05/31/2000 Env Bd Packet - Laserfiche WebLink

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• Minnesota Pollution Control Agency Environmental Outcomes Division Ground Water Monitoring & Assessment Program Phosphorus in Minnesota§ Ground Water What is phosphorus? Phosphorus is a chemical commonly found in soil, rocks and plants. It is an essential nutrient for plant growth. Consequently, phosphorus is an important fertilizer in agricultural production, and it is used widely in urban settings. Phosphorus is an important contaminant of surface water, since even low concentrations can lead to algal blooms, which diminish the recreational value of lakes and rivers. Phosphorus, particularly inorganic forms, is relatively immobile in soil. What are sources of phosphorus in ground water? Concentrations of phosphorus in rocks may be as much as 1,000 mg/kg (parts per million). Considerable amounts of phosphorus are tied up in vegetation. Humans have dramatically altered the phosphorus cycle. Phosphorus is an important fertilizer, but it is also present in human and animal wastes, insludges and in detergents. Therefore, concentrations in many soils are therefore likely to be considerably higher than under native conditions. May 1999 Phosphorus is immobile, however, and it will not reach ground water in appreciable quantities except under certain conditions. These include low soil attenuation capacity (for example, soil with low concentrations of iron, aluminum and manganese) or preferential transport of phosphorus - containing wastes through the soil to ground water. An example of this preferential transport is a septic system completed below the depth of the seasonal high water table. What is considered a safe level of phosphorus in ground water? There are no drinking water standards for phosphorus. The primary concern with phosphorus is discharge to surface waters. Concentrations of total phosphorus exceeding 100 pg/L (parts per billion) may represent a threat to surface water. Although 347 samples taken in Minnesota exceeded 100 pg/L, only 18 exceeded 500 pg/L. How is phosphorus distributed in Minnesota ground water? The overall median concentration of total phosphorus was 70 pg/L in wells sampled from the Ground Water Minnesota Pollution Control Agency, 520 Lafayette Rd. N., Saint Paul, MN 55155 -4194 (651) 296 -6300, toll -free (800) 657 -3864, TTY (651) 282 -5332 or (800) 657 -3864 This material can be made available in alternative formats for people with disabilities. Printed on recycled naner cnntaininn at least 90 nerrent fillers from naner recvrled by consumers.