WRC studies shed light on groundwater polluting chemicals

Abstract

Groundwater pollution Dense non-aqueous phase liquids (DNAPLs) are chemicals or mixtures of chemicals that are heavier than water, and are only slightly soluble in water. This means that when released into the environment in sufficient quantities, they can move through soils and groundwater until they encounter an impermeable layer that will impede further mass vertical movement and allow the liquid to pool or move along the dip of an impermeable layer or within a fracture. DNAPLs have thus the potential to move in the opposite direction to that of the localised groundwater flow direction. Contamination with DNAPLs is a worldwide phenomenon, but to date there has been limited awareness and understanding of the problem locally. There are thousands of potential sites in South Africa, as elsewhere in the world, were DNAPLs may have been released to the subsurface in varying quantities. Examples include chlorinated solvents (degreasers and dry-cleaning fluids), creosote, coal tar, and polychlorinated biphenyls (as found in dielectric oils, for example).

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