Supplementary material to "A novel analytical approach for the simultaneous measurement of nitrate and DOC in soil water"

In this paper, we present a novel approach, enabling the measurement of nitrate concentrations in natural 10 soil porewater containing natural soil dissolved organic carbon (DOC). The method is based on UV absorbance spectroscopy, combined with fluorescence spectroscopy, for simultaneous analysis of DOC and nitrate concentrations. The analytical procedure involves deduction of the absorption caused by the DOC from the total absorbance in the UV range that is attributed to both DOC and nitrate in the water solution. The analytical concept has been successfully tested in soil water samples obtained from five agricultural sites, as well as in water samples 15 obtained from a commercial hummus soil mixture. We believe that the new analytical concept can provide a scientific foundation for developing a sensor for real-time nitrate concentration measurements in agricultural soils. As such, it can play a significant role in reducing nitrate pollution in water resources, optimizing input application in agriculture, and decreasing food production costs. 20 https://doi.org/10.5194/hess-2020-417 Preprint. Discussion started: 10 September 2020 c © Author(s) 2020. CC BY 4.0 License.