Concentration dynamics of coarse and fine particulate matter at and around signalised traffic intersections

Abstract

The understanding of rapidly evolving concentrations of particulate matter (PMC) at signalised traffic intersections (TIs) is limited, but it is important for accurate exposure assessment. We performed "mobile" and "fixed-site" monitoring of size-resolved PMCs in the 0.25-34 μm range at TIs. On-road mobile measurements were made inside a car under five different ventilation settings on a 6 km long round route, passing through 10 different TIs. Fixed-site measurements were conducted at two types (3- and 4-way) of TIs. The aims were to assess the effects of different ventilation settings on in-vehicle PMCs and their comparison during delay conditions at the TIs with those experienced by pedestrians while crossing these TIs. We also estimated the zone of influence (ZoI) for PM10, PM2.5 and PM1 under different driving conditions and fitted the probability distribution functions to fixed-site data to understand the concentration and exposure dynamics of coarse and fine particles around the studied (3- and 4-way) TIs. The fine particles (PM2.5) showed a strong positive exponential correlation with the air exchange rates under different ventilation settings compared with coarse particles (PM2.5-10) showing an opposite trend. This suggested that the ventilation system of the car was relatively more efficient in removing coarse particles from the incoming outside air. On-road median PM10, PM2.5 and PM1 during delays at the TIs were ∼40%, 16% and 17% higher, respectively, compared with free-flow conditions on the rest of the route. About 7% of the average commuting time spent during delay conditions over all the runs at the TIs corresponded to 10, 7 and 8% of the total respiratory deposition dose (RDD) for PM10, PM2.5 and PM1, respectively. The maximum length of the ZoI for PM2.5 and PM1 was highest at the 4-way TI and the maximum length of the ZoI for PM10 was highest at the 3-way TI. The on-road average RDD rate of PM10 inside the cabin when windows were fully open was up to ∼7-times that for pedestrians at the TIs.

A review of factors surrounding the air pollution exposure to in-pram babies and mitigation strategies

“…The increase in roadside concentrations of fine particles (PM 2.5 ) is usually dominated by exhaust emissions (Amato et al, 2009;Kumar and Goel, 2016;Kumar et al, 2018) as opposed to coarse particles (PM 2.5-10 ) coming from sources such as resuspension of road dust, brake and tyre wear (Kumar et al, 2017). With an increase in traffic density, both the concentrations of fine and coarse particles should generally increase.…”

Risk effects of near-roadway pollutants and asthma status on bronchitic symptoms in children

“…13 Cold starts, which are more likely to occur near residences and thus non-freeway roads, result in higher levels of pollutants generated due to catalytic converters having not reached optimal temperature to efficiently reduce emissions. 45 Another study found that PM concentrations were higher during delay periods at signalized traffic intersections compared to free-flowing traffic 17 . More research is needed to better characterize differences in near-roadway pollutants from freeways and non-freeway roadways and to determine whether differences in composition may explain the difference in observed associations.…”

“…These near-roadway pollutants include oxides of nitrogen (NO x ), ultrafine particles, carbon monoxide (CO), EC, and gaseous and particle phase organic compounds such as polycyclic aromatic hydrocarbons (PAHs), all of which are correlated and decay sharply with increasing distance away from a roadway. 12–15 Because exposure to vehicle emissions from freeways and non-freeway roads are likely to be different mixtures due to differences in proportion of heavy-duty trucks, vehicle speed, traffic volumes, and frequency of acceleration, braking, and cold starts, 15–17 we investigated whether the associations varied for exposures from freeways and non-freeway roads. Furthermore, since previous studies have shown that regional air pollution is strongly associated with bronchitic symptoms, and traffic is an important contributor to regional pollution in southern California, we were interested in whether the effect of near-roadway air pollutants differed across communities with higher and lower levels of regional pollution.…”

Exposure to Aerosols Particles on an Urban Road

“…DF values of 0.25 and 0.65, respectively were assumed for the purpose of estimating the deposition rate of the number of inhaled ultrafine and large particles [Sturm 2016, Joodatnia et al 2013]. For the mass of the inhaled particles, DF values were adopted from Kumar and Goel [2016] and for PM 2.5 and PM 10 amounted to respectively 0.23 and 0.88 (commuters) and 0.14 and 0.88 (pedestrians).…”