Comparative study on organic constituents in polluted and unpolluted inland aquatic environments—V: Organic carbons and hydrocarbons in sediments

Abstract

Organic carbons and hydrocarbons were analysed for polluted sediments from Tama River and sludges from night soil and sewage treatment plants in the Tokyo area and unpolluted sediments from river and reservoirs from Chichi-jima Island in the Ogasawara (Bonin) Islands to characterize their features for polluted and unpolluted aquatic environments. In addition the relationships of the features of organic constituents between waters and sediments were given. The contents of n-alkanes (C 14-C 36). squalane and unresolved complex mixture of hydrocarbons (UCMH) for the sediments from Tama River ranged from 16 to 94, 0.86–15 and 250–1100 μ g −1 dry base, which are much higher than those of the sediments from Chichi-jima Island. The major constituents of hydrocarbons in the sediments and sludges from the Tokyo area were mainly odd-carbon numbered n-alkanes and squalane, whereas those of the island were only odd-carbon numbered n-alkanes. Hydrocarbons as carbon (total content × 0.851. as C 20H 42, HCC)/total organic carbon (TOC), HCC/extractable organic carbon with ethyl acetate (EOC), squalane as carbon (SqC)/TOC. SqC/EOC and UCMH/ n-Alkane (C 15-C 33) values for the sediments from Tama River were much higher than those of the sediments from the island, while carbon preference index (CPI H) values for the sediments of Tama River were considerably lower than those of the island. It was thus indicated that HCC/TOC, HCC/EOC, UCMH/ n-Alkane and CPI H values should be the important indicators of hydrocarbon pollution for aquatic environments. In addition SqC/TOC and SqC/EOC ratios are apparently useful measures of urban-industrial activities on aquatic environments. The similarity of the nature of hydrocarbons of sediments and sludges from the Tokyo area indicated that the sewage contributed considerably to urban river sediments. Further it was also indicated that hydrocarbons were concentrated in sedimentary environments, although the features of hydrocarbons in sediments are generally similar to those of waters.