Water Quality: The Basics

Transcription

1 Water Quality: The Basics Environmental Science Why is Water Quality Important? Effects all humans Safe drinking water Allows for food productions and SAFE food products Effects Wildlife Health domestic and wild animals Diversity of Life (insects or macroinvertebrates) Recreation Swimming Water Sports Fishing What determines the Quality of Water? Individual test parameters: ph Dissolved Oxygen Biochemical Oxygen Demand Temperature Clarity Turbidity Secchi Total Nitrogen Total Phosphorus Fecal Coliform 1

2 ph The ph test measures the H+ ion concentra2on of liquids and substances. Each measured liquid or substance is given a ph value on a scale that ranges from 0 to 14. ph Changes in the ph value of water are important to many organisms. Most organisms have adapted to life in water of a specific ph and may die if it changes even slightly. In the United States, the ph of natural water is usually between 6.5 and 8.5, although wide variations can occur. At extremely high or low ph values, the water becomes unsuitable for most organisms. Immature stages of aquatic insects and young fish are extremely sensitive to ph values below 5. Waters with high acidic values can also cause heavy metals, such as copper and aluminum, to be released into the water. Heavy metals can accumulate on the gills of fish or cause deformities in young fish, reducing their chance of survival. ph changes Changes in ph could be caused from - rocks and minerals in the area - downwind of urban and industrial areas 2

3 Dissolved oxygen Dissolved oxygen (often referred to as D.O.) is essential for healthy lakes and impounded rivers. The presence of oxygen in water is a positive sign, while the absence of oxygen is a signal of severe pollution. Rivers range from high to very low levels of D.O. in the water - so low, in some cases, that they are practically devoid of aquatic life. Dissolved Oxygen Depletions in dissolved oxygen can cause major shifts in the diversity of aquatic organisms found in water bodies <5 ppm dangerous zone 5 10 ppm adequate zone >10 ppm good Reason why DO might be low Time of day Climate of the region Sewage treatment plant Too much fer2lizers or organic waste BOD Biochemical Oxygen Demand When organic matter decomposes, microorganisms (such as bacteria and fungi) feed upon it and eventually it becomes oxidized (combined with oxygen). Biochemical oxygen demand is a measure of the quantity of oxygen used by these microorganisms in the aerobic oxidation of organic matter. 3

4 In rivers with high BOD levels, aerobic bacteria consume much of the available dissolved oxygen, robbing other aquatic organisms of the oxygen they need to live. Organisms that are more tolerant of lower dissolved oxygen levels may appear and become numerous, such as carp, midge larvae and sewage worms. Organisms that are intolerant of low oxygen levels, such as caddisfly larvae and mayfly and stonefly nymphs, will not survive. BOD What would cause a high BOD pulp or paper mills, meat- packing plants, food processing industries or wastewater treatment plants sep2c systems near the river or lake camle feedlots, dairies or barnyards Important because: Dissolved Oxygen Temperature = Temperature Dissolved Oxygen -Decreases in Dissolved Oxygen can cause problems for wildlife (ex. fish kills) Why is the temperature of the water so high? thermal pollu2on weather condi2ons trees or bushes providing shade Fluctuations can cause problems for many plants which moves up the food web. 4

5 Why is the temperature of water so important? Temperature affects: the amount of oxygen that can be dissolved in the water; the rate of photosynthesis by algae and larger aquatic plants; the metabolic rates of aquatic organisms; and, the sensitivity of organisms to toxic wastes, parasites and diseases. Some organisms prefer cooler water, such as trout and stonefly nymphs, while others thrive under warmer conditions, such as carp and dragonfly nymphs. Clarity Turbidity A measure of the suspended solids, which reduce the transmission of light through scattering or absorption. Secchi Measuring how far down a person can see the secchi disk. Somewhat objective, but fairly accurate. Easy to discuss results among non-scientists. Turbidity Sources Higher turbidity can be caused by human activity like cutting trees and removing vegetation next to a body of water. Trees provide shade to keep the water cooler, and trees and other plants help block mud and soil from washing into the water. When roads and parking lots are constructed without the proper silt fencing, more soil and mud are likely to reach the water. Turbidity Another effect is that the floating particles may clog fish gills. When these particles sink, they can smother and kill fish and aquatic insect eggs that lay on the bottom. Turbidity can also limit plant growth. This happens when sunlight cannot reach the plants leaves. 5

6 Turbidity High amounts of soil in the water will block sunlight from reaching the bottom of a river or a lake in shallow water. When the water is turbid, floating particles absorb heat from the sun and cause the water temperature to rise. Higher temperatures cause oxygen levels in the water to fall, limiting the ability of fish and insects to survive there. Nitrogen Nitrogen is a nutrient, like calcium or potassium. Nitrogen is available in the environment naturally. The problem is when more is added fertilizers or confinements. Nitrogen Because nitrogen, in the form of ammonia and nitrates, acts as a plant nutrient, it also causes eutrophication. Eutrophication is the enrichment of water with nutrients, usually phosphorous and nitrogen, which stimulates the growth of algal blooms and rooted aquatic vegetation. Eutrophication promotes more plant growth and decay, which in turn increases biochemical oxygen demand. Nitrates in excess amounts can have a significant impact on water quality. Sources of nitrogen Fer2lizers an overabundance of blue- green algae in the river or lake sewage treatment plant nearby sep2c systems near the river or lake camle feedlots, dairies or barnyards swamps or marshes been drained recently 6

7 Phosphorus Phosphorus is also a nutrient, like nitrogen, calcium, or potassium. It is also available in the environment naturally, but phosphorus is more limiting in freshwater ecosystems. Adding too much phosphorus (making it no longer limiting) can cause algal blooms. Why is the phosphorous so low? an overabundance of blue- green algae in the river or lake sewage treatment plant nearby sep2c systems near the river or lake camle feedlots, dairies or barnyards swamps or marshes been drained recently Fecal Coliform Fecal coliform bacteria are found in the feces of human beings and other warm-blooded mammals, and birds. Fecal coliform by themselves are generally not pathogenic. Pathogenic organisms include bacteria, viruses and parasites that cause diseases and illnesses. Fecal coliform bacteria are already inside of you! They occur naturally in the human digestive tract and aid in the digestion of food. However, when a human being or other warm-blooded animal is infected, pathogenic organisms are found along with fecal coliform bacteria. 7

8 Coliform If fecal coliform counts are high in a river or lake, there is a greater chance that pathogenic organisms are also present. If you are swimming in waters with high levels of fecal coliform, you have a greater chance of developing a fever, nausea or stomach cramps from swallowing disease-causing organisms, or from pathogens entering the body through cuts in the skin, the nose, mouth, or ears. Some examples of diseases and illnesses that can be contracted in water with high fecal coliform counts include typhoid fever, hepatitis, gastroenteritis, dysentery and ear infections. Questions? 8