We experimented with the use of lithium heteropolytungstate (LST) as a heavy liquid to concentrate pollen in sediments from a desert paleolake with low pollen abundances. LST is one of several non-toxic heavy liquids based on inorganic tungsten that are replacing an older generation of heavy liquids that are harmful to human health, such as zinc bromide, zinc chloride, and bromoform. Several researchers have reported on the use of sodium heteropolytungstate (SPT) in processing pollen samples, but we found no previous reports of using LST in pollen preparation. For our low-pollen desert samples, we developed a palynological preparation procedure with LST heavy liquid separation that entails fewer chemical treatments and washes than standard protocols to minimize the laboratory destruction or loss of pollen. In the heavy liquid step, we varied centrifuge times and the specific gravity of the LST solution in an effort to extract the most pollen possible. Ultimately our samples proved too pollen-poor to yield countable residues, even under the best circumstances. But our protocols and results can serve as models for experimenting with LST with other sediments.

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