Institute of Ecosystem Studies

2007 BES Annual Meeting Presentation and Poster Abstracts

Isotopic investigation of anthropogenic sources of atmospheric nitrogen and carbon to vegetation along an urban to rural gradient
Middlecamp, Katherine
Co-Authors: Katherine Middlecamp1, Emily M. Elliott1, John Hom2 1. Department of Geology & Planetary Science, University of Pittsburgh 2. Northern Global Change Research Program, U.S. Forest Service
Abstract: Although urban areas are key contributors to atmospheric CO2, a major greenhouse gas, and NOx, a precursor to acid rain and smog, little is known about how urban ecosystems compensate for higher local CO2 and NOx emissions. This research will examine the role of urban vegetation as a sink for atmospheric C and N by using stable isotope analysis of plant tissue along the Baltimore Ecosystem Study urban to rural gradient. Plant tissue is known to incorporate atmospheric CO2 and Nox and thus reflects the isotopic composition of local emissions sources. In this study, we will measure d15N and d13C of plant tissue and ambient CO2 and NOx along the gradient and in multiple CO2 and NOx sources. We hypothesize that in rural areas the NOx and CO2 source will be primarily biogenic and soil processes while in urban locations it will originate from fossil fuel combustion. Plant tissue should reflect the distinct isotope signatures of these sources. In addition, we will use plant tissue to examine contributions of stationary and mobile sources of atmospheric NOx from fossil fuel combustion. Previous studies have shown stationary sources regionally distribute NOx, but mobile sources can increase N deposition in the immediate vicinity of roadways. Because automobile emissions account for ~40% of U.S. NOx emissions, it is critical to identify their fate. We will measure the isotopic composition of plant tissue and dry nitrogen deposition along a short gradient perpendicular to the roadway to determine local vehicle NOx deposition and effects on vegetation.