A demonstration of acid rain and lake acidification: wet deposition of sulfur dioxide

摘要

Acid rain is a familiar environmental problem that is sometimes discussed in general chemistry lectures. Several demonstrations pertaining to acid precipitation have been published in this Journal (1-3) but none of these illustrate the dissolution of acidic oxides in airborne water droplets, or "wet deposition", in the manner in which it occurs in the atmosphere. nitrogen oxides come from cars and other combustion sources, whereas atmospheric sulfur oxides are a result of coal-fired power plants and the roasting of metal sulfide orea in smelters (4). Cloud droplets then scavenge these oxides. Acification of lakes in areas geographically removed from the source can results when this acidified precipitation is deposited in lakes with no natural buffering capacity. A lake underlain by limestone will be resistant to acidification due to the buffering capacity of CaCO_3 while a lake underlain by granite will not, since granite contains silicates rather than carbonates (5). In the United States, lake acidification has received the most attention in the Northeast where the bedrock is primarily granite (6).