Adaptive Kalman Filtering Scheme For The Simulation Of Benzene In Subsurface Environment

Environmental legislation in several states has become more stringent on the clean up procedures for benzene and other toxic chemicals since the enactment of the Comprehensive Environmental Response, Compensation, and Liability Act (Superfund). In order to comply with the Superfund requirements for hazardous pollutants, accurate information about the nature of contaminants is required to carry out risk assessment and effective site remediation. The use of subsurface contaminant transport models, coupled with stochastic data assimilation schemes, can provide accurate predictions of contaminant transport to enhance the reliability of risk assessment in the area of environmental remediation. In this study, a two-dimensional deterministic model was used to simulate the advective and diffusive transport of benzene in the subsurface. A robust Adaptive Kalman Filter (AKF) has been constructed as a stochastic data assimilation scheme to improve the prediction of the benzene contaminant plume. The AKF has been proposed to improve the performance of the conventional Kalman Filter (KF) by reducing the uncertainties associated with the process and observation noise statistics. The impact of the adaptive filter on the KF performance was examined by comparing model predictions with a simulated true field which was created by introducing some random Gaussian noise into an observation model. The simulation results indicated an improvement in filter performance after the implementation of the adaptive Kalman filter scheme. Although the Kalman filter was successful in reducing the prediction error of the deterministic model from 5.0 mg/L to 1.1 mg/L at the end of the simulation period, the introduction of the AKF scheme further improved the prediction accuracy of the KF by about 18%. In all, the AKF scheme successfully improved the prediction accuracy of the deterministic model by about 82%. Furthermore, the results of sensitivity test suggest that for the AKF under consideration, using a window size of five can give a much improved accuracy and stability

Review on the Fate of Contaminants in the Niger Delta Environment

Niger Delta environment had suffered from impacts of waste over the years. The significant wastes in the region are crude oil and municipal wastes. Studies have shown the effect and fate of contaminants in the environment and human life. This paper reviews the impact and fate of contaminants in the Niger Delta environment with the focus on crude oil waste and municipal waste. The substantial quantities of waste generated resulted from unreasonable consumption and production, non-compliance to environmental laws and regulations, migration to urban cities, and sporadic expansion of unregulated industrial operations. These contaminants affect various life forms, natural resources, and increase the rate of global warming. It is of urgent importance for concerted efforts from corporate bodies, government, and individuals to ensure proper implementation of effective, safe management of waste. This review used Niger Delta environmental contaminant analysis and remediation case studies to highlight the fate of organic and inorganic contaminants and their associated adverse effects on the environment. This review contains secondary data from online journal articles, radio, symposium, doctoral thesis, organisations, and websites. Keywords: Crude oil, Heavy hydrocarbons, Spills, Dumpsite, Pesticides, Fate, contaminants, Toxic, Degradation. DOI: 10.7176/JEES/10-5-05 Publication date:May 31st 202

Characterization of Soil and Sediment Parameters of Jisike-Izombe Upper Aquifer System for Assessment of the Potential of Groundwater Pollution

The JES field, an onshore field in the Jisike – Izombe area of southeastern Nigeria had a number of oil-producing wells before it was abandoned over a decade ago. By means of soil/sediment samples retrieved from three strategically located boreholes around the field, the subsurface units were delineated and the physical characteristics of the vadose zone were determined in order to predict the groundwater pollution potential of the upper aquifer system in the area. Ground conditions were found to be approximately 1metre (3.043ft) of loamy top soil overlying about 1.2metres (3.65ft) of clayey laterite which overlies 19.4 – 24.6metres i.e (60ft – 75ft) of reddish-brown silty sand, beneath which is medium – coarse grained white sand which constitutes the aquifer system with estimated hydraulic conductivity in the range 1 x 10-1 to 169 x 10-1 mm/sec. Flow analysis of groundwater indicates a southwesterly flow with the River Niger as possible discharge zone. The high leaching potentials and high transmissive properties of the sediments below the clayey laterite suggests a vulnerability of the aquifer to pollution through vertical infiltration. However, borehole water quality parameters for the area show that groundwater quality is not in anyway compromised when compared to the WHO limits. Rather, it is argued that the groundwater is naturally well protected by the upper part of the vadose zone where the clayey lateritic soil with iron oxide cementation of soil particles provides an appreciable degree of barrier to downward movement of contaminants. Because of the clayey behavour of the near-surface soils and their affinity for the retention of contaminants, it is concluded that the area is not a locus of groundwater pollution. © JASE