EFFECTS ON TREES , CROPSAND SOILS
One of the most serious impacts of acid precipitation is on forests and soils. Great damage is done when sulphuric acid falls onto the earth as rain. Not most of the sulphur dioxide is converted into sulphuric acid. In fact, a substantial amount can float into the atmosphere, move over to another area and return to the soils uncovered. As this gas returns back to earth, it clogs up the stomata in the leaves, thus hindering photosynthesis.
Scientists have studied acid rain a long time. They know that it can damage trees and forests but they are still not sure how.
| It is clear that there is damage to trees on the Camels Hump Mountain in Vermont's Green Mountains. In 1965, the peak, which is 4100 feet high, was covered with evergreen forests. Some of the red spruce on the highest slopes were three hundred years old. |
Scientists have found out that trees on Camels Hump have three times as much aluminum as they did 25 years ago. Scientists don't know exactly how aluminum hurts trees or how acid rain weakens and kills trees but they do know trees are dying in the areas that get a lot of acid rain.
Scientists do not yet have enough information on the effects of acid rain on crops. Some scientists who work for power companies say acid rain is good for crops. They say it puts nitrogen and sulfur in the soil, and helps feed the crops. Other scientists say this idea is just plain crazy. They point out that there are many different kinds of soil. Some soils are naturally more acid than the others. Different soils need different fertilizers, and so do different crops.
Acid soil also kills useful insects and bacteria. Bacteria are used for growth of plants. Many kinds of worms work for the health of the soil in many different ways. The worms can't live with high acid levels either. There are also problems with metal. Acid rain dissolves metals in the soil. Like spruce trees, grasses and plants absorb metals along with the water. Cows and other farm animals also eat these plants. So far scientists have not found dangerous levels of mercury in these animals. However, they have found high mercury levels in seals, ducks, and fish in the far north.
Effects on man-made materials and structures
Acid rain does not only damage the natural ecosystems, but also man-made materials and structures. Marble, limestone, and sandstone can easily be dissolved by acid rain. Metals, paints, textiles, and ceramic can effortlessly be corroded. Acid rain can downgrade leather and rubber. Man-made materials slowly deteriorate even when exposed to unpolluted rain, but acid rain helps speed up the process. Acid rain causes carvings and monuments in stones to lose their features. In limestone, acidic water reacts with calcium to form calcium sulfate. CaCO3 + H2SO4 -> CaSO4 + H2CO3 For iron, the acidic water produces an additional proton giving iron a positive charge. 4Fe(s) + 2O2(g) + 8 (aq) -> 4Fe2+ (aq) + 4H2O(l) When iron reacts with more oxygen it forms iron oxide (rust). 4Fe2+ + (aq) + O2(g) + 4H2O(l) -> 2Fe2O3(s) + 8H+ + (aq)
Effect on architecture
Acid particles are also deposited on to buildings and statues, causing corrosion.
For example, the Capitol building in Ottawa has been disintegrating because of
excess sulphur dioxide in the atmosphere. Limestone and marble turn to a
crumbling substance called gypsum upon contact with the acid, which explains the
corrosion of buildings and statues. In addition, bridges are corroding at a faster
rate, and the railway industry as well as the airplane industry have to expend more
money in repairing the corrosive damage done by acid rain. Not only is this an
economically taxing problem caused by acid rain, but also a safety hazard to the
general public; as an illustration, in 1967, the bridge over the Ohio River collapsed
killing 46 people - the reason? Corrosion due to acid rain.
