How Acid Rain Affects the Aquatic Ecosystem
This paper shows that acid rain is a reality. It is destroying our freshwater ecosystems and must be stopped in order to save them. If the problem is not fixed soon the aquatic ecosystems will be destroyed.
Table of Contents
1. What is acid rain?
2. Acidification of Freshwater
3. Effects of Freshwater Acidification
4. Where is Affected the most?
5. What is being done to fix it?
What is acid rain?
Acid rain is polluted rain, snow, or fog. The burning of fossil fuels, base metal smelting, and fuel combustion in vehicles emits sulfur dioxide (SO2) and nitrogen oxides (NOx) (FAQ Acid Rain). These gases enter the atmosphere and transform into sulfuric acid (H2SO4) and nitric acid (HNO3), which then acidify the water vapor. The acidified water vapor will then fall to the earth as acid rain, snow, or fog (Acid Rain and the Aquatic). This is called ìwet depositionî. There is also ìdry depositionî which falls to the ground in particulate form (FAQ Acid Rain).
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Acidification of Freshwater
The acidification of freshwater lakes and streams is not a new problem. Fish stocks probably died out in many lakes in Norway as early as the turn of the century. In the 1950ís and 1960ís this was finally associated to acid rain. Yet, it wasn't generally accepted by scientists until the 1970ís (Rivers and Lakes).
Acid rain either falls directly onto the lake or enters through the catchment (Buchdahl). A very small percentage enters directly so the majority enters through the catchment. The alkaline rich catchments can neutralize the rain. However, not all types of bedrock have the same capability of neutralizing acid (FAQ Acid Rain). The areas highly affected by acid rain are those with shallow soil cover or poorly weathering bedrock, such as granite and quartzite. These types of soil and bedrock do not contain carbonates to neutralize the acid. Limestone catchments contain large amounts of carbonates and thus neutralize acid very effectively (Acid Rain and The Aquatic).
In addition to the acidification of lakes, acid rain can strip toxic metals from the catchment and contaminate the lake. These metals include aluminum, manganese, iron, zinc, copper, nickel, vanadium, lead, and mercury (Buchdahl). These metals can be very toxic for fish as well as humans. Aluminum concentrations as low as 0.05 mg 1-1 can kill fish and macro invertebrate fauna. Lower levels of aluminum may not kill but can severely impair growth and reproductive ability, and hinder respiratory ability of fish (Acid Rain and The Aquatic). Aluminum has been shown to cause Alzheimer's and mercury can cause brain damage in humans. The tissue of fish absorbs mercury so it can not be cooked or filleted out. Even at very small input rates, mercury biomagnifies from the bottom to the top of the food chain (Krabbenhoft).
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