A description of aggregate liberation and dispersion in A horizons of Australian Vertisols by ultrasonic agitation

A theory is proposed which is analogous to a first-order consecutive reaction to describe the stepwise breakdown of an aggregate hierarchy for Vertisols subjected to ultrasonic agitation. To explain the liberation and subsequent dispersion of microaggregates as increasing ultrasonic energy is applied the aggregate liberation and dispersion curve (ALDC) is developed. It is found that the prominence and shape of the curve is dependent on the rate constants, which explain the rate of microaggregate liberation and subsequent dispersion. From this curve it is possible to estimate the maximum mass of microaggregates, which is not only dependant on the rate constants, but also the availability of clay that farm the microaggregates. The resulting ALDC for the sample also enables the estimation of the total energy applied needed to initiate dispersion of the liberated microaggregates. It is found that the relative stability of the micoraggregates are correlated with some of the chemical properties (ESP and CaCO3) of the samples. (C) 1999 Elsevier Science B.V. All lights reserved.