Correcting Laser-Based Water Stable Isotope Readings Biased by Carrier Gas Changes.
Recently, laser-based water stable isotope spectrometers have become popular as they enable previously impossible approaches of environmental observations. Consequently, they have been subjected to increasingly heterogeneous atmospheric conditions. However, there is still a severe lack of data on the impact of nonstandardized gas matrices on analyzer performances. Against this background, we investigated the influence of changing proportions of N2, O2, and CO2 in the carrier gas on the isotope measurements of a typical laser-based water stable isotope analyzer (Picarro L2120-i). We combined environmentally relevant mixtures of N2, O2, and CO2 with referenced, flash-evaporated water and found that isotope readings of the same water were altered by up to +14.57‰ for δ(18)O and -35.9‰ for δ(2)H. All tested relationships between carrier gas changes and respective isotope readings were strongly linearly correlated (R(2) > 0.99). Furthermore, an analyzer-measured variable allowed for reliable postcorrection of the biased isotope readings, which we additionally tested on field data. Our findings are of importance for environmental data obtained by analyzers based on the same technology. They are relevant for assays where inconsistent gas matrices or a mismatch in this regard between unknown and reference analyses cannot be excluded, which is in particular common when investigating the soil-vegetation-atmosphere continuum.
Institute of Groundwater Ecology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) , Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
Benjamin
B
Gralher
Hydrology, Faculty of Environment and Natural Resources, Albert Ludwig University of Freiburg , Fahnenbergplatz, 79098 Freiburg, Germany.
Barbara
B
Herbstritt
Hydrology, Faculty of Environment and Natural Resources, Albert Ludwig University of Freiburg , Fahnenbergplatz, 79098 Freiburg, Germany.
Markus
M
Weiler
Department of Geological Sciences, University of Saskatchewan , Saskatoon, Saskatchewan S7N 5E2, Canada.
Leonard I
LI
Wassenaar
Institute of Groundwater Ecology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) , Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
Christine
C
Stumpp
D002247:Carbon Isotopes; D007834:Lasers; D010103:Oxygen Isotopes; D012987:Soil; D014867:Water
D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D012987:Soil; D014867:Water