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Acid Deposition Impact on Ecosystems • The study of environmental chemistry involves more than just the detection of substances. • Scientists who study the environment conduct investigations to determine whether there is evidence of change in the environment. • Predictions currently being made by scientists rely upon the knowledge that comes from careful study of interactions within the environment. • Since the environment is the one thing that all organisms share, research is necessary to understand its ability to cope with stress from pollution. Relationship between Two Variables Direct Variation: A relationship between two related variables where an increase in the magnitude of one variable results in an increase in the magnitude of the related variable Inverse Variation: A relationship between two related variables where an increase in the magnitude of one variable results in a decrease in the magnitude of the related variable No Relationship: a situation where no recognizable pattern is demonstrated between two variables Example Higher levels of sulfates and nitrates in rainwater result in a higher concentration of hydronium ions in the water (direct variation) and, thus, results in a lower pH (inverse variation). • Wind Patterns • Remember to consider what influences weather patterns might have on acid deposition. • Wind patterns like the jet stream provide a way for acid deposition to be transported. • The predictability of wind patterns provides a way to trace the path of acid deposition back to its source. Define the term jet stream. State the general direction of the jet stream. The jet stream is an air current located at the boundary between major air masses (pressure systems). The location of the pressure systems determines the direction of this air current. Generally, the jet stream moves from west to east across North America. Explain the effect the jet stream has on weather and climate in western Canada. The position of the jet stream indicates the main direction of the winds across Alberta (from west to east). The position also influences weather because low-pressure systems (which usually bring moisture) track along the jet stream. Winds are directed toward the jet stream. Cold air from the north is drawn toward the jet stream, whereas warm air from the Pacific Ocean is drawn toward the jet stream from the south. When the position of the jet stream moves downward, more of Alberta is subject to colder air. During the winter months, this causes extremely cold temperatures Comment on the statement, “Wind patterns in Canada and Alberta are always the same.” The position of the jet stream is quite variable, influencing weather across Canada. In general, however, winds move eastward across North America. Alberta generally has winds that track eastward. • Does Canada’s position in the northern hemisphere ensure that air transported by currents, such as the jet stream, are relatively clean and unpolluted? • North America has regions that are densely populated and industrialized. • In general, the jet stream often dips southward around the Great Lakes region and tracks over the northeastern US; then it tracks in a northeasterly direction toward Canada. • As the northeastern US is heavily populated and industrialized, emissions from this area are drawn toward Ontario, Quebec, and the Atlantic provinces. • The eastward direction of the winds across western Canada draws emissions originating in Alberta toward Saskatchewan. Effects of Acid Deposition on the Environment and Ecosystems Acid Deposition Effects the pH of water Caused by hydronium ions being formed during a reaction of acids and water. Carbonate Ions • CO3 are a naturally occurring base present in many bodies of water and in the soil. • In Alberta, the pH of most lakes is above 7 and can be as high as 8.3 • The slightly alkaline pH of the lake water is due to the presence of dissociated carbonate ions that enter the water from dissolving minerals, such as calcium carbonate and magnesium carbonate present in limestone. oceans were made up of calcium carbonate, CaCO3(s). Over time, the layers of calcium carbonate formed into limestone—a type of sedimentary rock. As limestone undergoes erosion, small crystals of calcium carbonate present in the limestone form particles in the soil. The carbonate ions, acting as acceptors for hydrogen ions, convert hydronium ions into water molecules, thereby neutralizing the acid. Only a small percentage of soils in Canada have a high potential for neutralizing acid deposition. Much of the soil within the province of Alberta has a high potential, mainly due to the presence of carbonate. Student Hand-out Answers • 29. No, there is a range of abilities to neutralize acid deposition across Canada. • 30. The highest potential for reducing acid deposition occurs in Alberta (except in the extreme north), the • southern half of Saskatchewan, the southern half of Manitoba, part of northern Ontario, and Quebec. • 31. Yes, there is a correlation between rock type (sedimentary) and higher potential to reduce acid input. • 32. Regions in Canada with the least ability to reduce acid deposition include the coastal mountains of British Columbia, Districts of Mackenzie and Nunavut, southern Ontario, Quebec, most of Newfoundland and Labrador (except the west coast of Labrador), Nova Scotia, and parts of New Brunswick and Prince Edward Island. • 33. Yes, rock types in more sensitive areas tend to be volcanic, intrusive, or metamorphic. • 34. No, southern Alberta has a high potential, whereas northern Alberta has moderate potential and, in a few extreme northern locations, low acid-reducing potential. • 35. Answers will vary. In areas with a high neutralizing capacity, pH should remain constant. In regions with a low neutralizing potential, there may be a lowering of soil and lake-water pH. • 36. a. Quebec, 82% • b. Alberta, 6% • c. Yes, Alberta has soils that are, for the most part, highly tolerant to acid inputs and few lakes that are sensitive. Quebec has few regions with soils that are highly tolerant and has a very high percentage of sensitive lakes. • d. Composition of soils and bedrock provide the ability to neutralize acid deposition. If substances are not present, then sensitivity to acid deposition will increase.