| MadSci Network: Botany |
Acid rain contains a high concentration of hydrogen ions (H+) as either sulfuric acid or nitric acid. It lowers the soil pH. The hydrogen ions can displace calcium ions from cell membranes due to cation exchange. This prevents normal functioning of cell membranes. Cell membranes often become "leaky" meaning they cannot retain absorbed mineral nutrients. Calcium in the soil solution is absolutely essential for normal root growth. Some of the damaging effects of low rootzone pH can be reversed by adding sufficient levels of calcium ions. Hydrogen ions can also solubilize toxic compounds such as aluminum. Under acidic condition, the soluble aluminum ion (Al 3+) is released from insoluble aluminum hydroxide, i.e. Al(OH)3 + 3H+ -----> 3H2O + Al +3 Low soil pH caused by acid rain also increases the availability of some essential mineral nutrients and reduces the availability of other essential mineral nutrients. Some students do acid rain experiments with vinegar, which is very artificial. Vinegar adds an excess of undissociated acetic acid which has undesirable osmotic effects. Acid rain should not have a major osmotic effect on plant growth. A seedling damaged by acid rain may be able to grow into a plant. It depends how badly damaged it was and if the acid rain effects on the soil are reversed by adding fertilizer or raising soil pH by liming. References Re: Why do roots require calcium ions for normal functioning? CALCIUM DELAYS SENESCENCE-RELATED MEMBRANE LIPID CHANGES AND INCREASES NET SYNTHESIS OF MEMBRANE LIPID COMPONENTS IN SHREDDED CARROTS Relationship Of Soil pH To Nutrient Availability Soil Chemical Properties Re: How does acid rain affect soil? Soil Chemistry / Soil pH Aluminum Toxicity in Rice
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