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Particle size distribution fitting of surface detrital sediment using the Swrebec function

Abstract:

Purpose: The development of mathematical models to accurately represent the particle size distribution (PSD) of sediment has been addressed by different authors. Here, we introduce the three-parameter Swrebec function as a tool to fit the PSD of sediments. Moreover, we also assess the physical meaning of the undulation parameter (b) in the function. Materials and methods: We performed PSD by means of laser diffraction spectroscopy. Then, sediments were classified and the statistical parameters (mean, skewness, sorting and kurtosis) calculated using GRADISTAT software, according to the Folk and Ward’s method. Subsequently, the Swrebec function (programmed in Matlab) was applied to the data and its goodness-of-fit were evaluated by means of the adjusted coefficient of determination (R2-Adj) and the root mean squared error (RMSE). The results obtained by Swrebec were also compared with other functions using the Ezyfit toolbox. Results and discussion: The Swrebec model provided excellent correlations and low RMSE when fitting all grain size data. Furthermore, a correlation between b and both the skewness and RMSE was established. This indicates that the greater the asymmetry of the function, and therefore the larger the presence of coarse-grained particles, the lower the performance of the function. It was also observed that a change in the behaviour of all trends seems to occur at a b value of ~4.5. Conclusions: Results suggest that the studied function could be a simple approach for modelling PSD, with potential applications in soil and sediment science, geochemistry, sedimentology and coastal research modelling.