air pollution and stratospheric ozone depletion chapter 15

Air Pollution and Stratospheric Ozone Depletion

Chapter 15

Air Pollution

• “introduction of chemicals, particulate matter (PM), or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings or alter ecosystems”

• “pollution of troposphere” or “ground-level pollution”

• Sources a. natural - volcanoes - forest fires - plants

b. anthropogenic - on-road vehicles (largest source of CO and NOx)

- industry - power plants

Major Air Pollutants

• Six pollutants (criteria) – U.S. Clean Air Act a. SO2

b. NOx

c. CO d. PM e. tropospheric ozone f. lead

• Sulfur Dioxide (SO2)

a. corrosive gas b. combustion of fossil fuels (coal and oil) c. respiratory irritant d. released from volcanoes and forest fires

• Nitrogen Oxides a. NOx (NO or NO2)

b. NO 1. colorless, odorless gas c. NO2

1. pungent, reddish-brown gas d. nitrogen (N2)

1. makes up 78% of atmosphere

• Carbon Oxides a. CO 1. colorless, odorless gas 2. vehicle exhaust b. CO2

1. colorless, odorless gas 2. photosynthesis/cellular respiration 3. burning of fossil fuels

• Particulate Matter (PM) a. solid or liquid particles suspended in the air b. sizes 1. ranges 0.001 micrometer to 100 micrometer 2. larger than 10 - can be filtered out by nose and throat 3. PM10 – not filtered and deposited in

respiratory tract 4. PM2.5 – BIG health concern

c. scatter and absorb sunlight

• Photochemical Oxidants a. sunlight acting on NOx and SO2

b. main focus – O3 (ozone) 1. most abundant in troposphere 2. respiratory inflammation 3. reacts with NOx and sulfur to form smog - photochemical * LA type, brown - sulfurous * London type, gray - atmospheric brown cloud * seen in Asia

• Lead (Pb) a. occurs naturally in rocks and soil b. has been added to gasoline c. persistent

• Mercury (Hg) a. coal and oil – released into atmosphere b. toxic to CNS

• VOCs (volatile organic compounds) a. become vapors at typical atmospheric temperatures b. hydrocarbons c. gasoline, lighter-fluid, oil-based paints d. strong aromas e. lead to ozone formation

Primary and Secondary Pollutants• Primary a. direct source b. CO, CO2, SO2, NOx, most PM and VOCs

• Secondary a. product of primary pollutant undergoing a reaction ex) ozone (O3)

Photochemical Smog• Smog a. originally – smoke, fog, and sometimes SO2

due to burning of coal b. today – brown smog still a problem c. typically urban areas, but some rural (trees and shrubs, forest fires) d. atmospheric conditions (higher temperatures) 1. emission of VOCs 2. NOx emissions from electric utilities

c. no VOCs or photochemical oxidants 1. ozone (O3) forms during the day and breaks

down at night 2. little to no photochemical smog

d. VOCs present 1. VOCs combines with NOx

2. NOx no longer available to recombine with

O3 in atmosphere, therefore the O3

accumulates over time

e. Thermal inversion 1. warm layer of air at mid-altitude covers a layer of cold, dense air below 2. warm inversion layer - traps emissions causing severe pollution - vehicle exhaust and industrial emissions

http://news.bbc.co.uk/2/hi/uk_news/magazine/7532603.stm

Acid Deposition

• Formation a. NOx and SOx released into atmosphere

(primary) nitric acid and sulfuric acid (secondary) nitrate, sulfate, and hydrogen ions (generate acidity in acid deposition b. fall as wet or dry deposition c. reduced in US due to Clean Air Act

• Effects a. lowers pH of water b. detrimental to aquatic organisms c. decrease in species diversity d. erode statues, monuments, and buildings e. harm tree species (Red Spruce in NE US)

Stratospheric OzoneTropospheric Ozone Stratospheric Ozone

Oxidant that harms respiratory systems

Protective shield against radiation from Sun (UV-B)

Air pollutant damaging lung tissue and plants

Critically important to life

“ground-level ozone” “global sunscreen”

UV-A reaches this layer Absorbs UV-B and UV-C

• Formation and Breakdown of Ozone - occurs in closed loop cycle a. O2 + UV-C 2O

b. O2 + O O3

c. O3 + UV-B or UV-C O2 + O

• Ozone continuously formed/broken down in presence of sunlight

• Anthropogenic Contributions to Ozone Destruction a. Chlorine 1. major source – CFCs 2. O3 + CL ClO + O2

ClO + O Cl + O2

O3 + O 2 O2

3. catalyst, does not get used up 4. ozone no longer able to absorb UV-B

• Depletion of Ozone layer a. greatest at the poles since 1970 b. “ozone hole” in Antarctica 1. seasonal depletion 2. cold weather - build up of ice crystals mix with NO - accumulation of Cl 3. sunny weather - UV breaks down more Cl catalyzing ozone destruction

• Effort to reduce ozone depletion a. Montreal Protocol on Substances that Deplete the Ozone Layer - reduce CFC production 50% by 2000

Indoor Air Pollution

• Causes more deaths each year than outdoor air pollution

• Developing v. developed

• Asbestos a. insulating properties b. respiratory diseases (lung cancer) c. not dangerous until disturbed

• Carbon Monoxide a. malfunctioning exhaust system - typically natural gas b. binds with hemoglobin more efficiently than O2

c. lead to oxygen deprivation in brain

• Radon a. Radon-222, decay of uranium b. exists in bedrock c. seep through crack in foundation d. second leading cause of lung cancer

• VOCs in home products a. strong aroma b. glues, paints, formaldehyde c. burning sensation of eyes, throat

• Sick Building Syndrome a. high levels of VOCs and other pollutants b. headaches, sore throat, fatigue c. sources - mold, pollen - cleaning agents