Department of Geology and Geophysics, University of Utah, 115 S 1460 E, Salt Lake City, UT, 84112, USA.
Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA.
Environ Monit Assess. 2018 Oct 18;190(11):644. doi: 10.1007/s10661-018-7038-z.
The spatial distribution of trace elements in hair is highly heterogeneous at the microscale. The relatively mild spatial variation of endogenous signal incorporated during hair growth may be amplified by orders of magnitude due to later exogenous contaminations. Here, we studied the longitudinal and transverse distributions of trace elements in elephant and giraffe hair and discussed the possible endogenous and exogenous contributions. Laser ablation ICP-MS analyses were performed on cross sections of hair to assess the surface contamination and transverse variation. We also removed the contaminated surface layer at various distances from hair root of single hair strands using physical abrasion and measured the concentrations by microwave digestion followed by ICP-MS. By comparing the concentrations of 11 trace elements between the intact and abraded hair segments as a function of distance from root and their laser ablation profiles, we rationalized the endogenous and exogenous contributions: Al and Ti concentrations are dominated by the exogenous contamination on the elephant hair surface, probably in the form of insoluble particles, but not in the giraffe hair; Mg, Ca, Sr, Ba, and Mn are enhanced on the elephant hair surface by exogenous contaminations, but a comparable amount was found in the hair interior suggesting migration of these elements from the surface towards the core; Cu, Zn, Se, and Pb did not have surface accumulation and thus were dominated by the endogenous signal. Overall, giraffe hair had minimal surficial contamination, suggesting the origin of its trace elements is predominantly endogenous, except for Mn, which might get contaminated with airborne particles. We thus demonstrate that contamination of hair may be strongly related to behavioral traits and that the interpretation of trace elemental analyses in hair as a biomonitor or for provenance studies would be highly dependent on the species considered.
微量元素在毛发中的空间分布在微观尺度上具有高度的不均匀性。在毛发生长过程中纳入的内源性信号的相对温和的空间变化可能会因后来的外源性污染而放大几个数量级。在这里，我们研究了大象和长颈鹿毛发中微量元素的纵向和横向分布，并讨论了可能的内源性和外源性贡献。我们对毛发的横截面进行了激光烧蚀 ICP-MS 分析，以评估表面污染和横向变化。我们还使用物理磨损从单根毛发的发根去除不同距离的污染表面层，并通过微波消解和 ICP-MS 测量浓度。通过比较完整和磨损毛发段之间 11 种微量元素的浓度作为距发根距离的函数及其激光烧蚀曲线，我们合理地解释了内源性和外源性的贡献：在大象毛发表面上，Al 和 Ti 的浓度主要由外源性污染决定，可能是不溶性颗粒的形式，但在长颈鹿毛发中则不是；Mg、Ca、Sr、Ba 和 Mn 在大象毛发表面上由于外源性污染而增强，但在毛发内部也发现了相当数量的元素，表明这些元素从表面向核心迁移；Cu、Zn、Se 和 Pb 没有表面积累，因此主要由内源性信号决定。总的来说，长颈鹿毛发的表面污染最小，这表明其微量元素的来源主要是内源性的，除了 Mn，Mn 可能会被空气中的颗粒污染。因此，我们证明毛发的污染可能与行为特征密切相关，并且毛发中微量元素分析作为生物监测或起源研究的解释将高度依赖于所考虑的物种。
