Nitrate (NO₃)

Status and Trends

Nitrate (NO₃) is highly soluble (dissolves easily) in water and is stable over a wide range of environmental conditions. It is easily transported in streams and groundwater. Nitrates feed plankton (microscopic plants and animals that live in water), aquatic plants, and algae, which are then eaten by fish.

If excessive amounts of phosphorus and nitrates are added to the water, algae and aquatic plants can be produced in large quantities. When these algae die, bacteria decompose them, and use up oxygen. This process is called eutrophication. Dissolved oxygen concentrations can drop too low for fish to breathe, leading to fish kills.

Nitrate was analyzed in samples from all 37 stations east of Hancock, MD. Median concentrations of NO₃ ranged from a low of 0.63 mg/L on the Potomac at US 522 to a high of 4.55 mg/L on Antietam Creek at Poffenberger Road. Thirty-eight percent of the stations exhibited median concentrations of NO₃ that exceeded 2.10 mg/L. Eight percent had median concentrations less than 1.10 mg/L.

Significant downward trends in concentration were observed at 49% of all stations. No single stations exhibited increasing trends in NO₃ concentration.

Nitrate data for sampled locations are summarized in these plots.

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This page was updated on 12/5/2005