GIS-Based Spatial Vulnerability and Environmental Risk Assessment of Industrial Wastewater Discharges on Urban Communities in Benin City, Nigeria. 

Rapid urban expansion in Benin City, Nigeria has significantly increased the volume of untreated wastewater discharges from industries, threatening urban infrastructure, public health and receiving ecological systems. Despite regulatory guidelines established by the National Environmental Standards and Regulation Enforcement Agency (NESREA), compliance remains critically inconsistent and a comprehensive spatial assessment of pollution vulnerability remains limited. This study aimed to assess the physicochemical quality of industrial effluents and to develop a GIS-based spatial vulnerability model that maps pollution hotspots and evaluates environmental risk severity across Benin City. Wastewater samples were collected from 14 geo-referenced industrial points (Agricultural, Bakery, Carbonated Soft Drink and Textile) and analysed for heavy metals (Pb, Zn, Cu, Cd, Cr, Fe), Chemical Oxygen Demand (COD), chlorides and other parameters (pH, EC, TDS, nitrate, sulfate) using standard laboratory procedures. A Composite Wastewater Pollution Index (WWPI) was calculated and spatial distribution was modeled using Inverse Distance Weighting (IDW) and Kriging. Findings reveal gross non-compliance with NESREA limits across all sectors. The Bakery industry presented the most extreme contamination, recording peak COD levels of 5125 mg/l and chloride concentrations of 12101 mg/l. The Textile sector exhibited severe alkaline discharge (pH 9.5) and significant heavy metal loading, while Agricultural effluents recorded toxic zinc concentrations reaching 0.874 mg/l. Spatial modeling revealed distinct contamination behaviors; IDW mapping demonstrated a highly localized, extreme organic pollution spike isolated at the bakery source, whereas Kriging indicated a broader, more diffused regional spread of Lead (Pb) across the central-northern industrial cluster. This study provides the first GIS-based spatial vulnerability assessment of industrial wastewater pollution in Benin City, showing widespread non-compliance and identifying high-risk zones requiring urgent intervention. It underscores the need to integrate spatial mapping with environmental quality data, providing regulatory agencies with a precise, targeted framework to enforce Effluent Treatment Plant (ETP) adoption, mitigate urban exposure to heavy metals, and safeguard public health.