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United States Department of Agriculture

Agricultural Research Service

Title: Measurement of Phosphorus in Water

Authors
item Eghball, Bahman
item Pote, Daniel

Submitted to: Encyclopedia of Water Science
Publication Type: Other
Publication Acceptance Date: July 29, 2002
Publication Date: February 1, 2003
Citation: EGHBALL, B., POTE, D.H. MEASUREMENT OF PHOSPHORUS IN WATER. ENCYCLOPEDIA OF WATER SCIENCE. P 666-668. 2003.

Interpretive Summary: Phosphorus (P) is an essential nutrient for growth and development of algae and other aquatic plants. However, P can cause water pollution if sufficient concentration (0.025 to 0.1 ppm, eutrophic condition) is present in water. Eutrophication (nutrient-rich condition) can significantly increase growth of aquatic plants, algae, and sometimes strains of algae that cause taste, odor, or toxicity problems for drinking water supplies. During the night, when there is no photosynthetic activity to renew oxygen supplies for the dense concentrations of living cells, dissolved oxygen levels may become so depleted that fish and other aquatic animals cannot survive. Furthermore, many of the blue-green algae that cause the most serious water-quality problems require P inputs to grow and flourish, but they do not need high concentrations of N in lake water because they are able to utilize atmospheric N. Accelerated eutrophication of lakes, streams, and coastal waters remains a serious problem and has grown worse in many regions. Therefore, management plans for minimizing eutrophication should be designed to limit P inputs to surface water. Phosphorus occurs in water in many different forms that need to be evaluated to identify the overall effects of P on water quality. These include dissolved or soluble, bioavailable (P available to algae), particulate, and total P. Measuring these P forms in water is critical for distinguishing among them and assessing their effects on water quality.

Technical Abstract: Phosphorus (P) is an essential nutrient for growth and development of algae and other aquatic plants. However, P can cause water pollution if sufficient concentration (25 to 100 µg total P L-1, eutrophic condition) is present in water. Eutrophication (nutrient-rich condition) can significantly increase growth of aquatic plants, algae, and sometimes strains of algae that cause taste, odor, or toxicity problems for drinking water supplies. During the night, when there is no photosynthetic activity to renew oxygen supplies for the dense concentrations of living cells, dissolved oxygen levels may become so depleted that fish and other aquatic animals cannot survive. Furthermore, many of the blue-green algae that cause the most serious water-quality problems require P inputs to grow and flourish, but they do not need high concentrations of N in lake water because they are able to utilize atmospheric N. Accelerated eutrophication of lakes, streams, and coastal waters remains a serious problem and has grown worse in many regions. Therefore, management plans for minimizing eutrophication should be designed to limit P inputs to surface water. Phosphorus occurs in water in many different forms that need to be evaluated to identify the overall effects of P on water quality. These include dissolved, bioavailable, particulate, and total P. Measuring these P forms in water is critical for distinguishing among them and assessing their effects on water quality.

Last Modified: 8/22/2014