Multi-Compartment Fate Modelling and Health Risk Characterisation of Persistent Organic Pollutants in the Kano Tannery-Dye Industrial Ecosystem, North West Nigeria

The Kano tannery and textile dyeing industrial ecosystem discharges a complex mixture of persistent organic pollutants, including polychlorinated biphenyls from dielectric fluids, polycyclic aromatic hydrocarbons from combustion, and azo dye degradation products, into a multi-compartment urban environmental system where soil, canal sediment, groundwater, air, and human exposure pathways are interconnected in ways that single-compartment studies fundamentally cannot capture. This study develops and validates an original multi-compartment environmental fate model for persistent organic pollutants in the Kano industrial ecosystem using a modified Level III fugacity model framework calibrated with site-specific physicochemical, meteorological, and hydraulic data. Primary measurement campaigns quantify persistent organic pollutant concentrations in surface water, canal sediment, soil, ambient air (particulate and vapour phases), and indoor dust from residential areas adjacent to the industrial cluster using gas chromatography-high-resolution mass spectrometry after comprehensive extraction and cleanup procedures. Seasonal model validation is performed comparing predicted and measured concentrations across all compartments for two dry season and two wet season sampling campaigns. Inter-compartment transfer fluxes quantify the dominant migration pathways governing long-term persistence and accumulation. An aggregate multi-pathway probabilistic health risk assessment, integrating inhalation, dermal, dietary (including locally grown vegetables and fish from canals), and incidental ingestion exposure routes, is conducted for adult and child receptor populations using Monte Carlo simulation with 50,000 iterations. Sensitivity analysis identifies the parameters and exposure pathways contributing most to risk uncertainty. The original theoretical contribution is a validated fugacity model parameterised for a West African industrial urban environment, substantially extending the applicability of fugacity modelling frameworks beyond temperate climate contexts. Keywords: fugacity model, persistent organic pollutants, multi-compartment fate, Kano, health risk characterisation