Abstract
Monitoring ambient concentrations of ultrafine particles (UFPs) is important due to their negative impact on human health. This paper provides measurements of UFP concentrations near roadways because emissions from light duty vehicles (LDVs) and heavy duty vehicles (HDVs) have been shown to be a major source of UFPs. The concentration of UFPs was measured near two different roadways in Chicago IL for 2 to 4 hours on 52 days between 2014 and 2016. One of the sites was restricted to LDVs (Lake Shore Drive, LSD) and had a near roadway concentration from vehicles (background subtracted) that averaged nearly 8,000 particles cm–3. The other site had a mix of LDVs and HDVs (Dan Ryan Expressway, DRE) and the near roadway concentration from the vehicle fleet (background subtracted) averaged nearly 11,000 particles cm–3. The contribution of UFPs from HDVs was almost 80% of the total emissions on the DRE demonstrating that HDVs emit many more UFPs than LDVs. Background concentrations of UFP were measured upwind of the near roadway sampling sites and were subtracted from the near roadway measurements in order to determine the vehicle contribution to the total UFP concentration. The background concentrations varied with wind direction and therefore were divided into ambient background categories based on wind direction. The four different background categories are defined as remote, lake, industrial and urban. Each category has a distinct different average ambient background concentration (particles cm–3) as follows: remote, 2,700; lake, 6,000; industrial 12,000 and urban 11,000. The large background concentrations in urban areas indicate that total near roadway measurements are generally near 20,000 particles cm–3 with 50 to 60% from vehicles and reach to 60,000 particles cm–3 depending on the background and traffic emission. The results indicate high UFP readings near roadway and one possible solution is mitigation of traffic congestion.
Highlights
Ultrafine particles (UFPs) are defined as particles with diameter less than 0.1 μm and recent studies have shown an association between ultrafine particles (UFPs) and adverse health effects (Pope III et al, 2002; Oberdörster et al, 2004; Sioutas et al, 2005; Pope III and Dockery, 2006; Samet et al, 2009; Brook et al, 2010; Chen et al, 2017)
This paper provides measurements of UFP concentrations near roadways because emissions from light duty vehicles (LDVs) and heavy duty vehicles (HDVs) have been shown to be a major source of UFPs
The UFP background concentrations for the industrial sector are much higher than the lake sector backgrounds and shows significantly more variation as indicated by the higher standard deviations
Summary
Ultrafine particles (UFPs) are defined as particles with diameter less than 0.1 μm and recent studies have shown an association between UFPs and adverse health effects (Pope III et al, 2002; Oberdörster et al, 2004; Sioutas et al, 2005; Pope III and Dockery, 2006; Samet et al, 2009; Brook et al, 2010; Chen et al, 2017). On and near roadway field measurements of UFP concentrations have been made by a number of investigators (Morawska et al, 1999; Zhu et al, 2002a, b; Kittelson et al, 2004; Westerdahl et al, 2005; Zhang et al, 2005; Zhai et al, 2015; Xiang et al, 2018). They demonstrate that UFPs are significantly elevated on
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