WATER QUALITY

Sources of Water Pollution Water pollution results from some physical or chemical change that adversely affects human health or the health of organisms in an ecosystem. Some water pollution comes from natural sources. Example: a mud slide would increase siltation in a water body.

Most water pollution is caused by humans. There are two types of human caused water pollution: Point source pollution: enters the environment at specific, identifiable sites. Sewage treatment plants generally discharge through pipes as do factories there the contaminants can by traced back to these processes.

Nonpoint source pollution: originates from scattered locations across a watershed. Example: precipitation moves over and through the soil, picking up and carrying with it pollutants that are eventually deposited in lakes, rivers, wetlands,

Any other examples of nonpoint source pollution? - Fertilizers - Pesticides - Pathogens (biological agents that cause disease) - Livestock waste

Types of Water Pollution Pollutants are classified based on their consequences and types. (see sheet)

Examples of Water Pollution

Sedimentation and Siltation Soil erosion is a result of agricultural practices, development, construction, logging, strip mining and overgrazing of rangelands.

Siltation is a process by which water becomes dirty as a result of fine mineral particles in the water.

What problems could arise from having cloudy (silt-filled) water? - Light penetration is reduced, therefore PS is restricted, which alters the entire food web

- Concentrations of dissolved substances (nutrients) increase with sedimentation. Many chemicals like pesticides and phosphorus are adsorbed on the surface of silt particles and carried directly to the water.

- Siltation also has an impact on fish spawning and can clog gills of different species.

Increasing Oxygen Demand An increase in the amount of organic matter in an aquatic ecosystem sets off a chain of events. Decomposers eat the organic matter and their populations increase Cellular respiration by decomposers increase. Oxygen is removed from the water for respiration and depletes the amount of DO

This increase in oxygen demand causes an oxygen sag which could be significant enough to kill fish Scientists must determine the biochemical oxygen demand of organic matter before it is released into a surface water body.

Increasing Nutrients Human activities increase the levels of nitrogen and phosphate in water bodies. This increase of nutrients by humans is called cultural eutrophication. Sources of nutrients are generally from: - sewage and agricultural runoff - Organic waste, soaps and detergents

Lakes downstream in a watershed are impacted by the accumulation of these nutrients, develop algal blooms and sometimes the BOD is high enough that they develop hypoxic zones. Examples of these “dead zones” can be found in Lake Winnipeg and the Gulf of Mexicodead zones

The Dead Zone in the Gulf of Mexico (US) - By Henry Steinberg: First came Hurricane Katrina, taking their houses. Now the Dead Zone is taking their hope. The shrimpers on Grand Isle, Louisiana, are hit hardest by an environmental disaster that summer after summer is killing all life in a vast area of the Gulf of Mexico. We need to be honest with ourselves. What we have created is the largest inland freshwater dead zone in the world. At 15,000 square kilometres in area, algal blooms in Lake Winnipeg are now larger than the record 8,500- square-mile area of the dead zone in the Gulf of Mexico. We need to admit that we are nowhere near to solving the Lake Winnipeg problem. Nor are we as a nation taking the problem as seriously as we should.

Groundwater Contamination Infiltration of contaminants from the surface to unconfined or even confined aquifers causes groundwater contamination. Example: Erin Brockovich What Erin discovered was that Pacific Gas & Electric had allowed the leakage of a contaminant called Chromium 6 into the well-water of Hinkley, California, for over 30 years. Several residents of this small desert community were suffering from ailments ranging from chronic nosebleeds to cancer.