Abstract
Cyclists might experience increased air pollution exposure, due to the proximity to traffic, and higher intake, due to their active travel mode and higher ventilation. Several local factors, like meteorology, road and traffic features, and bike lanes features, affect cyclists’ exposure to traffic-related pollutants. This paper investigates the concentration levels and the effect of the features of the bike lanes on cyclists’ exposure to airborne ultrafine particulate matter (UFP) and black carbon (BC) in the mid-sized city of Piacenza, located in the middle of the Po Valley, Northern Italy. Monitoring campaigns were performed by means of portable instruments along different urban bike routes with bike lanes, characterized by different distances from the traffic source (on-road cycle lane, separated cycle lane, green cycle path), during morning (9:00 am–10:00 am) and evening (17:30 pm–18:30 pm) workday rush hours in both cold and warm seasons. The proximity to traffic significantly affected cyclists’ exposure to UFP and BC: exposure concentrations measured for the separated lane and for the green path were 1–2 times and 2–4 times lower than for the on-road lane. Concurrent measurements showed that exposure concentrations to PM10, PM2.5, and PM1 were not influenced by traffic proximity, without any significant variation between on-road cycle lane, separated lane, or green cycle path. Thus, for the location of this study PM mass-based metrics were not able to capture local scale concentration gradients in the urban area as a consequence of the rather high urban and regional background that hides the contribution of local scale sources, such as road traffic. The impact of route choice on cyclists’ exposure to UFPs and BC during commuting trips back and forth from a residential area to the train station has been also estimated through a probabilistic approach through an iterative Monte Carlo technique, based on the measured data. Compared to the best choice, a worst-route choice can result in an increased cumulative exposure up to about 50% for UFPs, without any relevant difference between cold and warm season, and from 20% in the cold season up to 90% in the warm season for equivalent black carbon concentration (EBC).
Highlights
The shift from motor vehicle use to an active transport mode, like bicycling, for short trips in urban areas has been considered helpful to reduce traffic volume and related air pollution emission.In addition, the shift to active transport improves public health thanks to the increased physical activity [1,2,3]
For the location of this study PM mass-based metrics were not able to capture local scale concentration gradients in the urban area as a consequence of the rather high urban and regional background that hides the contribution of local scale sources, such as road traffic
As the warm season distributions are shifted towards lower concentrations values, outliers observed in this season both for ultrafine particulate matter (UFP) and equivalent black carbon concentration (EBC) and more frequently for the sectors where the are mainly observed in this season both for UFPs and EBC and more frequently for the sectors where proximity to vehicle exhaust is higher (i.e., S1—on-road cycle lane (S1-OCL) and S4—no cycle lane (S4-NCL))
Summary
The shift from motor vehicle use to an active transport mode, like bicycling, for short trips in urban areas has been considered helpful to reduce traffic volume and related air pollution emission. This work provides some additional knowledge by investigating the concentration levels of airborne UFPs and BC, based on field measurements performed while travelling different bicycle routes in the urban area of a mid-sized city in Northern Italy. Both these pollutants trace traffic source emissions and BC were recognized as valuable air quality indicators where primary combustion particles dominate [26]. The impact of route choice on cyclists’ exposure during commuting trips is estimated through a Monte Carlo approach, based on the measured data
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