Nitrate isotope database for meteoric waters, surface waters, soil waters, and groundwaters

This data publication includes water chemistry, nitrate isotopic values (δ15N and δ18O), apportioned amounts of unprocessed atmospheric nitrate in freshwaters, streamflow, streamflow apportioned into quick flow, and associated metadata. Data were collected from forested or predominantly forested catchments in the United States and Canada. Some samples were collected for this study or were compiled from published and unpublished studies. The compiled data are from many individual studies on more than 100 catchments measured between 1995 and 2016 from the United States and Canada. The sample types include precipitation (bulk and wet deposition), snow, snow melt, throughfall, stream water, seep water, spring water, soil water, and groundwater. While the data are freely and publicly available, we urge users to cautiously consider limitations of data. Values in this data publication were measured using several different methods (column, bacterial denitrifier, and chemical denitrifier). The absolute values of δ18O in nitrate from the column method may be inaccurate due to particular methodological steps that were used to prepare and analyze samples prior to 2003. Despite absolute errors, distinct end-members and mixed waters (when all were measured) maintain relative ranges. As such, the data from the column method before 2003 may be interpretable for some studies, while inappropriate for other data analyses and interpretations. After 2003, there was general movement to assess and correct exchange and fractionation via use of a more consistent and expansive suite of reference standards. Plus, the denitrifier methods emerged at about that time, and has effectively supplanted use of the column method and led to improved accuracy and precision in nitrate isotope studies. Future contributions of data are welcome and additional data can be added to this repository via contact with the lead author.
We measured water chemistry and isotopic tracers of nitrate sources and reanalyzed data from other studies to determine when, where, and how unprocessed atmospheric nitrate was transported in catchments. We compiled data to create a repository for nitrate isotope data from freshwaters in the USA and Canada.
Original metadata date was 02/28/2019. Metadata updated on 04/08/2019 to include information about a newly published article. On 06/24/2019 a few longitude measurements were updated in \Supplements\CatchmentInfo.csv.