356-8 Isotope tracers with emerging organic compounds to elucidate the anthropogenic impact on groundwater quality

Abstract:

This communication presents an approach integrating environmental and hydrologic isotope tracers (δ¹⁸O_H2O, δ²H_H2O, δ¹⁵N_NO3, δ¹⁸O_NO3, and δ¹¹B) with emerging organic compounds (EOCs) to acquire an enhanced understanding of the anthropogenic impact on groundwater quality. This multi-tracer approach is applied to a Mediterranean aquifer underlying a strategic agricultural area affected by various anthropogenic stressors and random urban development. In this study, the measured nitrate concentrations in water samples revealed high concentrations of up to 180 mg/L indicating an anthropogenic-based contamination. By combining the results of the analyzed isotope tracers δ¹⁵N_NO3 and δ¹¹B, nitrate is found to be mainly sourced from manure that is used on agricultural fields. There was no isotope evidence that nitrate was sourced from inorganic fertilizers or human wastes. However, some EOCs of human origin were detected in groundwater and surface water samples with concentrations >10 ng/L, suggesting contamination spread via possible groundwater-surface water interaction, which was supported by observation from δ¹⁸O_H2O and δ²H_H2O values. In this study, bisphenol A was detected in all water samples with high concentrations of up to 123,000 ng/L in groundwater. This indicates the impact of plastic-derived contamination, which is suspected to originate from discharged urban wastewater, from contaminated leachate derived from a neighbouring landfill, or derived from plastic pipes used during irrigation activities. This study highlights the integration of common environmental isotope tracers with EOCs as an effective method for investigating the anthropogenic impact on groundwater quality.

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