Contaminant Transport in Soil from a Point Source

Authors: S. A. Nta, M. J. Ayotamuno, A. H. Igoni, R. N. Okparanma

Abstract:

The work sought to understand the pattern of movement of contaminant from a continuous point source through soil. The soil used was sandy-loam in texture. The contaminant used was municipal solid waste landfill leachate, introduced as a point source through an entry point located at the center of top layer of the soil tank. Analyses were conducted after maturity periods of 50 and 80 days. The maximum change in chemical concentration was observed on soil samples at a radial distance of 0.25 m. Finite element approximation based model was used to assess the future prediction, management and remediation in the polluted area. The actual field data collected for the case study were used to calibrate the modeling and thus simulated the flow pattern of the pollutants through soil. MATLAB R2015a was used to visualize the flow of pollutant through the soil. Dispersion coefficient at 0.25 and 0.50 m radial distance from the point of application of leachate shows a measure of the spreading of a flowing leachate due to the nature of the soil medium, with its interconnected channels distributed at random in all directions. Surface plots of metals on soil after maturity period of 80 days shows a functional relationship between a designated dependent variable (Y), and two independent variables (X and Z). Comparison of measured and predicted profile transport along the depth after 50 and 80 days of leachate application and end of the experiment shows that there were no much difference between the predicted and measured concentrations as they were all lying close to each other. For the analysis of contaminant transport, finite difference approximation based model was very effective in assessing the future prediction, management and remediation in the polluted area. The experiment gave insight into the most likely pattern of movement of contaminant as a result of continuous percolations of the leachate on soil. This is important for contaminant movement prediction and subsequent remediation of such soils.

Keywords: Contaminant, dispersion, point or leaky source, surface plot, soil.

References:

[1] S. Renou, J. G. Givaudan, S. Poulain, F. Dirassouyan, & P. Moulin. “Landfill Leachate Treatment: Review and Opportunity”, Journal of Hazardous Materials, Vol. 150(3), (2008). pp.468-493.
[2] S. Park, K. S. Choi, K. S. Joe, W. H. Kim, & H. S. Kim, “Variations of landfill Leachate’s Properties in Conjunction with the Treatment Process”, Environmental Technology, Vol. 22, 2001, pp. 639–645.
[3] M. B. McBride, “Environmental Chemistry of Soils”, Oxford University Press, New York, (1994).
[4] M. Alexander, “Biodegradation and Bioremediation”, San Diego, Academic Press, (1999).
[5] E. D. Kristin, “Remediation of Materials with Mixed Contaminants-Treatability, Technology and Final Disposal”, Örebro University Publishers, (2009).
[6] R. Miroslav, & N. B. Vladimir, “Practical Environmental Analysis”. Royal Society of Chemistry, Thomas Graham House. Science Park. Milton Road, Cambridge CB4 OWF. UK 1998.
[7] W. L. Lindsay, & W. A. Norvell, “Development of a DTPA Soil Test for Zinc, Iron, Manganese, and Copper”. Soil Science Society of America Journal 42: 1978, pp.421-428.