In the Rocky Mountains, there is uncertainty about the source areas and emission types that contribute to nitrate (NO3) deposition, which can adversely affect sensitive aquatic habitats of high-elevation watersheds. Regional patterns in NO3 deposition sources were evaluated using NO3 isotopes in five National Parks, including 37 lakes and 7 precipitation sites. Results indicate that lake NO3 ranged from detection limit to 38 ??eq/L, ??18O (NO3) ranged from -5.7 to +21.3???, and ??15N (NO3) ranged from -6.6 to +4.6???. ??18O (NO3) in precipitation ranged from +71 to +78???. ??15N (NO 3) in precipitation and lakes overlap; however, ??15N (NO3) in precipitation is more depleted than ??15N (NO3) in lakes, ranging from -5.5 to -2.0???. ??15N (NO3) values are significantly related (p < 0.05) to wet deposition of inorganic N, sulfate, and acidity, suggesting that spatial variability of ??15N (NO3) over the Rocky Mountains may be related to source areas of these solutes. Regional patterns show that NO3 and ??15N (NO3) are more enriched in lakes and precipitation from the southern Rockies and at higher elevations compared to the northern Rockies. The correspondence of high NO 3 and enriched ??15N (NO3) in precipitation with high NO3 and enriched ??15N (NO3) in lakes, suggests that deposition of inorganic N in wetfall may affect the amount of NO3 in lakes through a combination of direct and indirect processes such as enhanced nitrification. ?? 2008 American Chemical Society.
Additional publication details
Evaluating regional patterns in nitrate sources to watersheds in national parks of the rocky mountains using nitrate isotopes