ACID RAIN

Acid rain is rain or any other form of precipitation that is unusually acidic, i.e. elevated levels of hydrogen ions (low pH). It has harmful effects on plants, aquatic animals, and infrastructure. Acid rain is mostly caused by emissions of compounds of sulfur, nitrogen, and carbon which react with the water molecules in the atmosphere to produce acids. However, it can also be caused naturally by the splitting of nitrogen compounds by the energy produced by lightning strikes, or the release of sulfur dioxide into the atmosphere by phenomena of volcano eruptions.
The term acid rain was first used by Robert Angus Smith, a scientist working in Manchester in the 1870s.
he burning of fossil fuels (coal, oil and gas) produces sulphur dioxide and nitrogen oxides which can increase the acidity of rain or other precipitation. Sources of sulphur dioxide and oxides of nitrogen may be natural such as volcanoes, oceans, biological decay and forest fires, or may arise from combustion sources. The increasing demand for electricity and the rise in the number of motor vehicles in recent decades has meant that emissions of acidifying pollutants have increased dramatically from human sources, particularly since the 1950s. Emissions of such pollutants are heavily concentrated in the northern hemisphere, especially in Europe and North America. As a result, precipitation is generally acidic in these countries.
The pH scale is used to measure the acidity of acid rain which is determined by the hydrogen ion content (H+). This scale was invented by a Danish scientist called Sorenson in 1909.