Identification of heteroaromatic and other organic compounds in ground water at creosote-contaminated sites in Denmark

The occurrence of heteroaromatic compounds (NSO) and their degradation products in ground water at creosote-contaminated sites in Denmark was investigated, NSO are of special interest because of their high polarity. toxicity, and adverse organoleptic properties. In total, the content of about 50 organic tar compounds and the chemical redox parameters of ground water from three creosote-contaminated sites were determined. The organic contamination of ground water varied considerably between sites and wells with concentrations up to mg/L level. The major organic contaminants were NSO, phenols, and monoaromatic hydrocarbons, which are among the most water-soluble creosote compounds. High concentrations (several mu g/L) of these compounds were observed downgradient of the contamination source. Within a distance of 50 to 80 m from the source. the concentrations of most compounds were reduced significantly, often below detection limits. The NSO constituted from 0.1 percent to 73 percent of all organic compounds determined by gas chromatography (GC) with an increasing dominance downgradient of the source. Among the 17 studied NSO, carbazole, thiophene, benzothiophene, dibenzothiophene, benzofuran, and dibenzofuran were observed most frequently (detection frequency > 60 percent). High concentrations (> 100 mu g/L) of some NSO such as benzothiophene, carbazole, hydroxyquinolines, and basic N-compounds were observed occasionally. Other recent studies on creosote contamination support the present observations of high ground water concentrations of basic N-compounds and the high detection frequency of the aforementioned NSO. However, unlike the other studies, we did observe thiophene (1-10 mu g/L).