ClNO2 (Φ(ClNO2)), which had medians of 1.6 μg m−3 hr−1, 0.076, and 0.220, respectively. While fit values of γ(N2O5) may be biased high by a potential under-measurement in aerosol surface area, other fit quantities are unaffected. Lastly, additional model simulations suggest nocturnal N2O5 uptake produces 3.9 μg m−3 of nitrate per day, when considering the possible effects of dilution. This nocturnal production is sufficient to account for 86 % of the daily observed surface-level build-up of aerosol nitrate, though accurate quantification is dependent on modeled dilution and mixing processes.

scholarly journals Composition and secondary formation of fine particulate matter in the Salt Lake Valley: Winter 2009

2014 ◽  
Vol 64 (8) ◽  
pp. 957-969 ◽  
Author(s):  
Roman Kuprov ◽  
Delbert J. Eatough ◽  
Tyler Cruickshank ◽  
Neal Olson ◽  
Paul M. Cropper ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Salt Lake ◽  
Fine Particulate Matter ◽  
Salt Lake Valley ◽  
Fine Particulate ◽  
Secondary Formation

scholarly journals Carbonaceous Aerosols in Fine Particulate Matter of Santiago Metropolitan Area, Chile

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Richard Toro Araya ◽  
Robert Flocchini ◽  
Rául G. E. Morales Segura ◽  
Manuel A. Leiva Guzmán
Keyword(s):  
Particulate Matter ◽  
Organic Carbon ◽  
Environmental Protection Agency ◽  
Fine Particulate Matter ◽  
Warm Season ◽  
The United States ◽  
Carbonaceous Aerosol ◽  
World Health ◽  
Carbonaceous Aerosols ◽  
Fine Particulate

Measurements of carbonaceous aerosols in South American cities are limited, and most existing data are of short term and limited to only a few locations. For 6 years (2002–2007), concentrations of fine particulate matter and organic and elemental carbon were measured continuously in the capital of Chile. The contribution of carbonaceous aerosols to the primary and secondary fractions was estimated at three different sampling sites and in the warm and cool seasons. The results demonstrate that there are significant differences in the levels in both the cold (March to August) and warm (September to February) seasons at all sites studied. The percent contribution of total carbonaceous aerosol fine particulate matter was greater in the cool season (53 ± 41%) than in the warm season (44 ± 18%). On average, the secondary organic carbon in the city corresponded to 29% of the total organic carbon. In cold periods, this proportion may reach an average of 38%. A comparison of the results with the air quality standards for fine particulate matter indicates that the total carbonaceous fraction alone exceeds the World Health Organization standard (10 µg/m3) and the United States Environmental Protection Agency standard (15 µg/m3) for fine particulate matter.

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