Adsorption Of Polychlorinated Biphenyls Research Articles

Airborne PCB as a contamination risk on freeze-drying of sediment

In a study of polychlorinated biphenyls (PCB) in freeze-dried sediments from Swedish lakes, the samples were found to contain unexpectedly high concentrations of PCBs. In one of the lakes (Björken), e.g. the concentration of PCB-28 was found to be 189 ng/g dw after freeze-drying compared to 7 ng/g dw after air-drying of the sediment and therefore our hypothesis was that the contamination had occurred during the freeze-drying procedure. Hence, a dry reference sediment (RS) was used in order to identify potential sources of PCB contamination. The investigation included freeze-drying of the dry RS in five different laboratories, exposure to the air in the freeze-drying room, storage at room temperature and air-drying in a certain fume hood and in a laminar flow clean bench. The pattern and concentrations of PCBs detected in the exposed RS were strongly influenced by low chlorinated PCB congeners under all of these conditions with exception for air-drying in the fume hood. Storage in the laboratory air resulted in a slight elevation in the concentrations of low chlorinated PCB congeners, whereas higher concentrations of all PCB congeners were observed after freeze-drying. In all experiments the contamination appeared to be due to adsorption of PCB from the laboratory air. On the basis of these findings we recommend that reference material be subjected to the entire procedure, including sample preparation, in order to monitor contamination and that a procedure involving solvent extraction of wet sediment samples is used, whenever possible, instead of procedures involving dry samples.

Decontamination of wastewater contaminated by polychlorinated biphenyls (PCBs)

Wastewater contaminated by PCBs obtained from three different sources was treated at both laboratory and pilot plant scale conditions by ultraviolet oxidation of organics at the presence of hydrogen peroxide after partial adsorption of impurities and PCBs on activated carbon and/or activated bentonite. The procedure was conducted both with and without a Fe(II) catalyst and considerable reduction of PCB concentration was achieved in both cases. In pilot plant scale experiments, activated carbon polishing step followed UV oxidation. The following three types of contaminated waste water were examined: a) aqueous extracts originated in the course of clean-up of contaminated soil by extraction with aqueous solvents. Concentrations of PCBs in extracts were between 1 microg/L to 3,000 microg/L; b) wastewater condensates originated in the process of thermal desorption of PCB from soils. Concentrations of PCBs in condensates were between 300 microg/L and 5,000 microg/L. c) underground water contaminated by PCBs extracted from the sites of old contamination. The content of PCBs was up to 50,000 ng/L. Biodegradation of PCBs with a mixture of indigenous soil bacteria (selected strains of Pseudomonas and Acitenotobacter) was also tested. It was carried out in a reactor with volume of 1.5 m3 by application of the bacteria in a slurry of bentonite with adsorbed PCBs.

Miniaturized and automated sample pretreatment for determination of PCBs in environmental aqueous samples using an on-line microporous membrane liquid-liquid extraction-gas chromatography system.

A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L(-)(1)-1 microg L(-)(1)), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), and low detection limits (2-3 ng L(-)(1)). Acetonitrile had to be added to the samples in order to overcome the influence of PCB adsorption on the repeatability of extraction and enrichment and to minimize the overall memory effect (OME). OME and carryover depended not only on the concentration of the organic solvent added to the sample and that used in the washing procedure but also on whether the extracting card was changed or not. When an optimized washing procedure was applied, the OME was approximately 0.2% at high concentrations (i.e., 1 microg L(-)(1)). When each extraction took place in a new extraction card, no OME was detected. Additionally, no significant adsorption onto glass surfaces or a matrix effect on extraction was noticed. The main features of this methodology are good extraction repeatability, low detection limits at short extraction time, and the unsurpassed characteristic of no detectable OME in the entire system when each sample is processed in a new card. The total consumption of organic (nonchlorinated) solvents is less than 5 mL per sample.

Rhizospheric effects of alfalfa on biotransformation of polychlorinated biphenyls in a contaminated soil augmented with Sinorhizobium meliloti

The effects of plant–microbe–soil interactions on the biotransformation of polychlorinated biphenyls (PCBs) in a rhizosphere soil were investigated. Containers packed with 350 g of a soil contaminated with Aroclor 1242, 1248, 1254 and 1260, were planted with alfalfa ( Medicago sativa L.) and augmented with its symbiotic N 2-fixing host rhizobium ( Sinorhizobium meliloti, strain A-025). The four treatment setups comprised a factorial combination of the presence/absence of alfalfa with the non-inoculation/inoculation of soil with S. meliloti in a completely randomized design with two replicates. Up to 44 days after planting, when the alfalfa was not fully developed, alfalfa and S. meliloti together were the most effective in PCB transformation/depletion, whereas alfalfa only was the least effective. However, by the last day of the experimental period (Day 270), when alfalfa growth was robust and full, alfalfa alone was the most effective, whereas S. meliloti alone was the least. In rhizobium-inoculated soil, soil hardness increased, soil moisture contents decreased, and both plant growth and yield were lowered, compared to non-inoculated soil. The depletion, loss or change in PCB levels may be attributed to either direct or indirect biotransformation, biotranslocation and adsorption of PCBs due to the presence of alfalfa and/or rhizobial inoculation. Either possibility underscores the possibility of using plant-rhizobacterial associations to phytoremediate soils contaminated with PCBs.

Iron-mediated reactions of polychlorinated biphenyls in electrochemical peroxidation process (ECP)

A study was conducted to explore some of the basic processes of polychlorinated biphenyl (PCB) destruction by a new technology termed electrochemical peroxidation process (ECP). ECP represents an enhancement of the classic Fenton reaction (H 2O 2+Fe 2+) in which iron is electrochemically generated by steel electrodes. Focus was on the extent of adsorption of a mixture of Aroclor 1248 on steel electrodes in comparison to iron filings. Commercially available zero-valent iron filings rapidly adsorbed PCBs from an aqueous solution of Aroclor 1248. Within 4 h, all the PCBs were adsorbed at 1%, 5%, and 10% Fe 0 (w/v) concentrations. Little difference in adsorption was found between acidic (2.3) and unamended solutions (pH 5.5), even though significant differences in iron oxidation state and Fe 2+ concentrations were measured in solution. PCB adsorption also occurs on steel electrodes regardless of the pH or electric current applied (AC or DC), suggesting the combination of oxidizing (free radical-mediated reactions) and reducing (dechlorination reactions) iron-mediated degradation pathways may be possible. Extraction of the iron powder after 48 h of contact time yielded the progressive recovery of biphenyl with increasing Fe mass(from 0.4% to 3.5%) and changes of the PCB congener-specific pattern as a consequence of dechlorination. A variety of daughter congeners similar to those accumulated during anaerobic microbial dechlorination of Aroclor 1248 in contaminated sediments indicate preferential removal of meta- and para-chlorines.

Characteristics of sorption losses of polychlorinated biphenyl congeners onto glass surfaces

Sorption losses to glass surfaces of five polychlorinated biphenyl (PCB) congeners in aqueous solutions were investigated. Adsorption/desorption experiments were conducted under conditions that simulated actual sample handling procedures for environmental samples. It was found that the adsorption loss is related to the degree of chlorination. PCB congener 180 lost the most onto glass surfaces, followed by congeners 138, 101/28, and 52, in decreasing order. More PCB adsorption occurred onto glass under conditions of agitation and higher temperature (22°C) during the five-day experimental period. The salinity effect (“salting out effect”) was also observed in this work. The efficiency of desorption (rinsing three times with solvent) was found to be ineffective in extracting adsorbed PCBs. It was necessary to use mechanical shaking for extraction. Storage of samples up to five days resulted in sorption losses as much as 30%, 17%, 30%, 40%, and 55% of PCB 28, 52, 101, 138, and 180, respectively. Sorption losses need to be considered when conducting water sampling or toxicological studies to avoid underestimation of the actual PCB concentrations and their toxic effects.

Coating effects on the glass adsorption of polychlorinated biphenyl (PCB) congeners

The effects of coating materials on polychlorinated biphenyl (PCB) adsorption in aqueous solution were assessed in an attempt to minimize PCB sorption loss during sampling processes. A coating material, which enhances PCB adsorption and allows adsorbed PCBs to be readily extracted by solvents, can act as a sampling concentrator to reduce PCB losses from both adsorption and evaporation. Several coating materials were evaluated, including paraffin oil, silicone oil, dimethyldichlorosilane (Sylon-CT), Prosil 28 ® and polydimethylsiloxane (PDS) with viscosity 0.65, 50 (PDS 50), and 500 (PDS 500) cSt. PDS and silicone oil enhanced adsorption for all five congeners examined (IUPAC No. 28, 52, 101, 138, and 180). Sylon-CT, paraffin oil and Prosil 28 ® had inconsistent effects on adsorption of different congeners. Desorption of adsorbed PCBs onto all coating types was assessed. The recovery efficiency of extracting PCBs with solvents was enhanced greatly with all coatings as opposed to non-coated surfaces, with the exception of paraffin oil. Coating with silicon oil, PDS 50, and 500 resulted in virtually 100% recovery of adsorbed PCBs. It was also found that Teflon containers were poor substitutes for glass containers and failed to minimize PCB losses. Among the materials studied, the best coating that could be used as a sampling concentrator was PDS 500.

Determination of adsorbed and absorbed polychlorinated biphenyls (PCBs) in seawater microorganisms

Abstract To distinguish between adsorbed and absorbed PCBs in seawater microorganisms , 2,2′,4,4′,5,5′-hexachlorobiphenyl (IUPAC #153; HCB) was added to a pure culture of Chrysochromulina apheles Moestrup et H.A. Thomsen. After the addition of the HCB , the cells were immediately harvested onto 2 μm polycarbonate filters and rinsed with a gradient of ethanol concentrations. Rinsing with 40% ethanol (v/v) was found to remove 80% of the HCB, which was loosely adsorbed to the cell surfaces, but did not extract the interior of the cells, as tested by chlorophyll a analysis. This method was used in a time course experiment which estimated PCBs adsorption and absorption to different groups of plankton organisms. Three different 14 C -PCBs, 4-chlorobiphenyl (IUPAC #3; MCB), 2,2′,5,5′-tetrachlorobiphenyl (IUPAC #52; TCB), and 2,2′,4,4′,5,5′-hexachlorobiphenyl (IUPAC #153, HCB), were incubated in seawater from the northern Baltic Sea during a spring bloom. Samples were taken every third day and separated by filtration into three fractions; 0.2–2 μm (bacteria), 2–10 μm (flagellates), and >10 μm (microplankton; phytoplankton and protozoa). Two subsamples were retained from each size fraction. One of the subsamples was left untreated, to obtain adsorbed plus absorbed PCB, while the other subsample was rinsed with 40% of ethanol, to obtain the absorbed PCB. The sorption was found to vary depending on the hydrophobicity of the compounds, the structure of the cell membranes, and the lipid content and composition of the cells. The absorption increased for the TCB and the HCB in the largest size fraction over time, which coincided with an increase of the neutral and non-polar lipids .

Evaluation of Column Cleanup for Chlorobenzenes, Polychlorinated Biphenyls, Polychlorinated Dibenzo-p-dioxins, and Polychlorinated Dibenzofurans in MM5 Flue Gas Analysis

The recoveries of chlorobenzenes (CBs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) from the acid-base-on-silica column (ABS), the silver nitrate-on-silica column (SNS), and the alumina column (ALM) were investigated using eluents with various concentrations of dichloromethane in hexane. PCBs recoveries from the ABS and ALM columns are generally increased with increasing number of chloro substituents. However, PCBs recoveries are also complicated by the inductive and resonance contributions due to the different conformation and electron density of the congeners. The recoveries of PCBs with lower number of chloro substituents decreased with increasing silver nitrate content coated on silica. With 2% dichloromethane in hexane (as normally used in MM5 analysis), the recoveries of all CBs and trichloro- to decachlorobiphenyls from ABS, 10% SNS, and ALM columns in series are ≥80%. However, the 2,4-dichlorobiphenyl is only 16% recovered, and monochlorobiphenyls are not recovered at all. Under these conditions, the recoveries of PCDDs/PCDFs from ABS and 10% SNS columns in series are ≥80%. With 60% dichloromethane in hexane, PCDDs/PCDFs recoveries from ALM column are ≥80%. The implication of the selective adsorption of PCBs on the fractionation of CBs/PCBs and PCDDs/PCDFs from these MM5 cleanup columns is discussed.

Vapor pressures and predicted particle/gas distributions of polychlorinated biphenyl congeners as functions of temperature and ortho-chlorine substitution

Parameters are given for calculating saturation liquid-phase vapor pressures ( p L 0, Pa) of 180 polychlorinated biphenyl (PCB) congeners as functions of temperature and ortho-chlorine substitution. These are slopes ( m L) and intercepts ( b L) of the equation logp 0 p= m L T+B L Values of m L and b L were obtained from gas chromatographic retention data for 32 PCB congeners. These slopes varied regularly with homolog (number of total chlorines) and also with the number of orthochlorines. From this information, m L and b L values were estimated for 148 other PCBs whose vapor pressures had been reported at only a fixed temperature. Vapor pressure data were applied to predicting the adsorption of PCBs to aerosols at 10 and 25° C, using the Junge-Pankow equation. Particulate percentages increased with homolog number, from 2–5% for trichlorobiphenyls to > 90% for octachlorobiphenyls at 10° C. Within each homolog, PCBs with fewer ortho-chlorines (and consequently lower p L 0) had increased particulate percentages. These results suggest that the more highly toxic mono- and non-ortho-PCBs are associated to a greater degree with particles in ambient air, and consequently more likely to be removed by precipitation and dry deposition.

Analysis of Polychlorinated Biphenyls in Aqueous Samples Using C18 Glass Column Extraction

Abstract A method for polychlorinated biphenyl (PCB) trace extraction from contaminated water at the part-pertrillion levels is described. This procedure involves quantitative adsorption of PCBs on Cis glass microcolumns. PCBs are retained on the surface and subsequently eluted with n-hexane (5 mL) before gas chromatography. Recovery of water fortified with PCBs was 83.6-108.5%. Compared to liquid-liquid extraction methods, the Cis glass microcolumns give comparable results, lessen solvent costs, and are less time-consuming.

Behaviour of polychlorinated biphenyls (PCBs) in soils and plants

A review of the literature indicates that polychlorinated biphenyls (PCBs) are not leachable in soils and that they are readily adsorbed by soil constituent. It appears that lower chlorinated PCBs are less adsorbed and thus slightly mobile in soils. Total organic matter content of soils seems to be more important than total clay content or total surface area in explaining adsorption of PCBs by soils. There have been few reports of the effect of PCBs on plants. These reports indicate that plants absorb PCBs, but in very low amounts. PCBs appear to have some effect on photosynthesis and respiration in plants.

Influence of Polychlorinated Biphenyls (PCBs) on Growth of Freshwater Algae

The toxicity of PCBs (Aroclor 1242) to freshwater algae was analyzed. In two closely related species of Chlorella, one was found to be extremely resistant and the other sensitive. Chlamydomonas reinhardi strains showed temporary sensitivity, which was overcome after 3 days of culture. Results from abiotic preculture indicated that in all cases enzymatic degradation or adsorption of PCBs by cells were not mechanisms explaining the observed differential sensitivities. However, adsorption of PCBs to glass surfaces, coupled with apparent differential uptake properties of the algal species studied, was shown to be the cause of the differential growth effects of PCBs on freshwater algae.

Studies on the vapor behavior of selected polychlorinated biphenyls.

The vapor loss of several PCB isomers from stainless steel planchets surfaces has been studied. Experiments were carried out under two different conditions. In one case, the vapor loss was observed from 2 molecular layers of PCB, while in the other series, the loss from approximately 200 molecular layers was observed. In both cases the loss of PCB from the surface was substantial, although the controlling mechanism of vapor loss was different. In the first case, the transport was approximated by a simple first order rate law, whereas in the latter case, it was a diffusion controlled process. In general, the vapor loss decreased with increasing number of chlorine atoms present in the isomer. The 4,4(1)-dichlorobiphenyl showed a deviation as compared to others indicating that such factors as the electronic distribution, position of chlorine atom on the biphenyl ring and symmentry of the molecule are also important in discussing the vapor transport.