Structures, Syntheses, and Origin

In addition to chlorocymenes and chlorocymenenes, four groups of persistent alkylaromatk chlorohydrocarbons have been detected and characterized from chlorobleaching of pulp. They were assumed to be planar aromatic chlorocom-pounds (PLAC) because they were found in cleanup fractions of PCDDs and PCDFs after reversed elution with toluene from a carbon column [39]. PLAC groups were alkyl-polychloronaphthalenes (RPCN), alkyl-polychlorobibenzyls (RPCBB), alkyl-polychlorofluorenes (RPCFL), and alkyl-polychlorophenan-threnes (RPCPH). Among the latter, chlororetenes are most abundant [40]. 

Occurrence of alkyl polychloronaphthalenes (RPCN) in spent bleach liquors was first time reported in 1979 [8], Their structure was deduced to contain one methyl and one isopropyl group [8] which indicates origin from wood. Later analyses indicated that most common RPCNs in kraft pulp mill effluents and sludges were mono- to tetramethyl polychloro naphthalenes (C1-4PCN) [41-45]. In sludges their total contents were 28-72 ng g1 dw and in effluents only trace levels of a few ng 1 1 [42, 45]. Their origin was suggested to be chlorination of alkyl naphthalenes abundant in oil-based defoamers used in pulp mills [42]. 

No source of environmental RPCNs other than chlorination in bleaching-related processes is known. Analysis of urban air of Bordeaux showed abundant occurrence of methyl, dimethyl, and trimethyl naphthalenes (obvious oil components) and also mono- and dichloro naphthalenes (combustion products), but no traces of RPCNs [46]. 

C5-PCBBs were first detected as TeCDD imposters in analyses of coffee filter paper and pulp mill effluent by monitoring tetrachloro dib enzo -p - dioxins in GC/LRMS/SIM with ions m/z = 320 and 322. Their large peaks at the TeCDD window had intensity ratio peak 320 peak 322 = 100 65 which corresponded to two chlorines in the molecule instead of the four of TeCDD. 

The compounds were proposed to be dichloro C6-polychlorodibenzo-furans [46]. Similar observations from pulp mill samples were done by Kuehl et al. [47]. They suggested the structures of these compounds to be chlorinated xanthenes and xanthones. Buser et al. reported the occurrence of methyl-, polymethyl-, and alkyldibenzofurans in pulp mill sludge and sediments [48], Later, C5-PCBBs were detected as three dichloro and four trichloro congeners in pulp mill effluents, recipient sediment, and mussels incubated in recipient water [49]. Mass spectra of these congeners ruled out the structure of alkyl polychlorodibenzofurans and supported chlorinated alkyl bibenzyls instead, which was verified by model compound syntheses of the both structure types [50-52]. 

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