What is in Polluted Runoff

There are six major types of pollutants that affect water quality. Some are primarily a human problem, but others can damage the entire ecosystem.

 

Sediment:

Dirt and sand are natural substances that become pollutants when they end up in the water in excessive quantities. Sediment changes the shape of streambeds, smothers feeding and nursery areas of aquatic animals, and carries other pollutants into the water. Erosion from poorly managed construction sites, agricultural fields, or suburban gardens are major sources of sediment pollution. Another major source is road sand applied to improve winter driving conditions.

Debris:

Non-degradable trash, mostly plastic, when carelessly disposed of, will often end up in a nearby water body. Humans find it ugly, as well as hazardous when it entangles boat propellers. Aquatic animals can also become entangled, or mistake plastic for food, and strangle or starve.

 

Pathogens:

Pathogens are the bacteria and viruses that cause disease. They generally come from fecal material from humans and their pets, or from wild animals and birds. When the potential concentration of pathogens in the water exceeds certain limits, areas must be closed to fishing or swimming in order to prevent infections or disease outbreaks. Major sources of pathogens include: failing septic systems, leaky sewer lines, and concentrations of animal waste from pets, farm animals or wildlife.

 

Toxic Contaminants:

Many of the tens of thousands of chemicals in use today are harmful to both humans and aquatic organisms. Some of these chemicals can be passed through the food chain and concentrate at the top of the food chain where the humans are. Extremely small concentrations of some toxic materials in the water can kill the eggs and larvae of many animals. Sources of toxic contaminants range from the exhaust and fluids that come from automobiles to the cleaning and disinfectant products used in homes to the pesticides used in yards, farms and parks.

 

Nutrients:

Materials that are necessary for plant growth, primarily nitrogen or phosphorus, are known as nutrients. When too many nutrients end up in an aquatic system, they alter the natural plant community and can cause massive plant growth known as algal “blooms” which deplete oxygen concentrations in the water. Excess nitrates in drinking water have been linked to human health problems, including heart conditions and birth defects.

 

Thermal Pollution:

During summer months, thermal pollution (i.e., unnatural warming of waters) can make the water too warm for sensitive native plants and animals to survive. Overheated water can result from the removal of vegetation that shade the stream, runoff from hot roofs and parking lots, or the collection of water in shallow, unshaded ponds.