NSF Grant Facilitates Unique Collaboration in Chemical Engineering and Archaeochemistry

A recently awarded National Science Foundation grant has permitted a unique fusion between chemical engineering and archaeochemistry researchers to improve radiocarbon-based dating techniques as applied to fibers, macroflora, charcoals, rock paintings and burial gauzes from Egyptian mummies.

The collaborators — Jerry King, a professor in the Ralph E. Martin department of chemical engineering, professor Karen Steelman of the chemistry department at the University of Central Arkansas and professor Marvin Rowe of Texas A&M University and Conservation Laboratory of the Museum of New Mexico in Santa Fe — are investigating the use of supercritical fluids, such as carbon dioxide under pressure, to remove organic contamination from archeological artifacts prior to carbon 14 dating.

Utilization of supercritical fluid carbon dioxide (SC-CO2) along with small quantities of organic solvents removes organic contaminants such as lipids and waxes used in embalming and humic acid residues due to contaminating soil matter. The supercritical fluid cleaned artifacts are then further treated using plasma oxidation to collect microscopic amounts of carbon (approximately 100 micrograms of carbon, or the equivalent of 50 specks of dust) from an artifact surface non-destructively prior to analysis using accelerator mass spectrometry.

This combined use of SC-CO2 extraction and plasma oxidation has the potential to resolve one of the major problems facing archaeologists working with rare, unique or sacred objects where the need to place artifacts in a chronological context is often offset by their destruction by using a small specimen from the artifact removed for combustion using current dating methods. This can be minimized using the above non-intrusive method thereby permitting more accurate dating on ultra small samples, such as those from Indian burial sites, with no visible change to the artifact's matrix.

Artifact matrices such as wood, charcoal, animal skin, bone from a mummy, and ostrich egg shells as old as 5,000 years have proven amenable to the technique while the combination of techniques is being applied to hydrocarbon-like residues found in resins used to cover Egyptian mummy gauzes. The above dualistic treatment approach replaces acid-base treatments normally used to clean the artifact, resulting in improved accuracy in dating artifacts up to 50,000 years in age.

The new method has potential for application to the repatriation of human remains from Native American burials as well as precious museum artifacts. King remarked that the SC-CO2 based process has also been applied commercially for dry cleaning, degreasing of metal parts, as well as the preparation of samples for electron microscopy. King also noted that there is a historic connection with the University of Arkansas since professor Rowe obtained his doctoral degree in nuclear chemistry in 1966 while a graduate student at the university.