By Robert Hazen, George Mason University
There are some modern environmental problems that are affecting the human society. It is important to remember, though, that the most demanding questions about the environment, which remain unanswered, relate to specific human actions and the effects of those actions. One such major global-scale problem is acid rain.
Environmental Crises
Whenever we pick up a newspaper, there’s likely to be a story about one of these great environmental crises. Scientific conclusions about the environment often seem to reflect individual prejudices—ideologies about the way the Earth might work.
Some observers tend to think of the environment as being very fragile, constantly in peril; under assault by opportunistic industry, a government which really doesn’t care that much, and the exploding world populations. On the other hand, there are people who believe that the environment is robust, that the Earth is resilient, and any insults that we can throw at it will just be taken in stride.
Cause and Effect
However, we must understand the causes and effects of our actions on environment.
In the case of acid rain, the cause and effect are not at issue. Burning is the chemical reaction of oxidation. This reaction inevitably introduces gaseous molecules into the atmosphere. Carbon dioxide and water vapor are always produced, because fossil fuels are primarily hydrocarbons; we are oxidizing carbon and hydrogen.
However, fossil fuels also always have a small amount of sulfur and nitrogen, and these elements form oxides during burning as well. These are the compounds that contribute to the formation of what’s known as acid rain.
Sulfur and Nitrogen Oxides
First let’s look at nitrogen. Nitrogen oxides form by the chemical reaction of N2 gas, nitrogen, and O2, oxygen. Whenever air is heated to above 500 degrees centigrade, nitrogen oxides get formed. There are several different compounds, and they go by the general listing of NOX compounds. They include nitrogen monoxide, or NO; nitrogen dioxide, NO2; and others as well. In the atmosphere, these nitrogen oxides react with water molecules to form molecules of nitric acid; that’s HNO3. Nitric acid is one of the components of acid rain.
Sulfur does the same thing. When we burn fuels with sulfur, we get sulfur dioxide, SO2, as one of the byproducts. Sulfur dioxide reacts with water in the atmosphere to form sulfuric acid, that’s H2SO4; sulfuric acid is another component of acid rain.
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Acid Rain
Most of these harmful sulfur and nitrogen emissions come from power plants and factories that burn dirty fossil fuels, as well as automobile emissions, and other gasoline-burning engines. Catalytic converters certainly cut down on the emissions, but we just can’t eliminate them altogether.
What happens in the atmosphere is that we have these molecules of nitric and sulfuric acid, and then raindrops concentrate these molecules, and they become acid rain. The acid rain causes rapid dissolution of limestone and other soft, sedimentary rocks. It’s causing outdoor sculptures to decay in many cities in Europe and the United States. Limestone buildings begin to see a weathered pattern that we would never have seen 100 years ago.
When acid rain falls in high mountainous areas, the lakes, ponds, and groundwater may become extremely acidic, dramatically altering ecosystems, killing forests in some cases.
Political Difficulty
The political difficulty in dealing with acid rain is that the sources of the nitrogen and sulfur pollutants are usually far from the sites where the acid rain actually falls; the acid rain falls far downwind from the plants that are producing most of the acidic emissions.
For example, we have tall smokestacks in the Midwest that cause acid rain in New England. Then, there are factories in one European country that cause acid rain in other countries. So, for example, acid rain in one European country might kill a forest someplace far away. The cause and effect can be identified, but still, we have two different political systems: one that wants to be able to burn this material, the other that wants to save its forest.
Solutions and Objections
We can solve this problem. Smokestacks can be outfitted with complex devices called scrubbers, which remove sulfur; automobile emissions can be greatly reduced or eliminated, for example, with electric cars, or with better catalytic converters. But these modifications cost money; they’re going to cost consumers money. They’re probably going to eliminate factory jobs, in some vicinities, because it no longer becomes economically viable to run a factory when one has to have these costly scrubbers in place. Jobs are going to be lost to countries with less-stringent pollution laws.
This was one of the big objections, for example, to NAFTA, the North American Free Trade Agreement. The idea is that Latin American countries have less stringent pollutant controls than the United States, and therefore, jobs are inherently cheaper to perform, and much business might be lost to South America for that reason. Ultimately, the global community has to establish its priorities on an issue like acid rain. The problem of the acid rain has a pretty straightforward cause-and-effect relationship.
The problems can be solved with money, and with goodwill.
Common Questions about Acid Rain
When we burn fuels with sulfur, we get sulfur dioxide, SO2, as one of the byproducts. Sulfur dioxide reacts with water in the atmosphere to form sulfuric acid, that’s H2SO4; sulfuric acid is a component of acid rain.
Most of the harmful sulfur and nitrogen emissions come from power plants and factories that burn dirty fossil fuels, as well as automobile emissions, and other gasoline-burning engines.
The political difficulty in dealing with acid rain is that the sources of the nitrogen and sulfur pollutants are usually far from the sites where the acid rain actually falls; the acid rain falls far downwind from the plants that are producing most of the acidic emissions.
