Tuesday, July 12, 2011

How Does Acid Precipitation Affect Trees?


1. What are probable sources of acid precipitation in your community? What impact can this have on the environment in your region?

The answer will vary with your region. Urban areas would get acid precipitation from air pollution produced by industries and traffic. Prevailing winds can also transport the acid precipitation from these sources to areas downwind. In rural areas, acid precipitation is probably imported from nearby industries or urban areas. Effects of acid precipitation would also vary with the area. The impacts can range from loss of forests and wildlife to probable crop losses.

2. What factors apart from acid rain could be killing trees?

Other types of air pollution such as ozone or soot could be factors. Also, insects or plant diseases can damage trees. Drought or unusual temperature patterns might also be factors.

3. Limestone, an underlying material for many soils, dissolves and corrodes when exposed to high concentrations of hydrogen ions. How is this information important in understanding the effects of acid precipitation?

Acid rain can cause the loss of lime soils and possibly decay the underlying material until the ground collapses. This is currently being seen in areas of Florida. Any limestone structures, such as buildings and statues, will also corrode, as is currently taking place in the eastern United States and Europe.

4. Acid precipitation is considered severe if it falls below pH 4. Considering the pH of rainwater, how easy would it be to convert the rainwater to acid precipitation?

Rainwater has a pH of 5, so it should not take too much acid pollution to drop it to pH 4.

5. Carbon dioxide forms a weak acid called carbonic acid when dissolved in water. How can this be a significant factor in the formation of acid rain?

Areas that have large amounts of automobile and industrial pollution will be producing carbon dioxide as well as sulfur dioxide and nitrogen oxides. High levels of carbon dioxide will also contribute to acid rain.

6. Frogs are very sensitive to acid rain. How could this information be used to investigate your observation about the trees dying in the forest?

The loss of trees can be correlated with a simultaneous decline in the frog population. Acid rain is the probable cause of the forest's decline if the numbers of trees and frogs are decreasing.

7. What events could have created the increase in acid precipitation between 1955 and 1990?

A rapid growth in manufacturing industries following World War increased the amount of pollution. Most of the early industrial growth occurred in the Midwest, creating a high concentration of acid precipitation in that region. Much of the precipitation traveled east with the prevailing winds, producing more acid precipitation for the eastern states. Also, the increased use of automobiles corresponding with suburban development and the creation of interstate highways aggravated the acid rain problem.

8. Why is the Canadian government particularly concerned about negotiating clean air agreements with the United States?

The eastern Canadian forests are very sensitive to acid precipitation, much of which is from air pollution produced in the United States.

9. What is the average number of leaves per tree and the percentage of damaged leaves for both the experimental and control plants over the duration of the experiment?

The average number of leaves was 4 for the experimental plants and 11 for the control plants. The average percentage of damaged leaves was 80% for the experimental plants and 20% for the control plants.

10. What can you conclude from these results?

The results demonstrate that the trees in the experimental group had, on average, fewer leaves and a greater percentage of leaf damage than those in the control group. These results support the hypothesis that acid precipitation (simulated by giving plants acidic and normal water) damages the leaves of young red oak trees. This conclusion is consistent with the hypothesis that acid precipitation may be detrimental to forests and may be responsible for the dying trees you originally observed.