雅鲁藏布江上游干、支流沉积物总有机碳分布特征初探  

A preliminary study on distribution characteristics of total organic carbon in sediment in upper reaches of the Yarlung Zangbo River

作　　者：李世剑 康满春 刘流 彭辉[1,2] 刘佳[1,2] 胡杰茗[1,2] 肖尚斌[1,2] LI Shijian;KANG Manchun;LIU Liu;PENG Hui;LIU Jia;HU Jieming;XIAO Shangbin(Engineering Research Center of Eco-Environment in Three Gorges Reservoir Area,Ministry of Education,Yichang 443002,Hubei,China;College of Hydraulic and Environmental Engineering,China Three Gorges University,Yichang 443002,Hubei,China;Yunnan Key Laboratory of Plateau Geographic Processes and Environment Change,Faculty of Geography,Yunnan Normal University,Kunming 650500,China)

机构地区：[1]三峡库区生态环境教育部工程研究中心,湖北宜昌443002 [2]三峡大学水利与环境学院,湖北宜昌443002 [3]云南师范大学地理学部云南省高原地理过程与环境变化重点实验室,云南昆明650500

出　　处：《冰川冻土》2024年第2期443-456,共14页Journal of Glaciology and Geocryology

基　　金：第二次青藏高原综合科学考察研究项目(2019QZKK0207-02-05)资助。

摘　　要：为探究雅鲁藏布江(雅江)上游干、支流沉积物总有机碳(TOC)含量分布特征及其影响因素,研究了雅鲁藏布江上游干、支流沉积物TOC含量对粒度的响应,并基于随机森林分析(RFA)解释了流域内土地利用类型对沉积物TOC含量空间变化趋势的影响。结果表明,雅江上游沉积物TOC含量均值[(6.56±6.37)g·kg^(-1)]低于其他地区大中型河流[范围为5.95~49.06 g·kg^(-1),均值为(19.77±14.05)g·kg^(-1)]。其中,河源段沉积物TOC含量均值最低[(2.57±0.97)g·kg^(-1)],所有采样点沉积物TOC含量与黏土含量占比呈极显著正相关(r=0.64,P<0.01)。根据统计结果,包括雅江上游在内,河流沉积物TOC含量与粒径小于63μm颗粒含量具有极显著指数相关关系(r=0.77,P<0.01)。随机森林分析进一步表明,雅江上游沉积物TOC陆源贡献率中草地贡献率最大(48.12%),且受土地利用方式从以低覆盖度草地、裸土地为主导(上游头段)逐渐过渡到以中、高覆盖度草地和农、牧、一类工业用地(M1类)等为主(上游中、末段)的影响,沉积物TOC含量在空间上表现为随流向逐渐增加的趋势。总体上,人为干扰因素少及河流沉积物以砂质为主体是雅江上游沉积物TOC含量较低的重要原因。本研究深化了对雅鲁藏布江上游沉积物总有机碳含量分布特征及其影响因素的理解,可为进一步探究高原河流碳循环、生态环境保护以及区域可持续发展提供科学依据。To investigate the spatial characteristics of total organic carbon(TOC)content in sediment in upper and tributary streams of the Yarlung Zangbo River(YZR)and its influencing factors,responses of TOC content in sediment on particle size were studied and effects of land use in the watershed on spatial trends of TOC were analyzed based on the random forest analysis(RFA).The results indicate that the mean TOC[(6.56±6.37)g·kg^(-1)]in upper reaches of the YZR is lower than that of other large-and medium-sized rivers,which ranges from 5.95 to 49.06 g·kg^(-1) with a mean value of(19.77±14.05)g·kg^(-1).With the lowest TOC in sediment[(2.57±0.97)g·kg^(-1)]in headwater,TOC is highly positively correlated(r=0.64,P<0.01)with clay content in sediment in the YZR.Based on literatures and results of this study,a highly significant exponential correlation between TOC in sediment and the content of particles smaller than 63μm(r=0.77,P<0.01)was found across rivers,and thus,the content of particles smaller than 63μm could be an indicator of TOC in sediment in rivers.Furtherly,RFA results indicate that in upper reaches of the YZR,TOC in sediment is majorly terrestrially sourced from grassland(48.12%)and increased spatially along the direction of water flow due to transitioning of land use from low-coverage grassland and bare land in headwater to medium,high-coverage grassland,as well as to agricultural,pastoral,and industrial(Class M1)land in upper-middle and upper-end sections of the YZR.We,therefore,concluded that the lower TOC in upper reaches of the YZR can be generally attributed to less anthropogenic activities and predominant sandy texture.

关 键 词：雅鲁藏布江上游 沉积物总有机碳 粒度 空间异质性 

分 类 号：P512.2[天文地球—地质学] X833[环境科学与工程—环境工程]