Stable isotope ratio data are useful in understanding biosphere-atmosphere fluxes and the roles of different sources contributing to these fluxes. The carbon isotope ratio data are useful in understanding aspects of the carbon cycle, while oxygen isotope ratios provide information about the vegetation and the water cycle.

Presented here are long-term observations of the carbon and oxygen isotope ratios and concentrations of atmospheric carbon dioxide measured in an urban setting. These data These Salt Lake City observations were made on the roof of a 4-story building at the University of Utah campus (latitude 40.76348 degrees north, longitude -111.84834 degrees west, 1820 meters elevation). Current carbon dioxide concentration data streams can be obtained online at http://air.utah.edu.

These methods used in data collection, data analyses, and quality control can be found in the following publications:

Pataki, D. E., D. R. Bowling, and J. R. Ehleringer (2003), Seasonal cycle of carbon dioxide and its isotopic composition in an urban atmosphere: Anthropogenic and biogenic effects, Journal of Geophysical Research-Atmospheres, 108(D23).

Pataki, D. E., T. Xu, Y. Q. Luo, and J. R. Ehleringer (2007), Inferring biogenic and anthropogenic carbon dioxide sources across an urban to rural gradient, Oecologia, 152(2), 307–322.

These data are used in the following publication:
B. Raczka, S. C. Biraud, J. R. Ehleringer, C. Lai, J. B. Miller, D. E. Pataki, S. Saleska, M. S. Torn, B. H. Vaughn, R. Wehr, D. R. Bowling. 2017. Does vapor pressure deficit drive the seasonality of δ13C of the net land-atmosphere CO2 exchange across the United States? Journal of Geophysical Research Biogeosciences

All stable isotope ratio analyses were conducted at Utah’s Stable Isotope Ratio Facility for Environmental Research (SIRFER, http://sirfer.utah.edu).

The carbon dioxide concentration data are presented as parts per million (ppm). The carbon isotope ratio of atmospheric carbon dioxide are presented as per mil relative to the PDB international standard. The oxygen isotope ratio of atmospheric carbon dioxide are presented as per mil relative to the SMOW international standard.

Data flag information:

Flag1
-2, discard for 18O only
-1, discard for 13C only
0, good data
1, low pressure - suspect
2, bad fill suspected
3, low pressure - discard
4, bad fill - discard
5, discard other (use if both -1 and -2 apply)
6, suspect other (bad run on the mass spec)

Flag2
1, morning rush hour
2, evening rush hour
3, nighttime
4, diurnal