Thank you for tuning in to another entry on my blog! Today, we will address the question that I posed at the end of my previous entry – would air pollution occur even without human interference? Despite a lack of evidence indicating the presence of air pollution before humans existed , several naturally occurring phenomena are recognized for their varying extents of contribution to air pollution.
We’ve all heard about volcanic eruptions – but what do they entail? Simply put, volcanic eruptions occur when rocks within the extremely hot core of Earth melt to form liquid magma which rises and eventually escapes through the Earth’s surface along with other materials. Aside from the lava flow and hot rocks, volcanic gases and ash are significant air pollutants that accentuate the risks associated with eruptions. Water vapour, carbon dioxide, and sulphur dioxide constitute approximately 99% of the gases emitted during an eruption (USGS, n.d.)
Figure 1. Volcanic gas compositions of 3 different volcanoes (George, 2014)
H2O, CO2, SO2 refer to water vapour, carbon dioxide, and sulphur dioxide respectively
Figure 2. Annual carbon dioxide emissions (Gt/y) by selected sources. (George, 2014)
The yearly carbon dioxide emission from volcanoes exceeds that of Argentina and Pakistan; hence the role of volcanic eruptions in aggravating the greenhouse effect is surely one that cannot be understated. On the other hand, sulphur dioxide, which is highly reactive and has a residence time ranging from months to years, will react with other atmospheric elements to produce sulphuric acid, sulphate, and volcanic smog (vog) which worsens air pollution both locally and downwind (George, 2014)
Figure 3. Satellite image of a dust storm emerging from Gobi Desert on 27 April 2012 (Byrd, 2012)
Dust storms (or sandstorms) are common occurrences in arid and semi-arid parts of the world. They are defined as “the result of surface winds raising large quantities of dust into the air and reducing visibility at eye level (1.8 m) to less than 1000 m” (UNEP et al., 2016). A combination of meteorological conditions (high temperatures, low rainfall) and seasonal wind patterns (EEA, 2012) are responsible for uplifting sand and dust that are transported across various parts of the world. Particularly, the Gobi and Sahara deserts are recognized as the main source of atmospheric dust in Asia and across the globe respectively. In fact, an estimated 2,150 teragrams (2,150 trillion grams) of dust is transported by air globally every year (Perkins, 2001).
A time-lapse video illustrating the movement of dust (coloured brown) moving across Earth’s surface (CAMS, 2022).
Arid environments produce more than just dust storms. According to the World Health Organization (n.d.), wildfires are “unplanned fires that burn in natural areas such as forests, grasslands, or prairies”. Under dry climatic conditions, trees and vegetation turn into dry, flammable fuel that is easily ignited with a natural source of spark such as lightning (Wolters, 2019). Combined with an oxygen-rich open environment that promotes combustion, the flames grow rapidly, burning through large areas. More importantly, wildfires are known to emit huge amounts of smoke that contain gaseous pollutants and harmful particulate matter. A study on the effects of smoke ‘ageing’ revealed that particles in smoke have residence times of weeks, during which they become more toxic by oxidising into damaging free radicals that are transported to other parts of the world (Gray, 2020). The Copernicus Atmosphere Monitoring Service (2022) estimates that 1,455 megatonnes of carbon was emitted from wildfires in 2021. Their video depicts the unyielding nature of global wildfire activities across 11 months, giving us an idea of the perpetual flux of wildfire-emitted pollutants globally.
It appears that these are all indeed forces of nature that we have no control over; but is this TRULY the case? Orlovsky et al. (2004) suggest that the rising frequency of dust storms in the Aral Sea basin region can be partially imputed to anthropogenic creation of solonchaks (salty pans) that increases the availability of aerosols for air transport. Meanwhile, the US National Park Service (n.d.) reported that humans are responsible for 85% of the wildfires in US which have also been found to be more destructive than those that occur naturally (Joosse, 2020)
I find it atrocious that the extent of human influence has not only disrupted nature, but also begun to modify natural processes. The rising frequency and intensity of natural disasters is a clear signal for mankind to take a step back and rethink our actions. Starting from the next entry, we will begin to delve into the various consequences of tampering with nature’s wrath.
Until then, breathe safe and be safe!
References
Byrd, D. (2012). View from space: Dust storm in Gobi Desert. Retrieved January 29, 2023, from https://earthsky.org/earth/view-from-space-dust-storm-in-gobi-desert/
CAMS. (2022). CAMS: Monitoring extreme wildfire emissions in 2022. Copernicus Atmosphere Monitoring Service. Retrieved January 29, 2023, from https://atmosphere.copernicus.eu/cams-monitoring-extreme-wildfire-emissions-2022
CAMS. (2022). What is desert dust and how does it change atmosphere and the air we breathe? Homepage. Retrieved January 29, 2023, from https://atmosphere.copernicus.eu/what-saharan-dust-and-how-does-it-change-atmosphere-and-air-we-breathe
EEA. (2012). Sahara dust, sea spray and fires contribute to Bad Air Quality. European Environment Agency. Retrieved January 29, 2023, from https://www.eea.europa.eu/highlights/sahara-dust-sea-spray-and
George, S. (2014). Volcanic Pollution. International Pollution Issues. Retrieved January 29, 2023, from https://intlpollution.commons.gc.cuny.edu/volcanic-pollution/
Gray, R. (2020). ‘four times more toxic’: How wildfire smoke ages over time. Horizon Magazine. Retrieved January 29, 2023, from https://ec.europa.eu/research-and-innovation/en/horizon-magazine/four-times-more-toxic-how-wildfire-smoke-ages-over-time
Joosse, T. (2020). Human-sparked wildfires are more destructive than those caused by nature. Science. Retrieved January 30, 2023, from https://www.science.org/content/article/human-sparked-wildfires-are-more-destructive-those-caused-nature
National Park Service. (2022). Wildfire causes and evaluations. National Park Service. Retrieved January 30, 2023, from https://www.nps.gov/articles/wildfire-causes-and-evaluation.htm
Orlovsky, L., Tolkacheva, G., Orlovsky, N., & Mamedov, B. (2004). Dust storms as a factor of atmospheric air pollution in the Aral Sea basin . Air Pollution XII, 74, 353–362. https://doi.org/10.2495/AIR040351
Perkins, S. (2001). Dust, the thermostat. Science News. Retrieved January 29, 2023, from https://www.sciencenews.org/article/dust-thermostat
UNEP, WMO, & UNCCD. (2016). (rep.). Global Assessment of Sand and Dust Storms. United Nations Environment Programme. Retrieved January 29, 2023, from https://wesr.unep.org/redesign/media/docs/assessments/global_assessment_of_sand_and_dust_storms.pdf.
USGS. (n.d.). What gases are emitted by Kīlauea and other active volcanoes? What gases are emitted by Kīlauea and other active volcanoes? | U.S. Geological Survey. Retrieved January 29, 2023, from https://www.usgs.gov/faqs/what-gases-are-emitted-kilauea-and-other-active-volcanoes
Wolters, C. (2019). Here’s how wildfires get started-and how to stop them. Environment. Retrieved January 29, 2023, from https://www.nationalgeographic.com/environment/article/wildfires
World Health Organization. (n.d.). Wildfires. World Health Organization. Retrieved January 29, 2023, from https://www.who.int/health-topics/wildfires#tab=tab_1