Environmental pollution (Barking, Essex : 1987) ·12 Nov 2026 ·Added 13 Nov 2026

The deeper, the more protected? Shallow soils and fractured aquifers override depth-based protection against progesterone contamination in groundwater: evidence from an agro-intensive region of southern Brazil (Santa Catarina).

Raquel de Brito, Emanuel Rampanelli Cararo, Lucilene Bergman, Eduarda Camara Sangiogo, Bárbara Lopes Körner, Adilson Pinheiro, Jacir Dal Magro, Renan de Souza Rezende

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Abstract

Steroid hormones are increasingly recognized as environmentally relevant contaminants due to their endocrine-disrupting effects at trace concentrations, yet their occurrence in deep groundwater remains poorly characterized, particularly in fractured aquifer systems. Here, we investigated the occurrence and environmental controls of progesterone in surface waters and deep groundwater (100-282 m) across an agro-intensive landscape in southern Brazil characterized by shallow soils and fractured basaltic aquifers. Progesterone was quantified by solid-phase extraction coupled with gas chromatography-mass spectrometry in selected ion monitoring mode (SPE-GC-MS/SIM). The hormone was detected in 41 of 72 samples (57%), with comparable mean concentrations in surface water (0.31 μg L-1) and groundwater (0.34 μg L-1) and a maximum of 1.32 μg L-1 in a 222-m-deep well. Mixed models showed that progesterone occurrence and concentrations were not explained by well depth or by individual physicochemical or socioeconomic predictors. Instead, multivariate analyses associated progesterone distribution with the convergence of shallow, weakly developed soils and pasture-dominated land use, indicating that surface-groundwater connectivity is mediated by preferential flow in fractured bedrock and limited attenuation in the vadose zone. The wells sampled supply public drinking water, and the concentrations measured exceed by one to two orders of magnitude those reported to alter gene transcription in aquatic organisms. Our findings challenge depth-based assumptions of groundwater protection and support vulnerability-oriented monitoring frameworks that incorporate endocrine-disrupting compounds in agroecosystems underlain by structurally connected aquifers.