Geospatial Analysis and Physicochemical Assessment of Groundwater Quality Vulnerability to Municipal Solid Waste from Landfills

Abstract

This study aims to find a more realistic management approach to Municipal solid waste (MSW), focusing on Ndokwa West LGA, Delta State, Nigeria. It employs a combination of geospatial analyses and laboratory examination of water samples from three borehole locations congruent to landfills in the study area. GPS-measured positions of the five landfill sites were plotted on the topographic plan of the study area and analysed. This landfills’ location, which is the southeastern part of the area, is a lowland. By hydraulic gradient and flow pattern of the area deducted from DEM, these landfills are within the pathway of major groundwater resources. Proximity analyses with 5 to 10 km buffer zones show that most of the topographic features are at risk of considerable pollution due to landfill’s leachate into the surrounding area. Groundwater vulnerability map shows 21.5% of the studied area at a high risk of contamination, 7.5% at medium, and ~71% at low risk. The Dissolved Oxygen (DO) levels from the three boreholes were significant, suggesting severe pollution, and pointing to the landfill as the main cause. Colour showed an unobjectionable state and signified pollution of the wells. Temperature (0°C) ranged from 20 to 26°C, much higher than the 5°C limit, set by the WHO and NSDWQ. The water pH ranges from 6.05 to 7.02, suggesting traces of heavy metals in water samples. Nitrate and nitrite have values ranging from 5.0 to 6.162 and 0.251 to 0.455 mg/l, suggesting the water samples contain some contaminants. Lead (Pb) (from 0.25 to 0.65 mg/l) is practically beyond the WHO and NSDWQ permissible limits for heavy metals. The accumulation of lead in landfills has substantial effects on groundwater pollution. The Heavy Metal Index Calculation scale rated the result of heavy metals analyses as ‘VI,’ representing a ‘Seriously Affected’ water supply system.