Role of multiple stressors on watershed nitrogen response across New York State

Anthropogenically-accelerated inputs of reactive nitrogen (N) to watersheds across the world have resulted in a suite of concerns, such as surface water eutrophication, threats to benthic communities, and human health issues. This dissertation assesses the role of multiple stressors on watershed N response across diverse scales. The main goals of the research were to: (1) Examine how N fluxes issuing from streams can be estimated as a function of landscape characteristics of their watersheds (focusing on a set of contrasting sub-watersheds draining to Cayuga Lake, in the Finger Lakes Region of New York); (2) Quantify the spatial distribution and rates of wet atmospheric N deposition inputs across heterogeneous landscapes (focusing on watersheds defined at nested scales across New York state); and (3) Assess simple methods for evaluating spatial patterns of dry atmospheric N deposition (focusing on measurements of nitric acid, a key component of dry deposition, at point locations in New York state). Approaches for the first project involved utilizing multiple spatial datasets of landscape factors and synoptic stream chemistry. The second project included scaling point atmospheric concentration data from monitoring networks to state and multi-scale watershed levels. The third project reviewed current passive sampling methods and designed a passive sampler for measuring N species in ambient air.; Results highlight surface water regions with high NO3 - export potential, suggesting that inputs of N from agricultural systems are particularly important regulators of NO3-N fluxes in the Finger Lakes region, but that urban sprawl is a growing concern for water quality. Further, landscape factors and hydrologic connectivity work concomitantly to regulate NO3-N fluxes, but the relative role of each depends on seasonally-driven antecedent moisture conditions. Results also confirm that areas of elevated contemporary N deposition are, for the most part, spatially distributed according to relative location from sources and the Great Lakes system, and are related to elevation. Seasonal variations affect the relative importance of these factors. Finally, a simple, affordable passive sampling technique for detecting the spatial distribution and levels of ambient atmospheric nitric acid provides promise for ecological studies that investigate impacts of dry N deposition inputs to ecosystems.