Purdue University, Department of Earth and Atmospheric Sciences, West Lafayette, IN 47907-2051, USA.
Forensic Sci Int. 2011 May 20;208(1-3):156-66. doi: 10.1016/j.forsciint.2010.11.021. Epub 2011 Feb 21.
Previous work suggests that δ(18)O values of human hair can be used to constrain the region-of-origin of unknown individuals, but robust assessments of uncertainties in this method are lacking. Here we assess one source of uncertainty - temporal variation in the δ(18)O value of drinking water - using a monthly tap water survey of δ(18)O to develop geospatial models (i.e., maps) of the intra-annual variation (seasonality) in tap water δ(18)O for the contiguous USA. Temporal variation in tap water δ(18)O was correlated with water-supply type, and was related to geographic patterns of precipitation δ(18)O seasonality and water residence time. The maps were applied in a Bayesian framework to identify the geographic origin of an unidentified woman found in Utah, based on measured δ(18)O of scalp hair. The results are robust in specifying parts of the western USA as the most likely region-of-origin. Incorporation of tap water δ(18)O seasonality in the analysis reduces the precision of geographic assignments, but other sources of uncertainty (e.g., spatial interpolation uncertainty) have an equal or larger effect.
先前的研究表明，人体头发的 δ(18)O 值可用于限制未知个体的来源地区，但该方法的不确定性评估仍存在不足。本研究利用每月对自来水 δ(18)O 的调查，评估了一个不确定性来源，即饮用水 δ(18)O 的时间变化，并使用该数据开发了美国连续地区自来水中 δ(18)O 年内变化（季节性）的地理空间模型（即地图）。自来水 δ(18)O 的时间变化与供水类型相关，且与降水 δ(18)O 季节性和水停留时间的地理模式有关。然后，我们在贝叶斯框架中应用这些地图，根据在犹他州发现的一名身份不明女性的头皮毛发实测 δ(18)O 值，确定其最可能的来源地区。研究结果表明，西部地区是最有可能的来源地区，但具体到某些地区时结果并不明确。在分析中纳入自来水 δ(18)O 季节性会降低地理归属的精度，但其他不确定性来源（例如，空间插值不确定性）的影响则相等或更大。
