Determination of Heavy Metal Concentrations in Roadside Soils Using X-Ray Fluorescence in Port Harcourt

Vehicular traffic and industrial emissions are known to deposit heavy metals in roadside soils, creating localized contamination that can enter food chains through dust inhalation and agricultural use. This study determines the concentrations of heavy metals including lead, zinc, copper, cadmium, iron, and nickel in roadside soils collected from six major roads in Port Harcourt, Rivers State, South South Nigeria, using energy-dispersive X-ray fluorescence spectrometry. Soil samples were collected at lateral distances of 1 m, 5 m, and 15 m from road edges to assess spatial gradients of contamination. Sample preparation followed standard digestion and pelletizing protocols, and instrument calibration was performed using certified reference materials. Measured lead concentrations at high-traffic road edges ranged from 85 mg/kg to 342 mg/kg, significantly exceeding the Dutch Intervention Value of 530 mg/kg in some locations but raising concern relative to background values. Zinc and copper showed similar elevated patterns near fuel stations and bus terminals. The geo-accumulation index and contamination factor were calculated to classify contamination severity at each sampling point. Statistical correlation between traffic density estimates and measured metal concentrations confirms vehicular exhaust and tire wear as primary contributors. The study maps contamination risk zones and recommends immediate restrictions on subsistence agriculture within 5 meters of major arterial roads. Keywords: heavy metals, X-ray fluorescence, roadside soil, Port Harcourt, contamination