Part 5. Human Activities

1
Part 5. Human Activities

• Chapter 14
• Human Effects Air Pollution and Heat Islands

2
Introduction

• Air pollutants are gases, liquids or solids in
  the air that can adversely affect plant and/or
  animal life
• Primary pollutants are pollutants that are
  emitted directly by natural or anthropogenic
  (manmade) processes
• Secondary pollutants are pollutants that arise
  from chemical reactions of atmospheric gases with
  gases emitted by natural or anthropogenic
  processes

3
Important Air Pollutants

• Particulates (aerosols) are solid or liquid
  particles suspended in the air (from .1 to 100 mm
  in size)
• Natural sources -- fires, volcanic eruptions,
  salt spray from the oceans, pollen, dust storms
• Anthropogenic sources -- combustion of fossil
  fuels
• PM10 (lt 10 mm) enters lungs (associated with
  asthma) PM2.5 even more dangerous (lung cancer)
• Particulates stay in the atmosphere no more than
  a few years

4

• Carbon oxides - COx
• CO -- Carbon monoxide
• Colorless, odorless gas from volcanic eruptions,
  forest fires, bacterial activities, fuel
  combustion
• Dangerous to humans and animals in high
  concentrations
• CO2 -- Carbon dioxide
• Colorless, odorless gas from volcanic eruptions,
  forest fires, bacterial activities, fuel
  combustion
• Is an important greenhouse gas in high
  concentrations can displace oxygen (CO2 is denser
  than O2)

5
(No Transcript)
6

• Sulphur oxides - SOx
• Have both gaseous and aerosol forms
• Natural sources are bacterial release, volcanic
  eruptions, sea spray
• Anthropogenic sources are combustion of fossil
  fuels and ore smelting
• SO2 is a respiratory irritant
• SO3 contributes to acid fog and acid rain

7
Acid precipitation across North America
Factories and power plants in the midwest and
northeast contribute sulphur oxides to the air.
These pollutants cause acid rain downwind of
their sources of emission.
8
Acid deposition weathers monuments and buildings
Acid rain dissolves limestone components of
buildings.
9

• Nitrogen oxides - NOx
• Nitric oxide (NO) and Nitrogen dioxide (NO2)
• Natural sources are biological processes in soil
  and water
• Anthropogenic sources are fossil fuel combustion
• NO2 is a toxic yellow to reddish-brown gas (like
  Los Angeles smog) that is pungent and corrosive
• Can cause pulmonary health problems

10
Nitrogen dioxide pollution in Hong Kong
11

• Volatile organic compounds or VOCs (hydrocarbons)
• Methane, butane, propane, octane, gasoline, paint
  thinners, etc.
• Natural sources are organic emissions and
  decomposition of organic matter
• Anthropogenic sources are primarily combustion
  from automobiles, trucks, buses, and other fossil
  fuel motors also evaporation of gasoline and
  other chemicals
• Combines with solar radiation to form Los
  Angeles-type photochemical smog ozone is a major
  secondary pollutant from VOCs
• Ozone causes respiratory and heart problems

12
Photochemical smog in Los Angeles
13
U.S. Anthropogenic Air Pollution Sources Major
Sources -Fuel combustion (electricity generation
and heating) -Transportation -Industrial Processes
14

• Atmospheric Controls on Air Pollution
• High concentrations of pollutants in a small area
  (usually due to anthropogenic sources) are the
  biggest air pollution problems
• The horizontal and vertical transport of air
  pollutants by winds help control the local
  concentrations of pollutants
• Concentrations are inversely proportional to wind
  speed
• Eddies can mix air vertically
• Inversions can trap pollutants near the Earths
  surface

15
Effect of wind speed on pollution
Lower winds allow greater concentrations of
pollutants.
Greater winds reduce concentrations of pollutants
by spreading them faster and farther.
16
Smokestacks are designed to lift pollutants
17
U.S. pollution trends since 1977 Anthropogenic
pollution has been decreasing since the first
clean air laws were passed in the 1970s. Lead
was prohibited in gasoline in the mid 1970s.
18

• Urban Heat Island effect -- cities have higher
  average temperatures at night than surrounding
  area
• Causes of the urban heat island effect low
  albedo, low evaporation, IR radiation trapped by
  tall buildings, heat absorption by roads and
  other surfaces, few trees and plants, etc.
• High particulate concentrations in cities reflect
  some sunlight and can stimulate downwind
  cloud/precipitation processes

19
City center is warmer than the surrounding
suburbs and countryside.
20
Effect of buildings on solar radiation receipt
21
Heat island magnitude varies with city population
22
End of Chapter 14 Understanding Weather and
Climate 4th EditionEdward Aguado and James E.
Burt