CO2 in Breath as a Short-Term Record of Geographic Movement

O'GRADY, SHANNON P; REMIEN, CHRISTOPHER H; ENRIGHT, LINDSEY E; VALENZUELA, LUCIANO O; CHESSON, LESLEY A; PODLESAK, DAVE; CERLING, THURE E; EHLERINGER, JAMES R

Conferencia; Forensics Isotope Ratio Mass Spectrometry Conference; 2010

Stable isotope ratios in biological materials can yield information about movement and migratory patterns in animals, including humans. The isotopic composition of tissues such as bone, hair and teeth offer a long-term record of that movement, while analyses of breath CO2 potentially provide a more short-term record of movement. In order to correctly interpret movement patterns relayed by breath CO2, it is essential to know the rapid turnover rate of the 18O isotope ratio of CO2 in breath. To simulate geographic movement across a gradient in the isotope ratios of water, we raised rats on three isotopically distinct waters and then, upon adulthood, performed a water switch. The waters used were depleted 18O, depleted 2H (DD); depleted 18O, enriched 2H (DE); and enriched 18O, enriched 2H (EE). The water switch covered both the heavy-to-light and light-to-heavy isotope transitions. We measured the isotopic composition of CO2 in breath for four weeks following the water switch. The Cerling et al. reaction progress method adequately describes the turnover of CO2 in breath. Based on these observations, the isotope ratio signal of the previous environment can be detected for several days if the differences in the isotope ratios of water in the two environments are sufficiently different.