PCB soils

DELFIA PCB (soil and food) Hybrizyme http //www.hybrizyme.com/... 

PCB Soil and water Adsorbed to soil Biomediated degradation... 

In situ bench-scale microcosms as well as field pilot studies have been conducted to optimize in situ PCB soil biotreatment processes. This work has focused on dilute PCB contamination (less that 100 mg/kg) because of the current rate limitations of... 

CPCDD/F and PCB soil concentrations are taken from references 10 and 11, respectively. 

Corrective Action Application At a Navy facility in Guam, approximately 25 tons of PCB contaminated soil was treated using the KPEG (potassium polyethylene glycol) process. PCB concentrations were reduced from 3000 ppm to less than 5 ppm. Upon completion of treatment using the KPEG process, the soil was neutralized from a pH of 14 to 7. A full-scale system for this process is currently under development. 

Although the major concern about the fate of organic pollntants in soil has been about pesticides in agricultural soils, other scenarios are also important. The disposal of wastes on land (e.g., at landfill sites) has raised questions about movement of pollutants contained in them into the air or neighboring rivers or water conrses. The presence of polychlorinated biphenyls (PCBs) or PAHs in snch wastes can be a significant source of pollution. Likewise, the disposal of some industrial wastes in landfill sites (e.g., by the chemical industry) raises questions about movement into air or water and needs to be carefully controlled and monitored. 

Contaminated soil has been inoculated with bacteria of established capacity for degradation of chlorobenzoates (Hickey et al. 1993). In the presence of added biphenyl, mineralization of PCBs was shown, although it was pointed out that there may exist incompatibility between the prodnction of chlorocatechols from chlorobenzoates and their inhibition of dihydroxybiphenyl-2,3-dioxygenase that catalyzes the ring fission of many PCBs. 

As for PAHs, attempts have been made to increase bioavailability by use of surfactants, and a complex picture has again developed (Fava and Di Gioia 1998). Triton-100 exerted both positive and negative effects in soil slurries even though it was not metabolized by the soil microflora, it adversely affected the degradation of chlorobenzoate intermediates, whereas in fixed-bed reactors, depletion of PCBs was enhanced. 

Barriault D, M Sylvestre (1993) Factors affecting PCB degradation by an implanted bacterial strain in soil microcosms. Can J Microbiol 39 594-602. 

With the recent Increase In activity at hazardous waste sites where cleanup and remedial action are underway, there has emerged a need for rapid analytical methods for assessing contamination in water, sediment, and soil. Of special Interest, because of widespread use and disposal. Is the group of materials known as PCB s (polychlorinated biphenyls). 

Field Experience. On the first day of field use, 40 soil and 10 QC samples were analyzed in six hours. This included lunch and 40 minutes down time when the field generator ran out of gasoline. Most runs were completed in less than nine minutes, and many very low level samples had the run aborted after about four minutes when it was evident that the second major 1254 peak was almost totally absent. Concentrations were calculated from periodic standard runs, and PCB levels ranged from less than. 2 ppm to 24,000 ppm of 1254. 

SFE is used mainly for nonpolar compounds [e.g. polychlorinated biphenyls (PCBs)]. Typically, small aliquots of soil (0.5-10 g) are used for extraction. The extraction solvent is a supercritical fluid, most commonly carbon dioxide, which has properties of both a liquid and gas. The supercritical fluid easily penetrates the small pores of soil and dissolves a variety of nonpolar compounds. Supercritical carbon dioxide extracts compounds from environmental samples at elevated temperature (100-200 °C) and pressure (5000-10 000 psi). High-quality carbon dioxide is required to minimize... 

This is a relatively new technique that is used for PCBs and other nonpolar, volatile and semi-volatile organic compounds. Typically, a small aliquot of soil sample (0.5-20 g) is used for the extraction. Soil samples are extracted with one or more organic solvents using microwave energy at elevated temperature (100-115 °C) and pressure (50-175 psi). This method uses less solvent and takes significantly less time than Soxhlet extraction but is limited to thermally stable compounds. 

Sonication of polychlorinated biphenyls (PCBs) from soils has been the subject of an interlaboratory study [196] with 129 participants. Two standard methods of extraction were evaluated EPA method 3540 for Soxhlet extraction and EPA method 3550 for sonication... 

It is not uncommon that extraction techniques are unfairly compared. Appropriate interlaboratory studies are few. Soxhlet and sonication extraction (EPA methods 3540 and 3550, respectively) were compared in an interlaboratory study (129 participants) for PCBs in soil. Results from laboratories using Soxhlet extraction were significantly more accurate than those obtained using sonication, especially at higher concentrations, but with equal precision [196]. This is rationalised by the observation that the Soxhlet procedure presents the sample with fresh solvent so that the extraction solvent is never saturated, unlike the sonication procedure. Sonication is very sensitive to the solvent polarity, nonpolar solvents producing considerably less accurate results than polar solvents. It is not as sensitive to clean-up procedures as... 

With suitable adjustments to the temperature, also subcritical water extraction (SWE) or pressurised hot water extraction (PHWE) allows selective extraction of polar (chlorinated phenols), low-polarity (PCBs and PAHs) and nonpolar (alkanes) organic compounds from industrial soils [418]. 

Rhizodegradation Soils, sediments, land application of wastewater Organic compounds (TPH, PAHs, BTEX, pesticides, chlorinated solvents, PCBs) Phenolics releasers (mulberry, apple, osage orange) Grasses with fibrous roots (rye, fescue, Bermuda) for contaminants 0-3 ft deep Phreatophyte trees for 0-10 ft Aquatic plants for sediments... 

Phytostabilization Soils, sediments Metals and metalloids (As, Cd, Cr, Cu, Pb, Zn, U, Se) Hydrophobic organics (PAHs, PCBs, dioxins, furans, pentachlorophenol, DDT, dieldrin) Phreatophyte trees to transpire large amounts of water for hydraulic control Grasses with fibrous roots to stabilize soil erosion Dense root systems are needed to sorb/bind contaminants... 

Various immobilization and stabilization methods can be applied to soils contaminated with heavy metals, petroleum products, PCB, peroxyacetyl nitrate (PAN), and so on.17 The disadvantages of immobilization and stabilization methods include the following ... 

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