鄂陵湖晚全新世沉积物记录的黄河源区气候环境变化  

LATE HOLOCENE CLIMATIC AND ENVIRONMENTAL VARIATION IN THE SOURCE AREA OF THE YELLOW RIVER RECORDED BY SEDIMENTS FROM THE LAKE NGORING,NORTHEASTERN QINGHAI-TIBETAN PLATEAU

作　　者：蒲阳 韩悦 张虎才 常凤琴 PU Yang;HAN Yue;ZHANG Hucai;CHANG Fengqin(School of Geographical Sciences,Nanjing University of Information Science&Technology,Nanjing 210044,Jiangsu;Institute for Ecological Research and Pollution Control of Plateau Lakes,School of Ecology and Environmental Science,Yunnan University,Kunming 650504,Yunnan)

机构地区：[1]南京信息工程大学地理科学学院,江苏南京210044 [2]云南大学生态与环境科学学院,高原湖泊生态与污染治理研究院,云南昆明650504

出　　处：《第四纪研究》2021年第4期1000-1011,共12页Quaternary Sciences

基　　金：国家自然科学基金项目“山西阳城岩溶湖泊年分辨率类脂生物标志物气候环境意义研究”(批准号:41877453);国家自然科学基金国际(地区)合作与交流项目“IODP361航次U477孔岩芯记录的距今15万年以来南非季风演化及海陆人类相互作用”(批准号:41820104008)共同资助。

摘　　要：通过对青藏高原黄河源区鄂陵湖35 cm长的沉积物岩芯(NR-1)中总有机碳含量(TOC)、总氮含量(TN)、碳氮比值(C_(org)/N_(tot))以及有机碳同位素(δ^(13)C_(org))和总氮同位素(δ^(15)N_(tot))等地球化学指标的分析,并结合青海地区文献资料记载的人口数量变化以及高原湖泊水位记录,对研究区近1500 a以来的气候环境变化进行了深入探讨。结果表明:近两百多年以来鄂陵湖沉积物中TOC和TN指标呈现明显上升的趋势,与青海东部地区人口数量变化趋势一致,表明近代人类活动已经对青藏高原最大淡水湖生态系统产生了显著的影响;而沉积物中δ^(13)C_(org)值变化与青海湖水文环境重建指标具有可比性,说明高原大型淡水湖泊沉积物δ^(13)C_(org)值可指示湖泊水位波动;此外δ^(15)N_(tot)值变化趋势与青藏高原东北部已有的古温度记录总体一致,推测鄂陵湖沉积物δ^(15)N_(tot)值可能响应了湖泊水体营养状态的变化,间接指示了湖泊夏季表层水温的波动。本研究为青藏高原腹地高海拔现代湖泊沉积物中有机碳和总氮含量及其同位素指标的解译提供了全新的思路。On basis of the organic geochemical indexes including total organic carbon(TOC),total nitrogen(TN),carbon nitrogen ratio(C_(org)/N_(tot)),organic carbon isotope(δ^(13)C_(org))and total nitrogen isotope(δ^(15)N_(tot))in the sediment core(NR-1)collected from the Lake Ngoring in the source area of Yellow River(SAYR),northeastern Qinghai-Tibetan Plateau(QTP),the climatic and environmental variations during last 1500 years were reconstructed.A gravity core(NR-1)was taken at a water depth of 31.8 m in Lake Ngoring at a GPS location of 35°02'10″N,97°42'24″E in July 2009.The core was 35 cm in length and 55 sedimentary samples were obtained.The results show that TOC and TN in the sediments of Lake Ngoring have increased significantly in the past 200~300 years,which is consistent with the population trend in eastern Qinghai Province.Also,the trends of TOC and TN are comparable with the variation of atmospheric CH_(4)concentration and the change of agricultural production pattern that the former nomadic pastoral lifestyles gradually being transformed into permanent settlements since the early eighteenth century,indicating that the sedimentary organic matter for the last 200~300 a in Lake Ngoring mainly respond to the increased human activities in the SAYR.The variation ofδ^(13)C_(org) value in sediments is consistent with the fluctuation of water level,which indicates that the sedimentaryδ^(13)C_(org) values in large freshwater lakes in SAYR might be a reliable proxy to reflect the change of lake water level.In addition,the variation ofδ^(15)N_(tot) accords with the temperature records in the northeastern QTP.So theδ^(15)N_(tot) value of sediment in Lake Ngoring might respond to the change of nutrient level of lake water and indirectly indicate the fluctuation of lake surface water temperature.This study provides a new idea for the interpretation of organic carbon and total nitrogen contents and their isotopic values in lake sediments collected from the interior region of the QTP.

关 键 词：黄河源区 湖泊水位 水文条件 气候变化 环境演变 人口数量 

分 类 号：P593[天文地球—地球化学] P941.78[天文地球—地质学]