Potential to reduce the concentrations of short-lived climate pollutants in traffic environments: A case study in a medium-sized city in Brazil

Abstract

Understanding the spatio-temporal variation of short lived climate pollutants (SLCP) over cities is critical to protect public health and mitigate climate change. There is a lack of knowledge about the distribution of SLCP in South America, mainly in medium-sized cities (<1 million inhabitants). This work reports on results of a campaign conducted at several sites (street canyon, urban background, and suburban) in Londrina, Brazil. The pollution datasets (black carbon BC, nitrogen oxides NOx, ozone O3, fine particles PM2.5, and particle number PN) were analyzed by using descriptive statistics, diurnal cycles, time-space correlations, and establishing linkages with traffic rates and with wind conditions. Hourly mean (±standard deviation) BC concentrations ranged from 0.58 (±0.54) in the suburban area to 3.43 (±2.69) µg m−3 at the street canyon site (10,150 vehicles d−1 on weekdays), showing a high spatio-temporal variability even at short scales. PN (mean of 17,469 cm−3) and NOx (mean of 51.58 µg m−3) concentrations tracked BC levels and traffic rates, particularly the number of diesel buses at the canyon site. PM2.5 and O3 levels presented a lower spatial variability, with poor correlation with traffic rates in the canyon and were more tied to regional sources. NOx, BC, and PN showed the highest reduction potentials connected to the abatement of traffic emissions in the city center, particularly by targeting heavy-duty diesel vehicles. The reduction of PM2.5 and O3 concentrations is more challenging due to a significant regional contribution that requires cutting down emissions at state, national or even transboundary scales.