2007-16

2007-16

The goal of this research is to develop a technique for conducting “non-destructive” radiocarbon dating of perishable archaeological artifacts. It is not truly non-destructive because microscopic amounts of carbon must be removed form the surface. But the aim is to make the technique so that no visual change is observed. There are two very destructive steps in radiocarbon dating as it is now practiced. ( 1) Pre-cleaning to rid organic artifacts of the commonly occurring humic acid and carbonate/oxalate contaminants are accomplished by serial strong acid, strong base, and strong acid treatments. This leaves the typical sample looking  nothing like its original form. In fact, the samples are highly degraded in these washes. (2) Collection of carbon from the samples to be dated is accomplished by high temperature combustion to carbon dioxide.  This step is totally destructive for all organic artifacts that are radiocarbon dated.

A method has already been developed in my laboratory that renders the second step virtually non-destructive for many organic materials: plasma-chemical extraction of organic carbon [1-3]. This technique, developed for dating rock paintings [4-6, and Texas A&M University references therein] –plasma-chemical extraction, also eliminated the need for the two acid steps required in step (I) [7 ,8]. Plasma oxidation may also be preferable for any type of sample containing significant amounts of oxalate-containing minerals. Two previous studies, one from our laboratory [9] and one from the Oxford Accelerator mass spectrometry laboratory [1 0] found that in some circumstances, traditional acid treatment does not remove all of the contaminant calcium oxalate minerals. All that remains to obtain “non-destructive” radiocarbon dating of perishable artifacts is a non-destructive substitution for the strong base wash currently used to extract any contaminating humic acids. We investigate here the possibility of using supercritical fluid cleaning to extract humic acids from organic archaeological artifacts.

This research was made possible through Grant MT-2210-04-NC-07 from the National Center for Preservation Technology and Training (NCPTT).

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