AQ Info

The Air Quality Index Explained: What It Means and How to Stay Safe

Source: https://www.nytimes.com Aug 2021

"According to E.P.A. data from 2019, about 82 million Americans — 25 percent of the population — lived in counties with air quality concentrations above the safe level for one or more of the air quality pollutants, like particulates and ozone. And researchers have found that people of color are disproportionately exposed to more pollution from nearly every source.

The country’s average air quality index in 2020 was 40, according to IQAir, a Swiss air quality technology company. Twenty-two countries had cleaner air than the United States, and 83 fared worse."

Air Quality Index: What to do when the air quality is bad in your area

Source: https://www.cnet.com/ Nov 2019

"What is the AQI?

The AQI reports on how clean or polluted the air in your area is, and what effects breathing the outdoor air may have on your health. The AQI forecast is available in 400 US cities, and you can view regional maps that rate the air quality across the US and Canada. The index is on a scale of 0 to 500 (0 being clean air and 500 being heavy pollution). Outside the US, you can check the World Air Quality Index for air pollution ratings across the globe.

The AQI takes into account five of the major air pollutants that are regulated under the Clean Air Act. These pollutants are ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide."

Extremely High Levels of PM2.5: Steps to Reduce Your Exposure

Source: https://www.airnow.gov/ (n.d.)

"How will I know when conditions are better?

• Air quality conditions can change rapidly. Check airnow.gov or your local air agency website for the most recent hourly air quality conditions. This information can help you determine when to take steps to reduce your exposure.

• Also pay attention to weather forecasts; these can help you plan your activities for times when air quality improves, such as when winds are forecast that clear the air. When the air clears, and AQI readings are low, take advantage of these times to get outdoors."

Flocke, Frank, Gabriele Pfister, James H. Crawford, Kenneth E. Pickering, Gordon Pierce, Daniel Bon, and Patrick Reddy. 2020. “Air Quality in the Northern Colorado Front Range Metro Area: The Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ).” Journal of Geophysical Research: Atmospheres 125(2). doi: 10.1029/2019JD031197.

Abstract:

We describe the resources used, the deployment strategy, and the outcomes of the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) experiment, which took place in the summer of 2014 in the Front Range of Colorado. We provide a history of air quality of the region and the outcomes of previously conducted experiments, describe the atmospheric conditions encountered during the campaign, and summarize the scientific findings that the campaign produced, together with the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) intensive, simultaneously carried out by the National Aeronautics and Space Administration. The goal of FRAPPÉ was to measure emission tracers and photochemical tracers from the ground and by aircraft to be able to quantify the contributions of various emission sectors to the photochemical production of ozone in the Colorado Front Range. We found major contributions from the fossil fuel extraction sector as well as the transportation sector, with minor contributions from agriculture, energy generation, and industry. The meteorological conditions were also found to be critical in creating situations conducive to high ozone in the area.

Bahreini, R., Ahmadov, R., McKeen, S. A., Vu, K. T., Dingle, J. H., Apel, E. C., Blake, D. R., Blake, N., Campos, T. L., Cantrell, C., Flocke, F., Fried, A., Gilman, J. B., Hills, A. J., Hornbrook, R. S., Huey, G., Kaser, L., Lerner, B. M., Mauldin, R. L., … Weinheimer, A. (2018). Sources and characteristics of summertime organic aerosol in the Colorado Front Range: perspective from measurements and WRF-Chem modeling. Atmospheric Chemistry and Physics, 18(11), 8293–8312. https://doi.org/10.5194/ACP-18-8293-2018

Abstract:

The evolution of organic aerosols (OAs) and their precursors in the boundary layer (BL) of the Colorado Front Range during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ, July–August 2014) was analyzed by in situ measurements and chemical transport modeling. Measurements indicated significant production of secondary OA (SOA), with enhancement ratio of OA with respect to carbon monoxide (CO) reaching 0.085±0.003 µg m−3 ppbv−1. At background mixing ratios of CO, up to  ∼  1.8 µg m−3 background OA was observed, suggesting significant non-combustion contribution to OA in the Front Range. The mean concentration of OA in plumes with a high influence of oil and natural gas (O&G) emissions was  ∼  40 % higher than in urban-influenced plumes. Positive matrix factorization (PMF) confirmed a dominant contribution of secondary, oxygenated OA (OOA) in the boundary layer instead of fresh, hydrocarbon-like OA (HOA). Combinations of primary OA (POA) volatility assumptions, aging of semi-volatile species, and different emission estimates from the O&G sector were used in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) simulation scenarios. The assumption of semi-volatile POA resulted in greater than a factor of 10 lower POA concentrations compared to PMF-resolved HOA. Including top-down modified O&G emissions resulted in substantially better agreements in modeled ethane, toluene, hydroxyl radical, and ozone compared to measurements in the high-O&G-influenced plumes. By including emissions from the O&G sector using the top-down approach, it was estimated that the O&G sector contributed to  <  5 % of total OA, but up to 38 % of anthropogenic SOA (aSOA) in the region. The best agreement between the measured and simulated median OA was achieved by limiting the extent of biogenic hydrocarbon aging and consequently biogenic SOA (bSOA) production. Despite a lower production of bSOA in this scenario, contribution of bSOA to total SOA remained high at 40–54 %. Future studies aiming at a better emissions characterization of POA and intermediate-volatility organic compounds (IVOCs) from the O&G sector are valuable.

Detlev Helmig; Air quality impacts from oil and natural gas development in Colorado. Elementa: Science of the Anthropocene 1 January 2020; 8 4. doi: https://doi.org/10.1525/elementa.398

Abstract:

The rise of hydraulic fracturing techniques has fostered rapid growth of oil and natural gas (O&NG) extraction in areas across the United States. In the Denver-Julesburg Basin (DJB), which mostly overlaps with Weld County in the Northern Colorado Front Range (NCFR) north of the City of Denver Metropolitan Area (DMA), the well drilling has increasingly approached, and in many instances moved into urban residential areas. During the same time, the region has also experienced steady population growth. The DMA – NCFR has been in exceedance of the ozone U.S. National Ambient Air Quality Standard (NAAQS) and was designated a non-attainment area of the standard in 2007. Despite State efforts to curb precursors, ozone has consistently remained above the standard. A growing number of atmospheric studies has provided an ever increasing body of literature for assessing influences from O&NG industry emissions on air quality in the DMA-NCFR. This paper provides 1. An overview of available literature on O&NG influences on the regional air quality, 2. A summary of the pertinent findings presented in these works, 3. An assessment of the most important pollutants and air quality impacts, 4. Identification of knowledge and monitoring gaps, and 5. Recommendations for future research and policy.

Gratz, L., Eckley, C., Schwantes, S., & Mattson, E. (2019). Ambient Mercury Observations near a Coal-Fired Power Plant in a Western U.S. Urban Area. Atmosphere, 10(4), 176. MDPI AG. Retrieved from https://doi.org/10.3390/atmos10040176

Abstract:

We report on the continuous ambient measurements of total gaseous mercury (TGM) and several ancillary air quality parameters that were collected in Colorado Springs, CO. This urban area, which is located adjacent to the Front Range of the Rocky Mountains, is the second largest metropolitan area in Colorado and has a centrally located coal-fired power plant that installed mercury (Hg) emission controls the year prior to our study. There are few other Hg point sources within the city. Our results, which were obtained from a measurement site < 1 km from the power plant, show a distinct diel pattern in TGM, with peak concentrations occurring during the night (1.7 ± 0.3 ng m⁻³) and minimum concentrations mid-day (1.5 ± 0.2 ng m⁻³). The TGM concentrations were not correlated with wind originating from the direction of the plant or with sulfur dioxide (SO₂) mixing ratios, and they were not elevated when the atmospheric mixing height was above the effective stack height. These findings suggest that the current Hg emissions from the CFPP did not significantly influence local TGM, and they are consistent with the facility’s relatively low reported annual emissions of 0.20 kg Hg per year. Instead, variability in the regional signal, diurnal meteorological conditions, and/or near-surface emission sources appears to more greatly influence TGM at this urban site.

Cheadle, L. C., Oltmans, S. J., Pétron, G., Schnell, R. C., Mattson, E. J., Herndon, S. C., Thompson, A. M., Blake, D. R., & McClure-Begley, A. (2017). Surface ozone in the Colorado northern Front Range and the influence of oil and gas development during FRAPPE/DISCOVER-AQ in summer 2014. Elementa: Science of the Anthropocene, 5(61). https://doi.org/10.1525/elementa.254.

Abstract:

High mixing ratios of ozone (O3) in the northern Front Range (NFR) of Colorado are not limited to the urban Denver area but were also observed in rural areas where oil and gas activity is the primary source of O3 precursors. On individual days, oil and gas O3 precursors can contribute in excess of 30 ppb to O3 growth and can lead to exceedances of the EPA O3 National Ambient Air Quality Standard. Data used in this study were gathered from continuous surface O3 monitors for June–August 2013–2015 as well as additional flask measurements and mobile laboratories that were part of the FRAPPE/DISCOVER-AQ field campaign of July–August 2014. Overall observed O3 levels during the summer of 2014 were lower than in 2013, likely due to cooler and damper weather than an average summer. This study determined the median hourly surface O3 mixing ratio in the NFR on summer days with limited photochemical production to be approximately 45–55 ppb. Mobile laboratory and flask data collected on three days provide representative case studies of different O3 formation environments in and around Greeley, Colorado. Observations of several gases (including methane, ethane, CO, nitrous oxide) along with O3 are used to identify sources of O3 precursor emissions. A July 23 survey demonstrated low O3 (45–60 ppb) while August 3 and August 13 surveys recorded O3 levels of 75–80 ppb or more. August 3 exemplifies influence of moderate urban and high oil and gas O3 precursor emissions. August 13 demonstrates high oil and gas emissions, low agricultural emissions, and CO measurements that were well correlated with ethane from oil and gas, suggesting an oil and gas related activity as a NOx and O3 precursor source. Low isoprene levels indicated that they were not a significant contributor to O3 precursors measured during the case studies.