Magnetic characterisation of London's airborne nanoparticulate matter
Magnetic characterisation of London's airborne nanoparticulate matter
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DOI：
10.1016/j.atmosenv.2022.119292
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发表时间：
2022-10
影响因子：
5
通讯作者：
A. Muxworthy;Claire Lam;David Green;Alison Cowan;B. Maher;T. Gonet
中科院分区：
文献类型：
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作者：
A. Muxworthy;Claire Lam;David Green;Alison Cowan;B. Maher;T. Gonet
众所周知，车辆排放产生的含铁颗粒物是有毒的。为了更好地量化潜在的健康风险，我们对伦敦市中心的三个监测站（马里波恩路、伯爵宫路和牛津街）2010年和2012年捕获的伦敦可吸入颗粒物（<10μm，PM10）的时间序列进行了首次磁性研究。我们对所有样本进行了室温分析，并在高温和低温下对有限数量的样本进行了分析。高温测量确定磁铁矿是主要磁相。低温测量显示存在大量纳米粒子，假设是磁铁矿，其粒径范围为 1–4 nm。据估计，10 K 下总磁信号的 ∼40% 来自 <4 nm 的粒子，这些粒子在室温下是磁“不可见”的，并且在基于室温的磁研究中通常被低估。根据低温测量，磁铁矿的总浓度估计为 ∼7.5%，明显高于之前报道的水平。将室温磁数据与其他污染数据（例如NOX和PM10）以及气象数据进行比较。研究发现，诸如饱和磁化强度之类的质量相关项与 NOX 和 PM10 表现出很强的相关性，表明这些污染物有一个共同来源，即车辆排放。磁矫顽力测量结果与丰度无关，并提供晶粒尺寸信息，在所有三个采样地点都是一致的，再次表明了一个主要的主导来源。矫顽力的相对较小的变化与气象事件（例如温度和降水）相关，表明优先去除较大的空气颗粒，即> 50 nm。
Iron-bearing particulate matter produced by vehicle emissions is known to be toxic. To better quantify potential health risks, we have conducted the first magnetic study of a time-series of London's inhalable particulate matter (<10 μm, PM10), captured by three monitoring stations in central London (Marylebone Road, Earl's Court Road and Oxford Street) through 2010 and 2012. We conducted room-temperature analysis on all the samples, and a limited number of samples were analysed at both high and low temperatures. The high-temperature measurements identified magnetite as the dominant magnetic phase. The low-temperature measurements revealed high numbers of nanoparticles, which, assuming magnetite, are in the grain-size range 1–4 nm. It is estimated that as much as ∼40% of the total magnetic signal at 10 K is from particles <4 nm, that are magnetically ‘invisible’ at room-temperature and are being routinely under-estimated in room temperature-based magnetic studies. From the low-temperature measurements, the total concentration of magnetite was estimated at ∼7.5%, significantly higher than previously reported. The room-temperature magnetic data were compared with other pollution data, e.g., NOXand PM10, and meteorological data. Mass-dependent terms like the saturation magnetisation were found to display a strong correlation with NOXand PM10, indicating a common source for these pollutants, i.e., vehicle emissions. Magnetic coercivity measurements, which are independent of abundance, and provide information on grain-size, were consistent across all three sampling localities, again suggesting a major dominant source. Relatively small variations in coercivity were correlated with meteorological events, e.g., temperature and precipitation, suggesting preferential removal of larger airborne grains, i.e., >50 nm.