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分析了珠江口外两个短沉积柱状样的叶蜡正构烷烃单体稳定碳同位素组成(δ~(13)C),讨论了它在揭示年代际尺度上流域环境变化的能力.长链正构烷烃主峰为C_(29)或C_(31),且表现出明显的奇数碳优势,说明这些烷烃主要来自维管束植物的叶蜡.所有的沉积样品中,C_(29)和C_(31)正构烷烃的δ~(13)C值在-28.8‰-31.2‰变化,这与珠江流域以C_3植物为主的陆地生态系统相吻合.两个沉积柱的δ~(13)C时间变化序列是相似的.从20世纪初期到70年代末这段时间都呈现出一个持续减小的趋势.但在随后的大约15年时间里,δ~(13)C值趋势反转,开始不断增大.在校正了大气CO_2浓度上升和δ~(13)Catm下降所带来的影响后,δ~(13)C_(29)记录基本上仍保留了上述变化规律,但在80年代δ~(13)C值的上升趋势表现得更加明显.通过与实测资料比较,我们认为,1980年之前δ~(13)C校正值的轻微减小趋势应该和珠江流域降水量的增加有关,之后的δ~(13)C值上升则很可能是受干旱气候条件以及人为森林砍伐的影响.因此,我们的结果表明,埋藏于珠江口外沉积物中的叶蜡正构烷烃可以很好地反映该流域在过去一个世纪里的气候变化和人类活动情况.
The stable carbon isotope compositions (δ ~ (13) C) of two waxy columnar waxy waxes outside the Pearl River Estuary were analyzed, and their ability to reveal the environmental changes of the watershed at the decadal scale was discussed. The main peak of alkane is C_ (29) or C_ (31), and shows obvious odd-numbered carbon predominance, indicating that these alkanes are mainly from leaf wax of vascular plants.In all sedimentary samples, C_ (29) and C_ Δ 13 C value of alkanes changed from -28.8 ‰ to -31.2 ‰, which accorded with C 3 plant-based terrestrial ecosystems in the Pearl River Basin.The δ 13 C time series of the two sedimentary columns were Similarly, the period from the early 20th century to the late 1970s showed a decreasing trend, but in the following 15 years, the trend of δ ~ (13) C reversed and began to increase. After the correction of the increase of atmospheric CO2 concentration and the decrease of δ ~ (13) Catm, δ ~ (13) C_ (29) records basically retained the above variation, but in the 1980s δ ~ (13) The upward trend of C value is more obvious.Comparing with the measured data, we think that the slight decrease tendency of δ ~ (13) C correction value before 1980 should be similar to that of the Pearl River valley The increase of δ 13 C value is likely to be affected by arid climatic conditions and artificial deforestation. Therefore, our results show that the waxy n-alkanes embedded in sediments outside the mouth of the Pearl River, It can well reflect the climate change and human activities of the basin over the past century.