典型岩溶区地下河中溶解态脂类生物标志物来源解析及其变化特征

利用气相色谱-质谱联用仪(GC-MS)测定了青木关地下河中溶解态类脂物的含量.研究了其在地下河中的来源、组成及迁移特征.结果表明,7~11月,各溶解态类脂物的平均含量随着青木关地下河运移距离的增加呈降低趋势,其中以溶解态饱和直链脂肪酸的下降最为显著,即由最初的5 704 ng·L~(-1)下降到1 043 ng·L~(-1),减少了约81.71%.正构烷烃能够较为详尽地指征地下河中溶解性有机质来源,而饱和直链脂肪酸、脂肪醇则对藻类和细菌等微生物有较好的指示意义.随着地下河运移距离增加,有机质输入类型呈现多样化,可能与岩溶地表不均一性有关.正构烷烃三端元图解中,水生植物的输入为地下河中溶解性有机质的主要来源,其次分别为陆地高等植物和藻类、细菌等微生物,但随着地下河运移距离的增加水生植物的相对贡献量逐渐减少.青木关地下河中正构烷烃TAR值对降雨有一定的指示意义,而饱和直链脂肪酸CPI、L/H值则指示细菌降解活动.

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 5704 ng·L^-1 to 1043 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.