Chlorobiphenyls discussion

The following section discusses the priming of PCB-dechlorinating microorganisms with various compounds, such as (1) chlorobiphenyls, (2) bromobi-phenyls, and (3) benzoate ions. 

Most of the side reactions have already been discussed in Section 26.1.3.3. (dediazoniation in organic solvents). Chlorinated aliphatic solvents, such as 1,2-dichloroethane and dichloro-methane, lead to an extensive formation of chloroaromatics, and aromatic solvents, even halogenated examples, can be arylated to some extent by arenediazonium tetrafluoroborates (vide supra). For example, during dediazoniation of benzenediazonium tetrafluoroborate in toluene, chlorobenzene, bromobenzene or anisole, 3-5 % of substituted biphenyls Ph-C6H4-X (X = Me, Cl, Br, OMe) are formed together with 0.5-0.8% of fluorobiphenyls.5 Fluorobiphenyls are formed through an ionic pathway (only 2- and 4-isomers are formed) whereas chlorobiphenyls result from a radical process (X = Cl, 2-/3-/4-isomer 26 47 27).243... 

We report here on the distributions of several chlorobiphenyls In samples of water, sediment and biota of the Acushnet River Estuary - New Bedford Harbor, Buzzards Bay, Massachusetts, U.S.A. Our general objective Is to gain Information of generic utility In addition to providing specific data and Interpretations of assistance to remedial action at this Superfund site. Our specific objectives In this paper are to 1) document the composition of Individual chlorobiphenyls In biota normally harvested by commercial and recreational fishermen and discuss factors which could lead to the observed distributions and potential Implications for public health standards for PCBs In fish and 11) to Investigate, In a preliminary manner, the adherence of bloconcentratlon of PCBs to predictions based on equilibrium assumptions and octanol/water (Kg ) partition coefficients (, 22). 

Examination of the gas chromatograms of PCBs In the samples of lobster and crab reveals the marked contrast In composition of PCBs In these types of biota samples and the composition of PCBs In water, sediment, bivalves and Aroclor mixtures. For example, the chlorobiphenyl composition of the lobsters are dominated by lUPAC chlorobiphenyl (CB) numbers 118, 153 and 138 while numbers 118 and 153 dominate the composition In the crab (Figure 2). Several more chlorobiphenyls, e.g. 28, 52, 44, 70, 95, 101, 110, are present In the mussel and sediment samples In addition to 118, 153 and 138 (Figure 2). PCBs In flesh of flounder species (L. maculata and P. amerlcanus) were Intermediate In composition between the lobsters and the mussels based upon examination of the gas chromatograms (not shown), I.e. 118, 153 and 138 predominate but not as much as In the lobsters. The possible reasons for these differences will be discussed below. 

Table 111 contains data for concentrations of several Individual chlorobiphenyls dissolved In the water or associated with particulate matter In the water column, and In surface sediments and pore waters. Concentrations of total PCBs estimated from these data are quite high for water, sediments and biota (2, ). There are few quantitative data for Individual chlorobiphenyls In water samples and this prevents extensive comparisons with other data of this type. The concentrations we report are within a factor of two to four of Individual chlorobiphenyl data for a few water samples from the upper Hudson River (31). We have discussed water column and sediment data In more detail In two other papers (W, 30). 

The 15 halogenated POPs (Table I) actually consist of more than 5(X) individual components ranging from mono-chlorobiphenyls and monochlorodibenzo-p-dioxins/dibenzo-furans, to decachlorobiphenyls, decachlorobomanes and mirex. The above chemicals are all semi-volatile to varying degrees, which means that they may be found in gas phase and in condensed phases (water, soil, sediments) at ambient temperatures and pressures. The lower chlorinated PCBs, HCH isomers and other components with higher vapor pressures have the capacity to evaporate in warm environments and condense when they encounter cold temperatures at high latitudes (e.g., Wania Mackay, 1993, 1996) and altitudes (Blais et al., 1998). This fractionation process has raised concerns for more remote ecosystems that may be impacted by industrial and agricultural activities in tropical and temperate latitudes, as discussed further below. 

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