Page 112 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

76 part I The Energy–Atmosphere System
Wildfire smoke contains particulates (dust, soot, ash), nitrogen oxides, carbon monoxide, and volatile organic compounds (discussed in the next section). In southern California, recent wildfire smoke was linked to respira- tory problems and increased hospital admissions, as well as lower birth weight for babies born to women living in smoke-exposed areas.
In 2006, scientists established a connection between climate change and wildfire occurrence in the western United States, where higher spring and summer tempera- tures and earlier snowmelt result in a longer fire season. These connections are valid for Canada, and indeed occur across the globe, as in drought-plagued Australia, where thousands of wildfires burned millions of hectares in re- cent years. (See the Chapter 5 opening photo and caption.)
The natural events that produce atmospheric con- taminants, such as volcanic eruptions and wildfires, have occurred throughout human evolution on Earth. They are relatively infrequent in timing, but their ef- fects can cover large areas. In contrast, humans did not evolve in environments with anything like the recent concentrations of anthropogenic (human-caused) con- taminants now present in our metropolitan regions. Currently, our species is contributing significantly to the creation of the anthropogenic atmosphere, a tenta- tive label for Earth’s next atmosphere. The urban air we breathe may just be a preview.
Anthropogenic Pollution
Anthropogenic air pollution remains most prevalent in urbanized regions. According to the World Health Orga- nization, urban outdoor air pollution causes an estimated 1.3 million deaths worldwide.
As urban populations grow, human exposure to air pollution increases. A recent study using satellite data identified India, with an urban population of 31%, as hav- ing the worst air quality out of 132 countries surveyed. Over half the world’s population now lives in metropoli- tan regions, some one-third with unhealthful levels of air pollution. This represents a potentially massive public- health issue in this century.
Table 3.4 lists the names, chemical symbols, prin- cipal sources, and impacts of urban air pollutants. The first seven pollutants in the table result from
combustion of fossil fuels in transportation (specifically cars and light trucks). For example, carbon monoxide (CO) results from incomplete combustion, a failure of the carbon in a fuel to burn completely because of in- sufficient oxygen. The toxicity of carbon monoxide is due to its affinity for blood hemoglobin, as explained in GeoReport 3.5. The main anthropogenic source of car- bon monoxide is vehicle emissions.
Motor vehicle transportation is still the largest source of air pollution in Canada and the United States, despite improvements in vehicle emissions over the past 30 years. Reducing air pollution from the transportation sector involves available technologies that result in mon- etary savings for consumers and lead to significant health benefits. This makes the continuing reluctance of the in- dustry to work at achieving better fuel efficiency all the more confusing. Further improvements in fuel efficiency and reductions in fuel emissions, either through techno- logical innovation or by promoting other forms of trans- portation, are critical for reducing air pollution.
Stationary pollution sources, such as electric power plants and industrial plants that use fossil fuels, contrib- ute the most sulfur oxides and particulates. Concentra- tions are focused in the Northern Hemisphere, especially over eastern China and northern India.
Photochemical Smog Although not generally present in human environments until the advent of the automo- bile, photochemical smog is now the major component of anthropogenic air pollution; it is responsible for the hazy sky and reduced sunlight in many of our cities. Photo- chemical smog results from the interaction of sunlight and the combustion products in automobile exhaust, pri- marily nitrogen oxides and volatile organic compounds (VOCs), such as hydrocarbons that evaporate from gaso- line. Although the term smog—a combination of the words smoke and fog—is generally used to describe this pollution, this is a misnomer.
The connection between automobile exhaust and photochemical smog was not determined until 1953 in Los Angeles, long after society had established its depen- dence upon cars and trucks. Despite this discovery, wide- spread mass transit declined, the railroads dwindled, and the polluting, inefficient individual automobile re- mains America’s preferred transportation.
Georeport3.4 NASA’sGlobalHawksMakeScientificFlights
Small unpiloted aerial vehicles (UAVs) are lightweight aircraft guided by remote control. These instrumental drones can gather all types of data and carry various remote-sensing devices. Since 2010, NASA’s unpiloted Global Hawk aircraft have completed numerous scientific missions, flying for up to 32 hours or more on preprogrammed flight paths to altitudes above 18.3 km
carrying instruments that sample ozone-depleting substances, aerosols, and other indicators of air quality in the upper troposphere
and lower stratosphere. The first Global Hawk flew over Hurricane Karl in the Atlantic Ocean, collecting new and unprecedented data for hurricane research. Two 2012 Global Hawks are part of a multiyear study of hurricane formation and intensification in the Pacific. Smaller UAVs, designed and built in Waterloo, Ontario, are being used by researchers for many field studies (www.aeryon.com/products/ avs/aeryon-skyranger.html).