Intensive agriculture, a pesticide pathway to >100 m deep groundwater below dryland agriculture, Cordoba Pampas, Argentina

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dc.contributor.authorCabrera, Aen_AU
dc.contributor.authorCendón, DIen_AU
dc.contributor.authorAparicio, VCen_AU
dc.contributor.authorCurrell, MJen_AU
dc.date.accessioned2025-01-10T00:33:33Zen_AU
dc.date.available2025-01-10T00:33:33Zen_AU
dc.date.issued2024-11en_AU
dc.date.statistics2024-10-16en_AU
dc.description.abstractGroundwater pesticide pollution in shallow groundwater is a well-established global phenomenon. However, deep aquifers are widely thought to be naturally protected from such modern contaminants, by confining geological barriers and upwards hydraulic gradients. Here we document pervasive pesticide pollution in >100 m deep artesian wells in a sedimentary aquifer below dryland agriculture. The vertical distribution of key groundwater markers, including numbers and concentrations of pesticides, stable (δ18O & δ2H) and radioactive (3H & 14C) isotopes and ion concentrations were used to develop a conceptual model of pollutant transport to deep groundwater. Tritium, stable isotope and pesticide distributions in unconfined groundwater indicate that water table rise to <1 m below the surface (due to anthropogenic landscape modification and periodic flooding), has created a rapid pollutant ‘doorway’ to groundwater. Despite a lack of deep borehole pumping for irrigation, these rising water tables have permanently inverted previously upward hydraulic gradients towards the underlying semi-confined aquifer in some areas. Physical heterogeneities and/or leaky domestic boreholes then act as preferential transport avenues for surface pollutants to both unconfined and semi-confined groundwater. These pathways allow small aliquots of highly contaminated surface water and modern unconfined groundwater to mix with the pre-existing pre-modern deep groundwater, resulting in mixed isotopic signatures in deep wells (e.g., radiocarbon <5 pMC but detectable tritium) and detections of multiple synthetic pesticides in the deep aquifer, including AMPA at concentrations up to 4.93 µg/L and Metolachlor up to 0.015 µg/L. Our results demonstrate how semi-confined deep groundwaters may be contaminated by current agricultural techniques even where deep groundwater exploitation is limited. We urge measures to eliminate these pollutant pathways. © 2024 The Authors. Published by Elsevier B.V. Open Access.en_AU
dc.identifier.articlenumber131989en_AU
dc.identifier.citationCabrera, A., Cendón, D. I., Aparicio, V., & Currell, M. J. (2024). Intensive agriculture, a pesticide pathway to >100 m deep groundwater below dryland agriculture, Cordoba Pampas, Argentina. Journal of Hydrology, 643, 131989. doi:10.1016/j.jhydrol.2024.131989en_AU
dc.identifier.issn0022-1694en_AU
dc.identifier.journaltitleJournal of Hydrologyen_AU
dc.identifier.urihttps://doi.org/10.1016/j.jhydrol.2024.131989en_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15889en_AU
dc.identifier.volume646en_AU
dc.languageEnglishen_AU
dc.language.isoenen_AU
dc.publisherElsevier BVen_AU
dc.subjectAgricultureen_AU
dc.subjectGroundwater rechargeen_AU
dc.subjectPesticidesen_AU
dc.subjectArgentinaen_AU
dc.subjectPollutionen_AU
dc.subjectHydraulicsen_AU
dc.subjectAquifersen_AU
dc.subjectIsotopesen_AU
dc.subjectIonsen_AU
dc.subjectTritiumen_AU
dc.subjectStable isotopesen_AU
dc.subjectMoleculesen_AU
dc.subjectContaminationen_AU
dc.subjectWaterfloodingen_AU
dc.titleIntensive agriculture, a pesticide pathway to >100 m deep groundwater below dryland agriculture, Cordoba Pampas, Argentinaen_AU
dc.typeJournal Articleen_AU
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