The Mystery Of Haze: Understanding The Air We Breathe

Haze is a phenomenon that reduces visibility and is caused by a variety of factors, both natural and anthropogenic. Natural haze can be caused by volatile gases emitted by trees, as seen in the Blue Ridge and Great Smoky Mountains of the Appalachians. However, haze is often a result of air pollution, such as the combustion of sulfur-containing coal, oil refining, and steel manufacturing, which releases sulfur dioxide gas and contributes to the formation of haze droplets. Wildfires, which have been exacerbated by climate change, also release fine particles of soot containing dust, heavy metals, and organic chemicals, leading to hazy skies. This pollution has various detrimental effects on human health, including respiratory ailments and increased anxiety and depression. Additionally, haze contributes to extreme weather patterns and warming effects, impacting regions like the eastern United States and China, which are plagued by acid rain.

Haze from wildfires

Haze is often a result of smoke from wildfires. In 2021, smoke from wildfires in the Western United States and parts of Canada stretched across North America, reaching the East Coast. California alone recorded more than 5,000 fires, burning over 200,000 acres—a significant increase compared to the previous year. The smoke from these fires, carried by high-level winds, created a thick blanket of haze in the sky, impacting air quality and leading to health concerns.

The Bootleg Fire in Oregon, for instance, scorched an area larger than Los Angeles and contributed to the haze. This fire was so intense that it created its own weather system, joining numerous other destructive blazes across the country. The smoke from these wildfires affected visibility, with CNN meteorologist Chad Myers describing his experience in the Vail Valley of Colorado, where there was no blue sky or stars visible due to the haze.

The haze from wildfire smoke can travel long distances and affect areas far from the flames. In some instances, the smoke has reached ground level, posing health risks and prompting air quality alerts in regions like Pennsylvania and New York. The National Weather Service has provided updates on the haze and its impact on sunshine and air quality.

While the haze from wildfires can have immediate impacts on visibility and air quality, it also serves as a stark reminder of the destructive nature of these fires and the ongoing challenges posed by drought, heat, and wind conditions that contribute to their spread. The efforts of firefighting teams are crucial in combating these wildfires and mitigating their impact on the environment and human health.

Haze from industrial sources

Haze is caused by the accumulation of dust and smoke particles in dry air. Haze from industrial sources, also known as smog, is a result of industrial pollution. It is a mixture of smoke and other pollutants that concentrate and form a usually low-hanging shroud, impairing visibility and posing respiratory health risks.

Industrial fuel burning and manufacturing processes are major human-caused sources of haze. These activities emit fine particles and gases, such as sulfur dioxide and nitrogen dioxide, that contribute to the formation of haze. Motor vehicles and electric utilities also fall into this category of human-caused haze contributors. The impact of these sources can be far-reaching, with haze often observed in areas devoid of significant local pollution sources.

In the United States, the Interagency Monitoring of Protected Visual Environments (IMPROVE) program was established through a collaboration between the US EPA and the National Park Service. The program aims to determine the chemical composition of haze in national parks and implement air pollution control measures. The Clean Air Act mandates the restoration and maintenance of visibility in 156 Class I Federal areas across the country.

Washington State, with its eight Class 1 Areas, has been actively working to improve visibility in scenic regions like Mount Rainier and the North Cascades. Their efforts include monitoring air quality, implementing emission reduction technologies, and setting long-term goals to enhance visibility by 2064.

Haze has also been a pressing issue in Southeast Asia, with Indonesia, Malaysia, and Singapore being significantly affected. Forest fires set by farmers, plantation owners, and miners for land clearing have resulted in haze spreading across the region, causing respiratory issues and environmental damage.

Volcanic haze

In May 2018, the Kilauea volcano in Hawaii began erupting, with molten rock pouring into the Pacific Ocean and creating laze. The trade winds blew the laze towards the southwest, putting the southeast shore of Kilauea at the highest risk of exposure to the plume. The Hawaii Volcano Observatory warned that the plumes could travel up to 15 miles downwind, prompting authorities to urge the public to stay away from the area.

The Kilauea eruption also resulted in the release of volcanic smog, or "vog", which is primarily composed of sulfur dioxide and acid particles. The levels of sulfur dioxide emissions in Hawaii were reported to be "1,000 times greater" than the EPA's definition of a major pollution source, according to a 2016 report in the scientific journal Environmental International. This led to an increase in the number of people seeking treatment for vog-related symptoms at the Hilo Medical Center.

The volcanic haze caused by the Kilauea eruption posed a significant risk to public health, with authorities urging people to avoid the area. The laze and vog created by the interaction of lava and seawater produced toxic gases and particles that could cause a range of health issues, particularly for those with pre-existing conditions, the elderly, children, and pregnant women.

Haze from burning fossil fuels

Haze can be caused by a variety of factors, including wildfires, fossil fuel combustion, and agricultural activities. While wildfires and agricultural practices can contribute to haze formation, the combustion of fossil fuels is a significant contributor to haze episodes, particularly in urban areas.

Fossil fuel combustion releases a range of pollutants into the atmosphere, which can reduce air quality and have detrimental effects on human health and the environment. These pollutants include greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O), as well as harmful substances like sulfur dioxide, nitrogen oxides, and airborne particles such as soot and sulfate aerosols.

The release of these pollutants from burning fossil fuels can lead to the formation of secondary aerosols, which are a primary component of haze. For example, nitrogen oxides (NOx) emitted from fossil fuel combustion can react with other pollutants, such as coal-burning sulfur dioxide (SO2), to form sulfate aerosols. These aerosols contribute to the haze and can remain suspended in the atmosphere, affecting air quality and visibility.

In urban areas, such as Beijing, fossil fuel combustion-related emissions have been identified as a dominant source of atmospheric ammonia (NH3) during severe haze episodes. The use of stable isotopes of NH4+ has helped attribute the source of these emissions to fossil fuel combustion in power plants and vehicles. Additionally, the quick transformation of primary gaseous pollutants into secondary aerosols, driven by atmospheric conditions, further exacerbates haze formation.

To mitigate haze and improve air quality, it is crucial to reduce emissions from fossil fuel combustion and transition towards cleaner energy sources. This includes implementing measures to limit the burning of oil, coal, and natural gas, as well as addressing other sources of emissions, such as vehicle emissions and biomass burning. By reducing these emissions, we can decrease the formation of secondary aerosols and improve overall air quality, benefiting human health and the environment.

Haze from drought conditions

Haze is a common phenomenon during the summer in many parts of the world. While it is often associated with warm and humid weather, haze can also be caused by other factors such as drought conditions.

Droughts are characterized by a lack of available water, which can have far-reaching consequences for communities, including limited access to water for essential activities and agriculture. Droughts can also impact air quality and contribute to haze formation. During droughts, plants and trees may emit volatile organic compounds (VOCs) that react with other chemicals in the atmosphere to create ground-level ozone, a harmful air pollutant. This can lead to respiratory issues and exacerbate lung damage.

In regions like California, which has experienced prolonged drought conditions, researchers have studied the impact of drought on air quality. They found that while absorption of ozone by plants decreased during severe drought years, trees and other plants maintained their production of isoprene, an ozone-forming VOC that helps them withstand heat stress. The complexity of atmospheric chemistry means that drought can have varying effects on air pollution levels, and regulators struggle to factor drought into their air pollution models effectively.

Additionally, drought-fueled wildfires can further contribute to haze and air pollution. Wildfires release smoke and pollutants into the atmosphere, reducing air quality and posing risks to human health, especially for those with respiratory illnesses. The smoke from wildfires can drift over large areas, affecting regions beyond the immediate vicinity of the fire.

Haze caused by drought conditions can have significant impacts on visibility, aviation safety, and human health. It is important for communities and regulators to understand the complex interactions between drought and air pollution to effectively mitigate the negative consequences and improve resilience to drought conditions.

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