Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
1999-12-08
2001-10-16
Griffin, Steven P. (Department: 1754)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C210S602000
Reexamination Certificate
active
06303844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of efficiently decontaminating a medium which contains polychiloinated biphenyls (hereinafter abbreviated as PCBs) or polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (hereinafter abbreviated as dioxins), such as soil or a lake or marsh contaminated with PCBs or dioxins, through utilization of plants' capability of absorbing, or absorbing and decomposing, PCBs or dioxins.
2. Description of the Related Art
Since PCBs are chemically very stable and exhibit excellent electrical insulating properties, they have been widely used in, for example, insulating oils of capacitors or transformers, thermal media, machine oils, and pressure-sensitive paper.
Since recognition of biological toxicity of PCBs (for example, in the Kanemi Oil case in Japan), production of PCBs has been regulated. However, contamination with PCBs has spread globally, and the effect of PCBs has lasted over a long period of time.
Recent reports have pointed out the toxicity of PCBs as endocrine disrupters and that even a very small amount of PCBs has an adverse effect on the environment.
PCB decomposition processes approved in Japan under the Waste Disposal and Public Cleansing Law are an incineration process, a base-catalyzed decomposition (BCD) process, a chemical extraction-decomposition process (DMI/NaOH process), a potassium tertiary butoxide process (t-BuOK process), a catalitic hydrogenation-dechlorination process (+t-BuOK process), and a supercritical water oxidation process (SCWO process).
Such chemical or physical decomposition processes exhibit relatively high decomposition efficiency, but conventionally involve high processing cost. Also, these processes are suited for decontaminating a contaminated medium of high contamination concentration, but are not suited for practical decontaminating of a large-scale, contaminated medium of low contamination concentration.
Meanwhile, dioxins, which are very toxic, are chemically relatively stable and thus are not easily decomposed. Since dioxins are soluble in oils and fats, once food contaminated with dioxins is taken into the human body, dioxins are absorbed by the organs. Since ingested dioxins are hardly egested, dioxins reportedly not only keep accumulating within the human body but are also transmitted from a mother to a fetus via the womb.
In recent years, as the action of dioxins as endocrine disrupters has become clear, the effect of dioxins on future generations has become of serious concern.
Dioxins are generated mainly in an incineration process at a temperature of about 300-850° C., as in a refuse incineration furnace, and are released into the atmosphere in the form of exhaust gas. Thus-released dioxins are primarily accumulated in, for example, soil, lakes and marshes, and rivers. Since measures against dioxin sources have begun to work, fresh generation of dioxins tends to be suppressed. However, dioxins in the soil have been left accumulated over a long period of time without deterioration or decomposition, so that the soil contaminated with dioxins has become a secondary source of dioxins.
Incineration at high temperature is the most effective process for decomposing dioxins. This incineration process is not suited for treating a large amount of contaminated media and involves considerable treatment. According to a conventional method for disposing of, for example, contaminated soil, the contaminated soil is excavated and relocated to a disposal yard, where the contaminated soil is filled into an excavated hole and covered with sealing soil. This method is conventionally employed, since a relatively large amount of contaminated media can be disposed of.
This filling-up method is a tentative one—a medium contaminated with dioxins is merely moved from one location to another. The relocated, contaminated medium may raise another environmental contamination problem in the new location. Efficient, perpetual measures to treat dioxins have not been achieved.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of efficiently decontaminating soil or a lake or marsh contaminated with PCBs or dioxins; particularly, a medium contaminated widely and at low concentration with PCBs or dioxins, through utilization of plants' capability of absorbing, or absorbing and decomposing PCBs or dioxins.
The present inventors studied hairy roots derived through infection with
Agrobacterium rhizogenes
(hairy-root disease bacteria), or soil bacteria. The hairy roots are derived through incorporation into a plant-cell chromosome of the T-DNA region of the Ri plasmid present in the body cell of
Agrobacterium rhizogenes
followed by development thereof. As compared to common roots, which cannot survive unless special measures are taken, the hairy roots can survive in a common sterile medium and grow abundantly. Even when
Agrobacterium rhizogenes
is completely sterilized by means or, for example, antibiotics, the hairy roots grow abundantly without losing their properties. The hairy roots can regenerate into plantlets under appropriate culture conditions. The regenerated plantlets are characterized by development of a root system.
The present inventors reached the inventive concept of decontaminating soil or a lake or marsh contaminated with PCBs or dioxins through utilization of the abundantly growing hairy roots or regenerated plantlets derived from the hairy roots and through reinforcement of their inherent capability of absorbing, or absorbing and decomposing PCBs or dioxins. On the basis of this idea, the inventors conducted various experiments and achieved the present- invention.
According to a method of the present invention of decontaminating a medium containing PCBs or dioxins, the contaminated medium is brought into contact with hairy roots derived through introduction of an Ri plasmid from
Agrobacterium rhizogenes
into a plant capable of absorbing, or absorbing and decomposing PCBs or dioxins, or is brought into contact with regenerated plantlets derived from the hairy roots, to thereby cause the hairy roots or regenerated plantlets to absorb, or absorb and decompose PCBs or dioxins.
The decontaminating method of the present invention not only is efficient but also enables low-cost treatment, plain treatment not involving excavation, on-site treatment not involving relocation of contaminated soil, and perpetual treatment capable of extinguishing PCBs or dioxins. Planting prevents diffusion of soil contaminated with PCBs or dioxins which would otherwise take place through outflow or scattering of surface soil; i.e., contaminants can be decomposed or cleaned up while revegetation is carried out. Even when PCBs or dioxins are not satisfactorily decomposed, undecomposed PCBs or dioxins are absorbed into plants to be condensed and fixed therein, thereby preventing diffusion of contamination. The plants may be reaped and incinerated.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As used herein, the expression “medium containing PCEs or dioxins” refers to a contaminated medium, such as soil, a lake or marsh, or a river contaminated with PCBs or dioxins.
A plant used in the present invention is not particularly limited so long as it has the capability of absorbing, or absorbing and decomposing PCBs or dioxins. Examples of planes capable of absorbing, or absorbing and decomposing PCBs include plants belonging to Solanaceae, Cruciferaa, or Umbelliferae; specifically,
Atropa belladonna, Wasabia japonica
, and
Armoracia rusticana
. Particularly,
Atropa belladonna
is preferred. Examples of plants capable of absorbing, or absorbing and decomposing dioxins include plants belonging to Solanaceae, Cruciferae, Umbelliferae, Chenopodiaceae, Leguminiosae, Compositae, or Saxifragaceae. Among those plants, those belonging to Cruciferae are preferred.
Atropa belladonna
is particularly preferred. These plantlets may be used in their original form. Alternatively, a portion of a plantlet, such as seeds, hairy roots, root tis
Fuse Osamu
Kamiya Takashi
Manabe Eichi
Maruta Toshihisa
Morita Masatoshi
Griffin Steven P.
Nave Eileen E.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Taiheiyo Cement Corporation
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