Water Quality Parameters to Know for AP Environmental Science

Water quality parameters are crucial for understanding aquatic ecosystems and their health. Key factors like pH, dissolved oxygen, and temperature influence the survival of aquatic life and the overall quality of water, impacting everything from fishing to conservation efforts.

1. pH

   • Measures the acidity or alkalinity of water on a scale from 0 to 14.
   • A pH of 7 is neutral; values below 7 indicate acidity, while above 7 indicates alkalinity.
   • Affects the solubility and availability of nutrients and metals in water.
   • Influences aquatic life; most organisms thrive in a pH range of 6.5 to 8.5.

2. Dissolved Oxygen (DO)

   • Indicates the amount of oxygen available for aquatic organisms.
   • Essential for the survival of fish and other aquatic life; low levels can lead to hypoxia.
   • Influenced by temperature, turbulence, and organic matter decomposition.
   • Measured in milligrams per liter (mg/L); levels below 5 mg/L can be harmful to aquatic life.

3. Temperature

   • Affects the physical and chemical properties of water, including DO levels.
   • Influences metabolic rates of aquatic organisms; warmer water holds less oxygen.
   • Can impact species distribution and ecosystem health.
   • Temperature changes can indicate pollution or thermal discharges.

4. Turbidity

   • Refers to the cloudiness or haziness of water caused by suspended particles.
   • High turbidity can reduce light penetration, affecting photosynthesis in aquatic plants.
   • Can indicate the presence of pollutants or sediment runoff.
   • Measured in Nephelometric Turbidity Units (NTU); higher values indicate poorer water quality.

5. Conductivity

   • Measures the water's ability to conduct electricity, which correlates with ion concentration.
   • Higher conductivity indicates higher levels of dissolved salts and minerals.
   • Useful for assessing water quality and identifying pollution sources.
   • Measured in microsiemens per centimeter (µS/cm); changes can indicate contamination.

6. Total Dissolved Solids (TDS)

   • Represents the total concentration of dissolved substances in water, including salts and minerals.
   • High TDS levels can affect water taste, quality, and aquatic life.
   • Measured in milligrams per liter (mg/L); levels above 500 mg/L may be unsuitable for drinking.
   • Can indicate pollution or changes in water sources.

7. Biochemical Oxygen Demand (BOD)

   • Measures the amount of oxygen required by microorganisms to decompose organic matter in water.
   • High BOD levels indicate high levels of organic pollution, which can deplete DO.
   • Important for assessing the impact of wastewater on water bodies.
   • Measured in milligrams per liter (mg/L); lower values indicate better water quality.

8. Chemical Oxygen Demand (COD)

   • Indicates the total amount of oxygen required to chemically oxidize organic and inorganic substances in water.
   • Higher COD values suggest higher levels of pollution and organic matter.
   • Useful for assessing water quality and treatment efficiency.
   • Measured in milligrams per liter (mg/L); provides a broader measure than BOD.

9. Nitrates

   • Essential nutrients for plant growth, but excessive levels can lead to eutrophication.
   • Commonly found in fertilizers and wastewater; can contaminate drinking water.
   • Measured in milligrams per liter (mg/L); levels above 10 mg/L can be harmful to human health.
   • Can lead to algal blooms, which deplete oxygen and harm aquatic life.

10. Phosphates

    • Another key nutrient that supports plant growth; excessive levels can also cause eutrophication.
    • Often derived from agricultural runoff, detergents, and wastewater.
    • Measured in milligrams per liter (mg/L); levels above 0.1 mg/L can trigger algal blooms.
    • Can lead to decreased water quality and biodiversity loss.

11. Chlorophyll-a

    • A pigment found in algae and aquatic plants; indicates the presence of phytoplankton.
    • Used as a measure of primary productivity in aquatic ecosystems.
    • High levels can indicate nutrient enrichment and potential algal blooms.
    • Measured in micrograms per liter (µg/L); helps assess ecosystem health.

12. Fecal Coliform

    • Bacteria found in the intestines of warm-blooded animals; indicates potential contamination by fecal matter.
    • Used as an indicator of waterborne pathogens and overall water quality.
    • Measured in colony-forming units per 100 milliliters (CFU/100 mL); levels above 200 CFU/100 mL are concerning for recreational waters.
    • High levels can pose health risks to humans and wildlife.

13. Salinity

    • Refers to the concentration of salts in water, typically measured in parts per thousand (ppt).
    • Influences the types of organisms that can thrive in a water body; essential for estuarine ecosystems.
    • Changes in salinity can indicate freshwater inflow or pollution.
    • Important for understanding habitat conditions for aquatic species.

14. Hardness

    • Refers to the concentration of calcium and magnesium ions in water.
    • Measured in milligrams per liter (mg/L) or degrees of hardness; affects water's taste and suitability for various uses.
    • High hardness can lead to scaling in pipes and appliances.
    • Important for aquatic life; some species prefer softer water.

15. Alkalinity

    • Measures the water's capacity to neutralize acids, primarily due to bicarbonate and carbonate ions.
    • Important for maintaining stable pH levels in aquatic systems.
    • Higher alkalinity can indicate better buffering capacity against acid rain and pollution.
    • Measured in milligrams per liter (mg/L) of calcium carbonate (CaCO3); essential for aquatic life health.