定量表征河流砂颗粒的形状——在西藏帕隆藏布的尝试

Quantitative characterization of grain shape signals of river sand——An attempt in Parlung Tsangpo,Xizang(Tibet)

河流搬运体系中,颗粒的形状属性可以反映其来源、搬运、沉积的过程。长期以来沉积学界缺乏相对统一的定量的、多维的颗粒形状参数。本研究以西藏雅鲁藏布江支流帕隆藏布为例,运用图像分析、软件分析等计算机辅助技术,对8个天然河流砂样品中的2276个颗粒开展碎屑成分鉴定和形状参数量化等工作。重点评估了11个颗粒形状参数,通过因子分析等统计方法提取并定义了3个形状信号,包括圆形度因子、规则度因子和平滑度因子。这些参数可用于表征颗粒宏观形状上接近圆形的程度、中观尺度上轮廓规则的程度及轮廓平滑的程度。挖掘天然河流砂的重要形状特征后,进一步探索了这些形状参数与颗粒成分、粒度的关系。本研究成果为解释河流系统中颗粒的形状信号、理解颗粒自身微观属性和外部物理过程等提供重要借鉴。

Objectives:In the natural fluvial systems,the shape attribute of particles can reflect their source,transportation,and deposition processes.For a long time,the sedimentologic community lacked relatively uniform quantitative and multidimensional particle shape parameters.This study aimed to quantify particle shape of modern sands,find a better shape characterization,and advance the understanding of shape properties in sedimentary grains.Methods:Taking the Parlung Tsangpo as an example,Tibet,a tributary of the Yarlung Tsangpo,computeraided technologies such as image analysis and software analysis were used to identify the detritus composition and quantify the shape parameters of 2276 particles in 8 river sand samples.The shape signals of these grains were processed using statistical methods such as principal component analysis and factor analysis.Results:Eleven particle shape parameters were evaluated,and 3 shape signals,including circularity factor,regularity factor and smoothness factor,were extracted and defined by factor analysis.Conclusions:These parameters can be used to characterize particles by the degree of circularity(macroscopic shape),contour regularity,and contour smoothness at the meso scale.Their relationship with the particle composition and size was thus further explored.The results of this study provide important references for interpreting the shape signals of particles in fluvial systems,understanding their microscopic properties and external physical processes.