CHARACTERIZATION OF WATER-EXTRACTABLE DICARBOXYLIC-ACIDS IN NEOGENE SEDIMENTS OF THE SHINJO BASIN, JAPAN

Water-extractable dicarboxylic acids (C-3-C-9) were detected in sedime nts of a stratigraphic sequence from Miocene to Pliocene in the Shinjo basin, Japan. Contents of these acids in the sediments ranged from 0. 01 to 10 n mol g(-1), showing generally succinic acid the most abundan t of all. The saturated normal dicarboxylic acids generally showed a d ecrease in contents with an increase of carbon numbers in their molecu lar distribution patterns. Unsaturated acids exhibited strong predomin ance of cis isomer over trans one with the C-4 and C-5 acids in the lo wer part of the sequence. Optical isomers of branched dicarboxylic aci ds, especially, methylsuccinic acid and 2-methylglutaric acid were pre sent in racemic mixtures in the lower part of the sequence. The depth profile of the contents of the saturated normal dicarboxylic acids as well as their molecular distribution patterns was different from that of monocarboxylic acids (C-3-C-9) in the same sediments (Shimoyama et al., 1991), suggesting different chemical forms of the two kinds of th e carboxylic acids in the sediments.