Acidic Soil & Acid Rain
Acid rain contains sulfuric and nitric acids. Acidic soils are naturally present due to climate, vegetation types and kind of parent rock. The impact of acid rain depends on the kind of acid soil it enters.
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Neutralization
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The acid in acid rain can be neutralized by coming into contact with an alkaline substance. Therefore, acid rain has less of an impact when it falls on alkaline soil. Acid rain effects are greater in areas with acidic soil simply due to lack of neutralization.
Buffering
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Some mildly acidic soils that are high in organic materials can also lessen the impact of acid rain. This is possible because the organic components of the soil absorb the dangerous sulfate and nitrate ions released by acid rain.
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Leaching
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When acid rain falls and interacts with soil, it also releases positively charged hydrogen ions. If not neutralized, these hydrogen ions replace ions in the soil that are necessary for plant growth. These ions include calcium, magnesium and potassium. The useful ions can then be washed out of the soil. This means that acidic soils have decreased availability of elements necessary to plant growth.
Toxic Metals
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Soils with a pH of 5 or lower that contain aluminum hydroxide can be toxic to plants. When acids in the soil break down the aluminum hydroxide, toxic aluminum ions are released. If the soil becomes more acidic, other metal ions are also freed, such as mercury, lead, iron and copper. Although metals are necessary to plants in trace amounts, high quantities are poisonous.
Effects on Organisms
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Plant growth can be stunted from lack of essential elements and presence of metal ions. Toxic metals also deplete populations of soil bacteria, fungi and earthworms, which are necessary for recycling decaying vegetation into nutrients for new plants.
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References
- Photo Credit acid image by charles taylor from Fotolia.com
