Beard B L, Johnson C M
University of Wisconsin-Madison, Department of Geology and Geophysics 53706, USA.
J Forensic Sci. 2000 Sep;45(5):1049-61.
The Sr isotope composition measured in skeletal elements (e.g., bone, teeth, or antlers) can be used to infer the geographic region that an animal or human inhabited, because different regions tend to have distinct Sr isotope compositions, and natural variations in the relative abundance of Sr isotopes are not changed as Sr is processed through the food chain. Therefore, an organism that ingests Sr from one region can have a Sr isotope composition that is different than that of an organism that ingests Sr from another region. The Sr isotope composition of skeletal elements is a reflection of the concentration-weighted average of dietary Sr that was ingested while that skeletal element was produced. Because different skeletal elements grow and exchange Sr at different stages during the life times of organisms, Sr isotope analysis of different skeletal elements can be used to infer changes in geographic location at different stages in an organism's life. The Sr isotope composition measured in human teeth will reflect the average Sr isotope composition that was ingested as a child, due to the immobile nature of Sr and Ca in teeth after formation, whereas the Sr isotope composition of bone will reflect the average isotopic composition over the last ten years of life, due to continuous biological processing of Sr and Ca in bone. Inferring the average isotopic composition of dietary Sr is best done by analyzing skeletal fragments from control groups, which might be animals that have the same feeding habits as the animal in question, or, in the case of humans, analysis of close family relatives. In cases where it is not possible to construct a Sr isotope database from control groups, it becomes necessary to estimate the isotopic composition of dietary Sr based on geologic principles. We present three case studies from our research that illustrate a range of approaches: (1) results from a criminal case where a deer was illegally harvested and the location of the deer was important to establish, (2) a pilot study of commingled human remains from a burial in Vietnam, associated with the Vietnam Conflict, and (3) a study of 13th and 14th century migration of peo ple from an archeological site in the Southwest United States.
在骨骼元素（如骨骼、牙齿或鹿角）中测量的锶（Sr）同位素组成可用于推断动物或人类曾经居住的地理区域，因为不同地区往往具有不同的Sr同位素组成，并且Sr同位素相对丰度的自然变化在其通过食物链传递过程中不会改变。因此，从一个地区摄取Sr的生物体，其Sr同位素组成可能不同于从另一个地区摄取Sr的生物体。骨骼元素的Sr同位素组成反映了在该骨骼元素形成时摄入的膳食Sr的浓度加权平均值。由于不同的骨骼元素在生物体生命的不同阶段生长并与Sr进行交换，因此对不同骨骼元素进行Sr同位素分析可用于推断生物体生命不同阶段的地理位置变化。由于牙齿形成后其中的Sr和钙具有不可移动的特性，因此在人类牙齿中测量的Sr同位素组成将反映儿童时期摄入的Sr同位素平均组成，而骨骼的Sr同位素组成将反映生命最后十年的平均同位素组成，这是因为骨骼中Sr和钙会持续进行生物过程。推断膳食Sr的平均同位素组成最好通过分析对照组的骨骼碎片来完成，对照组可能是与所研究动物具有相同饮食习惯的动物，或者对于人类而言，是分析近亲的情况。在无法从对照组构建Sr同位素数据库的情况下，就有必要根据地质原理估算膳食Sr的同位素组成。我们展示了来自我们研究的三个案例研究，它们说明了一系列方法：（1）一个刑事案件的结果，其中一头鹿被非法猎取，确定鹿的位置很重要；（2）对与越南冲突相关的越南一处墓葬中混合的人类遗骸进行的初步研究；（3）对美国西南部一个考古遗址中13世纪和14世纪人群迁移的研究。
