River Pollution: How Does it Happen?

By Graig Mihok

The ecosystem of a river can be very complex. When a river is polluted the delicate balance of its ecosystem is thrown into disorder. The oxygen in water is often affected by pollution and this can be a large problem for the animals that help regulate the habitat.

Sewage and fertilizers often contain nutrients like nitrates and phosphates that can over stimulate the growth of algae and plants. This growth can clog waterways, block light in deeper waters, and consume dissolved oxygen as it decomposes. This can affect the respiratory ability of fish and other animals that live in the polluted waters.

Organic pollution can also have the same effect. Runoff from livestock, leaves, and grass clippings causes the natural bacteria and protozoans to break down these materials, and in turn begin to use the oxygen dissolved in the water. If the oxygen gets too low, many fish and organisms cannot survive, particularly when levels of dissolved oxygen drop below two to five parts per million. Once the level of pollution is high enough to cause this much of a disruption, organisms die at a rate that begins to affect the food chain.

Pathogens from sewage, septic tanks, farm runoff, and storm drains are another form of pollution that can wreck havoc on a river's ecosystem. Despite the fact that they are microscopic, the danger of disrupting an ecosystem through bacteria, viruses, and protozoans is still very real.

One of the most familiar forms of pollution is petroleum. Oil from spills can cause catastrophic damage to a body of water. The Exxon Valdez spill along the coast of Alaska and the more recent BP spill in the Gulf Mexico should be sufficient in showing the effects of oil in a water body. While rivers mostly only see the petroleum from boats or cars or nearby manufacturing plants, rivers also tend connect to larger bodies of water. A study about the transportation of oil from supertankers and off shore drilling found that for every million tons of oil that is transported roughly one ton is spilled.

Heat is an often less considered form of pollution that seems to stay under the radar in terms of clean up priority. Power plants and factories often use natural bodies of water for cooling, in turn changing the temperature of the water enough to kill organisms and change the ecosystem.

Many of the actions that cause these forms of pollution can be altered to significantly lower the amount of pollution that directly affects rivers and other water bodies. The largest obstacle for clean up is convincing major polluters like industrial factories that the methods they use to obtain their capital are hazardous to the environment. As humans we are part of the environment, thus it would be in every living thing's best interest to find safer, less hazardous ways to run their operations.