i
Detection and variability of combustion-derived vapor in an urban basin
-
2018
-
-
Source: Atmospheric Chemistry and Physics, 18, 8529–8547
Details:
-
Journal Title:Atmospheric Chemistry and Physics
-
Personal Author:
-
NOAA 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:
-
Source:Atmospheric Chemistry and Physics, 18, 8529–8547
-
DOI:
-
Document Type:
-
Funding:
-
Place as Subject:
-
Rights Information:CC BY
-
Compliance:Submitted
-
Main Document Checksum:
-
Download URL:
-
File Type: