Isotope analysis

Isotope analysis is the identification of isotopic signature, the distribution of certain stable isotopes and chemical elements within chemical compounds. This can be applied to a food web to make it possible to draw direct inferences regarding diet, trophic level, and subsistence. Variations in isotope ratios from isotopic fractionation are measured using mass spectrometry, which separates the different isotopes of an element on the basis of their mass-to-charge ratio.

The ratios of isotopic oxygen are also differentially affected by global weather patterns and regional topography as moisture is transported. Areas of lower humidity cause the preferential loss of ¹⁸O water in the form of vapor and precipitation. Furthermore, evaporated ¹⁶O water returns preferentially to the atmospheric system as it evaporates and ¹⁸O remains in liquid form or is incorporated into the body water of plants and animals.

Isotopic oxygen is into the body primarily through ingestion at which point it is used in the formation of, for archaeological purposes, bones and teeth. The oxygen is incorporated into the hydroxylcarbonic apatite of bone and tooth enamel.

Bone is continually throughout the lifetime of an individual. Although the rate of turnover of isotopic oxygen in hydroxyapatite is not fully known, it is assumed to be similar to that of collagen; approximately 10 years. Consequently, should an individual remain in a region for 10 years or longer, the isotopic oxygen ratios in the bone hydroxyapatite would reflect the oxygen ratios present in that region.

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