APES Unit 7: Atmospheric Pollution

SO₂

Sulfur Dioxide. Corrosive, comes from coal + oil combustion. Precursor to acid rain/acid deposition.

NO_x

Nitric oxide (NO) and nitrogen dioxide (NO₂). Comes from all combustion. Irritant, tropospheric O₃ precursor, can convert into nitric acid → harmful to marine life.

CO

Carbon monoxide. Asphyxiant → death if exposed too much. Comes from bad exhaust, incomplete combustion, poor ventillation w/ combustion.

PM

Particulate Matter. Comes from biofuel + biomass combustion + certain activities. Reduces visibility, exasperates respiratory issues + cardiovascular issues + cancer.

O₃

Ozone. Secondary pollutant when in the troposphere. Degrades plant surfaces, reduces lung function, + damages materials (ex: rubber + plastic).

Pb

Lead. Used to be a gas additive. Impairs central nervous system + impairs ability to learn/concentrate.

Clean Air Act

Required lead to be phased out as a gas additive between 1975-1996. In 2021 no lead in gasoline anywhere.

Secondary Air Pollutants

Pollutants that have undergone transformation in sun, water, or air. Caused by primary pollutants → into secondary pollutants.

Ozone is the major one!! Formed from NO_x + VOCs

Photochemical Smog

Polluted orangey-brown haze formed by sunlight driven chemical reactions.

NO_x + VOCs → O₃ + PANs (family of smog chemicals, stable in cool air so travel long distances)

Irritates eyes + throat + triggers coughing + asthma. PANs = acute tissue irritant esp for plants. O₃ reduced photosynthesis.

Reducing Photochemical Smog

Reduce vehicle use, use EVs, vapor recovery nozzle at gas stations

Catalytic converter: VOCs, NO_x, CO → N₂, H₂O, O₂, CO₂

Thermal Inversions

Ground cools rapidly at night → air near surface cools, becomes dense, + sinks.

Warmer layer of air above (often strengthened by sinking, warning air in high pressure systems) prevents vertical mixing.

Pollutants get trapped near ground → more smog

PM₁₀ vs PM_2.5

Larger than PM₁₀ (10mm) usually filtered by nose + throat, but PM₁₀ and less are not.

PM_2.5 even more of a concern because they travel further + can be composed of more toxic material.

Radon

Naturally occurring radioactive gas, comes from decay of uranium in rocks + soil. Can enter home through cracks in foundation. Exposure can lead to cancer (2nd leading cause of lung cancer, after smoking).

VOCs

Found in many building materials, furniture, glues, paints, detergents, cleaners, air fresheners Formaldehyde is one of the most toxic (common in new homes, found in particle board and carpeting glue) + is carcinogenic.

Can cause burning sensations in eyes and throat, + breathing difficulties and asthma

Sick Building Syndrome

A buildup of toxic pollutants in weatherized newer buildings containing synthetic materials (most common in office buildings).

Crushed Limestone

Combines w/ SO₂ to make calcium sulfate, reducing SO₂ emissions. Calcium sulfate can be used for gypsum wall board or for foundations.

Dry Scrubbers

Big column w/ chemical that absorbs/neutralizes NO_x, SO₂, + VOCs. Often calcium oxide because calcium oxide + SO₂ → calcium sulfite

Wet Scrubbers

Chemicals + mist nozzles trap PM in water, mist falls to the bottom or gets trapped at top, sludge collection systems → dispose of polluted water.

Fluidized Bed Combustion

Jets of oxygen make combustion more effiecent + bring SO₂ into contact w/ more crushed limestone + reduce temps (reduce NO_x)

Acid Depostion

Process where acidic pollutants from the atmosphere fall to Earth’s surface in wet (rain, fog, snow) or dry (dust, gas) form.

Primarily caused by burning fossil fuels. Acidifies bodies of water, harms wildlife, and corrodes buildings + man-made structures

 NOx + SO₂

Primary pollutants that cause acid deposition. Both react w/ O₂ and water in the atmosphere.

SO₂ - produced mostly from coal fired power plants, sulfuric acid.

NO_x -  produced mostly from vehicle emissions and coal power plants, nitric acid.

Decreases pH (increases acidity) of soil + water.

Limestone

Limestone (calcium carbonate) is a natural base that can neutralize acidic soil/water. Regions w/ limestone bedrock have some natural buffering of acid rain. Can also be added to neutralized.