New Insights into Aerosol Chemistry and Air Quality in Extreme Winters

  • December 17, 2024
  • Posted by: OptimizeIAS Team
  • Category: DPN Topics
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New Insights into Aerosol Chemistry and Air Quality in Extreme Winters

Sub: Env

Sec : Pollution

Why in News

  • A recent study by researchers from the University of Alaska Fairbanks and the Georgia Institute of Technology has uncovered a new chemical pathway responsible for worsening air quality during harsh winters.

Contrasting Air Quality: Dras vs. Fairbanks

  • Dras (Ladakh, India)
    • Winter temperature: Around -20°C.
    • Air quality: Remarkably clean and healthy.
  • Fairbanks (Alaska, USA)
    • Winter temperature: Around -22.4°C.
    • Air quality: Among the worst in the U.S., ranked first in particle pollution (PM).

Particulate Matter (PM):

  • PM10-2.5: Particles with diameters between 2.5 and 10 micrometres (μm).
  • PM2.5: Ultrafine particles smaller than 2.5 μm, capable of penetrating the lungs and causing severe health issues such as asthma and premature death.
  • PM 10 and PM 2.5 are smaller than 10 and 2.5 microns in their diameter, respectively.
  • The PM 2.5 particles can easily bypass the nose and throat and can enter the circulatory system.
  • The particles can also lead to chronic diseases such as asthma, heart attack, bronchitis and other respiratory problems.
  • Byproducts of emissions from factories, vehicular pollution, construction activities and road dust, such particles are not dispersed and stay suspended in the air that we breathe.
  • PM2.5 Nonattainment Area: Designation for areas where PM2.5 levels exceed the permissible limit of 35 μg/m³ of air. Fairbanks was declared such an area in 2009 due to emissions from wood stoves, fuel oil burning, industrial sources, and automobiles.

Hydroxymethanesulphonate Formation:

Hydroxymethanesulfonate (HMS) is an organosulfur compound formed through the aqueous-phase reaction between formaldehyde (HCHO) and Sulphur dioxide (SO₂).

This reaction typically occurs in atmospheric water droplets, such as those found in fog or clouds.

Formation Mechanism:

  • HMS is produced when formaldehyde reacts with dissolved Sulphur dioxide in the presence of liquid water.
  • Elevated relative humidity provides the necessary aqueous medium for the reaction.
  • Colder conditions enhance the solubility of gases like SO₂ and HCHO in water droplets, promoting HMS formation.
  • Aerosol particles with moderate pH levels facilitate the reaction.

Environmental Impact:

  • HMS can constitute a significant fraction of fine particulate matter (PM2.5) in the atmosphere, especially during severe pollution episodes.
  • The presence of HMS in aerosols contributes to haze formation and deteriorates air quality, posing health risks.
  • As a component of aerosols, HMS influences the Earth’s radiative balance by affecting cloud formation and atmospheric albedo.
  • Research in Fairbanks, Alaska, has shown that during winter, lower sulphate concentrations combined with low temperatures lead to less acidic PM particles, increasing HMS production.
  • Implications for Emission Controls: Studies suggest that reducing emissions of formaldehyde and other volatile organic compounds may decrease particulate Sulphur levels, indicating a potential co-benefit for air quality management.

Global Significance: HMS has been detected in various regions worldwide, indicating its global relevance in atmospheric chemistry.

Health Considerations: Fine particulate matter containing HMS can penetrate deep into the respiratory tract, potentially leading to adverse health effects.

Aerosol:

  • An aerosol is a suspension of fine solid particles or liquid droplets in a gas.
  • In the Earth’s atmosphere, aerosols play a crucial role in environmental and climatic processes.
  • These particles can originate from natural sources (e.g., volcanic eruptions, sea spray) or human activities (e.g., industrial emissions, vehicle exhaust).

Types of Aerosols

  • Natural Aerosols:
    • Dust: Fine particles from soil or deserts, carried by wind.
    • Sea Spray: Salt particles formed when ocean waves break.
    • Volcanic Ash: Tiny particles ejected into the atmosphere during volcanic eruptions.
    • Biogenic Aerosols: Organic particles like pollen, spores, or microbial fragments.
  • Anthropogenic (Human-Made) Aerosols:
    • Industrial Emissions: Sulfates, nitrates, and other pollutants released by factories.
    • Combustion Products: Black carbon and organic carbon from vehicle exhaust and biomass burning.
    • Urban Pollution: Aerosols formed due to vehicular traffic and industrial activities.

Role of Aerosols in the Atmosphere

  • Radiative Forcing:
    • Cooling Effect: Aerosols like sulfate reflect sunlight back into space, reducing the Earth’s surface temperature.
    • Warming Effect: Black carbon absorbs sunlight, contributing to atmospheric warming.
  • Cloud Formation: Aerosols act as cloud condensation nuclei (CCN), enabling water vapor to condense and form clouds.
  • Air Quality Impact: High concentrations of aerosols reduce visibility and degrade air quality, posing health risks.
  • Impact on Climate: Aerosols influence the global climate by affecting the energy balance of the Earth and modifying cloud properties (indirect effect).
Environment New Insights into Aerosol Chemistry and Air Quality in Extreme Winters