HR: 1340h
AN: B13B-1198    [Abstracts]
TI: The isotopic composition of urban plants as indicators of the distribution of air pollution in the Los Angeles Basin
AU: * Wang, W
EM: wenwenw@uci.edu
AF: University of California, Irvine, Croul Hall, Irvine, CA 92691-3100, United States
AU: Pataki, D E
EM: dpataki@ucui.edu
AF: University of California, Irvine, Croul Hall, Irvine, CA 92691-3100, United States
AB: Many isotopes in plant biomass reflect either the isotopic composition of the physical environment or the biological responses of plants to their environment. Therefore, spatial variability in the isotopic composition of urban plants has great potential to provide information about the urban environment and its effect on plants and other organisms. We intensively sampled winter annual plants around the Los Angeles Basin in 2004 and 2005 and mapped their stable and radiocarbon isotopic composition (13C, 14C, 15N, 18O). Radiocarbon (14C), which is present in naturally-derived atmospheric carbon dioxide (CO2) but absent from fossil fuel-derived CO2, was most depleted in plants collected in downtown Los Angeles and enriched at greater distances from the urban center. The spatial pattern of plant radiocarbon was similar to the spatial pattern of carbon monoxide (CO), indicating similar combustion-related pollution sources. Stable carbon isotopes showed a similar trend, although with greater spatial variability, indicative of the many factors that influence photosynthetic fractionation. Stable nitrogen isotopes, on the other hand, were highly enriched along the urban coast and became depleted with increasing elevation and distance from the coast. Maps of NOx concentrations revealed an overlap between locations of 15N enrichment and high NOx emissions. In addition, enriched marine sources near the coast likely contributed to plant enrichment. In contrast, oxygen isotopes were most enriched in the hottest inland areas as a function of greater evaporative demand. Generally speaking, spatial patterns in all four isotopes corresponded to spatial patterns of climate and/or air pollutant concentrations and gradients of urbanization. Plants appear to serve as very useful biomonitors of environmental conditions in urbanized and polluted regions.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0493 Urban systems
SC: Biogeosciences [B]
MN: 2007 Fall Meeting