Principles of Air Pollution: Exam 3

Pressure Gradient Force

A force that arises from differences in atmospheric pressure, driving air from high-pressure to low-pressure areas.

Coriolis Force

An apparent force caused by the rotation of the Earth, affecting the direction of winds and ocean currents. (90* to the right) Zero at equator max at poles

Depends on:

• latitude

• wind speed

• mass & angular spin

generates westerlies and NE trade winds

Geostrophic Wind

Balance between the pressure gradient force and the Coriolis force

ITCZ (Intertropical Convergence Zone)

A belt of low pressure near the equator where the trade winds of the Northern and Southern Hemispheres meet.

Hadley Cells

Large-scale atmospheric circulation cells that influence tropical weather patterns, characterized by rising air at the equator and descending air at subtropical latitudes.

Urban Heat Island Effect

• Less wet areas = heating up surfaces → Higher temperatures

• Increased mixing depths

• Sometimes higher wind velocities

• Enhanced thunderstorm activity

  Effects of local Meteorology on air pollution

Solar Radiation Attenuation

The reduction in intensity of solar radiation as it passes through the atmosphere, affected by gases and particles.

Acid Rain and Fog

pH of 2-5.6 Precipitation that contains elevated levels of sulfuric and nitric acids, often resulting from atmospheric pollution. Rain itself is naturally acidic pH of 5.6

acif fog is worse because of the smaller droplet size leading to a higher concentration

Pathways of Air Pollutants in the Human Body

The routes by which different types of air pollutants enter and affect the human body.

nose and lungs

Smog

A type of air pollution characterized by a mixture of smoke, fog, and other pollutants, often associated with urban areas.

London: Sulfuric Acid

LA: nitric acid

reddish brown color caused by NO2, nitrated PAH and soil dust aerosol

Friction Force

• Magnitude proportional to wind speed (v), opposite direction of the wind, decreases with height

• Depends on roughness of earth‘s surface (k)

Gradient Winds includes

• CF

• PGF

• Centrifugal force

centrifugal force

is an apparent force that acts outward on a body moving in a circular path

Surface Winds includes

• FF

• CF

• PGF

• centrifugal force

Single-Cell Circulation Model

Simple model assumption: non-rotating, non-tilted, ocean covered earth and only uses hadley cell

Three-Cell Circulation Model

• Rotating earth:the single splits into three cells(Hadley,Ferrel and Polar)

What happens to soils with increasing specic heat

increase in soil water content

Effects of local Meteorology on air pollution

Cloud Cover

• Reduction of UV radiation —> less photolysis rates

• Pollutants dissolve in cloud water —> rain out possible

Polar Front

Extends over the polar regions and redistributes cold air

Adiabatic Compression

warming

Adiabatic Expansion

cooling

Stability

Temperature Inversion

increasing temperature with altitude (traps pollution)

When and why does radiation inversion occur

long calm dry cloud free nights when the ground loses heat rapidly through radiation, cooling down more quickly than the air above. This creates a temperature gradient where the air near the surface is cooler than the air above it

large-scale subsidence inversion

descending of air mass (e.g. in H-systems) —> adiabatic heating

Pressure thickness ( = mass) remains the same —> altitudes different

Marine Inversion

Often associated with cold ocean surface water --> cooling surface layers (warmer layers aloft)

Frontal Inversion

Cold front air masses move into warm air masses (change of air masses)

Wind speed

Usually increasing dilution with increasing wind speed

helps horizontal pollutant transport

Expection:Ozone because it is higher up in the atmosphere and no point source it is secondairly formed

Horizontal pollutant transport

• wind speed

• wind direction

• long range transport or air polluntant

Ground Temperatures

• Warm ground temperatures = thick mixing depths (same as higher boundary layer heights)

• cold ground temperatures = thin mixing depths (same as lower boundary layer heights)

• Warm ground temperatures = convection

• Ground temperatures control biogenic emissions and evaporation

  Effects of local Meteorology on air pollution

Local winds

• Sea, lake, and bay breezes

• Valley and mountain breezes

• Effects of Sea and Valley breezes on Pollution

• Chimney effect and elevated pollution levels

  Effects of local Meteorology on air pollution

sea breeze

regional effect

switches direction every 12 hours

scatttering

depends on the size of the objects, in particular on the ratio diameter of objects vs wavelength

Rayleigh regime (D/λ < 0.03)

Mie regime (0.03 ≤ D/λ < 32)

Gas Absorption

at UV and visible range

Aerosol and Hydrometeor Particle Absorption

All aerosol and hydrometeor particles absorb thermal-IR and near-IR radiation, but only a few absorb visible and UV radiation

Reflection

The angle of incidence Θ1 equals the angle of reflection Θ 3.

Refraction

• Change of medium of different density

• Speed of wave changes

• If wave travels into a medium of higher density it refracts toward the surface normal

• depends on wavelength

Diffraction

• Wavefront encounters an object causing series of secondary concentric waves (“Huygens’s principle”)

• Waves overlap

• “bending of light”

Rainbow

a combination of dispersive refraction and reflection

Purple color in the skie is caused by

volcanic eruptions

Coal first and largest source of anthropogenically produced atmospheric acids

Sulfuric acid (H2SO4), Hydrochloric acid (HCl)

*oil is also a source*

Natural causes of Acidity

• Carbonic acid (rainwater pH = 5.6) »

• Volcanos: SO2, HCl

• Phytoplankton: dimethylsulfide (DMS)

• Gas-phase oxidation of natural NO2: HNO3

Sulfuric Acid Deposition

Nitric Acid Deposition

Wet Deposition

• Clouds, fog, interception, rain – Important in mountainous regions

• In central Europe between 600-1300 m a.s.l.: interception 30-70% of annual rainfall! –

• Also important in tropical rain forests or mountaineous cloud forests

• serves as a nutrient source

not the same level of precipation at top than from the bottom

Acids effects on lakes

• pH < 5.5 – reproductive failures and mutations in fish and amphibians

• pH < 5.0 – aquatic insects, algae, and plankton die » starvation of species at higher levels of the food chain

Development of air quality modeling

• RADM (Regional Acid Deposition Model)

• Basis for all later air chemistry models

Acid Depostion effects on soil and biomass

Soil

• Acid raindrops enter soil and groundwater

• Sulfuric and nitric acid dissolve and carry away mineral nutrients (Na, Ca, K, Mg)

• At pH < 4.2 releasing of Al, Cu, Zn, Cd, Mn, Pb > poisoning of soil, groundwater etc.

Biomass

• Sulfuric acid on leaves or needles » Liquid film of low pH » Erosion of the cuticle wax » Drying out and injury to the leaf or needle

• Damage on the root system through acidification of the soil » Disturbance of nutrient and water budgets of plants

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