Nanus, Leora听1听;听Williams, Mark W听2听;听Campbell, Donald H听3听;听Kendall, Carol听4;听Elliott, Emily M听5
1听乐播传媒 Boulder, US Geological Survey
2听乐播传媒 Boulder
3听US Geological Survey
4听US Geological Survey
5听University of Pittsburgh
In the Rocky Mountains, there is uncertainty in the source areas and emission types that contribute to nitrate deposition, which can adversely affect sensitive aquatic habitats of high-elevation watersheds. Regional patterns in sources of nitrate deposition were evaluated using nitrate isotopes at sites across five National Parks, including 37 lakes and 7 precipitation sites. Results indicate that nitrate(NO3) concentrations collected from lakes ranged up to 38 microequivalents per liter, d18O(NO3) values ranged from -5.7 to +21.3 permil, and d15N(NO3) values ranged from -6.6 to +4.6 permil. d18O(NO3) in precipitation ranged from +71 to +78 permil. d15N (NO3) in precipitation and lakes overlap; however, precipitation is lighter than lakes ranging from -5.5 to -2.0 permil. d15N(NO3) values are significantly related (r-squared = 0.6, p < 0.05) to wet deposition estimates of inorganic N, sulfate, and acidity, suggesting that the spatial variability of d15N(NO3) over the Rocky Mountains may be related to source areas of these solutes. Regional patterns show that NO3 concentrations and d15N(NO3) values are heaviest in lakes and precipitation from the Southern Rockies and at higher elevations, compared to lower elevations and the Northern Rockies. The correspondence of higher NO3 concentrations and higher d15N(NO3) values in precipitation with higher NO3 and higher d15N(NO3) values in lake waters, suggests that atmospheric deposition of NO3 may affect the amount of NO3 in lakes through either direct (wet deposition) or indirect processes (enhanced nitrification).