Developing the soil pollution potential as an environmental management cost estimation index for washing inorganic pollutants from soils
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This study investigated the concept of the Soil Pollution Potential (SPP), a concept analogous to the Global Warming Potential used to compare various chemicals during Life Cycle Analysis of industrial projects. The objective of the study was to identify a reference soil pollution scenario and a reference inorganic soil pollutant that provide the basis for calculating Soil Pollution Potentials for a wide range of soil pollution scenarios. The reference inorganic soil pollutant has been identified as Aluminium and a reference soil pollution scenario is also described in this dissertation, proving the hypothesis that such a reference pollutant could be identified through the use of statistical analysis of resulting modelling data for a wide range of parameter values. The reference pollutant was identified through a statistical evaluation of the model simulation time required to simulate the remediation of the soil profile. It was found that lower diffusion coefficients resulted in more time required, effectively limiting mass transfer in the soil profile. A regression equation was developed that simplifies the calculation of SPP values, reducing the need for complex numerical modelling. The regression equation describes approximately 96% of the variation found in the modelling data and is considered sufficiently accurate. A simpler form of the regression equation was also derived exhibiting a R2 of approximately 0.87. This dissertation also provides a simple equation to calculate the volume of flushing water required to remediate polluted soil profiles in other soil pollution scenarios within the parameter value ranges identified in this study. It is possible to repeat this study, but focussing on organic pollutants in the soil profile. Azelate has been identified as a possible candidate reference organic pollutant based on a similar diffusion coefficient in water as compared to that of Aluminium. A similar approach has been followed by ICI using Environmental Quality Standards and toxicity characteristics of Copper and Formaldehyde in the aquatic environment to select inorganic and organic reference chemicals. Such an organic reference will provide an important link in the SPP continuum and should be further investigated. This study has clearly and conceptually illustrated how the SPP can be used as an environmental management cost estimation index for different soil washing (flushing) scenarios. A generic equation for relative cost (cost index) was derived. Finally, SPP values were found to range from 9.81E-06 to 9.67 for the parameter values in this study, with an associated water cost ranging from R0.00 to R145.00 per m3 at an assumed cost of R3.00 per m3. Published soil flushing cost (water and operation of equipment) was found to range from R140.00 to R1400.00 per m3 of soil (year 2004); it appears less expensive than the published cost of soil washing. Furthermore does it appears that the cost of water accounts for approximately 10% of the published cost of soil flushing, but further investigation is required in future to confirm this.
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