PCBs in sediment

The sediment material of interest had to show a CB content sufficient to be determined with an acceptable precision and not reflecting heavy pollution such as harbour dredges. Based on records of the Dutch National Institute for Water Management and Waste Water Treatment (RIZA) on the concentrations of pollutants in the sediments of the big rivers, a sampling location was selected where the sediment was expected to meet the requirements mentioned above. A total of 1500 kg of wet material was taken from a sediment top layer of about 70 cm. 

A pilot study on the heat sterilisation process of the sediment material was performed to evaluate the losses of CBs. From the results it was concluded that the heat treatment has to be carried out at ca. 120°C over a period of 2 h in order to have the least effect on the CB content. Immediately after sampling, the sediment was air-dried at 40°C over a period of several weeks with continuous churning up and removal of larger objects. The dried sediment was then sieved (pore size 2 mm) and jet-milled for a particle size of less than 125 pm and heat sterilised at 120 C for 2 h, homogenised in a 250 L multi-purpose mixer during semi-automatic filling of bottles. The material was finally packed in 4400 bottles, each one containing 40 g. 

The within- and between-bottle homogeneity was verified and the variances were compared with the method variance (assessed on the basis of replicate analyses of an extract). A 500 mg portion of the sediment was extracted in a Soxhlet apparatus with 120 mL of a mixture of n-hexane and acetone 90/10 (v/v) for 6 h. The extract was concentrated and taken into a volume of 1 mL iso-octane. The concentrated extract was eluted over 2 g deactivated silica (with 15% water) with 15 mL of petroleum ether. The eluate was concentrated to a volume of 1 mL and treated with 1 mL of a solution containing 34 g L tetrabutylammonium sulphate, and sodium sulphite and isopropanol for the removal of sulphur. The concentrated eluate was cleaned over a column packed with 1.5 g deactivated silica (with 5% water). An internal standard solution (CB 198) was added to the clean extract. The mixture was separated on an Ultra-2 column (length 50 m, internal diameter 0.2 mm, film thickness 0.33 mm. He carrier gas, 65 min gradient from 90 to 275°C) with electron capture detection. No significant difference in the variance of the between- and the within-bottle series and the analytical method itself Therefore, it was concluded that the material is homogeneous for CBs. 

CRM 481, CBs in soil) has demonstrated a good stability of the CBs. As a consequence, storage of the sediment at a maximum of +20°C is recommended. 

The final determination of the CBs was performed by capillary gas chromatography using either mass selective detection or electron capture detection. Each participant had validated its method by performing experiments on recovery, extraction efficiency, procedure blanks and detector linearity. 

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MDGC has been used for separating eommereial formulations of PCBs (11, 12, 22, 23, 26) although it is not widely used on real samples. In some examples, MDGC has been applied to determine PCBs in sediment samples (13, 14, 27) and water-samples (14, 24). 

Certain anaerobic bacteria can reductively dechlorinate PCBs in sediments (EHC 140). Higher chlorinated PCBs are degraded more rapidly than lower chlorinated ones, which is in contrast to the trend for oxidative metabolism described earlier. Genetically engineered strains of bacteria have been developed to degrade PCBs in bioremediation programs. 

Bedard and May [452] used congener-specific GC with electron capture detection and mass spectrometric detection to determine the PCBs in sediments of Woods Pond (Lennox,MA). The congener distributions of all samples showed the hexa-, hepta-, and octachlorobiphenyls characteristic of Aroclor 1260, but key hexa- and hepta-CBs had decreased by as much as 45% relative to Aroclor 1260, and the tri-, tetra-, and penta-CBs had increased. GC-MS analysis revealed unusual tetra-, penta-, and hexa-CBs, many containing 2,4- and 2,4,6-chloro-phenyl rings, which are uncommon in higher Aroclors, and provided strong... 

Eromme H., T. Otto, K. Pilz, and E. Neugebauer (1999). Levels of synthetic musks Bromocyclene and PCBs in eel (Anguilla anguilla) and PCBs in sediment samples from some waters of Berhn/Germany. Chemosphere 39 1723-1735. 

In situ reductive dechlorination has been cited as an important pathway for biochemical weathering of PCBs in sediments (2, 5). The reductive dechlorination hypothesis is based on the premise that microbial action on PCB congeners is sterically selective for the chlorines in the meta and para positions on the biphenyl rings (i.e., 3, 3, 4, 4, 5, and/or 5 ). Such selectivity would result in the cleaving of the chlorines in these positions (5). If this process occurs, the terminal dechlorination products of the microbially resistant ortho-substituted congeners in the anaerobic environment should be 2,2 -DCB, 2,6-DCB, 2,2, 6-TrCB, and 2,2, 6,6 -TCB. Thus, the weight... 

Gabos S, Ikonomou MG, Schopflocher D, Fowler BR, White J, Prepas E, Prince D, Chen W (2001) Characteristics of PAHs, PCDD/Fs and PCBs in Sediment Following Forest Fires in Northern Alberta. Chemosphere 43 709... 

Thomas RL, Frank R (1983) Physical behavior of PCBs in the Great Lakes. In Mackay D, Paterson S, Eisenreich SJ, Semmens MS (eds) PCBs in sediment and fluvial suspended solids in the Great Lakes. Ann Arbor Science, Ann Arbor, MI, p 245... 

Among 21 published reports of concentrations of PCBs in sediments (Table 2.10), Masan inland (mean = 38.5 ng g-1 dw, n — 8, 2000) and Incheon Harbor (mean = 146 ng g-1 dw, n — 1, 1995) were identified as the most contaminated areas for freshwater and marine sediments, respectively. PCBs in freshwater sediments from six areas exceeded ERL for total PCBs (22.7 ng g-1, dw). However, the concentrations of sediment... 

Fig. 2.17. Comparison of measured levels and sediment quality guidelines (SQGs) for total polychlorinated biphenyls (PCBs) in sediments from the various sites, in South Korea (a) freshwater (n = 64), (b) brackish (n = 15), and (c) marine sediments (n = 362). Range indicates minimum (min), maximum (max), and arithmetic mean (avg.). Dotted lines represent SQGs of effect range low (ERL) and effect range median (ERM) for total PCBs (Long et al., 1995).

Lee, K.T., Tanabe, S., Koh, C.H., 2001a. Contamination of polychlorinated biphenyls (PCBs) in sediments from Kyeonggi Bay and Nearby Areas, Korea. Mar. Pollut. Bull. 42, 273-279. 

Zhang, P., Hong, H.S., et al., 1994. Concentrations and distribution of organochlorine pesticides and PCBs in sediments of Victoria Harbor, Hong Kong. J. Xiamen Univ. (Nat. Sci.) (Chinese) 33, 731-733. 

Figure 3 Accumulation of PCBs in sediments of lakes Superior, Michigan and Ontario with time33...

The rate constants calculated by EF profiles (Equation (4.6)) are necessarily crude as several assumptions must hold the initial enantiomer composition is known, only a single stereoselective reaction is active, and the amount of time over which transformation takes place is known. These assumptions may not necessarily hold. For example, for reductive dechlorination of PCBs in sediments, it is possible for degradation to take place upstream followed by resuspension and redeposition elsewhere [156, 194]. The calculated k is an aggregate of all reactions, enantioselective or otherwise, involving the chemical in question. This includes degradation and formation reactions, so more than one reaction will confound results. Biotransformation may not follow first-order kinetics (e.g. no lag phase is modeled). The time period may be difficult to estimate for example, in the Lake Superior chiral PCB study, the organism s lifespan was used [198]. Likewise, in the Lake Hartwell sediment core PCB dechlorination study, it is likely that microbial activity stopped before the time periods selected [156]. However, it should be noted that currently all methods to estimate biotransformation rate constants in field studies are equally crude [156]. 

R. Fuoco, M. P. Colombini, E. Samcova, Individual determination of ortho and non-ortho substituted polychlorobyphenyls (PCBs) in sediments by high performance liquid chromatographic preseparation and gas chromatography/ECD detection, Chromatographia, 36 (1993), 65-70. 

Allen-Gil SM, Gubala CP, Wilson R, et al. 1997. Organochlorine pesticides and polychlorinated biphenyls (PCBs) in sediments and biota from four US Arctic lakes. Arch Environ Contam Toxicol 33(4) 378-387. 

Vanier C, Sylvestre M, Planas D. 1996. Persistence and fate of PCBs in sediments of the Saint Lawrence River. Sci Total Environ 192(3) 229-244. 

Analysis of polychlorinated biphenyls. We have undertaken analysis of PCBs along the shores of Lake Victoria. Sampling stations were chosen to capture upstream activities, run offs and sediments brought along the rivers as souree of PCBs. Surface sediments from three different composite sites were sampled with a stainless steel shovel and combined to one pole sediment sample because PCBs in sediments can show a patchy distribution. Sediment samples were wrapped with aluminum foil, labeled and stored at -25°C. 

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