A comparative study on the grain-size parameters of marine sediments derived from three different computing methods

Grain-size parameters of marine sediments are the sensitive indexes for reflecting the sediment sources and hydrodynamic conditions. At present, the various methods for calculating the grain-size parameters of marine sediments partially restrict the integration and availability of grain-size data. Three hundred and four-eight surface sediments grain-size data from the offshore of the Changjiang River Estuary are used to calculate the grain-size parameters, respectively adopting the graphical method of Folk and Ward, the moment method of Collias et al. and the moment method of McManus. Correlation analysis and statistical analysis methods are employed to detect the differences of results from the above three different methods and their influencing factors. The mean grain-size and sorting coefficient derived from the graphical method and the moment methods are significantly correlative and stable, which are not affected by sediment sources. On the contrary, the values of skewness and kurtosis calculated from three different methods indicate low correlation or even no relativity. The results show that the differences of grain-size parameters calculated from the three methods depend both on sediment types and their form of distribution curve. When sediments components are uniform with a normal frequency curves, there are high correlation coefficients amount the grain-size parameters from different methods, While for the case of the coarse or fine sediments with the abnormal frequency curves of a long tail feature, the different of grain-size parameters using difference methods are increased. The results suggest that Collias et al. moment formulas are recommended to be used in the process of grain-size integration for their sensitivity and reliability in reflecting the grain-size distribution characteristic.