Evidence for an aquatic plant origin of ketones found in Taihu Lake sediments

This is the first time that aquatic plants have been singled out as the maj or source of alkan-2-ones in the sediments of a freshwater lake. Formerly a lkan-2-ones were regarded as products of microbiological oxidation of corre sponding alkanes or beta-oxidation and decarboxylation of fatty acids. The presence of alkan-2-ones in both the cyanobacteria, high aquatic plants and sediments of Taihu Lake in the eastern China is viewed as evidence for the biogenic origin of these compounds. Taihu Lake is one of the largest fresh water lakes in China. The dominant species in the West Taihu Basin is blue- green algae; the East Taihu Basin is covered by vascular plants. We have an alyzed the ketones and saturated hydrocarbons in the surficial sediments an d in plant samples from Taihu Lake. We found that the distribution models o f alkan-2-ones in the sediment samples from Taihu Lake were very similar to those that we found in the aquatic plants from the lake's western and east ern basins. The western basin interrelation coefficient was 0.91 and the Ea stern Basin interrelation coefficients were 0.80 and 0.75 for emergent plan ts and submergent plants, respectively. These are shown as the similar majo r carbon peaks, L/H, OEP and high abundance of 6,10,14-trimethylpentadecan- 2-one etc. But there are poor relationships between the alkan-2-ones in the sediment with corresponding the normal alkanes in the sediment of West Tai hu Basin (interrelation coefficient is 0.68) and in the East Taihu Basin (i nterrelation coefficient is 0.41). The alkan-2-ones of the surficial sedime nt in the West Taihu Basin are from blue-green algae and in the East Taihu basin are from vascular plants. The different distributions of sediment alk an-2-ones in the two basins are possible to be used as an indicator of alga e-type and macrophyte-type lakes.