An ultrasound accelerated sequential extraction method and its application for element partitioning studies in compost from mixed waste streams

A rapid ultrasound accelerated sequential extraction procedure is presented which is modified from the standard BCR protocol and validated using the BCR 601 reference material. The method is accelerated at the extraction steps: for example, in the standard method each extraction step takes 16 h whereas with the ultrasonic extraction method developed in this work each step took 15 min. This means a further step can be included in the protocol without greatly increasing the experimental time. An extraction with pyrophosphate solution was therefore included to provide more information about the interaction between the elements and humic substances during the composting process. The new method has been applied to monitoring the metal partitioning behaviours in a composting process involving mixed waste streams. The metal partitioning profiles obtained from this new method show that in many cases composting tends to redistribute the metals from more labile forms to combined forms, especially to forms combined with humic substances.