Identification, targeted extraction and source apportionment of magnetic micro- and nanoparticles in particulate matter

基于我们之前在1999-2001年期间对慕尼黑及其周边地区的人为和自然颗粒物（PM）的研究，我们提出了大约25年后PM的高分辨率微磁和电子显微镜研究。我们建议开发一种独特的系统，使我们能够从灰尘中提取单个微米大小的磁性颗粒，并通过闪热法测量它们的居里温度。令人惊讶的是，磁性分析在PM研究中很少进行，因为它们相对容易、敏感和成本效益高，再加上含铁颗粒可能对人类健康构成严重风险。例如，在2022年3月，大量的撒哈拉沙尘吹进慕尼黑，使天空变成黄色，覆盖了所有的表面。我们对尘埃的分析显示出惊人的高磁化；居里温度测量在770°C时产生了一个明显的信号，表明金属铁的存在。这就提出了一些重要的问题：铁是从哪里来的？它是如何运输的？在氧化成磁铁矿、赤铁矿或磁铁矿之前，它在金属阶段能维持多久？在慕尼黑的地方层面上，我们打算解决以下关于磁性PM的特征和发生的问题：1)1999-2001年和2023-2025年间，磁性PM成分的比例和组成是如何变化的？2)发射磁性粒子的源是什么？3)带磁性粒子到慕尼黑的运输路线是什么？为了识别和表征尘埃中的磁性成分，我们想进一步开发所谓的磁场——一种由四个电磁铁包围的高分辨率光学显微镜。我们打算用一个非常精确的微移液管提取器来补充磁谱仪。该集合将使我们能够有效地选择磁性颗粒，并自动将它们放置在SEM样品支架上，以进行后续显微镜检查或放置在网格上进行闪热测定。大量样品将进一步在现有设备上进行一套磁性测量，以进一步表征其磁性，以及x射线衍射和Mößbauer-spectroscopy等非磁性技术。这里的工作将成为博士论文的基础。样本将定期在慕尼黑地区的关键地点收集，这些地点是专门为从自然来源中揭示人为因素而选择的。此外，我们将与西班牙经验丰富的合作伙伴(Manuel Calvo Rathert, Uni。布尔戈斯;Eduardo Colombo, MAGIC Telescope, La Palma)和意大利(Fabio Florindo, Uni。罗马)，他将提供样品。对意大利、西班牙和加那利群岛的粉尘样本进行进一步分析，应有助于回答有关金属铁来源的关键问题，众所周知，金属铁对人体健康极为有害。与奥地利Hoher Sonnblick天文台的合作将使我们能够分析多年的PM记录。

Building on our previous work on anthropogenic and natural particulate matter (PM) in and around Munich during 1999-2001, we propose a high resolution micro-magnetic and electron microscopic investigation of PM some 25 years later. We propose to develop a unique system that will allow us to extract individual micron-sized magnetic particles from dust and measure their Curie temperatures via flash calorimetry. Magnetic analyses are surprisingly rarely made in PM studies, given their comparative ease, sensitivity and cost effectiveness, combined with the fact that iron bearing particles can be a serious risk to human health. For example, in March 2022, an enormous volume of Saharan dust blew into Munich that turned the sky yellow and blanketed all surfaces. Our analyses of the dust showed surprisingly high magnetizations; Curie temperature measurements yielded a distinct signal at 770°C, signifying the presence of metallic iron. This raises the important questions: where did the iron come from, how was it transported and how long can it last in the metal phase, before oxidizing to magnetite and then hematite or maghemite? On a local level in Munich, we intend to address the following questions regarding the characteristics and occurrence of the magnetic PM: 1) How did the proportion and composition of the magnetic PM component change between 1999-2001 and 2023-2025? 2) Which sources are emitting the magnetic particles? 3) What are the transportation routes that bring magnetic particles to Munich? To identify and characterize the magnetic components in the dust, we want to further develop the so called Magnetodrome - a high resolution optical microscope surrounded by four electromagnets. We intend to compliment the Magnetodrome with an extremely precise micro-pipette extractor. The ensemble will allow us to efficiently select magnetic particles and automatically place them on SEM sample holders for subsequent microscopy or onto grids for flash calorimetry. Bulk samples will be further subjected to a suit of magnetic measurements on existing equipment to further characterize their magnetic properties, as well as non-magnetic techniques like X-ray diffraction and Mößbauer-spectroscopy. The work herein will be the basis for a doctoral thesis. Samples will be collected at regular intervals at key places in the Munich area chosen specifically to unravel anthropogenic from natural sources. Moreover, we will cooperate with experienced partners in Spain (Manuel Calvo Rathert, Uni. Burgos; Eduardo Colombo, MAGIC Telescope, La Palma) and Italy (Fabio Florindo, Uni. Rome) who will provide samples. Further analyses of dust samples from Italy, Spain and the Canary Islands should help to answer the key questions concerning the source of metallic iron, which is known to be extremely hazardous to human health. A cooperation with the Hoher Sonnblick observatory in Austria will enable us to analyze years of PM recordings.