Efficacy of sonication-assisted sieving on Quaternary pollen samples

Debris in archaeological pollen samples can obscure pollen grains during microscopic analysis. When attempting to remove debris smaller than 10 microns from a pollen sample, screen openings can be too small, requiring the sample to be agitated in order to facilitate its passing through the screen. We recently developed a new method that uses a Branson((c)) S450 sonicating disruptor horn to agitate the sample, keeping the screen free from debris. Using this method, we have been successful in ridding the pollen sample of debris smaller than 10 microns. This paper presents the results of an investigation of the potential effects of sonication on pollen preservation. We selected 12 fresh pollen types based on a unique range of morphological characteristics, and subjected this assemblage to sonication for different lengths of time and at variable output intensities. Our studydemonstrated that when used for 3minutes at low to medium output intensities, a sonicating disruptor horn can aid in the removal of unwanted debris without considerably damaging pollen grains. We also did not find evidence that pollen colliding with other debris in a sample increased levels of degradation. Analysis on the efficacy of sonication-assisted sieving demonstrated that more tiny debris was removed from the sample at higher frequencies and over increasing durations.