Articles | Volume 21, issue 7
Hydrol. Earth Syst. Sci., 21, 3799–3810, 2017
Hydrol. Earth Syst. Sci., 21, 3799–3810, 2017

Research article 25 Jul 2017

Research article | 25 Jul 2017

Every apple has a voice: using stable isotopes to teach about food sourcing and the water cycle

Erik Oerter1,2,4, Molly Malone3, Annie Putman1,2, Dina Drits-Esser3, Louisa Stark3, and Gabriel Bowen1,2 Erik Oerter et al.
  • 1Department of Geology and Geophysics, University of Utah, 115 South 1460 East, Salt Lake City, UT 84112, USA
  • 2Global Change and Sustainability Center, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA
  • 3Genetic Science Learning Center, University of Utah, 515 100 South, Salt Lake City, UT 84112, USA
  • 4Current address: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA

Abstract. Agricultural crops such as fruits take up irrigation and meteoric water and incorporate it into their tissue (fruit water) during growth, and the geographic origin of a fruit may be traced by comparing the H and O stable isotope composition (δ2H and δ18O values) of fruit water to the global geospatial distribution of H and O stable isotopes in precipitation. This connection between common fruits and the global water cycle provides an access point to connect with a variety of demographic groups to educate about isotope hydrology and the water cycle. Within the context of a 1-day outreach activity designed for a wide spectrum of participants (high school students, undergraduate students, high school science teachers) we developed introductory lecture materials, in-class participatory demonstrations of fruit water isotopic measurement in real time, and a computer lab exercise to couple actual fruit water isotope data with open-source online geospatial analysis software. We assessed learning outcomes with pre- and post-tests tied to learning objectives, as well as participant feedback surveys. Results indicate that this outreach activity provided effective lessons on the basics of stable isotope hydrology and the water cycle. However, the computer lab exercise needs to be more specifically tailored to the abilities of each participant group. This pilot study provides a foundation for further development of outreach materials that can effectively engage a range of participant groups in learning about the water cycle and the ways in which humans modify the water cycle through agricultural activity.

Short summary
Fruits take up soil water as they grow, and thus the fruit water is related to the rain or irrigation the crop receives. We used a novel sampling system to measure the stable isotopes of H and O in the fruit water to determine its geographic origin by comparing it to maps of isotopes in rain. We used this approach to teach an audience of science students and teachers about water cycle concepts and how humans may modify the water cycle through agriculture and irrigation water diversions.