Introduction | Water Quality Overview
Note: Conceptual Diagram and parameter descriptions are still under development.
IAN Conceptual Diagram (Jump to water quality parameters)
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Water Quality Parameters (Jump to conceptual diagram)
Ammonium: a dissolved form of inorganic N, chemically NH4+, which is readily used by phytoplankton (algae). Ammonium is a rapidly cycled form of N that is only found in high concentrations in anoxic bottom waters and near wastewater treatment plants.
Chlorophyll A: the universal algal pigment which captures light energy for photosynthesis. Because this green pigment is found in all algae and is easily measured, concentrations of chlorophyll a are used as a measure of phytoplankton biomass.
Dissolved Oxygen: oxygen gas (O2) dissolved in water. Oxygen is produced by algal photosynthesis in the water and consumed by respiration in the water and sediments. If the water is undersaturated or supersaturated, oxygen is exchanged with the atmosphere.
Dissolved Organic Carbon: the carbon in various forms of organic matter dissolved in water. Chemically, dissolved organic carbon (DOC) is a complex mixture derived from the organic matter in soils, sediments, and the water column.
Nitrate-Nitrite: oxidized forms of inorganic N dissolved in water. Chemically, NO3- and NO2-, these forms are highly soluble and easily leach from septic drains and agricultural fields to ground waters. NO2- is usually not very abundant, whereas NO3- is usually >99%. NO3- is toxic when concentrations exceed 10 mg N/L.
Phosphate: the only environmentally significant form of P. It may be found in dissolved inorganic forms or combined with organic matter or metallic complexes (iron phosphate in sediments). Phosphate is an essential plant nutrient which is primarily regulated in lakes to control eutrophication; in estuaries it controls algal growth in winter through spring.
Salinity: the salt content of water. Originally expressed as g/L or parts per thousand (ppt), salinity is now measured by conductivity measurements and is unitless. Freshwaters have a salinity of 0.1-0.5, and full strength seawater is 35.
Secchi: a simple measure of water transparency measured visually by the disappearance of a white or patterned disk lowered into the water. Clear waters have Secchi transparencies >5 m, estuaries have transparencies of 0.5-2 m, and waters with poor quality are 0.1-0.5 m.
Silicate: an inorganic form of silicon (Si) dissolved in water. Chemically SiO4-3, silicate is an essential nutrient for phytoplankton called diatoms, which are important in aquatic food chains. Other forms of phytoplankton do not use or need silicate.
Temperature: water temperature is measured in degrees Celcius. Freezing occurs at 0 C, body temperature is 37 C, and water boils at 100 C. Chesapeake waters have temperatures primarily between 0 and 30 C.
Total Nitrogen: all forms of N, both dissolved and particulate, inorganic and organic. Abbreviated TN or total N, this chemical category includes the ammonium, nitrite, and nitrate described above, plus other types of N not described here.
Total Phosphorus: all forms of P, both dissolved and particulate, inorganic and organic. Abbreviated TP or total P, this chemical category includes the phosphate described above, plus other types of P not described here.
Total Suspended Solids: a measure of the weight of all particulates in a water sampled captured on a filter (usually a glass-fibre filter) which has been preweighed before filtration. Usually abbreviated TSS, total suspended solids is a measure of the water transparency.