The cleaning of burned and contaminated archaeological maize prior to 87Sr/86Sr analysis

Journal of Archaeological Science
By: , and 

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Abstract

Accurate trace-metal and strontium-isotope analyses of archaeological corn cobs require that metal contaminants be removed prior to chemical analysis. Archaeological cobs are often coated with construction debris, dust, or soil which contains mineral particles. In addition, most archaeological cobs are partially or completely burned and the burned parts incorporate mineral debris in their hardened residual structures. Unburned cobs are weak ion exchangers and most metals within a cob are not firmly bound to cob organic matter; therefore, immersing cobs in acids and rinsing them in deionized water to remove mineral contaminants may result in the undesirable loss of metals, including strontium, from the cob.

In this paper we show that some cob metal-pair ratios are not substantially changed when the cob is “cleaned” with deionized water, if the water-cob contact time does not exceed five minutes. Additionally, we introduce a method for eliminating mineral contaminants in both burned and unburned cobs, thus rendering them acceptable for strontium-isotope analysis. However, the decontamination procedure results in the rapid non-stoichiometric leaching of trace metals from the unburned cobs and it is possible that most metals will be extracted from the cobs during the lengthy decontamination process. Trace metals, in particular Al and Ca, should be analyzed in order to determine the presence and level of mineral contamination after cleaning.

Publication type Article
Publication Subtype Journal Article
Title The cleaning of burned and contaminated archaeological maize prior to 87Sr/86Sr analysis
Series title Journal of Archaeological Science
DOI 10.1016/j.jas.2009.09.005
Volume 37
Issue 1
Year Published 2010
Language English
Publisher Elsevier
Contributing office(s) National Research Program - Central Branch
Description 8 p.
First page 84
Last page 91
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