Geological Survey of Norway , N-7491 Trondheim, Sluppen, Norway.
Sci Total Environ. 2011 May 1;409(11):2252-60. doi: 10.1016/j.scitotenv.2011.02.018. Epub 2011 Mar 12.
Magnetic measurements are routinely used in geophysics and environmental sciences to obtain detailed information about concentrations and quality of iron minerals. Here, magnetic properties of 38 terrestrial moss samples (Hylocomium splendens) from a ~120km south-north transect through Oslo are studied to gain better insight into the nature and origin of their Fe fraction. The concentration-dependent quantities, magnetic susceptibility k, and isothermal remanent magnetization IRM(700mT) after weight normalization have significantly higher values in urban regions, and parallel the previously found concentration signals of 16 out of 29 chemical elements (Ag, Al, Au, Bi, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Pt, Sb, Ti, and Zn). Because there is no evidence that Hylocomium splendens produces biogenic magnetic remanence carriers, the increase in IRM is attributed to adsorption of dust containing iron oxide minerals. This agrees with previous observations that Ti concentrations, related to local mineral dust, have a peak in Oslo, and at sites close to known dust sources. Scanning electron microscopy images also showed an increased density of minerogenic particles on the moss surfaces in the urban samples, which qualitatively supports the dust based interpretation. The concentration-independent ratios k/Fe and IRM(700mT)/Fe also have extreme values in the urban parts of the transect. This indicates that more of the total iron occurs in magnetically ordered form and in remanence carriers, interpreted as adsorbed dust. In addition, purely magnetic ratios displayed differences in urban and rural areas, indicating that their magnetic dust particles are inherently of different types. Therefore, it is likely that anthropogenic dust sources contribute considerably to the magnetic signal. Urban dust enhancement is not exclusively due to increased erosion, leading to higher loads of geogenic dust in the atmosphere, but also to specific anthropogenic sources from combustion, corrosion, or other synthetic emitters.
磁学测量在地球物理学和环境科学中被广泛应用，以获取有关铁矿物浓度和质量的详细信息。在这里，我们研究了 38 个来自奥斯陆南北向约 120 公里的陆地苔藓样本（Hylocomium splendens）的磁性，以深入了解其铁分数的性质和来源。在城市地区，与重量归一化后的磁化率 k 和等温剩磁 IRM(700mT)相关的浓度依赖量具有更高的值，并且与之前发现的 29 种化学元素（Ag、Al、Au、Bi、Cd、Co、Cr、Cu、Fe、Mo、Ni、Pb、Pt、Sb、Ti 和 Zn）中的 16 种元素的浓度信号相吻合。由于没有证据表明 Hylocomium splendens 产生生物磁性剩磁载体，因此 IRM 的增加归因于铁氧化物矿物的吸附。这与之前的观察结果一致，即与当地矿物尘埃相关的 Ti 浓度在奥斯陆和靠近已知尘埃源的地点达到峰值。扫描电子显微镜图像还显示，城市样本中苔藓表面的矿化颗粒密度增加，这在定性上支持了尘埃的解释。浓度无关的比 k/Fe 和 IRM(700mT)/Fe 在该研究区域的城市部分也具有极值。这表明更多的总铁以有序磁的形式和在剩磁载体中存在，这被解释为吸附的尘埃。此外，城市和农村地区的纯磁性比存在差异，表明其磁性尘埃颗粒的类型不同。因此，人为尘埃源很可能对磁性信号有很大的贡献。城市尘埃的增强不仅是由于侵蚀增加，导致大气中更多的原生尘埃，而且还由于燃烧、腐蚀或其他合成排放源的特定人为源。
