EMMTE: An Excel VBA tool for source apportionment of nitrate based on the stable isotope mixing model

Xu Cao; Wei He; Wei He; Yuanyuan Shi; Tongyan An; Xiange Wang; Fei Liu; Yi Zhao; Pengpeng Zhou; Cuibai Chen; Jiangtao He

doi:10.1016/j.scitotenv.2023.161728

EMMTE: An Excel VBA tool for source apportionment of nitrate based on the stable isotope mixing model

Sci Total Environ. 2023 Apr 10:868:161728. doi: 10.1016/j.scitotenv.2023.161728. Epub 2023 Jan 18.

Authors

Xu Cao¹, Wei He², Wei He³, Yuanyuan Shi², Tongyan An², Xiange Wang⁴, Fei Liu⁴, Yi Zhao⁴, Pengpeng Zhou⁴, Cuibai Chen⁴, Jiangtao He⁴

Affiliations

¹ Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing 100037, China; Ministry of Education Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, China.
² Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing 100037, China.
³ Ministry of Education Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, China. Electronic address: wei.he@cugb.edu.cn.
⁴ Ministry of Education Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, China.

PMID: 36681342
DOI: 10.1016/j.scitotenv.2023.161728

Abstract

Dual nitrate stable isotopes combined with end-member mixing models are typically used to identify nitrate sources in fields of geochemistry and environmental science, which helps to quantitively depict the geochemical behaviors of nitrate and accurately control the sources of nitrate pollution in waters. Recently, various models with different computation principles, working efficiency, and operation difficulty have been developed and applied in the source apportionment of nitrate. In this paper, an end-member mixing model tool on Excel™, namely EMMTE, has been written with Visual Basic for Application (VBA) and built into a macro-enabled Excel™ spreadsheet. Monte Carlo simulation and constraint relative deviation between the observed and the predicted values were included in the working algorithm to solve the mass balance equation. After comparison with the internationally recognized Bayesian framework (mixing stable isotope analysis in R, MixSIAR) in different cases (three practical cases and one virtual case), the preliminary results showed that the contribution of various sources to groundwater nitrate calculated by EMMTE was highly consistent with that by MixSIAR and the performance of EMMTE seemed to be as good as that of MixSIAR as indicated by the higher goodness-of-prediction, lower root-mean-square error, and lower relative deviation. Therefore, EMMTE is applicable in the source apportionment of groundwater nitrate, and might also be extended to other water bodies and mixtures. It provides a simple, feasible, and user-friendly for front-line workers without experience with MixSIAR to quantitively source apportionment of nitrate in waters.

Keywords: End-member mixing model; Excel VBA; Groundwater nitrate; MixSIAR; Source apportionment.