International Journal of Environmental Science and Development

Abstract—In this study, a dual stable isotope approach and a Bayesian isotope mixing model (SIAR model) were applied to estimate the proportional contributions of multiple NO₃ ^- sources to shallow groundwater. The concentration of groundwater NO₃ ^- ranged widely from 5.7 to 26.2 mg/L, with the δ¹⁵N values changed from 7.1 to 11.3‰ and the δ¹⁸O values varied from 5.4 to 11.6‰. According to the classical dual isotope bi-plot, manure and sewage (M&S), soil N (Soil), NO₃ ^- in chemical fertilizer (NF), NH4 + in chemical fertilizer and precipitation (NP) were identified as the four potential NO3 - sources to groundwater. And the outputs of SIAR model showed some variability in the contribution of each NO₃ ^- source. "Soil" contributed the most (between 21% and 70%), followed by "NF" (between15% and 45%), "M&S" (between 4% and 39%), "NP" (between 0% and 20%). The SIAR model showed be considered as a reliable approach to quantify the proportional contributions of multiple NO₃ ^- sources in the mixture.

Index Terms—Dual stable isotopes, shallow groundwater, proportional contributions of NO3 - sources, SIAR model.

Wen Xu, Yanpeng Cai, and Yan Xu are with the School of Environment, Beijing Normal University, China (e-mail: xuwen8971@163.com, yanpeng.cai@bnu.edu.cn).
Qian Tan is with the Institute for Energy, Environment and Sustainable Communities, University of Regina, Canada.

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Cite: Wen Xu, Yanpeng Cai, Qian Tan, and Yan Xu, "Estimating the Proportional Contributions of Multiple Nitrate Sources in Shallow Groundwater with a Bayesian Isotope Mixing Model," International Journal of Environmental Science and Development vol. 7, no. 8, pp. 581-585, 2016.