Invisible Contaminants, Visible Sources: Spatiotemporal Mapping of Benzene, Toluene, and Xylene and Source Identification in Nakuru Town Groundwater, Kenya.

Urban groundwater in rapidly growing African towns is increasingly threatened by volatile organic compounds, yet forensic source apportionment remains limited. This study investigated the spatiotemporal distribution and sources of benzene, toluene, and xylene (BTX) in Nakuru town, Kenya. Water samples from 26 boreholes across diverse land-use zones were collected during the wet and dry seasons and analyzed by Headspace Solid-Phase Microextraction coupled with Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS). ArcGIS simple Kriging was used for spatiotemporal mapping, and diagnostic mass ratios toluene/benzene (T/B) and toluene/xylene (T/X) were used for source identification. Seasonal variation was observed; average concentrations surged, with xylene more than doubling from 1.368 µg/L in the wet season to 3.43 µg/L in the dry season, and toluene levels rising from a wet-season average of 0.555 µg/L to 1.383 µg/L in the dry season for positive samples. Additionally, T/X ratio analysis showed that 71.4–83.3% of calculable samples exhibited xylene-dominant signatures (T/X < 0.5). This indicates that Nakuru town’s groundwater is primarily impacted by non-petroleum sources, such as industrial solvents, municipal waste leachate, and sewage effluent, rather than solely by petroleum spills. T/B ratios, where detectable, confirmed localized fresh and weathered petroleum inputs. This study establishes a forensic framework for urban groundwater management, recommending that regulatory strategies expand beyond petroleum remediation to include stringent monitoring of industrial solvents and municipal waste discharges to safeguard vital water resources.

Benzene, Toluene, Xylene, Source Apportionment, Spatiotemporal Mapping, Diagnostic Ratios.

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