Saturday, October 23, 2010

Acid rain - Formation and impact

Acid rain is mostly caused by human emissions of different sulfur and nitrogen compounds which once in atmosphere produce acids. Main reason for acid rains is air pollution as a result of fossil fuels burning. Power plants (especially coal based), factories, cars, they all produce polluting gases and some of them when in atmosphere react with water in clouds to create sulphuric and nitric acids which are very harmful to our environment once they fall on Earth in the form of acid rain.

Acid rain can also take the form of snow, mists and dry dusts, although most common form is rain. The rain isn't always falling just on the polluted area as it can fall many miles away from the source of pollution. Wherever it falls, it has very harmful effect on soil, trees and water.

Acid rain impact can vary, from minimal to severe which depends on the region of the country and on the acidity of the rain as sometimes same amount of acid rains can have different effect in some areas than in others.

Forests exposed to acid rain lose valuable nutrients, trees grow more slowly and sometimes even stops to grow, leaves is damaged as their waxy protective coating wears away because of different acids. These harmful effects combined make trees more vulnerable to different diseases, weather and insects.

Acid rains are most obvious in waters, where they're increasing acidity of water which has tremendous negative impact on water ecosystems, often causing decline of fish and other water population and affecting variety of life in water ecosystems. Most visible effect in these water ecosystems is gradual disappearing of many fish species since their environment becomes intolerable and they're on the lookout for new habitats. Measure of the acidity in certain water ecosystem affected by acid rain is pH value. Here are the effects of an acidified ecosystem on certain pH value.

As water pH approaches
  • crustaceans, insects, and some plankton species begin to disappear.
  • major changes in the makeup of the plankton community occur.
  • less desirable species of mosses and plankton may begin to invade.
  • the progressive loss of some fish populations is likely, with the more highly valued species being generally the least tolerant of acidity.
Less than 5.0
  • the water is largely devoid of fish.
  • the bottom is covered with undecayed material.
  • the nearshore areas may be dominated by mosses.
  • terrestrial animals, dependent on aquatic ecosystems, are affected. Waterfowl, for example, depend on aquatic organisms for nourishment and nutrients. As these food sources are reduced or eliminated, the quality of habitat declines and the reproductive success of birds is affected.

What can be done to stop acid rains? Probably the best answer lies in the alternative energy sources as to avoid harmful burning of fossil fuels but renewable energy sector is still negligible compared to dominant fossil fuels, not only at this moment, but also in years to come.

There's also important to mention that damage done by acid rains can be restored in lake and rivers which can have powdered limestone added to them to neutralize the water - this method is called "liming", but unfortunately isn't used very often because it's very expensive since it needs to be done continuously many times, until the acid rain stops, otherwise its affects are only temporary.

Rich countries Sweden and Norway successfully used this method to restore their lakes and streams. But this solution isn't really a possibility in countries with major acid rain problems (i.e. China) since they have no funds available for this expensive method causing many of their lakes and rivers to stay acidified for many more years and even growing in acidity levels since because of dominant fossil fuels use and its burning these rains continue to fall making this problem more severe with every new acid rain.

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