Effects of Maceration on Light Stable Isotopic (δ13C, δ18O) Values of Pig (Sus scrofa) Rib Bone Carbonate Implications for Geolocation Estimates of Unidentified Human Remains

Abstract

Geoprofiling isotopic analyses provide investigative leads for unidentified human remains cases by determining possible regions of origin or excluding unlikely residences during life, which in turn can reduce the number of missing persons an investigator must consider. However, maceration methods involving heat, bleach, baking soda, and detergents have much potential to significantly change biogenic isotopic values in the structural carbonate phase of bone bioapatite. Here we test the impact of seven maceration methods on δ¹³C and δ¹⁸O values of bone carbonate (BC) of pig (Sus scrofa) ribs. Four of the seven maceration methods altered pig δ¹³CBC values with offsets ranging from 0.4‰ to 1.4‰; this amount of change would not severely impact human diet or geolocation interpretations. Five of the methods significantly decreased pig δ¹⁸OBC values by averages ranging between 1.0‰ and 2.6‰ likely due to the isotopic exchange between bone and heated water. As an illustrative exercise, we compared our study’s results to macerated rib δ¹³CBC and δ¹⁸OBC values of an identified New York City resident previously in the custody of the New York City Office of Chief Medical Examiner (NYC OCME). We suggest that maceration methods, especially those involving heated water, can potentially contribute to erroneous geolocation estimates garnered from rib δ¹⁸OBC values of unidentified individuals.