Comparative study on organic constituents in polluted and unpolluted inland aquatic environments—II: Features of fatty acids for polluted and unpolluted waters

Abstract

Fatty acids were analyzed for polluted river waters from the Tokyo area and unpolluted river, brook, reservoir and pond waters from the Ogasawara (Bonin) Islands to elucidate their features for polluted and unpolluted waters. Fatty acids ranging from the carbon chain length of C 8-C 34 including unsaturated and branched acids were found with the great predominance of even-carbon numbers and lower molecular weight ranges (C 13–C 19) in the water samples from the Tokyo area and Ogasawara Islands. It was thus confirmed that no marked changes in fatty acid composition between polluted and unpolluted waters are absent. However, the total contents of the acids (average, 270 ± 120 μ g 1 −1 at 90% confidence limits) as well as the FAC (fatty acids as carbon)/TOC (total organic carbon, 2.6 ± 0.93%) and FAC/EOC (extractable organic carbon with ethyl acetate, 16 ± 6.7%) of river water samples from the Tokyo area were considerably higher than those of the waters from the Ogasawara Islands ( 58 ± 29 μ g 1 −1, 0.79 ± 0.48% and 2.1 ± 0.51%, respectively). These higher values for the Tokyo area should be due to sewage. A filtering method showed that most of fatty acids ( >95%) was present in particulate fractions. In addition, the content of free fatty acids was fairly lower than that of combined fatty acids. Further, unsaturated fatty acids were detected only in combined forms both in particulate and dissolved fractions. They are considered to be present as esters in polluted and unpolluted waters.