Rapid Determination of Nitrate Nitrogen Isotope in Water Using Fourier Transform Infrared Attenuated Total Reflectance Spectroscopy (FTIR-ATR) Coupled with Deconvolution Algorithm

Nitrate is a prominent pollutant in water bodies around the world. The isotopes in nitrate provide an effective approach to trace the sources and transformations of nitrate in water bodies. However, determination of isotopic composition by conventional analytical techniques is time-consuming, laborious, and expensive, and alternative methods are urgently needed. In this study, the rapid determination of NO in water bodies using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) coupled with a deconvolution algorithm and a partial least squares regression ( ) model was explored. The results indicated that the characteristic peaks of NO / NO mixtures with varied N/ N ratios were observed, and the proportion of NO was negatively correlated with the wavenumber of absorption peaks. The models for nitrate prediction of NO / NO mixtures with different proportions were established based on deconvoluted spectra, which exhibited good performance with the ratio of prediction to deviation ( ) values of more than 2.0 and the correlation coefficients ( ) of more than 0.84. Overall, the spectra pretreatment by the deconvolution algorithm dramatically improved the prediction models. Therefore, FTIR-ATR combined with deconvolution and provided a rapid, simple, and affordable method for determination of NO content in water bodies, which would facilitate and enhance the study of nitrate sources and water environment quality management.