Hazardous Wastes in the Biosphere

As applied to hazardous wastes in the biosphere, distinguish among biodegradation, biotransformation, detoxification, and mineralization. 

High-level defense waste solutions resulting from plutonium recovery and waste processing activities currently are stored in mild steel-lined concrete tanks located underground at the U.S. Department of Energy s Hanford Site. Low radioelement solubility and extensive radioelement sorption on surrounding sediment help maintain isolation of hazardous radionuclides from the biosphere in the event of tank failure. 

The toxicity indices are not measures of hazards, in part because they take no account of the barriers that isolate these wastes from the biosphere or of the behavior of different radioactive elements with respect to these barriers. However, the long-term toxicities of the high-level reprocessing wastes are due to radium, which is the same element that controls the ore toxicity. The long-term radium toxicity of the reprocessing wastes is considerably less than the radium toxicity of the ore. It seems reasonable that high-level wastes can be geologically... 

In addition to their toxic effects in the biosphere, hazardous wastes can damage air, water, and soil. Wastes that get into air can cause deterioration of air quality, either directly or by the formation of secondary pollutants. Hazardous waste compounds dissolved in, suspended in, or floating as surface films on the surface of water can render it unfit for use and for sustenance of aquatic organisms. 

Some injected wastes are persistent health hazards that need to be isolated from the biosphere indefinitely. For this reason, and because of the environmental and operational problems posed by loss of permeability or formation caving, well operators seek to avoid deterioration of the formation accepting the wastes and its confining layers. When wastes are injected, they are commonly far from chemical equilibrium with the minerals in the formation and, therefore, can be expected to react extensively with them (Boulding, 1990). The potential for subsurface damage by chemical reaction, nonetheless, has seldom been considered in the design of injection wells. 

The systems produce no harmful emission, harmful or radioactive byproducts, hazardous wastes, or biospheric pollutants. As usage is phased in worldwide, a significant reduction of environmental pollutants and hazardous wastes will result, as will a cleaner biosphere. 

The objective of geologic isolation of radioactive wastes is to preclude their reaching the biosphere until after they have decayed to the extent that they no longer constitute a health hazard. Concern over radioactive wastes from military, industrial and research uses has elicited many lines of commentary and deep concern from many individuals. In California, the concern about waste disposal was the focal point in establishing a moratorium on the construction of new reactors until a satisfactory waste disposal technology could be demonstrated. 

Disposal of the waste by emplacing it in isolating surroundings, with no intent to retrieve it, for the purpose of preventing the hazardous substances from reaching the biosphere in unacceptable amounts (this does not mean that the waste is irretrievable if a particular disposal method does not prove satisfactory). 

In general, solidification/stabilization technology is considered a last approach to the management of hazardous wastes. The aim of these techniques is a stronger fixation of contaminants to reduce the emission rate to the biosphere and to retard exchange processes. Two objectives can be distinguished ... 

The overriding aim of this volume is to assess the extent to which chemical processes might contribute to the confinement of a particular waste within the geosphere. In any type of waste containment, it is not necessary to ensure that no waste will ever leak from the disposal site. Rather, it is required to show that for as long as the waste remains hazardous it poses an acceptably low risk to the biosphere. Thus, this volume is really concerned with the degree to which chemical processes will restrict the movement of contaminants through the geosphere. 

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