Amazon.com description: Product Description: This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1999-05 Excerpt: ... comparisons of average annual and average monthly concentrations to the drinking-water standard. In only two of all sampled rivers and streams did the average annual concentration of nitrate exceed the drinking-water standard. These two streams drained small agricultural watersheds in the Lower Susquehanna River and Willamette Basins, and neither was used to supply drinking water. 0 percent 0-100 100-200 Greater than 200 DEPTH TO GROUND WATER, in feet The percentage of ground-water samples with concentrations of nitrate exceeding the drinking-water standard of 10 mg/L decreases as depth to water increases. Mixing of shallow ground water with deeper, uncontaminated water and increased thickness of protective, impermeable geologic materials with depth may help explain this relation. From a national perspective, nitrate did not pose a health risk for residents who drank water from major aquifers buried relatively deep below the land surface. People drinking ground water from shallow wells in vulnerable geologic settings (sand, gravel, or karst) in rural agricultural areas, however, are at risk of exposure to nitrate contamination. Nitrogen and phosphorus have different effects on aquatic plant growth in freshwater and saltwater. Eutrophication of freshwater streams generally results from high phosphorus concentrations. In contrast, excess nitrogen, and nitrate in particular, can lead to algal blooms in coastal waters. The USEPA suggests a desired goal of 0.1 mg/L total phosphorus for freshwater streams, but there are no national criteria established for nitrogen concentrations to control excessive aquatic plant growth in coastal bays and estuaries. aquatic life Average annual and average monthly concentrations of un-ionized ammonia did not exceed USEPA aqu...