Impacts of the 2020 COVID-19 Shutdown Measures on Ozone Production in the Los Angeles Basin

In March and April 2020, the South Coast Air Basin of California (USA) experienced noticeable declines in on-road activity and primary traffic-related pollutant emissions. However, secondary ozone concentration trends were not consistent across the basin. This research letter explores the impact of meteorology and emissions during this time period. The study elucidates the potential impacts on ozone nonattainment status for the region.

Download Full-text

HFC-152a and HFC-134a emission estimates and characterization of CFCs, CFC replacements, and other halogenated solvents measured during the 2008 ARCTAS campaign (CARB phase) over the South Coast Air Basin of California

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-2655-2011 ◽

2011 ◽

Vol 11 (6) ◽

pp. 2655-2669 ◽

Cited By ~ 19

Author(s):

B. Barletta ◽

P. Nissenson ◽

S. Meinardi ◽

D. Dabdub ◽

F. Sherwood Rowland ◽

...

Keyword(s):

Los Angeles ◽

Population Data ◽

The United States ◽

Montreal Protocol ◽

South Coast ◽

Emission Rates ◽

The South ◽

Hfc 134A ◽

South Coast Air Basin ◽

Hfc 152A

Abstract. This work presents results from the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) study. Whole air samples were obtained on board research flights that flew over California during June 2008 and analyzed for selected volatile organic compounds, including several halogenated species. Samples collected over the South Coast Air Basin of California (SoCAB), which includes much of Los Angeles (LA) County, were compared with samples from inflow air masses over the Pacific Ocean. The levels of many halocarbon species were enhanced significantly over the SoCAB, including compounds regulated by the Montreal Protocol and subsequent amendments. Emissions estimates of HFC-152a (1,1-difluoroethane, CH3CHF2; 0.82 ± 0.11 Gg) and HFC-134a (1,1,1,2-tetrafluoroethane, CH2FCF3; 1.16 ± 0.22 Gg) in LA County for 2008 were obtained using the observed HFC:carbon monoxide (CO) enhancement ratio. Emission rates also were calculated for the SoCAB (1.60 ± 0.22 Gg yr−1 for HFC-152a and 2.12 ± 0.28 Gg yr−1 for HFC-134a) and then extrapolated to the United States (32 ± 4 Gg yr−1 for HFC-152a and 43 ± 6 Gg yr−1 for HFC-134a) using population data. In addition, emission rates of the two HFCs in LA County and SoCAB were calculated by a second method that utilizes air quality modeling. Emissions estimates obtained using both methods differ by less than 25% for the LA County and less than 45% for the SoCAB.

Download Full-text

Long-Term Trends of PM2.5 and its Carbon Content in the South Coast Air Basin: A Focus on the Impact of Wildfires

Atmospheric Environment ◽

10.1016/j.atmosenv.2021.118431 ◽

2021 ◽

pp. 118431

Author(s):

Faraz Enayati Ahangar ◽

Payam Pakbin ◽

Sina Hasheminassab ◽

Scott A. Epstein ◽

Xiang Li ◽

...

Keyword(s):

Carbon Content ◽

South Coast ◽

The South ◽

Long Term Trends ◽

South Coast Air Basin ◽

The Impact

Download Full-text

Impacts of electronically photo-excited NO<sub>2</sub> on air pollution control strategies in the South Coast Air Basin of California

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-18985-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 18985-19008

Author(s):

J. J. Ensberg ◽

M. Carreras-Sospedra ◽

D. Dabdub

Keyword(s):

Particulate Matter ◽

Ozone Concentration ◽

Pollution Control ◽

Control Strategies ◽

Reaction Rates ◽

South Coast ◽

Chemical Mechanism ◽

Air Pollution Control ◽

The South ◽

South Coast Air Basin

Abstract. A new path for hydroxyl radical formation via photo-excitation of nitrogen dioxide (NO2) and the reaction of photo-excited NO2 with water is evaluated using the UCI-CIT model for the South Coast Air Basin of California (SoCAB). Two separate studies predict different reaction rates, which differ by nearly an order of magnitude, for the reaction of photo-excited NO2 with water. Impacts of this new chemical mechanism on ozone and particulate matter formation, while utilizing both reaction rates, are quantified by simulating a two-day summer episode. In addition, sensitivity simulations are conducted to evaluate the uncertainty in the rate of reaction of photo-excited NO2 with water reported in the literature. Results indicate that the addition of photo-excited NO2 chemistry increases peak 1-h average ozone concentrations by up to 20.6%. Also, the new chemistry leads to moderate increases in particulate matter concentrations of up to 2.9%. The importance of this new chemistry is then evaluated in the context of pollution control strategies. A series of simulations are conducted to generate isopleths for ozone and particulate matter concentrations, varying baseline nitrogen oxides (NOx) and volatile organic compounds emissions. Results show that including NO2 photo-excitation increases the sensitivity of ozone concentration to changes in NOx emissions. Namely, increasing NOx when NO2 photo-excitation is included, while utilizing the higher reaction rate, leads to an increase in ozone concentration of up to 38.7% higher than a case without photo-excited NO2. Ozone and particulate matter control strategies rely heavily on the variation of NOx and VOC emissions and the addition of the new chemical mechanism increases peak ozone and 24-h average PM concentrations in all locations under all NOx and VOC scaling factors while utilizing both reaction rates. Therefore, three-dimensional air quality models should be modified to include this new OH production mechanism, especially if used to develop emission controls strategies.

Download Full-text

HFC-152a and HFC-134a emission estimates and characterization of CFCs, CFC replacements, and other halogenated solvents measured during the 2008 ARCTAS campaign (CARB phase) over the South Coast Air Basin of California

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-28017-2010 ◽

2010 ◽

Vol 10 (11) ◽

pp. 28017-28056

Author(s):

B. Barletta ◽

P. Nissenson ◽

S. Meinardi ◽

D. Dabdub ◽

F. Rowland ◽

...

Keyword(s):

Los Angeles ◽

Population Data ◽

Montreal Protocol ◽

South Coast ◽

Emission Rates ◽

The South ◽

The Pacific ◽

Hfc 134A ◽

South Coast Air Basin ◽

Hfc 152A

Abstract. This work presents results from the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) study. Whole air samples were obtained on board research flights that flew over California during June 2008 and analyzed for selected volatile organic compounds, including several halogenated species. Samples collected over the South Coast Air Basin of California (SoCAB), which includes much of Los Angeles (LA) County, were compared with samples from inflow air masses over the Pacific Ocean. The levels of many halocarbon species were enhanced significantly over the SoCAB, including compounds regulated by the Montreal Protocol and subsequent amendments (e.g., enhancements of 13 pptv and 11 pptv for CFC-11 and CFC-12, respectively). Emissions estimates of HFC-152a (0.98±0.05 Gg) and HFC-134a (1.40±0.11 Gg) in LA County for 2008 were obtained using the observed HFC:CO enhancement ratio. The emission rates were extrapolated to the SoCAB (1.48±0.07 Gg for HFC-152a and 2.12±0.17 Gg for HFC-134a) and US (30.1±1.5 Gg for HFC-152a and 43.0±3.4 Gg for HFC-134a) using population data. In addition, emission rates of the two HFCs in LA County and SoCAB also were calculated by a second method that utilizes air quality modeling. Estimates obtained using both methods agree well.

Download Full-text