The causes of water pollution vary and may be both natural and anthropogenic. However, the most common causes of water pollution are the anthropogenic ones including:
- Agriculture runoff - carrying fertilizers, pesticides/insecticides/herbicides and other pollutants into water bodies such as lakes, rivers, ponds). The usual effect of this type of pollution consists in algae growing in affected water bodies. This is a sign of increased nitrates and phosphates in water that could be harmful for human health.
- Storm water runoff – carrying various oils, petroleum products and other contaminants from urban and rural areas (ditches). These usually forms sheens on the water surface.
- Leaking sewer lines – may add trihalomethanes (such as chloroform) as well as other contaminants into groundwater ending up contaminating surface water, too. Discharges of chlorinated solvents from Dry Cleaners to sewer lines are also a recognized source of water pollution with these persistent and harmful solvents.
- Mining activities – mining activities involve crushing the rock that usually contains many trace metals and sulfides. The left material may easily generate sulfuric acid in the presence of precipitation water. Please, read more at Mining Sites.
- Foundries – have direct emissions of metals (including Hg, Pb, Mn, Fe, Cr and other metals) and other particulate matter into the air. Please, read more at Foundry.
- Industrial discharges – may add significant pollution to water bodies, but are usually regulated today. Please, read more at Industrial Sites.
- Accidental leaks and spills – associated with handling and storage of chemicals may happen anytime and, although they are usually contained soon after they occur, the risk of polluting surface and groundwater exist. An example are ship accidents such as Exxon Valdez disaster which spilled large amounts of petroleum products into the ocean;
- Intended/illegal discharges of waste – while such occurrences are less common today, they may still happen due to the high cost of proper waste disposal; illegal waste discharges into water bodies were recorded all over the world;
- Burning of fossil fuels – the emitted ash particles usually contain toxic metals (such as As or Pb). Burning will also add a series of oxides including carbon dioxide to air and respectively water bodies.
- Transportation – even though Pb has been banned in gasoline in the U.S. and many other countries, vehicle emissions pollute the air with various tailpipe compounds (including sulfur and nitrogen compounds, as well as carbon oxides) that may end up in water bodies via deposition with precipitation water.
- Construction activities – introduce a series of contaminants into the ground that may eventually end up in groundwater. Please, read more at Construction Sites.
- Plastic materials/wastes in contact with water – may degrade slowly releasing harmful compounds for both human health and ecosystem.
- Disposal of personal care products and household chemicals (including detergents and various cleaning solutions) – this is a serious problem since the releases to water are unpredictable and hard if not impossible to control. It is up to each of us to minimize this contribution to water pollution by controlling our consumption and disposal of such products as well as trying to recycle as much as we can!
- Improper disposal of car batteries and other batteries – may add metals
- Leaking landfills – may pollute the groundwater below the landfill with a large variety of contaminants (whatever is stored by the landfill).
- Animal wastes – contribute to the biological pollution of water streams.
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