A maximum of nine chemical tests are performed by students in the Rouge Education Project: dissolved oxygen, biochemical oxygen demand, pH, change in temperature, nitrates, turbidity, fecal coliform, total phosphates, and total solids. Elementary school students generally conduct the first six tests, while middle and high school students generally conduct all nine. Following are explanations of why we monitor these parameters.

Dissolved oxygen (DO)

Oxygen from the atmosphere is mixed in water by waves and tumbling water. Algae and rooted aquatic plants also put oxygen into water through photosynthesis. Most aquatic plants and animals must have some amount of oxygen to survive. Waters with consistently high levels of dissolved oxygen are considered to be stable ecosystems and able to support diverse populations of organisms.

Biochemical oxygen demand (BOD) is the measure of the amount of oxygen used by aerobic microorganisms (bacteria and fungi) as they feed upon decomposing organic matter, such as dead aquatic plants. Inputs of phosphates and nitrates (found in fertilizers) in water bodies stimulate the growth of aquatic plants. As these plants die and decompose over time, more and more oxygen is removed from the water by the microorganisms. High BOD levels can lead to fish kills because the aerobic bacteria use up the dissolved oxygen that fish need to live.

pH

Water (H₂O) is composed of OH- (hydroxyl) ions and H+ (hydrogen) ions. The pH test measures the concentration of H+ ions, and pH values range from 0-14. A pH value of 7 is considered neutral, less than 7 is acidic, and more than 7 is basic. Acidic water has more H+ ions than OH- ions, neutral water has equal numbers of H+ and –OH ions, and basic water has fewer H+ ions than –OH ions. The pH of natural water in the U.S. is usually between 6.5 and 8.5. Most organisms cannot live in water that has extremely high or low pH values (more than 9.6 or less than 4.5).

You may have heard of "acid rain." This is caused by nitrogen oxides and sulfur dioxides (primarily from automobile and coal-fired power plant emissions) that are converted to nitric acid and sulfuric acid in the atmosphere. These acids combine with water vapor in the atmosphere and return to land as acid rain or acid snow. This deposition may increase the acidity of a body of water, especially in freshwater systems that do not have a limestone buffer. Limestone neutralizes the effects of acid rain deposition.

For this test, water temperature is measured at the sampling site and a mile upstream from the site to determine the change in temperature. Most physical, biological and chemical processes in a river are directly affected by temperature. For example, temperature affects the amount of dissolved oxygen in water (cold water can hold more oxygen than warm water); the rate of photosynthesis by plants; the metabolic rate of aquatic animals; and the sensitivity of organisms to pollution, disease and parasites. Changes in water temperature may be the result of thermal pollution (adding warm water to a body of water), changes in the amount shade over the river, and soil erosion. Soil particles suspended in water absorb heat from sunlight.

All plants and animals require nitrogen to build protein. It is much more abundant than phosphorus and is most commonly found as atmospheric nitrogen (N₂). This form can’t be used by most aquatic plants, however, and must be converted to ammonia (NH₃) and nitrates (NO^-₃). In these forms, nitrogen acts as a plant nutrient and can cause eutrophication. Plants are less sensitive to changes in ammonia and nitrate levels than they are to phosphorus, however, because nitrogen rarely limits plant growth. Sources of nitrates added to rivers by humans include sewage, fertilizers, and runoff from dairies and barnyards.

Turbidity is a measure of water clarity. Murky water has a high turbidity, while clear water has a low turbidity. Suspended solids—such as soil particles, sewage, plankton and industrial wastes—in water increase turbidity and decrease the transmission of light. An increase in turbidity decreases biodiversity because more turbid waters are warmer and allow less sunlight through for photosynthsesis. Also, suspended solids harm aquatic organisms by clogging gills, increasing susceptibility to disease, slowing growth rates, and preventing the development of larvae and eggs.

Feces of humans and other warm-blooded animals contain fecal coliform bacteria. These bacteria do not cause disease or illness, but if fecal coliform levels are high, it is more likely that pathogens are also in the water. Sources of fecal coliform in the river include discharged sewage, wildlife wastes, and runoff from pet waste and livestock.

Phosphorus is a nutrient that plants need to grow. In most waters, phosphorus is present in very low concentrations, which limits plant growth. However, humans add phosphorus to water through human and industrial wastes, fertilizers, and disturbances to land and vegetation. When human activities add nutrients to water, it is called cultural eutrophication. Excess phosphorus stimulates plant growth and can cause algal blooms. When this vegetation decomposes, dissolved oxygen levels can drop dramatically, especially near the bottom of the body of water.

Total solids is a measure of the amount of dissolved and suspended solids in water. Suspended solids are solid matter that is trapped by a filter—such as soil particles, sewage, plankton and industrial wastes—and dissolved solids are solid matter that passes through a filter—such as bicarbonate, calcium, phosphorus, iron, nitrogen and sulfur. The flow of water in and out of aquatic organisms’ cells is regulated by total solids. Sources of total solids include urban runoff, lawn fertilizers, wastewater treatment plants, soil erosion and decayed plant and animal matter.