Polychlorinated naphthalene congener profiles in background sediments compared to a degraded Halowax 1014 technical mixture

Polychlorinated naphthalenes were quantified in 10 lake and sea sediment samples from sites with no known present local pollution source. Levels ranged from 0.14 to 7.6 ng/g (dry weight). The chlorinated naphthalene (CN) congener profiles showed an increased relative abundance of 1,3,5,7- and 1,4,6,7-substituted congener profiles as compared to the reported CN congener profiles of technical PCN and PCB. Further, a dominance of 1,2,3,4,5,6,7-hepta CN over 1,2,3,4,5,6,8-heptaCN was found in all samples in contrast to the ratio reported for technical PCN and PCB products. Some samples showed traces of 2,3,6,7-substituted CN congeners, indicative of thermal sources, such as municipal waste incineration. These profiles were compared with the profiles obtained from a Halowax 1014 technical mixture subject to aerobic microbial degradation and sunlight photolysis. The aerobic microbial culture gave no alteration of the CN congener profile of over a 28-day period, whereas sunlight exposure of Halowax 1014 in methanol yielded a more low chlorinated CN congener profile. Furthermore, CN congeners with chlorines in 1,8-positions were more affected than those with 1,3,5,7- or 1,4,6,7-substitutidn. These results indicate that photolysis may explain the enhancement of the relative abundance of some of the 1,3,5,7- and 1,4,6,7-substituted CN congeners in the environment but not the heptaCN profile.