Groundwater Contamination

Abstract

The term contamination is used for addition of any solute into the hydrological system as a result of man’s activity while the term pollution is restricted to a situation when the contamination attains levels that are considered to be objectionable (Freeze and Cherry 1979). There could also be deterioration in water quality due to natural reasons namely dissolution of rock material. Contamination of groundwater can take place from either a wider source like percolation from agricultural fields on account of application of fertilizers and pesticides or from a point source like waste disposal sites. Atmospheric composition will also affect the composition of precipitation and thereby causes water pollution. In a polluted atmosphere, many oxidizing compounds (e.g. ozone), acid-forming gases (oxides of nitrogen and sulfur) and particulate material will be higher than in an unpolluted atmosphere. This will be area specific depending on the anthropogenic activities. For example, combustion of fossil fuels results in acid rains containing H2SO4 and HNO3, which reduces the pH of source water. This induces greater solubility of aquifer material (see effect of Climate Change in Sect. 20.10). Overexploitation of groundwater, especially in coastal areas is also responsible for contaminating fresh water aquifers due to sea-water intrusion. This aspect is discussed in Sect. 20.7.