| Abstract: | Results of a national water quality assessment indicate that nitrate is detected in 71% of groundwater samples, more than 13 times as often as ammonia, nitrite, organic nitrogen, and orthophosphate, based on a common detection threshold of 0.2 mg/L. Shallow groundwater (typically 5 m deep or less) beneath agricultural land has the highest median nitrate concentration (3.4 mg/L), followed by shallow groundwater beneath urban land (1.6 mg/L) and deeper groundwater in major aquifers (0.48 mg/L). Nitrate exceeds the maximum contaminant level, 10 mg/L as nitrogen, in more than 15% of groundwater samples from 4 of 33 major aquifers commonly used as a source of drinking water. Nitrate concentration in groundwater is variable and depends on interactions among several factors, including nitrogen loading, soil type, aquifer permeability, recharge rate, and climate. For a given nitrogen loading, factors that generally increase nitrate concentration in groundwater include well-drained soils, fractured bedrock, and irrigation. Factors that mitigate nitrate contamination of groundwater include poorly drained soils, greater depth to groundwater, artificial drainage systems, intervening layers of unfractured bedrock, a low rate of groundwater recharge, and anaerobic conditions in aquifers. |
| Genre: | Article |
| ProdID: | 70022942 |
| Citation Author: | Nolan, B. T.; Stoner, J. D. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 1165 |
| Citation Issue: | 7 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Environmental Science and Technology |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 10 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | ACS |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Nutrients in groundwaters of the conterminous United States, 1992-1995; 2000; Article; Journal; Environmental Science and Technology; Nolan, B. T.; Stoner, J. D. |
| Citation Start Page: | 1156 |
| Citation Volume: | 34 |
| Citation Year: | 2000 |
| Type: | citation/reference |
| Text: | Nutrients in groundwaters of the conterminous United States, 1992-1995; 2000; Article; Journal; Environmental Science and Technology; Nolan, B. T.; Stoner, J. D. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1021/es9907663 |
| Date Other: | Sat, 1 Jan 2000 00:00 -0600 |
| Publisher: | ACS |
