摘要
柴达木盆地地处西北干旱区、青藏高原和东部季风区三大自然区域交汇地带,生态环境极其脆弱,是开展古气候研究的理想场所。本次以青藏高原柴达木盆地湖泊沉积物为研究对象,利用先进的前处理方法和气相色谱-质谱联用技术(GC-MS),探讨该区长链烯酮和中位酮的分布特征及指示意义。研究表明,青海湖、尕海湖、托素湖和可鲁克湖的湖泊表层沉积物中均含有长链烯酮系列化合物,并显示出C37优势模式。其中,尕海湖、托素湖和可鲁克湖具有相近的烯酮比值(C37/C38),暗示这3个湖泊可能具有相同的烯酮母源藻。而柴达木盆地湖泊中C37四不饱和烯酮含量(%C37:4指标)与盐度呈正相关关系,这与青海湖和已发表的结论相矛盾,可能是由于湖泊中藻类群落结构的差异性而导致的。在可鲁克湖湖边湿地钻取了520 cm的沉积物岩芯,将岩芯的烯酮数据与可鲁克湖和青海湖已发表的烯酮记录进行对比,发现存在一定的差异性,可能与采样的位置、烯酮母源藻物种效应和柴达木盆地湖泊的特殊自然条件有关。特别的是,本次研究在湖泊表层沉积物和沉积物钻孔中均检测出长链中位酮系列化合物(C31-16-one、C33-17-one和C35-18-one),且其表现为随着碳数增加,化合物丰度明显减小的变化趋势,即C31>C33>C35。通过与正构烷烃参数进行对比,发现C31-16-one可能来源于沉水植物,而C33-17-one和C35-18-one可能来源于高等植物贡献。在“8.2 ka”和“4.2 ka”冷事件中,C31-16-one的含量显著减小,而C33-17-one和C35-18-one增加,暗示中位酮系列化合物可能是指示古气候环境变化的潜在指标。
The long-chain alkenones(LCAs)unsaturation proxies have been widely applied for reconstructing paleotemperatures,but there are fewer studies on their applications in lacustrine system,especially for Qaidam Basin in Tibetan Plateau.The ecological environment of Qaidam Basin is extremely fragile due to it is located at the overlapping region of three climatic provinces of China,i.e.the northwest arid region,Qinghai-Tibetan Plateau and eastern monsoon region.In order to understand the application of LCAs in Qaidam Basin,organic geochemical analysis were employed on surface lacustrine sediments from Qinghai Lake,Gahai Lake,Toson Lake and Hurleg Lake.The Hurleg Lake is a freshwater lake with a water body salinity of about 1.0 g/L,while Qinghai Lake,Gahai Lake and Toson Lake are all saline lakes with water salinities of 14.6 g/L,94.4 g/L and 27.8 g/L,respectively.In addition,Toson Lake is the terminal lake of Hurleg Lake.The distribution of LCAs in the lake sediments of Qaidam Basin all showed the predominance of C37,and the abundance of C37:4 Me and C38:4 Et were relatively high.The C37/C38 rations were similar in Hurleg Lake,Toson Lake and Gahai Lake with the value of 1.12~1.96,but the Qinghai Lake with a high C37/C38 ratio of 7.10,suggesting that the Qinghai Lake may harbor different species of haptophyte algae with other three lakes.In addition,the study found that the%C37:4 value of lakes in the Qaidam Basin is positively correlated with changes in lake salinity,which may be caused by differences in haptophyte species and different response mechanisms to salinity.Further analysis of the LCAs records of the sediment core(37°15'10.91″N,96°51'06.06″E;520 cm)in the wetland of Hurleg Lake showed that alkenones were only detected during 10.5~7.7 cal.ka B.P.However,the paleotemperatures and%C37:4 values estimated by alkenones were different from the published records in this area,which may be caused by the location of sampling point,the species effect,changes in growth conditions(such as salinity and nutrient,etc.)
作者
张婷
王永莉
魏志福
汪亘
何薇
马雪云
马贺
玉晓丽
李尚昆
ZHANG Ting;WANG Yongli;WEI Zhifu;WANG Gen;HE Wei;MA Xueyun;MA He;YU Xiaoli;LI Shangkun(Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,Gansu;Key Laboratory of Petroleum Resources,Gansu Province/Key Laboratory of Petroleum Resources Research,Chinese Academy of Sciences,Lanzhou 730000,Gansu;Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;University of Chinese Academy of Sciences,Beijing 100049)
出处
《第四纪研究》
CAS
CSCD
北大核心
2021年第4期1056-1068,共13页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:41831176、41972030和41902028)
国家重点研究发展计划项目(批准号:2017YFA0604803)
第二次青藏高原科学考察与研究计划项目(批准号:2019QZKK0707)
中国科学院(B类)战略性先导科技专项项目(批准号:XDB26020302)
“西部之光”一般项目
甘肃省重点实验室开放课题(批准号:1309RTSA041)共同资助
关键词
长链烯酮
中位酮
烯酮母源藻
有机质来源
柴达木盆地
long-chain alkenones
mid-chain ketones
alkenone-producing algae
source of organic matter
Qaidam Basin
