Stable-isotope ratios of hydrogen and oxygen in precipitation at Norman, Oklahoma, 1996–2008

Precipitation samples for measurement of stable-isotope ratios of hydrogen (delta²H) and oxygen (delta¹⁸O) were collected at the Norman Landfill Research Site in Norman, Oklahoma, from May 1996 to October 2008. Rainfall amounts also were measured at the site (U.S. Geological Survey gaging station 07229053) during the collection period. The delta²H of precipitation samples ranged from -121.9 to +8.3 per mil, and the delta¹⁸O of precipitation ranged from -16.96 to +0.50 per mil. The volume-weighted average values for delta²H and delta¹⁸O of precipitation over the 12-year measurement period were -31.13 per mil for delta²H and -5.57 per mil for delta¹⁸O. Average summer-season delta²H and delta¹⁸O values of precipitation usually were more positive (enriched in the heavier isotopes) than winter values.