IMPORTANCE OF MINERALS TO ENVIRONMENTAL SCIENCE

Mineralogy is a foreign discipline to many environmental professionals, yet the behavior and characteristics of minerals are an integral part of all remediation of contaminated soils and groundwater. In general, the influence of minerals in soil and groundwater clean-up can be grouped into their effects on fate and transport of contaminants, their use as amendments to facilitate contaminant destruction or stabilization, their indirect influence on remediation, and their role as sources of “natural” contaminants.

The effect of mineralogy on fate and transport of contaminants is the most widely studied of these, but remains a challenging issue. Studies of contaminant adsorption range from single mineral to whole rock systems. However, integrating the results of these studies into generally applicable models remains elusive. This is because important factors such as reactive surface areas of minerals in aquifers, effects of natural variation in mineral composition, and alteration of minerals by plume chemistry are not well understood.

The use of minerals as amendments to limit migration of contaminants is widespread. Apatite, zeolite, illite, calcite, and other minerals have been used in a variety of applications. To understand the effectiveness of this approach and its longevity requires a thorough knowledge of the reactions of amendment minerals in the plume chemistry. For example, use of hydroxyapatite may be affected by elevated concentrations of fluoride causing surface precipitation of less reactive fluorapatite.

Reactions involving aquifer minerals can also complicate remediation. Technologies that rely on oxidation or reduction of contaminants must consider the presence of redox sensitive minerals that might interfere with the desired reaction. Other technologies can cause precipitation of minerals, lowering permeability.

Finally, aquifer minerals are the source for naturally occurring contaminants. Elevated concentrations of radium in coastal plain aquifers result from dissolution of their uranium-bearing minerals. Dissolution of aquifer minerals can also release contaminants such as lead and arsenic in response to aquifer disturbance or plume chemistry.