Pollution is an undesirable change in the physical, chemical, or biological characteristics of air, land, or water that adversely affects the living conditions for either humans or other living organisms. Water pollution is the impairment of the beneficial uses of water. Water quality can be adversely affected by direct and indirect sources. Direct sources are fairly obvious and include such practices as dumping waste and hazardous pollutants into streams. Indirect sources are called nonpoint source (NPS) pollution. Stormwater runoff, which may contain fertilizers and pesticides, soil lost from construction sites, and oil residue washed off streets, is NPS pollution. This type of pollution is much more difficult to pinpoint and control.
The Northern Virginia Soil and Water Conservation District identifies five types of nonpoint source (NPS) pollution.
Sediment: Sediments are soil particles dislodged by precipitation and deposited in streams, lakes, and rivers. While erosion of soil is a naturally occurring process, accelerated erosion from degraded streams and poor construction practices creates excess sediment. Sediments accumulate in waterbodies and destroy feeding grounds for aquatic life, clog fish gills, block light, and increase water temperature.
Nutrients and Organic Debris: Nutrients are essential to water life, but too much can harm more than help. Phosphorous, nitrogen, and potassium are nutrients that help plants and animals grow. Found in fertilizer, leaves, grass clippings, sewage, detergents, and animal wastes, these elements are not harmful to the environment in low doses. However, excess nutrients in an already healthy environment can be dangerous. Decaying organic matter depletes oxygen needed by aquatic life, leaving fish and shellfish to suffocate.
Trash: Garbage, construction debris, and animal waste become part of the runoff entering storm drains and local waterways and clogging the system.
Toxins: Toxins are chemicals that can cause human and wildlife health problems. They include organic chemicals and metals, pesticides, herbicides, household chemicals, paint, paint cleaners, gasoline, motor oil, battery acid, antifreeze, and roadway salt.
Pathogens: A pathogen is a specific causative agent of disease. The presence of bacteria in water, which normally are found in the intestinal tracts of humans and animals, signals that pathogens may be present.
What can citizens do to reduce nonpoint source pollution?
- Limit use of pesticides and fertilizer and use them at appropriate times of the year in recommended amounts. Introduce natural predators to your garden, and use pest resistant plants. Remove eggs, larvae, cocoons, and adults from plants by hand.
- Prevent property erosion by covering bare soil with vegetation and mulch.
- Participate in a stream cleanup program.
- Remove obstructions from stream channels and revegetate stream banks.
- Don’t mow all the way to the edge of a lake or pond. Leave a buffer of tall grasses or shrubs to filter pollutants.
- Landscape yards to minimize rainwater runoff.
- Preserve neighborhood trees that help minimize the damage caused by surface runoff.
- Place retaining walls or diversions on steeply sloping ground to reduce the rate of water flow and erosion.
- Make sure septic tanks work properly.
- Dispose of litter in garbage cans or in recycling bins. Recycle glass, aluminum, plastic, paper, motor oil, and newspapers.
- Compost yard and garden waste.
- Pick up pet waste and bag it with regular household trash or flush it in the toilet.
- And, never ever intentionally dump anything into a storm drain!