The spatial coverage of nitrate d15N and d18O measurements in the marine environment is limited. Inclusion of these isotopes as key parameters in the upcoming GEOTRACES program provides a unique opportunity to collect and analyze numerous samples from the world ocean's and further our understanding of the spatial gradients in nitrate isotopes and the processes they record. However, during this program, different laboratories from around the world would utilize their own sampling, preservation, analysis, and calibration techniques to measure these isotopes. To avoid the potential for analytical offsets due to differences in any of these components, a scientist from Woods Hole Oceanographic Institution has assembled an impressive group of national and international laboratories to participate in the upcoming GEOTRACES intercalibration effort. During the GEOTRACES intercalibration cruises in summer 2008 and 2009, different sample collection and preservation tests would be evaluated, a variety of intercalibration samples that span the natural range of nitrate concentration and d15N in seawater would be analyzed, the nitrate isotope ratio would be determined, and the results evaluated to ascertain that consistent analytical results are obtained amongst the participants in the intercalibration effort.
In terms of broader impacts, a protocol for the collection, storage, analysis, and calibration of seawater nitrate isotopes would be established and made available to the science community.
