Portable X-ray fluorescence spectrometry as a rapid and complementary approach for fecal pollution assessment in water

Field-deployable screening technologies are emerging as critical tools for water quality testing where laboratory capacity is limited. This pilot study evaluated portable X-ray fluorescence (pXRF) spectroscopy as a complementary approach for microbial water quality. Fifteen samples from surface waters and municipal wastewater were collected near Lavras, Minas Gerais, Brazil and analyzed for pH, turbidity, total coliforms and Escherichia coli , alongside elemental composition by pXRF in unfiltered water, filtered water, and particulates concentrated on filters scanned wet and after drying. Filter-based elemental fingerprints discriminated wastewater-impacted from ambient sites, whereas liquid-phase pXRF did not. Partial least squares–discriminant analysis classified samples by E. coli thresholds (≤100 vs >100 CFU 100 mL⁻¹) with 80% validation accuracy (Kappa = 0.62). P, Ca, and Fe were the strongest predictors. While not a substitute for microbiological assays, this pilot study shows that filter-based pXRF offers a rapid, field-ready screening tool to prioritize high-risk samples for confirmatory analysis in resource-limited settings.