Activity 3.3.1 - Air Pollution Core Activity

 Air Pollution Basics

    Inversions occur when a layer of cool air is trapped beneath a higher level of warmer air. This can trap pollutants created by burning fossil fuels. When accompanied by fog, this is often called smog. 

Sulfur Pollutants

    Sulfur dioxide and hydrogen sulfide are emitted into the atmosphere, oxidize, and form other compounds including sulfate. Volcanoes are one natural source of these sulfur emissions, however, humans are responsible for about four times the amount of natural emissions (Freedman 2018). Half of these anthropogenic emissions result from fossil fuel combustion. The amount of anthropogenic emissions have greatly increased due to industrialization and are continuing to increase as more countries become industrialized. Developed countries are attempting to decrease their emissions by using technology to remove sulfur from the fuels or the post-combustion gas, as well as switching to cleaner energy sources and conserving energy. These emissions pose a threat to plants, wildlife, and humans. While animals are less sensitive to sulfuric emissions than plants, exposure to these pollutants may induce asthma and impaired lung function in vulnerable humans (Freedman 2018).

Nitrogen Pollutants

    Nitrogen gases including nitric oxide, nitrogen dioxide, and ammonia may act as pollutants in the atmosphere. Ammonia is mostly naturally emitted from the anaerobic decomposition of dead biomass in wetlands. Anthropogenic emissions of ammonia are emitted from fossil fuel combustion as well as animal husbandry (Freedman 2018). Ammonia eventually oxidizes into nitrate in the atmosphere. Nitrous oxide, also known as laughing gas, is mostly emitted from microbial denitrification of soil and water. Anthropogenic emissions, namely modern agricultural practices, are though to have raised overall emissions by about 40% (Freedman 2018). Anthropogenic emissions of nitic oxide arises out of the combustion of fossil fuels, mostly from automobiles and power plants. This will eventually oxidize to nitrogen dioxide. These emissions are not typically harmful enough to injure vegetation or pose a threat to wildlife and humans. The biggest issue with nitrogen pollutants stems from the photochemical reactions that produce ozone (Freedman 2018).

Hydrocarbon and Volatile Organic Compound Pollutants

    Hydrocarbons are chemicals with molecular structures containing hydrogen and carbon atoms. The hydrocarbon methane has the highest background concentration in the atmosphere compared to other hydrocarbons (Freedman 2018). Methane emissions primarily come from fermentation or organic matter by microbes in anaerobic wetlands, with smaller amounts coming from wildfire, ruminant animals, and termites. Other hydrocarbons come from gases and vapors from living vegetation as well as fossil fuel deposits. Anthropogenic sources include unburned fuel, releases from fossil fuel mining and refining, and evaporation of solvents (Freedman 2018). Hydrocarbons rarely pose a threat to plants and animals, rather, they cause harm when they react to produce ozone. 

Comparison of Current AQI

    The air quality index (AQI) is a measure of how polluted the air in a certain area is. It can be a tool to tell if any adverse health affects may occur in a short amount of time due to the air quality. The higher the AQI value, the more risk pollution poses to the population. 

	Time of Day	AQI Current	AQI Forecast	PM2.5	O3
Corcoran, CA (highest)	6:00 pm	66	N/A	66	43
San Antonio, TX (Where I Live)	9:00 pm	32	Good	23	32
Los Angeles, CA	6:00 pm	42	Good	33	42

(Table Data Source: EPA 2022)

    The air quality in California is higher that it is in my current location, likely due to the time difference. People are driving home from work  in California, adding pollution to the air, while people in San Antonio are in bed at home. I am unsure of an explanation for Corcoran, California to have a higher AQI than Los Angeles, California. The forecast for both San Antonio, Texas and Los Angeles, California are good. There was no available forecast for Corcoran. In both San Antonio and Los Angeles, the PM2.5 is 9 points less than the O3 measurement. In Corcoran, PM2.5 is significantly higher than O3. 

Comparison of Current PM2.5/O3

    PM2.5 is particulate matter that is 2.5 microns or less in size. Because they are so small, the particles can linger in the air for extended periods of time and have a higher risk of being breathed in by the public (EPA 2019). Inhaling these particles has been shown to worsen chronic diseases as well as cause premature death from lung and heart disease.

    O3, also known as ozone, exists naturally in high concentrations in the stratosphere where it helps protect the earth's surface by absorbing UV radiation. Ozone in the troposphere, at the earth's surface, may cause damage to vegetation, materials, and human health. Smog contains high amounts of ozone and other oxidant gases. The concentration of ozone at ground level varies among regions (Freedman 2018). Ozone precursors, chemicals that will eventually produce ozone, occur mainly in cities. However, these gases can travel to more rural areas and damage the environment. In humans and animals, ozone can irritate and damage membranes of the eyes and respiratory system. It can cause asthma attacks, a loss of lug functioning, and exacerbate bronchitis and emphysema. In plants, ozone can diminish photosynthetic capacity, reducing productivity. Ozone may be the leading cause of damage to forests and other ecosystems (Freedman 2018).

National Standard	San Antonio Current measured over 1 hour	Time of Day
PM2.5 Average measured over 24 hours - 35 μg/m3	11.4 µg/m3	9:30 pm
O3 Average measured over 8 hours - 70 ppb (137 µg/m3)	40 ppb	9:30 pm

(Table Data Source: Texas commission on environmental quality 2022)


References

Freedman, B. (2018). Environmental science: A Canadian perspective. Halifax, Canada: Dalhousie University Libraries.

Texas commission on environmental quality. Current ozone 1-hour levels (2022). https://www.tceq.texas.gov/cgi-bin/compliance/monops/select_curlev.pl

Texas commission on environmental quality. Latest hourly Pm-2.5 levels (2022). https://www.tceq.texas.gov/cgi-bin/compliance/monops/select_curlev.pl?user_param=88502

US Environmental Protection Agency (EPA). (2019, June 18). Air quality index basics. Air Now. https://airnow.gov/index.cfm?action=aqibasics.aqi 

US Environmental Protection Agency (EPA). (2022). Interactive map of air quality. Air Now. https://gispub.epa.gov/airnow/?showgreencontours=false