Leachable material contaminants

Chemical stabilization of waste materials offers the potential to reduce the leachability of contaminants present in the waste. As shown in Fig. 1, it involves the conversion of the available fraction (or soluble species) of an element in a waste to an unavailable fraction (insoluble... 

Solidification/stabilization is a promising treatment technology for containing and immobilizing dredged material contaminants within a disposal site. While solidification/stabilization is not a solution to every disposal problem, the technology offers improved physical characteristics that reduce the accessibility of water to contaminated solids and reduced leachability for many contaminants. Leaching tests must be able to determine the (a) compounds that can be released from the waste (b) maximum concentration of these compounds in the leachate (c) quantities released per unit mass of waste (d) release rate of these compounds and (e) effects of a co-disposal of the waste. 

Landfills are simply buried containers designed to hold solid wastes while at the same time preventing waste materials from having a negative environmental impact. Such precautions are necessary, especially if land reuse for alternate purposes is a key issue. Consequently, it is best to regard a landfill site as merely a temporary disposal facility. For example, if the contents of a landfill site present an environmental contamination problem, they may have to be either relocated or rendered environmentally neutral (i.e., having no residual biodegradable oil and no residual content of leachable material). 

The best method for protecting soils from heavy metal contamination is prevention. It is very expensive and difficult to clean contaminated sods. Some treatments include high temperature methods to produce a non-leachable material, solidifying agents to make cement-like material, and a washing process to remove contaminants. Several other techniques involve soil and crop management by adjusting the pH of the soil and the use of plants to remove metals from soil and water. 

Brixie JM, Boyd SA (1994) Treatment of contaminated soils with organoclays to reduce leachable pentachlorophenol. J Environ Qual 23 1283-1290 Brown MJ, Burris DR (1996) Enhanced organic contaminant sorption on soil treated with cationic surfactants. Ground Water 34 734-744 Burris DR, Antworth CP (1992) In situ modification of an aquifer material by a cationic surfactant to enhance retardation of organic contaminants. J Contam Hydrol 10 325-337... 

The vendor claims that the CCBA process can be used on a variety of wastes, including sludges, sediments, and soils, contaminated with mixed organics and heavy-metal wastes. The process reduces the contaminated material to a nonleachable product composed of particles of sand to aggregate sizes. The treated wastes pass required leachability tests, and organic compounds are destroyed. The treated material can be disposed of on-site. 

Leaching of trace metals from CCB materials is of potential concern for contamination of natural water supplies. For example, Groenewold etal. (1985) found elevated levels of As, Cr, Mo, Pb, and Se in groundwater below a lignite fly ash landfill in North Dakota, and Shende et al. (1994) found stockpiled coal bottom ash contributed leachable metals to adjoining rivers. However, it also has been observed that weathered CCBs have the ability to retain many metals (Janssen-Jurkovicova et al. 1994 Steenari et al. 1999). 

The data shows an immediate decrease (the difference between untreated and 0 hours after treatment) in the TCLP leachable metals concentration for all seven metals. This indicated that the metals were bound immediately upon being treated. There would be no threat for contaminant leaching during the period it took for the CHEMFIX product to physically solidify. In addition, the TCLP leachable metal concentrations of those samples that were not allowed to cure (0 hours after treatment) all passed the TCLP regulatory limits. Therefore immediately after treatment the material can be classified as non-hazardous. 

The majority of toxicants in foods are contaminants, (e.g., microbial toxins, pesticide residues, leachable chemicals from packaging materials, food coatings, traces of heavy metals). However, the major issue in food safety is the contamination of food by mycotoxins in items such as milk and milk products, meat and meat products, and peanuts (groundnuts). Aflatoxin is highly toxic and lethal, and its carcinogenic potential is well established, even at doses as low as 0.05. ig. Mycotoxins also infect food products like rice, pulses, tapioca, and betelnuts. (Table 10-2). 

The type of design and, especially, the material used to construct closed vessels, should be chosen as a function of the type of treatment to be applied and the subsequent type of analysis to be performed on the sample. For example, materials such as PFA (a per-fluoroalkoxy resin) and TFM [a copolymer of tetrafluoroethylene and a small amount of perfluoro(propyl vinyl ether)] should be used in the microwave digestion of samples prior to ultratrace analysis, where the material should be inert to hot concentrated acids and contain minimal amounts of leachable contaminants (28). Raster electron microscopy has shown PFA to be the most suitable material for this purpose in fact, its surface was found to remain virtually unaltered even after 100 digestion cycles [29]. 

Ash Product Incineration of combustible materials produces a volume reduction, which can lead to higher concentrations of inorganic contaminants in the ash product and create leachability problems. Incineration of most contaminated soils produces only modest volume reductions, so inorganics are not significantly concentrated in the treated soil. 

Other cardiovascular uses have included coatings on pacemakers and pacemaker lead-wires for purposes of insulation and for achieving biocompatibility. Medical grade silicone elastomer has been widely used as a material of construction in experimental artificial hearts and heart assist devices. Silicone tubing is often preferred for use in roller-type blood pumps during cardiopulmonary bypass. Medical grade silicone elastomer contains no leachable or organic plasticizers and thus contributes minimal contamination in blood contact applications. 

There are two primary groupings related to materials testing for environmental contamination potential. These are total concentration and leachable concentration methods. Total concentration methods require the analyst to use the sample material in its as received state, with no physical or chemical modifications before analysis for the contaminants of interest. Leachable concentration methods require that the sample material be taken through a leaching process before the leachate is analyzed for the contaminant of interest. With leaching methods, one takes a sample of material and creates a leachate sample that is analyzed. The leached material is normally disposed after the leaching process is completed. 

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