Simulation of Transient Nitrate Contaminant Transportation in Open Municipal Dumpsite into Shallow Terrace Alluvium Aquifer of the Ogwashi-Asaba Formation, Niger Delta, Nigeria

Contaminant transport in groundwater poses significant risks to human health and ecosystems. Hence, the objective of this paper is to utilize the three-dimensional multi-species solute transport model (MT3DMS) computer programme to simulate nitrate contaminant transportation in open municipal dumpsite into shallow terrace alluvium aquifer of the Ogwashi-Asaba Formation, Niger Delta, Nigeria. Results show a spread of plume with depth and distance after 3650 days with concentrations of nitrate observed to have increased with distance from the source over time. The highest concentrations of each soil type beneath the dumpsite were observed at the following distances from the plume: laterite: 88.8 mg/l at 0 - 2.5 m; fine sand: 18.5 mg/l at 40.6 m; coarse sand: 0.85 mg/l at 274.9 m and clayey sand: 0.70 mg/l at 330 m. This is adduced to the laterites underneath the dumpsite acting as a secondary source of contamination as it slowly releases contaminants into the aquifer beneath and gives rise to contaminant plumes that lingers for long term. This research provides a reliable numeric model for spatial and temporal contaminant transport and ultimately crucial for monitoring, managing and evaluation of risk to this resource.