[Sources and Variation Characteristics of Dissolved Lipid Biomarkers in a Typical Karst Underground River]

Water samples in Qingmuguan underground river were collected to determine the concentration of dissolved lipids, and their sources, composition and migration characteristics in underground river were studied. The results were obtained as follows. (1) The average content of various dissolved lipids decreased with increasing distance of migration in Qingmuguan underground river, and the most distinctive was dissolved saturated straight chain fatty acids with its content decreasing by about 81.71%, from the initial 5,704 ng · L⁻¹ to 1,043 ng · L⁻¹. (2) N-alkane could indicate the sources of dissolved organic matter in underground river, but saturated straight chain fatty acid and fatty alcohol had the advantage in indicating algae, bacteria and other microorganisms. (3) With the increasing migration distance of Qingmuguan underground river, the input type of dissolved organic matter in underground river was different, which might be resulted from the heterogeneity of karst surface. (4) In ternary plot of alkane sources, aquatic plants constituted the major contribution of dissolved organic matter in Qingmuguan underground river, followed by higher plant, algae/ bacteria. Unlike higher plants and algae/bacteria, the contribution from aquatic plants decreased with increasing migration distance of underground river. (5) To a certain extent, TAR (alkane) values could reflect the rainfall, and the values of CPI, L/H in saturated straight chain fatty acids might indicate the degradation activities of bacteria.