Water Chemistry

Water Chemistry
What kinds of things limit the water that living things can use? Sediment,  pH, chemical pollutants such as fertilizers and herbicides, heat, amount of dissolved oxygen, organic wastes and decay, salts, etc. Use of water by organisms is based on chemistry.

pH
is a measure of acidity. Pure water has a pH of 7, which is considered neutral. In the United States, most rainwater is moderately acidic (5.5) due to contamination from acid-forming gases in the air. These gases include carbon dioxide, sulfur dioxide and nitrogen oxides. They come from the burning of fossil fuels. Acidity can cause toxic heavy metals to dissolve into the water.

Conductivity
measures how easily electricity flows through the water. Salts dissolved in water allow it to conduct more electricity. Other substances that may not be dissolved, but are suspended in the water, also cause it to conduct electricity more easily. These may also cause the water to appear cloudy or dark. Some common causes of higher conductivity include wastes from animals or humans and eroded soils that have washed into the water. Water in estuaries varies in salinity. Ocean water is called saltwater and is about 35 parts per thousand salt, or 3.5%. Texas' Laguna Madre has even higher salinities, due to little rainfall evaporation, and minimal exchange of water between the ocean and Laguna Madre waters.

Dissolved Oxygen
Dissolved oxygen is important to support aquatic life. In general, higher dissolved oxygen is better for fish and other aquatic life. Air is 21% oxygen or 210,000 parts per million. Most of Texas' waters are 0.0005- 0.0015% oxygen or between 5 and 15 parts per million. In hot summers oxygen levels may be lower.

Nitrates
Fertilizer and animal and human waste are common sources of nitrates in Texas' waters. Golf centers use a lot of fertilizer to keep their golf courses green. Nitrates may stimulate plant growth.

Phosphates
Phosphates come from fertilizers and from household detergents and stimulate plant growth.
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