Radiolytic decomposition of environmental contaminants and site remediation using an electron accelerator

Abstract

Halogenated and nonhalogenated hydrocarbon contaminants are currently found in natural waterways, groundwater, and soils as a result of spills and careless disposal practices. The development of proper treatment methodologies for the waste streams producing this environmental damage is now a subject of growing concern. A significant number of these waste stream compounds are chemically stable and are thus resistant to environmental degradation. Numerous researchers have investigated the use of ionizing radiation to decompose chlorinated hydrocarbons in diverse matrices and have proposed various free‐radical‐induced reaction mechanisms. This article is divided into two sections. First, we present data on experimentally measured, radiolytically induced decomposition of hazardous wastes and toxic substances using accelerator‐generated bremsstrahlung sources and gamma radiation from cobalt‐60. Data are presented on the radiolytically induced reduction in concentration of volatile organic compounds (VOCs) dissolved in water and in air, polychlorinated biphenyls (PCBs) dissolved in oil, high explosives dissolved in groundwater, and chemical weapon surrogates. The results of these studies suggest the potential use of ionizing radiation as a method of hazardous waste treatment. The second section of this article describes the technical aspects of a field‐scale radiolytic decomposition site cleanup demonstration using an electron accelerator. A portable, commercially available electron accelerator was set up at the Lawrence Livermore National Laboratory's (LLNL's) Site 300, a Superfund site, where vacuum extraction wells were removing trichloroethylene (TCE) vapor from a ground spill into the unsaturated soil zone. The accelerator was retrofitted into the existing vacuum extraction system such that the extracted TCE‐containing vapor passed through the accelerator beam for treatment. The concentration of TCE in the vapor was reduced by an amount dependent on the accelerator beam power. Production of reaction products in the vapor was measured as a function of absorbed dose.

The challenge of remediation technology development

“…(See Exhibit 1.) These range from simple encapsulation and stabilization techniques to treatment and destruction by ultraviolet, radio, and infrared frequencies; sonar and microwave destruction; arc plasma destruction; and electron laser beam destruction (Matthews et al, 1993). Practically every chemical and physical process known to man has been investigated for its application to waste destruction.…”

Application of gamma irradiation in ginseng for both photodegradation of pesticide pentachloronitrobenzene and microbial decontamination

“…Therefore, the method is hard to scale up. Radiation-induced degradation for pesticides has been widely applied in water samples for environmental protection, and cobalt-60 radiation has been proved to have a degradative effect on both insecticides and herbicides [14][15][16]. In addition, PCNB showed a photo-sensitive property, since its half-life value in sunlight irradiation was much shorter than that of non-irradiated control samples [10,17].…”

Degradation of Polychlorinated Biphenyls Induced by Ionizing Radiation in Aqueous Micellar Solutions

“…The radiation-induced decomposition of PCBs has been investigated in a variety of organic solvents ( − ), including mineral oils ( 22−25, 27 ), and in a 2-propanol soil slurry (). Detailed scavenger studies by Mincher et al () and Arbon et al () implicated the solvated electron as the major reactive species in the γ-radiation-induced destruction of PCBs in neutral solutions of both 2-propanol () and isooctane ().…”