Aquatic Sciences Meeting, Albuquerque 2001
| PC11 Human Activities and Aquatic Ecosystems |
| Date: Thursday, February 15, 2001 |
| Location: Southwest Hall |
| Chang, C, C, U.S. Geological Survey, Menlo Park, USA, ccchang@usgs.gov |
| Battaglin, W, A, U.S. Geological Survey, Lakewood, USA, wbattagl@usgs.gov |
| Campbell, D, H, U.S. Geological Survey, Lakewood, USA, dhcampbe@usgs.gov |
| Kendall, C, , U.S. Geological Survey, Menlo Park, USA, ckendall@usgs.gov |
| Silva, S, R, U.S. Geological Survey, Menlo Park, USA, srsilva@usgs.gov |
| THE USE OF NITRATE STABLE ISOTOPES TO RESOLVE NITRATE PATTERNS IN THE MISSISSIPPI RIVER BASIN |
 |
| Water samples were collected from large rivers and small basins with different land uses (23 sites) in the Mississippi River Basin for N-15 and O-18 analysis of NO3 to investigate whether information about NO3 sources and processes could be obtained. At low [NO3] (<4 ppm) the ranges of isotopic values for N and O were broad and unpredictable. Urban and undeveloped sites had the lowest [NO3] (<1.5 ppm), low N-15 (< +7 ) and were easily distinguished by their higher O-18 values (>+10). Urban sites had somewhat higher O-18 values (> + 19 ), than undeveloped sites consistent with an atmospheric source. Agricultural sites had higher [NO3], up to 18 ppm. The N-15 from sites with crops & animals tended to be negatively correlated with [NO3], the range heavier (+5.3 to +13) than at crop only sites. The narrower O-18 range (+5 to +13) at these sites was consistent with a significant manure component NO3 source. Large rivers (NO3 4ppm) had isotopic values similar to those of agricultural sites. The data suggest that isotopes, used in conjunction with traditional water quality data may be able to resolve NO3 patterns with different land uses. |
| This Session Listing |
