2008 BES Annual Meeting Presentation and Poster Abstracts
Isotopic Investigation of Anthropogenic Sources of Atmospheric Carbon and Nitrogen to Vegetation along an Urban to Rural Gradient
Co-Authors: Katherine Middlecamp *, Emily M. Elliott *, John Hom ** *Department of Geology & Planetary Science, University of Pittsburgh **Northern Global Change Research Program, U.S. Forest Service Corresponding author: Katherine Middlecamp (412) 779-2693
Abstract: Fossil fuel combustion in urban areas is a key contributor to atmospheric CO2, a major greenhouse gas, and NOx, a precursor to acid rain and smog. However, little is known about how metropolitan ecosystems compensate for higher local atmospheric CO2 and NOx concentrations. This research addresses this issue using stable isotope analysis of vegetation, ambient CO2 and dry nitrogen deposition along two urban to rural gradients in Baltimore, MD and Pittsburgh, PA. Major sources of CO2 and NOx, including fossil fuel and biogenic emissions, have distinct isotopic signatures. Plant tissue incorporates atmospheric CO2 and NOx and thus reflects the isotopic signature of local emissions. Therefore, isotopic analysis of C and N in plants can be used to trace the contribution of anthropogenic and biogenic sources of CO2 and NOx to vegetation. We hypothesize that plants in urban areas will be affected by local fossil fuel sources of CO2 and NOx and will exhibit a different isotopic composition than plants grown in rural areas. An additional study examines NOx deposition near a major roadway. Previous studies have shown stationary sources, like power plants, regionally distribute NOx but mobile sources increase N deposition close to roadways. Because automobile emissions constitute ~40% of U.S. NOx emissions, it is critical to identify the fate and impact of vehicle emissions on near-road ecosystems. For this study, we will measure the isotopic composition of plant tissue and dry nitrogen deposition along a gradient perpendicular to a highway to determine vehicle nitrogen deposition and effects on vegetation.