From: PO3::"sclay@MAIL.WSDOT.WA.GOV" "Scott Clay-Poole" 14-NOV-1995 23:18:45.48 To: Multiple recipients of list QUATERNARY CC: Subj: Re: Clay dispersal I dealt a great deal with clay samples in alluvium from the arid northeast corner of Arizona. This was the best bet to reduce the ionic binding potential of clay particles and separate these "sticky" clay units from the same sized pollen grain (at least that I was aware of at the time). If anyone can do me one better, that is, produce a better procedure I would love it, so pls. update me! I used a concentration of 44.6 g/liter and mixed a portion with my sample in a centrifuge tube and set it in a boiling water bath for 15 minutes. Sometimes I needed to do the procedure twice. Fortunately (or unfortunately) in alluvium, one finds more pollen in slower flowing water deposited sediments, so clay was always my nemesis. I did my work a couple of years ago in Flagstaff, at Northern Arizona University. I miss the the work and discoveries. For the ref., see Bates, C.D., P. Coxon and P.L. Gibbard 1978. A new method for the preparation of clay-rich sediment samples for palynological investigation. New Phytologist 81:459-463. >I would be very very grateful for any advice concerning means of clay >dispersal. >I am in the process of obtaining size fractions by settling in a tube, using >filtered seawater as the settling medium. I cannot use distilled water as I >want to measure the radioactivity of the size fractions obtained, >particularly for >Cs-137, Am-241 and Pu isotopes. Distilled water would cause desorption of some >of the adsorbed Cs. Unfortunately, Calgon does not seem to be very effective >as a dispersing agent in seawater. Any advice on other dispersing agents would >be very welcome. > >Thanks >Julian Clifton Scott Clay-Poole, Ph.D. Botany/Paleoecology (360) 754-3367 (360) 705-7409 work http://www.wsdot.wa.gov/eesc/environmental/Communications.htm From: PO3::"stagerc@NORTHNET.ORG" "Curt Stager" 26-NOV-1995 19:07:54.95 To: Multiple recipients of list QUATERNARY CC: Subj: clays Dear Quaternary folks; a while back some discussion was begun regarding clay dispersal. Here's a technique Dan Livingstone showed me about 15 years ago, based on Bates, Coxon, and Gibbard, 1978. New Phytologist 81:459-463. I've used it with great success in removing clays from African diatom samples, and hope it proves useful to some of you. Here's the summary from my old notes: "Suspend a sediment sample in 0.1M sodium pyrophosphate solution, vortex well, and heat in hot water bath for 15-20 minutes. Centrifuge 5 minutes at 1200 rpm, and examine a drop of supernatant under the microscope to check for diatoms (if present, keep centrifuging until they settle out). Decant, and repeat until the supernatant is clear (e.g. free of clays)." I suppose the pyrophosphate covers the clays with mutually repulsive charges so they disperse and float while smaller particles settle out during centrifuging. Works fine for me, anyway. Best of all, it's quick and easy. Best regards, Curt Stager.