Abstract
In the city of Guanajuato, Mexico, road tunnels offer drivers an effective means of avoiding traffic congestion. Additionally, they enable pedestrians to reduce their travel time and distance. However, exposure to elevated levels of carbon monoxide (CO) and particulate matter (PM), including PM2.5 and PM10 consisting of vehicle-emitted particles and resuspended dust, poses risks to human health. Hence, we monitored the CO, PM2.5, and PM10 concentrations; wind speed; and number of vehicles in three popular tunnels among pedestrians, all of which exhibited relatively high levels of pollution, in Guanajuato. We evaluated the CO concentration using a portable non-dispersive infrared radiation (NDIR) sensor (ALTAIR Pro Single-Gas Detector) and the PM2.5 and PM10 concentrations using a handheld mass monitor equipped with a high-precision laser sensor (Aerocet 831). We then employed X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) to analyze the mineralogy, chemical composition, and morphology of the PM, respectively. Although the average CO concentration fell below the World Health Organization (WHO)’s guideline of 50 ppm for a 30-minute exposure, the average PM10 concentration exceeded the guideline of 50 µg m–3 for a 24-hour exposure inside all three tunnels. The high emission factors we found demonstrate the necessity of installing ventilation systems in these passageways. Lastly, the chemical components of the PM corresponded to the mineral dust originating from the eroded rock (mainly rhyolite), soil, and fortifying construction material inside the tunnels.
Highlights
The oldest tunnels excavated in Egypt in the year 1500 B.C. and Jerusalem in the year 700 B.C. were built for water conduction
We evaluated the carbon monoxide (CO) concentration using a portable non-dispersive infrared radiation (NDIR) sensor (ALTAIR Pro Single-Gas Detector) and the PM2.5 and PM10 concentrations using a handheld mass monitor equipped with a high-precision laser sensor (Aerocet 831)
The number of vehicles passing through a tunnel contributes to higher concentrations of pollution and drivers can be exposed to the toxic carbon monoxide (CO), inhalable particulate matter PM10) and fine particulate matter (PM2.5), particles
Summary
The oldest tunnels excavated in Egypt in the year 1500 B.C. and Jerusalem in the year 700 B.C. were built for water conduction. The Romans carried out the construction of aqueducts for the expansion of their cities and were the first to open road tunnels when they built roads (El Salam, 2002; Priego, 2010). The road tunnels favored the continuous and safe passage of vehicles, through topographic obstacles (mountains), permitting shorter distances between two points with a minimum slope, reducing the travel time, energy, as well as the reduction of combustion gases to the atmosphere. Road tunnels have been built in crowded cities to solve many traffic problems and are designed to be safe and comfortable for human usage. Guanajuato, considered as a medium-sized, colonial city, is located in a hilly terrain of central
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