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Evaluation of partitioning coefficients for South African soils to inform the national framework for the management of contaminated land with emphasis on the protection of water resources
Expanded Title:Appropriate screening of contaminated land is imperative to the registration of contaminated land and has significant implications for industry, government and the environment. Inappropriate screening during initial investigations will result in some constituents and sites being screened for further detailed assessment and registered as contaminated land when in actual fact it could be naturally occurring soil concentrations. On the other hand, some constituents and sites that pose a potential risk may appear uncontaminated while further investigation is actually warranted. A high degree of uncertainty therefore exists in screening soils for further assessment and registration as contaminated land. The aim of this study was to address a number of uncertainties and to assist in refining the norms and standards for the assessment of contaminated land. Following the results obtained from this investigation, the following is recommended: • The 1:2.5 soil:solution ratio extract be used to estimate the pore water quality of soil. This is also the standard method used for the determination of soil pH(H2O) (a very important parameter that must be consider in any case) and therefore considered as an acceptable method and easily implementable by commercial laboratories; • Based on the Kds determined in this study for 10 different diagnostic South African soils horizons, preliminary additional soil screening values could be calculated which is specific for certain soil types. However, the SA baseline concentrations for natural soils were also considered. Based on these calculations, soil types were grouped together and preliminary risk based soil screening values (RBSSV) were established which can be used during Phase 1 contaminated land assessments; • During Phase 2 contaminated land assessments, where more information will be available on soil type and properties, the Kds can be used to further refine the soil screening values for specific soil types/horizons. Vertic soils, red oxidic soils with high clay content, melanic soils and gley soils can have higher soil screening values for Cu and Pb, since these soils have a strong sorption capacity and the risk for groundwater contamination will be less; • The Kds determined during this investigation showed a strong correlation with soil pH and therefore, soil pH can be used to refine the Phase 2 soil screening values. Preliminary recommended pH specific SSV (pH-SSV) for Cu, Pb and V were calculated which can be used during Phase 2 contaminated land assessments; • The potential risk that a contaminant may pose to groundwater can be assessed by determining the soluble fraction of the contaminant in the soil. A 1:2.5 deionised water extract can be conducted on soil samples during the Phase 1 screening level assessment and the results can be compared to the Water Quality Guidelines for the specific contaminant to indicate potential risk for groundwater contamination.
Date Published:01/05/2013
Document Type:Research Report
Document Keywords:Ground Water, Water Quality
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:2102/1/13
ISBN No:978-1-4312-0415-1
Authors:Herselman JE; Papenfus M; Steyn CE; De Jager PC; Tesfamariam EH
Project No:K5/2102
Originator:WRC
Organizations:Golder Associates (Pty) Ltd; University of Pretoria
Document Size:2 113 KB
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