Gas chromatographic-mass spectrometric analysis of chlorination effects on commercial coal-tar leachate

Abstract

Samples of leachate from a commercial coal tar have been analyzed for polycyclic aromatic hydrocarbons (PAHs) by capillary gas chromatography-mass spectrometry, using electronimpact and chemical ionization. Basneutral extracts Contained predominantly the parent PAHs and alkyl-and nitrogen-substituted PAHs. These compounds were considerably less abundant in samples of chlorinated leachate, which Contained, instead, a number of oxygenated and halogenated PAHs.In public water supply systems, storage tanks and pipes are often coated to prevent corrosion. Coal tar is one of the materials commony used (1-3). The potential for contamination of potable water by the coating material is of concern t o human health and can be assessed by analysis of leachate from the commercial product. Elevated concentrations of parent polycyclic aromatic hydrocarbons (PAHs) were found in the effluent of a storage tank coated with coal tar ( 4 ) . Evidence has also been reported that at least one parent PAH, fluoranthene, can be leached from bituminous linings of distribution pipes (5). Without identifying the possible sources of contamination, other investigators have also found low levels (ng/L) of PAHs in potable water systems (6-8). Recent mutagenicity studies indicate that concentrated extracts of water samples collected in distribution systems are more mutagenic than samples collected a t the corresponding treatment plants (9). However, the chemical basis for these observations is still not understood.In order to obtain background for more extensive field investigations, we investigated the effects of chlorination on the composition of the coal-tar leachate. A major advantage of the commercial coal tar for study is that it contains many compounds whose standards are not readily available. Its leachate thus simulates under controlled conditions the complexity of actual environmental samples. In addition, it can be coated in uniform layers on a well-defined surface area.T h e polarity of water biased by pH is expected to favor leaching of PAHs with polar functional groups. Water supplies typically range from pH 6 to 9 after treatment. Chlorination, as practiced for disinfection, should further modify the composition of PAHs in coal-tar leachate. Potable water is generally chlorinated to leave a residual of about 0.5 mg free chlorine/L. The water mains and storage tanks, after installation and maintenance, are disinfected at concentrations of 50,100, or 200 mg free chlorine/L, depending on the mode of application (10). Harrison et al. have shown that the parent PAHs are significantly degraded by free chlorine at 10 mg/ L (11,12). Aqueous chlorination products of standard PAHs include anthraquinone, fluoranthene chlorohydrin, and monochloro derivatives of fluorene, phenanthrene, methylnaphthalene, and methylphenanthrene (13).This paper deals primarily with identification of baseneutral compounds in the coal-tar leachate, since mutagenicity studies of coal-derived products have generally found activity highest in basic and neutral fractio...

Occurrence of chlorinated and brominated polycyclic aromatic hydrocarbons in surface sediments in Shenzhen, South China and its relationship to urbanization

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