Ralph AllenRalph O. Allen

 

Trace Analysis: Environmental, Archaeological, and Forensic Applications

The development of sensitive analytical methods has helped provide more detailed information about the small chemical differences between materials which seem similar but have different histories. In some cases, like geological samples, the large scale geochemical processes can give rise to subtle yet understandable differences in those elements which are present at trace levels. We have used instrumental neutron activation analysis and X-ray fluorescence to study several types of geological materials. These materials have been investigated as part of an ongoing effort to interpret the migration of trace elements during geochemical processes. In some cases, these same geological materials have been used by prehistoric humans and hence our studies have had archaeological implications.

In our studies of sediments from the Nile River in Egypt, we have discovered that if the unaltered mineral fragments are separated and analyzed there are differences in chemical composition. This has been explained by showing that over time the relative contributions of sediment load from the various drainage basins has changed. The implications of this work have been to provide a chemical method to distinguish Nile sediments from different time periods and to help interpret the archeological record of Egypt from the time before the pharaohs. Indirectly these studies have provided information on the ancient environmental conditions in central and northeastern Africa.

The investigation of geological materials plays another important role in studying the environment. The natural migration of trace elements during metamorphism of rocks allows one to predict the potential migration of radioactive isotopes from the long term storage of high level radioactive wastes. Decomposition of marble and other building materials due to acid rain depends upon many factors but geochemical studies can provide better information to predict the impact of this growing pollution problem. Our earlier studies have also shown the impact of acid rain and the long range atmospheric transportation of heavy metals on the chemistry of lakes and soils.

To provide accurate trace element data on large numbers of samples, we have investigated several other analytical methods. The inductively coupled plasma emission source used to provide ions for a quadrupole mass spectrometer (ICP-MS) holds considerable promise. This method is also being used to study soil and glass samples for applicability in the forensic laboratory. Our efforts in the forensic science field are part of a continuing cooperative effort with scientists at the FBI's research facilities. In the past, traces of explosive residues and epoxies have been analyzed to differentiate the sources of the materials. Chemical methods to identify and match soils or various polymeric materials have also been investigated as part of this cooperative program. The latest forensic science efforts have been directed toward the important new area of DNA "fingerprinting." This major forensic tool allows small amounts of genetic material to be used to match the DNA from a suspect. Our efforts are directed toward improving the sensitivity of the marker detection system by replacing the currently used radioactive labels.

Representative Publications

Archaeological Chemistry IV, ACS Advances in Chemistry Series, 220, Ralph O. Allen, Editor. ACS, Washington, DC. 1989.

Archaeological Implications of Differences in the Composition of Nile Sediments. R. O. Allen, H. Hamroush, and M. A. Hoffman. Advances in Chemistry (Archaeological Chemistry IV). 1989. 220: 33-57.

Trace Element Changes in Human Serum During Cancer Therapy. R. O. Allen, O. Bormer, and E. Steinnes. in Proc. Symp. of Applic. of Nuclear Tech. in Life Sciences, Munich, IAEA. 1989.

Risk Assessment Models for Mediation of Sites Contaminated with Heavy Metals. R. O. Allen, M. D. Lockhart, Y. Y. Haimes. Heavy Metals in the Environment, CEP Ltd., Edinburgh. 1989. 422-425.