Comparison of functions for evaluating the effect of Fe and Al oxides on the particle size distribution of kaolin and quartz

Although it is generally agreed that Fe and Al can act to bind soil particles, their relative efficiencies as aggregants are still disputed. In this work, the aggregating efficiencies of both aged and non-aged Fe and Al oxides precipitated on kaolin or quartz substrates were characterized by comparing their effects on particle size distributions (PSD). To facilitate comparison of PSD data, these were parameterized by fitting them with five different probability density functions (the normal, lognormal, Jaky, fractal and Rosin-Rammler functions). The best fits were given by the Rosin-Rammler function (R ² = 0.997), whose alpha parameter was used to compare the aggregating efficiency of Fe and Al oxides: in order of decreasing efficiency, non-aged Al > non-aged Fe nearly equal aged Fe > aged Al-precipitates.