Detection and variability of combustion-derived vapor in an urban basin

Details

• Journal Title:
  Atmospheric Chemistry and Physics
• Personal Author:
  Fiorella, Richard P. ; Bares, Ryan ; Lin, John C. ; Ehleringer, James R. ; Bowen, Gabriel J.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; CPO (Climate Program Office)
• Description:
  Water emitted during combustion may comprise a significant portion of ambient humidity (>  10 %) in urban areas, where combustion emissions are strongly focused in space and time. Stable water vapor isotopes can be used to apportion measured humidity values between atmospherically transported and combustion-derived water vapor, as combustion-derived vapor possesses an unusually negative deuterium excess value (d-excess, d  =  δ2H − 8δ18O). We investigated the relationship between the d-excess of atmospheric vapor, ambient CO2 concentrations, and atmospheric stability across four winters in Salt Lake City, Utah. We found a robust inverse relationship between CO2 excess above background and d-excess on sub-diurnal to seasonal timescales, which was most prominent during periods of strong atmospheric stability that occur during Salt Lake City winter. Using a Keeling-style mixing model approach, and assuming a molar ratio of H2O to CO2 in emissions of 1.5, we estimated the d-excess of combustion-derived vapor in Salt Lake City to be −179 ± 17 ‰, consistent with the upper limit of theoretical estimates. Based on this estimate, we calculate that vapor from fossil fuel combustion often represents 5–10 % of total urban humidity, with a maximum estimate of 16.7 %, consistent with prior estimates for Salt Lake City. Moreover, our analysis highlights that changes in the observed d-excess during periods of high atmospheric stability cannot be explained without a vapor source possessing a strongly negative d-excess value. Further refinements in this humidity apportionment method, most notably empirical validation of the d-excess of combustion vapor or improvements in the estimation of the background d-excess value in the absence of combustion, can yield more certain estimates of the impacts of fossil fuel combustion on urban humidity and meteorology.
• Keywords:
  Fossil fuels
• Source:
  Atmospheric Chemistry and Physics, 18, 8529–8547
• DOI:
  https://doi.org/10.5194/acp-18-8529-2018
• Document Type:
  Journal Article
• Funding:
  Grant no. NA14OAR4310178
• Place as Subject:
  Utah
• Rights Information:
  CC BY
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:f52b02c21cb12a73c55f6d14601ca2c85c798c45a579d07bf8e1005494d3e49f407b69097d2f5117ed52ed440db79bd49e88087989c4e7ffeae2d11c1ea50f21
• Download URL:
  https://repository.library.noaa.gov/view/noaa/24501/noaa_24501_DS1.pdf
• File Type:
  [PDF - 4.38 MB ]