Influence of aquatic plants on the hydrogen isotope composition of sedimentary long-chain n-alkanes in the Lake Qinghai region, Qinghai-Tibet Plateau  

作　　者：LIU Wei Guo YANG Hong WANG Huan Ye YAO Yuan WANG Zheng CAO Yun Ning 

机构地区：[1]State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences [2]School of Human Settlements and Civil Engineering, Xi'an Jiaotong University [3]Laboratory for Terrestrial Environment, Department of Science and Technology, College of Arts and Sciences, Bryant University

出　　处：《Science China Earth Sciences》2016年第7期1368-1377,共10页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 41573005);the National Basic Research Program of China (Grant No. 2013CB955901)

摘　　要：The hydrogen isotopic composition(δD) of leaf wax long-chain n-alkanes(C27, C29, and C31) from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. However, few studies have addressed whether the aquatic-derived n-alkanes can affect the δD values of lake sedimentary long-chain n-alkanes, which are usually regarded as a recorder of the terrestrial hydrological signals. Here we systematically investigated δD values of long-chain n-alkanes from modern aquatic plants, both near-shore and off-shore surface sediments, surrounding terrestrial plant litters, as well as river water and lake water in Lake Qinghai and its satellite lakes on the northeastern Qinghai-Tibet Plateau. Our data showed that(i) δD values of long-chain n-alkanes from aquatic plants varied from-184‰ to-132‰ for n-C27, from-183‰ to-138‰ for n-C29, and from-189‰ to-130‰ for n-C31, respectively, with no significant differences among the three n-alkanes homologues;(ii) δD values of long-chain n-alkanes from aquatic plants were generally more positive than those from surrounding terrestrial plants, possibly because that they recorded the D-enrichment of lake water in this semi-arid region;(iii) δD values of long-chain n-alkanes from surface sediments showed significant differences among the three n-alkanes homologues, due to the larger aquatic input of n-C27 to the sedimentary lipid pool than that of n-C31, and(iv) n-C27 δD values of near-shore aquatic plants and near-shore sediments are more negative than those from off-shore as a result of lower δD values of near-shore lake water. Our findings indicate that in this region(i) the offset between sedimentary n-C27 and n-C31 δD values(ΔδDC27-C31) could potentially be used to evaluate if sedimentary long-chain n-alkanes are derived from a single source;(ii) while δD values of n-C27 may be influenced by lake water hydrological changes, sedimentary n-C31 is derived predominantly from terrestrial plants and thus its δD can The hydrogen isotopic composition（δD） of leaf wax long-chain n-alkanes（C_27, C_29, and C_31） from lacustrine sediments has been widely applied to reconstruct terrestrial paleoclimatic and paleohydrological changes. However, few studies have addressed whether the aquatic-derived n-alkanes can affect the δD values of lake sedimentary long-chain n-alkanes, which are usually regarded as a recorder of the terrestrial hydrological signals. Here we systematically investigated δD values of long-chain n-alkanes from modern aquatic plants, both near-shore and off-shore surface sediments, surrounding terrestrial plant litters, as well as river water and lake water in Lake Qinghai and its satellite lakes on the northeastern Qinghai-Tibet Plateau. Our data showed that（i） δD values of long-chain n-alkanes from aquatic plants varied from-184‰ to-132‰ for n-C_27, from-183‰ to-138‰ for n-C_29, and from-189‰ to-130‰ for n-C31, respectively, with no significant differences among the three n-alkanes homologues;（ii） δD values of long-chain n-alkanes from aquatic plants were generally more positive than those from surrounding terrestrial plants, possibly because that they recorded the D-enrichment of lake water in this semi-arid region;（iii） δD values of long-chain n-alkanes from surface sediments showed significant differences among the three n-alkanes homologues, due to the larger aquatic input of n-C_27 to the sedimentary lipid pool than that of n-C_31, and（iv） n-C_27 δD values of near-shore aquatic plants and near-shore sediments are more negative than those from off-shore as a result of lower δD values of near-shore lake water. Our findings indicate that in this region（i） the offset between sedimentary n-C_27 and n-C_31 δD values（ΔδDC_27-C_31） could potentially be used to evaluate if sedimentary long-chain n-alkanes are derived from a single source;（ii） while δD values of n-C_27 may be influenced by lake water hydrological changes, sedimentary n-C_31 is derived predomina

关 键 词：Hydrogen isotope Long-chain n-alkanes Aquatic plants Paleohydrology proxy Lake Qinghai 

分 类 号：Q948.8[生物学—植物学]