图解法和矩值法粒度参数的定性对比:以琼州海峡岸滩表层沉积物为例

Qualitative comparative analysis on grain-size parameters of derived from graphic and moment methods:a case study of the surficial sediment of coastal beaches of Qiongzhou Strait

前人已开展了大量的关于图解法和矩值法数值结果的相关性分析和相互转换方程的确定工作,但针对定性结果的对比仍较为罕见。本文选取了琼州海峡两岸15个海滩22条断面105个表层沉积物为典型研究对象,分别采用Folk和Ward图解法和Friedman矩值法获取粒度参数结果,构建定量结果的回归关系和对比定性结果的异同。结合前人的研究成果,本文进一步探讨了两种方法结果的可对比性,并分析两种方法的方法差异对沉积物粒度信息提取及使用造成的可能影响。研究结果表明:(1)就定量结果而言,图解法和矩值法计算的平均粒径和分选系数具有强相关性(R2≥0.951),而偏态和峰态则表现为中等相关(R2=0.586)和不相关(R2=0.011),表明图解法和矩值法计算粒度参数定量结果之间的相关性并不稳定,这与前人的研究结果基本一致;(2)就定性结果而言,图解法和矩值法的结果之间存在较大偏差,分选系数、偏态和峰态不一致的占比分别达30.48%、55.24%和71.43%,这与定量结果的相关性存在一定程度的偏差,表明定量结果的相关性程度并不能完全用于指示定性术语结果的一致性程度。鉴于最大化地揭示沉积物的差异是粒度参数分析方法追寻的目标,在选择何种方法计算粒度参数时需充分考虑沉积物粒径概率分布曲线的特征。本文提供了一个以海滩沉积物为研究对象的图解法和矩值法粒度参数结果对比的典型案例,研究结果有助于提升对粒度参数分析方法的差异、原因和科学使用等方面的认识。

Little research attention has been paid to comparison of the descriptive terms used in graphical method and moment method for grains-size parameters,although some work has been done on comparison of the numerical values and mutual conversion equations.In this paper,105 surface sediments from 22 sections of 15 beaches on both sides of the Qiongzhou Strait are selected as typical research objects.The grain-size parameter results are obtained by the Folk & Ward graphic method and Friedman moment method respectively.The regression relationship of quantitative results is constructed and the similarities and differences of qualitative results are compared.Combined with the previous research results,this paper further discusses the comparability of the results of the two methods,and analyzes the possible impact of the differences between the two methods on the extraction and use of sediment particle size information.The results show that:(1) in terms of quantitative results,the average particle size and sorting coefficient calculated by graphic method and moment method have strong correlation(R2 ≥ 0.951),while the skewness and kurtosis show moderate correlation(R2 = 0.586) and uncorrelation(R2 = 0.011),indicating that the correlation between the quantitative results of particle size parameters calculated by the two methods is not stable,which is basically consistent with the previous research results;(2) as far as qualitative results are concerned,there is a large deviation between the results of graphic method and moment method.The proportion of inconsistent sorting coefficient,skewness and kurtosis is 30.48%,55.24% and 71.43% respectively,which deviates from the correlation of quantitative results to a certain extent,indicating that the correlation degree of quantitative results can not be fully used to indicate the consistency degree of qualitative term results.Since it is the goal of grain-size parameter analysis method to reveal the differences of sediments to the greatest extent,it is necessary to fully consider the characteristics of grain-size distribution curve when choosing which method to calculate grainsize parameters.This paper provides a typical case of comparing the results of graphical method and moment method for grain-size parameters of beach sediments.The research results help to improve the understanding of the differences,causes and scientific use of grain-size parameter analysis methods.