环雷州半岛海底表层沉积物brGDGTs组成分布特征及其环境意义

Composition and Distribution Characteristics of brGDGTs and Significance of Environment in Surface Sediments of Leizhou Peninsula

【目的】分析环雷州半岛近海海域表层沉积物中支链甘油二烷基甘油四醚化合物(brGDGTs)的组成、空间分布特征及来源,探讨brGDGTs相关生源环境指标的适用性。【方法】主要应用LC-MS技术对环雷州半岛近海表层沉积物中brGDGTs化合物进行分析鉴定。【结果】环雷州半岛近海海域brGDGTs组成与丰度具有明显的区域性分布特征,丰度较高的区域主要分布在环雷州半岛东北部、西北部海区,以及琼州海峡西侧,而总体上brGDGTs在西部海区的丰度高于东部海区。表层沉积物以无环和低甲基数brGDGTs化合物为主,其中以无环四甲基GDGT-Ia含量最高。【结论】环雷州半岛西北部海区存在水体自生brGDGTs化合物输入,在环雷州半岛近海表层沉积物中BIT指标具有一定物源指示作用。环雷州半岛东部海域沉积物brGDGTs的CBT-pH与半岛土壤pH数值相近,表明可利用环雷州半岛东部海域沉积物化合物环化指标CBT开展物源区古环境重建研究。MBT/CBT指标重建的温度可能反映河流流域平均气温。

【Objective】The composition,spatial distribution characteristics and input sources of branched glycerol dialkyl glycerol tetraethers compounds(brGDGTs)in offshore seafloor surface sediments of Leizhou Peninsula were analyzed,and aiming to discuss the implication of brGDGTs related environmental and source index in the near offshore region.【Method】The LC-MS technology was employed to detect the brGDGTs compounds in the offshore seafloor surface sediments surrounding Leizhou Peninsula.【Result】The composition and abundance of brGDGTs in the coastal waters have obvious regional distribution characteristics.The areas with higher abundance are mainly distributed in the northeast of the peninsula,the northwest and the west of the Qiongzhou Strait,while brGDGTs are generally located in the west.The abundance of the sea area is higher than that of the eastern sea area.Surface sediments are dominated by acyclic and low-methyl number brGDGTs compounds,of which acyclic tetramethyl GDGT-Ia has the highest content.【Conclusion】There is the input of brGDGTs from the water body in the northwest sea area,and the BIT indicator in the surface sediments of the Leizhou Peninsula has a certain provenance indicator.The CBT-pH of brGDGTs in the eastern sea area of the peninsula is similar to the pH value of soil in the peninsula,indicating that CBT can be used to study the paleo-environment reconstruction of the provenance area in the eastern sea of the Leizhou Peninsula.The temperature reconstructed by MBT/CBT indicators may reflect the average temperature of the river basin.