Spatial Distribution of Sulfur Isotope Ratios in Human Hair Across the USA

VALENZUELA, LUCIANO O; CHESSON, LESLEY A; O'GRADY, SHANNON P; CERLING, THURE E; EHLERINGER, JAMES R

Washington

Conferencia; Forensics Isotope Ratio Mass Spectrometry Conference; 2010

The use of stable isotope analysis to investigate the region-of-origin of food, or animal and human tissues is a rapidly growing field. Particularly within the USA, stable hydrogen and oxygen isotope analyses have been used because their ratios in drinking water vary across the landscape in a predictable pattern. Stable isotope analyses of carbon, nitrogen and sulfur also hold potential as geo-locating tools. These elements are incorporated from the diet and thus provide a record of dietary inputs that may also represent geo-based patterns. Here we present data on carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) isotope ratios of human hair collected across the USA. We detected predictable regional differences in hair δ34S across the USA, with the lowest values in the northern Great Plains and increasing values towards the east, west and south. Low δ34S values were also detected in central California. No spatial variation was found for δ13C and δ15N in human hair. Using Geographic Information System (GIS) we created prediction maps by interpolating the average δ34S values among the sampled cities. Because no a priori information on the mechanisms that influence variation of δ34S values across the landscape was known, we investigated consequences of various interpolation algorithms. The accuracy of the prediction maps were tested by correlating the predicted δ34S values for hair samples not included in the initial generation of the maps. Here we show that stable sulfur isotope analysis may represent a new statistically significant tool to investigate the region-of-origin of human remains.