Road tunnels have been a successful means of avoiding congestion in the city of Guanajuato.They are also used by pedestrians to reduce travel time and distance. However, exposure to elevated levels of carbon monoxide (CO) and particulate matter such as PM2.5 and PM10 from vehicle emissions, as well as the resuspension of particulate matter are risk factors for health. In the city of Guanajuato, the CO, PM2.5 and PM10 concentrations, wind speed and number of vehicles in three of the more polluted and most frequently used tunnels by pedestrians was monitored. To monitor the CO concentration, non-dispersive infrared radiation was used. The PM2.5 and PM10 concentrations were evaluated using a handheld analyzer with a high precision laser sensor (Aerocet-831). The mineralogy, chemical composition, and morphology of particulate matter were analyzed by XRD, XRF and SEM-EDS, respectively. The average CO concentration does not exceed 50 ppm for an exposure time of 30 minutes as recommended by the World Health Organization, however the average concentrations for PM10 in the three tunnels are above the permissible limit of 50 µg m -3 24-hour average for the air quality inside the tunnels. The high emission factors suggest the necessity of the implementation of a ventilation system inside the tunnels. The chemical composition of particulate matter corresponds to the mineral dust present.
The photo-degradation of persistent contaminants in aqueous systems such as drugs, pesticides or dyes has been proposed as an alternative for the remediation of aqueous systems. TiO2 is one of the main photocatalysts that have been used for these purposes, it has two phases with photocatalytic properties, anatase and rutile, the latter being the one with the lowest conduction band 3.0 eV. The present work shows the synthesis of TiO2 by sol gel process, observing that the rutile phase is favored with heat treatment at temperatures above 600ºC, the comparative study of the degradation kinetics of AMARANTH with synthesized TiO2 and commercial TiO2 was evaluated, observing a rate constant of 1.38 and 0.345 Lmol-1min-1 for commercial and synthetic TiO2, respectively.
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