Catchment environmental change over the 20th Century recorded by sedimentary leaf wax n-alkane δ^(13)C off the Pearl River estuary  

作　　者：XU ShenDong ZHANG Jie WANG XianXu JIA GuoDong 

机构地区：[1]Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences [2]Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China [3]State Key Laboratory of Marine Geology, Tongji University

出　　处：《Science China Earth Sciences》2016年第5期975-980,共6页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41061160498&41276072)

摘　　要：The compound-specific stable carbon isotope compositions(δ^(13)C) of leaf wax n-alkanes from two short sediment cores recovered off the Pearl River estuary(PRE) were analyzed to check for their capability of indicating decadal scale catchment environmental change. Sedimentary long-chain n-alkanes exhibited an odd-over-even predominance, with a maximum at n-C_(29) or n-C_(31), indicating their leaf wax origin was from vascular plants. The δ^(13)C values of C_(29) and C_(31) n-alkane in all the sediment samples were in the range of -28.8‰ to -31.2‰, consistent with the C_3 plant-dominated vegetation in the Pearl River catchments. The time series of δ^(13)C records from the two cores were comparable and displayed a decreasing trend from the early 20 th century to the end of the 1970s, followed by a reversal in that change leading to continued increase for ca. 15 years. After being corrected for the effect of atmospheric CO_2 rise and δ^(13)C_(atm) decline, the δ^(13)C_(29) records largely retained their raw changing pattern; the post-1980 increase being more conspicuous. The slightly decreasing trend in corrected δ^(13)C records before around 1980 may have been caused by an increase in precipitation, whereas the subsequent increase of δ^(13)C is likely associated with the observed dry climate and/or intensive anthropogenic deforestation. Our results thus demonstrate that leaf wax n-alkanes buried in the sediments off the PRE may well reflect change in the regional climate and/or human activity in the river catchments over the past century.The compound-specific stable carbon isotope compositions（δ^（13）C） of leaf wax n-alkanes from two short sediment cores recovered off the Pearl River estuary（PRE） were analyzed to check for their capability of indicating decadal scale catchment environmental change. Sedimentary long-chain n-alkanes exhibited an odd-over-even predominance, with a maximum at n-C_（29） or n-C_（31）, indicating their leaf wax origin was from vascular plants. The δ^（13）C values of C_（29） and C_（31） n-alkane in all the sediment samples were in the range of -28.8‰ to -31.2‰, consistent with the C_3 plant-dominated vegetation in the Pearl River catchments. The time series of δ^（13）C records from the two cores were comparable and displayed a decreasing trend from the early 20 th century to the end of the 1970s, followed by a reversal in that change leading to continued increase for ca. 15 years. After being corrected for the effect of atmospheric CO_2 rise and δ^（13）C_（atm） decline, the δ^（13）C_（29） records largely retained their raw changing pattern; the post-1980 increase being more conspicuous. The slightly decreasing trend in corrected δ^（13）C records before around 1980 may have been caused by an increase in precipitation, whereas the subsequent increase of δ^（13）C is likely associated with the observed dry climate and/or intensive anthropogenic deforestation. Our results thus demonstrate that leaf wax n-alkanes buried in the sediments off the PRE may well reflect change in the regional climate and/or human activity in the river catchments over the past century.

关 键 词：Leaf wax n-alkanes compound-specific δ^（13）C values environmental change Pearl River estuary 

分 类 号：P597[天文地球—地球化学]