Acid Rain

Pollution comes in various forms. Whether it’s toxic waste, CFC’s, or
sewage, they are all hazardous, to the earth. These can deplete the earth and
it’s inhabitants of resources, causing a harmful change. A product of
pollution is acid rain. We shall see that acidification is harmful to all forms
of life. Acid rain is any form of precipitation that is polluted by sulphur
dioxide (SO2), and nitrogen oxides (NOX). This acid precipitation can be in the
form of rain, snow, sleet, fog, or cloud vapors. The acidity of substances
dissolved in water are measured by their pH levels. Normal precipitation pH
levels fall between 5.0-5.6.2 When levels fall below these numbers, then the
precipitation is said to be acidic. There are two ways in which acid deposition
can form. The first way occurs when nitrogen oxides and sulphur dioxide land on
the Earth’s surface, and interact with frost or dew. The second way takes
place due to the oxidation of nitrogen oxides or sulphur dioxide gases that are
released into the air.3 Since it may take up to several days for the gases to be
altered into their acid counter-parts, the pollutants can travel miles away from
their original source. Emissions of (SO2) are responsible for the majority of
the acid deposition, which falls to Earth. When we burn coal, we are releasing
(SO2), into the air, since coal is slight made up of sulphur. Volcanic eruptions
can add a great deal of sulphur into the atmosphere. Everyday organic decay adds
sulphur into the air as well. (SO2) can hit the Earth’s surface in dry forms
or wet forms, by undergoing the following reactions: (SO2 + H20 *** H2SO3) (SO2
+ ½O2 *** SO3 + H2SO4)2 Human activity is the major cause for nitrogen
oxides’ presence in our atmosphere, such as forest fires and the combustion of
oil, coal, and gas. The other causes are due to nature. Lightning, volcanic
action, and bacteria in soil are just to name a few. The following chemical
reactions show how acids of nitrogen form: (NO2 + ½O2 *** NO2) (2NO2 + H2O ***

HNO2 + HNO3) (NO2 + OH *** HNO3)2 Acid rain can affect plant life directly when
the surface of leaves and needles come into contact with acid vapor or fog. This
causes a reduction in the tree’s ability to withstand the cold. A direct
result would be the tree\'s incapability of reproduction. It can also harm plant
life indirectly, by the acidification of soils. Acid rain can cause soil to
loose nutrients such as calcium, potassium, and magnesium. In very acid
conditions, aluminum becomes soluble, and is released from the soil. At high
enough concentrations, aluminum can cause damage to roots. Acid rain causes a
nutrient imbalance, in soil. Although it is true that nitrogen promotes forest
growth, plant life also needs other nutrients. Precipitation polluted by
nitrogen can contain heavy metals, such as mercury, cadmium, and lead. This
process is known as nitrogen saturation.1 These too, can cause damage to tree
roots. Besides trees, plants are also affected by acid rain. Reductions in pH
levels can cause seed germination to be inhibited. Plant structures become weak,
due to the loss of nutrients to the plant’s tissues.4 Flowering of certain
plants may not occur due to lack of essential minerals. Marine life is also
greatly affect by acid rain. Acid water can leach high levels of aluminum from
the bedrock. Rocks that contain great amounts of calcium or magnesium can act as
a neutralizer. Those rocks and soils that lack some sort of buffers can cause
grave damage to marine fish and plants. There are two ways in which aluminum can
harm aquatic environments. It can cause a fish to suffocate, because aluminum
precipitates in gills, thus interfering in the transport of oxygen. Secondly,
fish produce mucus to combat the aluminum, in their gills. The mucus then builds
up a clogs the fish’s gills.5 In middle latitudes many bodies of water
experience what is called "acid shock."4 Over the winter acid deposits can
build up on snow. As the snow melts, the acids are released. Most fish can
survive shock, but their eggs cannot adapt to acidification. When there is a
change in the chemistry of water, the ecology of the water begins to change. The
number and variety of species are altered. At a pH level of 6.0 certain types of
zooplankton and green algae begin to disappear. The loss of green plants allows
more UV light to penetrate to further depths, so certain types of snails and
phyto-plankton disappear. Frogs, toads, and salamanders are also affected