Catchment environmental change over the 20th Century recorded by sedimentary leaf wax n-alkane δ13C off the Pearl River estuary

• Published in: Science China. Earth sciences Vol. 59; no. 5; pp. 975 - 980
• Main Authors: Xu, ShenDong, Zhang, Jie, Wang, XianXu, Jia, GuoDong
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 2016
• Subjects: Earth and Environmental Science; Earth Sciences; Research Paper; alkanes; compound-specific; C values; environmental change; Pearl River estuary; Leaf wax
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-015-5206-3

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 20th 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.