High particulate matter (PM) concentrations have been measured on subway networks worldwide, with serious implications for human health. Such concentrations are known to be mainly produced by wear and friction of the metal parts and can accumulate in subways over time, causing a sort of age effect. Surveys have also shown that particle resuspension, caused by train arrivals and departures, significantly increases particulate matter concentrations. The research aim was threefold: (1) to provide a literature review on particulate matter concentrations in urban subway systems; (2) to measure the influence/incidence of the resuspension of PM_2.5 and PM₁₀ caused by subway train transit; and (3) to investigate the presence of a subway age effect. A sampling campaign was carried out on the station platforms of the Naples (Italy) Subway Line. The results show that particle resuspension significantly influences PM concentrations, reaching daytime values up to + 1200% greater than those at nighttime. Furthermore, to investigate any age effect, the results were compared with those of a previous study performed in 2014, concluding that, in the absence of tunnel cleaning and/or washing and with a standard ventilation system on station platforms, no statistically significant difference was observed between PM concentrations over the two measurement periods. These results suggest that the particles generated by mechanical wear-and-tear and friction processes constitute a very slow phenomenon. A useful solution could be tunnel washing, thereby removing fine particles that would no longer be available for resuspension.

中文翻译：

---

地下地铁系统中颗粒物悬浮物在PM浓度范围内的作用

在世界范围内的地铁网络中已测量出高颗粒物（PM）浓度，对人体健康具有严重影响。众所周知，这种浓度主要是由金属零件的磨损和摩擦产生的，并且会随着时间的推移积聚在地铁中，从而引起某种老化效应。调查还表明，由火车的进出引起的颗粒重悬浮会大大增加颗粒物浓度。研究目的是三方面的：（1）对城市地铁系统中的颗粒物浓度进行文献综述；（2）测量PM _2.5和PM _10重悬浮的影响/发生率由地铁运输引起；（3）调查地铁年龄效应的存在。在那不勒斯（意大利）地铁线的车站月台进行了抽样运动。结果表明，颗粒物重悬浮会显着影响PM浓度，白天的浓度比夜间的浓度高出1200％。此外，为了研究任何年龄影响，将结果与2014年进行的先前研究进行了比较，得出结论，在没有隧道清洁和/或冲洗的情况下，并且在站台平台上使用标准通风系统，没有统计学上的显着差异在两个测量周期内的PM浓度之间观察到。这些结果表明，由机械磨损和摩擦过程产生的颗粒构成了非常缓慢的现象。