Question

Describe how acid rain is formed. What types of industrial activities contribute to acid rain formation? Are there options for remediation of lakes that have been “killed” by acid rain?

Answer 1

Acid rain describes any form of precipitation with high levels of nitric and sulfuric acids. It can also occur in the form of snow, fog, and tiny bits of dry material that settle to Earth.

Rotting vegetation and erupting volcanoes release some chemicals that can cause acid rain, but most acid rain falls because of human activities. The biggest culprit is the burning of fossil fuels by coal-burning power plants, factories, and automobiles.

When humans burn fossil fuels, sulfur dioxide (SO2) and nitrogen oxides (NOx) are released into the atmosphere. These chemical gases react with water, oxygen, and other substances to form mild solutions of sulfuric and nitric acid. Winds may spread these acidic solutions across the atmosphere and over hundreds of miles. When acid rain reaches Earth, it flows across the surface in runoff water, enters water systems, and sinks into the soil.

Lakes that have become highly acidic, can be treated by adding large quantities of alkaline substances like quicklime, in a process called liming. Although it has worked in several places, it has not been successful where the lake is very large, making this procedure economically unfeasible, or in other lakes where the flushing rate of the lake waters is too large resulting in the lake becoming acidic again.

The best approach seems to be in prevention. To this end environmental regulations have been enacted to limit the quantity of emissions released in the atmosphere. Several industries have added scrubbers to their smoke stacks to reduce the amount of sulphur dioxide dumped in the atmosphere. Specially designed catalytic converters are used to ensure that the gases coming out from exhaust pipes of automobiles, are rendered harmless. Several industries which use coal as fuel have begun to wash the coal before using it thereby reducing the amount of Sulphur present in it, and consequently the amount of emissions. Usage of coal with a low Sulphur content also reduces the problem.

References:

http://environment.nationalgeographic.com/environment/global-warming/acid-rain-overview/

http://rashidfaridi.com/2008/05/10/acid-rain-causes-effects-and-solutions/