正构烷烃组成的古环境指示:以中全新世以来珠江口沉积物研究为例

doi:10.3969-j.issn.1001-909X.2023.01.010

摘要/Abstract

摘要：

该文分析了珠江口沉积物柱状样HKUV16中正构烷烃的长链奇碳烷烃含量(∑oddC_25~33)、碳优势指数(CPI)、平均链长(ACL)、C₃₁/C₂₇和海洋水生植物比重(P_mar-aq),探讨了中全新世以来正构烷烃来源变化及对珠江流域环境变迁的指示。HKUV16的长链正构烷烃特征指示其主要来自陆源高等植物。在8.0~7.0 ka BP期间,∑oddC_25~33、CPI值和P_mar-aq值增加,ACL和C₃₁/C₂₇为低值,指示该时期陆源有机质输入增加,木本植物占比大,珠江流域气候湿润。在7.0~3.2 ka BP期间,∑oddC_25~33降低,表明陆源有机质输入减少,而ACL和C₃₁/C₂₇呈增—减—增的变化趋势,指示珠江流域可能经历了干旱—湿润—干旱的气候变化。3.2~2.2 ka BP,ACL、C₃₁/C₂₇的高值显示此时草本植物占比明显增大,可能意味着该时期的气候较为干旱。多指标综合显示2.2 ka BP之前珠江口沉积物的正构烷烃变化主要受夏季风的影响,而2.2 ka BP以来不断增强的人类活动可能成为影响珠江流域生态环境的主导因素。

关键词: 珠江口, 正构烷烃, 中全新世, 夏季风

Abstract:

The multiple indices of n-alkanes including ∑oddC_25-33, CPI, ACL, C₃₁/C₂₇ and P_mar-aq from a sediment core HKUV16 retrieved in the Pearl River Estuary were analyzed to explore their sources and environmental changes since the mid-Holocene. The distribution features of n-alkanes of core HKUV16 indicated that they were mainly from terrestrial higher vegetation. From 8.0 to 7.0 ka BP, ∑oddC_25-33, CPI, and P_mar-aq increased, while ACL and C₃₁/C₂₇ were low, which showed that terrestrial organic matter input increased and woody vegetation increased. The decrease of ∑oddC_25-33 during 7.0~3.2 ka BP indicated that the input of terrestrial organic matter decreased, while the ACL and C₃₁/C₂₇ showed an increase-decrease-increase trend, suggesting that the Pearl River Basin might have experienced dry-wet-dry climate change. From 3.2 to 2.2 ka BP, high ACL and C₃₁/C₂₇ indicated that herbaceous plants expanded and the climate was relatively arid. The multi-indices showed that the input of n-alkanes to the Pearl River Estuary before 2.2 ka BP was mainly affected by East Asian summer monsoon. However, increasing human activities since 2.2 ka BP might have become the dominant factor for the ecological environment of the Pearl River Basin.

Key words: Pearl River Estuary, n-alkanes, mid-Holocene, summer monsoon

中图分类号:

P736.4

陈国生, 邱梓惠, 孔德明. 正构烷烃组成的古环境指示:以中全新世以来珠江口沉积物研究为例[J]. 海洋学研究, 2023, 41(1): 121-130.

CHEN Guosheng, QIU Zihui, KONG Deming. Paleoenvironmental indication of n-alkanes composition: A case study of sediments from the Pearl River Estuary since the mid-Holocene[J]. Journal of Marine Sciences, 2023, 41(1): 121-130.

图/表 7

图1 研究区域和采样点

Fig.1 Study area and sampling site

表1 柱状样HKUV16的放射性14C年龄

Tab.1 Radiocarbon ages of the core HKUV16

深度/cm	测试材料	测定年龄/a	校正年龄/a
40	贝壳	2 380±30	2 262.5
78	贝壳	570±30	477.5
143	贝壳	620±30	507.5
293	贝壳	3 680±30	3 858
454	贝壳	5 800±40	6 475.5
607	贝壳	4 140±40	4 517
932	贝壳	7 190±40	7 895

图2 柱状样HKUV16的深度-年龄模型[28]

Fig.2 Depth-age model of the core HKUV16[28]

图3 柱状样HKUV16中正构烷烃的组成分布

Fig.3 The n-alkanes distribution of the core HKUV16

图4 长链奇碳烷烃含量以及C25~C33烷烃的占比

Fig 4 Content of long-chainodd alkanes and the relative proportion of C25~C33

图5 正构烷烃指标与董哥洞石笋记录对比

Fig.5 Comparison of n-alkane indices with Dongge Cave Stalagmite records

图6 柱状样HKUV16中ACL与C31/C27的相关性

Fig.6 ACL vs C31 /C27 diagram of the n-alkanes in the core HKUV16

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