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Water: Ammonia

Draft 2009 Update of Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater

Fact Sheet: December 2009

EPA is publishing draft national recommended ambient water quality criteria for the protection of aquatic life for ammonia. These criteria are based on EPA’s Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses (1985), EPA 822/R-85-100. EPA is publishing these draft criteria in order to receive scientific input from the public.

What are aquatic life water quality criteria?

Aquatic life water quality criteria are numeric values that protect aquatic life from the harmful effects of pollutants in surface water. Under section 304(a) of the Clean Water Act (CWA), water quality criteria are based solely on data and scientific judgments about the relationship between pollutant concentrations and environmental and human health effects; economic or social impacts do not influence criteria recommendations.

EPA’s national recommended water quality criteria provide guidance to states, territories and authorized tribes in adopting water quality criteria that meet the requirements of the CWA. They are not regulations themselves and do not impose legally binding requirements on EPA, states, territories, authorized tribes or the public.

How were these water quality criteria for ammonia derived?

EPA derived these aquatic life water quality criteria for ammonia based on the Agency’s 1985 Aquatic Life Criteria Guidelines. These guidelines provide consistent, scientifically-based procedures for deriving ambient water quality criteria for the protection of aquatic organisms and their uses. Toxicity data and other information on the effects of ammonia were obtained from reliable sources and subjected to both internal and external peer review. The draft criteria update incorporates all toxicity data available since the last criteria update including new data on larval and juvenile freshwater mussels to reflect the latest science.

What are the draft aquatic life water quality criteria for ammonia?

Freshwater: Freshwater aquatic organisms and their uses should not be affected unacceptably if –

1. The one-hour average concentration of total ammonia nitrogen (in mg N/L) does not exceed, more than once every three years on the average, the CMC (acute criterion), which is dependent on the aquatic organisms present.

2A. The thirty-day average concentration of total ammonia nitrogen (in mg N/L) does not exceed, more than once every three years on the average, the CCC (chronic criterion), which is dependent on the aquatic organisms present.

2B. In addition, the highest four-day average within the 30-day period should not exceed 2.5 times the CCC.

The acute and chronic criteria concentrations are expressed as functions of temperature and pH, such that values differ across sites, and differ over time within a site. See draft criteria document (pp. 34-38) for actual equations describing this function. As temperature decreases, invertebrates, but not fish, become less sensitive to ammonia, and below a particular temperature threshold, fish become the most sensitive genera.

Acute Criteria: At pH=8, where freshwater mussels are present, the criterion concentration ranges from 1.90 mg N/L at 30° C to 9.81 mg N/L at 0° C. At pH=8, where freshwater mussels are absent the criterion concentration ranges from 3.29 mg N/L at 30° C to 9.99 mg N/L at 0° C.

Chronic Criteria: At pH=8, where freshwater mussels are present, irrespective of whether fish ELS are present or absent, the criterion ranges from 0.186 mg N/L at 30° C to 0.817 mg N/L at 0° C. When freshwater mussels are absent, the values range from 1.33 mg N/L at 30° C to 2.32 mg N/L at 0° C at times when fish ELS are present, and from 1.33 mg N/L at 30° C to 5.87 mg N/L at 0° C at times when fish ELS are absent.

     Draft 2009 Ammonia Criteria
   (at pH 8 and 25°C)
   Current 1999 Criteria
   (at pH 8 and 25°C)
  Acute    2.9 mg N/L mussels present
   5.0 mg N/L mussels absent
   5.6 mg N/L salmon present
  Chronic    0.26 mg N/L mussels present
   1.8 mg N/L mussels absent
   1.2 mg N/L fish early life stages present

Note: These criteria values are appropriate at the standard normalized pH and temperature; the criteria values are a function of the variability of pH and temperature.

The water quality criteria for ammonia saltwater are not being updated at this time.

Where can I find more information on the draft aquatic life water quality criteria for ammonia?

Contact Lisa Huff, U.S. EPA, Health and Ecological Criteria Division (4304T), 1200 Pennsylvania Ave., N.W., Washington, D.C. 20460; (202) 566-0787; huff.lisa@epa.gov.

You can find the Federal Register notice on national recommended water quality criteria online at http://www.epa.gov/waterscience/criteria/ammonia/. EPA has also established an official public docket for this action under Docket ID No. EPA-HQ-OW-2009-0921.

Scientific views on these draft criteria will be accepted for 90 days (upon Federal Register publication) via the docket webpage. The docket can be accessed at www.regulations.gov.

Additional Information

 


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