COMPARISON OF GRAIN SIZE PARAMETERS FROM GRAPHICAL AND MOMENT METHODS FOR SURFACE SEDIMENTS IN QUANZHOU BAY

Two methods, the moment and the graphic statistics methods, are used for calculation of grain size parameters for the 70 surface sediment samples taking from the Quanzhou Bay, Fujian Province. Comparison of the two sets of grain size parameters shows that the grain size parameters of the mean grain size, the sorting coefficient, skewness and kurtosis, are quite different derived from the two methods. The mean grain sizes from two methods are highly correlated, and interchangeable. The sorting coefficient has the similar result. But for the skewness and kurtosis, both of them have very weak correlation, so the values from two methods are not interchangeable. Then, comparing the contour maps of the two kinds of parameters, it is found that the results of the moment method are more sensitive in showing the horizontal change of grain size characteristics of sediments. By doing the Q type cluster analysis of the two groups of the grain size parameters, the results are well coincident with the sediment grain size probability classification, but the results of moment method looks more detailed in description of grain size variations. It is recommended using the moment method for data processing.