Air quality in the megacity of Sao Paulo: Evolution over the last 30 years and future perspectives

Road dust resuspension: A review

Characterization of major natural and anthropogenic source profiles for size-fractionated PM in Yangtze River Delta

Despite ethanol’s penetration into urban transportation, observational evidence quantifying the consequence for the atmospheric particulate burden during actual, not hypothetical, fuel-fleet shifts, has been lacking. Here we analyze aerosol, meteorological, traffic, and consumer behavior data and find, empirically, that ambient number concentrations of 7–100-nm diameter particles rise by one-third during the morning commute when higher ethanol prices induce 2 million drivers in the real-world megacity of Sao Paulo to substitute to gasoline use (95% confidence intervals: +4,154 to +13,272 cm−3). Similarly, concentrations fall when consumers return to ethanol. Changes in larger particle concentrations, including US-regulated PM2.5, are statistically indistinguishable from zero. The prospect of increased biofuel use and mounting evidence on ultrafines’ health effects make our result acutely policy relevant, to be weighed against possible ozone increases. The finding motivates further studies in real-world environments. We innovate in using econometrics to quantify a key source of urban ultrafine particles. The biofuel ethanol has been introduced into urban transportation in many countries. Here, by measuring aerosols in Sao Paulo, the authors find that high ethanol prices coincided with an increase in harmful nanoparticles by a third, as drivers switched from ethanol to cheaper gasoline, showing a benefit of ethanol.

/pdf/reduced-ultrafine-particle-levels-in-sao-paulo-s-atmosphere-75adau8f1b.pdf

Reduced ultrafine particle levels in São Paulo's atmosphere during shifts from gasoline to ethanol use.

We built an emission inventory (EI) for the megacity of Bogota, Colombia for 2012, which for the first time augments traditional industrial and mobile sources by including commercial sources, biogenic sources, and resuspended dust. We characterized the methodologies for estimating each source annually, and allocated the sources to hourly and 1 km2 spatial resolution for use as inputs for air quality modeling purposes. A resuspended particulate matter (RPM) emission estimate was developed using the first measurements of road dust loadings and silt content for the city. Results show that mobile sources dominate emissions of CO2 (80%), CO (99%), VOC (68%), NOx (95%), and SO2 (85%). However, the newly estimated RPM comprises 90% of total PM10 emissions, which are at least onefold larger than the PM10 emissions from combustion processes. The 2012 EI was implemented in a chemical transport model (CTM) in order to understand the pollutants’ fate and transport. Model evaluation was conducted against observations from the city’s air quality monitoring network in two different periods. Modeling results for O3 concentrations showed a good agreement, with mean fractional bias (MFB) of +11%, and a mean fractional error (MFE) of +35% with observations, but simulated PM10 concentrations were strongly biased high (MFB +57%, MFE +68%), which was likely due to RPM emissions being overestimated. NOx, CO, and SO2 were also biased high by the model, which was probably due to emissions not reflecting current fleet conditions. Future work aims to revise emission factors for mobile sources, which are the main sources of pollutants to the atmosphere.

https://www.mdpi.com/2073-4433/9/2/49/pdf

Development and Evaluation of a Comprehensive Atmospheric Emission Inventory for Air Quality Modeling in the Megacity of Bogotá

Many studies have been performed in order to characterize the sources of airborne particles in the Metropolitan Area of Sao Paulo (MASP), in Brazil. Those studies have been based on receptor modeling and most of the uncertainties in their results are related to the emission profile of the resuspended road dust particles. In this study, we analyzed the composition of resuspended road dust particles in different environments: local streets, paved roads inside traffic tunnels, and high traffic streets. We analyzed the samples to quantify the concentrations of trace elements and black carbon. On the basis of that analysis, we developed emission profiles of the resuspended road dust that are representative of the different types of urban pavement in the MASP. This study is important given the international efforts in improving emissions factors with local characteristics, mainly in South America and other regions for which there is a lack of related information. This work presents emission profiles derived from resuspended road dust samples that are representative of the different types of urban pavement in the Metropolitan Area of Sao Paulo.

https://www.mdpi.com/2073-4433/7/3/31/pdf

Ivan Gregorio Hetem

Papers

Characterization of Fine Particulate Matter Emitted from the Resuspension of Road and Pavement Dust in the Metropolitan Area of São Paulo, Brazil