Local and Regional Contributions to Black Carbon Aerosols in a Mid-Sized City in Southern Brazil

Abstract

Black carbon (BC) concentrations were monitored at three sites (suburban, street canyon and urban rooftop) in a midsized Brazilian city, from August 2014 to January 2015. The suburban site presented weak diurnal cycles, suggesting little influence of motorized traffic, but distinctively large 95 th percentile concentrations, reaching values as large as 11.04 and 3.34 µg m -3 in the evenings of the dry and wet season (respectively), likely attributable to local waste burning. Moreover, higher BC concentrations at the suburban site were observed throughout the dry period, primarily caused by long-range transport (LRT) of smoke from the central part of Brazil and neighboring countries, carried by WNW, SSW and NNE winds. Local traffic was by far the most important source of BC in street canyon, with mean hourly peaks of 5.8 µg m -3 (at 7:00) and 4.6 µg m -3 (18:00), coinciding with rush hour periods. The rooftop data showed a mean peak of 1.4 µg m -3 at 7:00, reflective of traffic on a busy avenue adjacent to the site. Meteorological data clustered into groups of similar air temperature (T air ) and relative humidity (RH) showed that BC concentrations were highest (18.3 µg m -3 ) at the suburban site during the evenings of dry (RH ca. 20%) and hot days (maximum T air ca. 30°C). Diurnal concentrations in the canyon and rooftop were linked to traffic patterns and showed no clear linkage to meteorological conditions. This study shows that the BC concentrations in the city are highly variable and that air quality diminishes considerably due to sporadic waste burning and LRT of biomass smoke, even in neighborhoods with little motor traffic. While air pollution due to transboundary smoke is more difficult to abate, these results suggest that targeting local backyard burning and traffic volume would lead to a depletion of BC concentrations in the city.

Screening of short-lived climate pollutants in a street canyon in a mid-sized city in Brazil

“…Other sources of air pollution are frequent and illegal fire activities to burn domestic waste, clear of leaves and crop residues (Targino and Krecl, 2016), restaurants and pizzerias that burn either charcoal or wood, and LRT of regional smoke, mainly from August to October matching the biomass burning season in South America (Ros ario et al, 2013).…”

“…All times are expressed in local time (UTC-2) and as 24-h format. Following the method proposed by Virkkula et al (2007), a compensation for the loading effect was applied to all BC measurements as described in Targino and Krecl (2016). No correction was applied for the scattering effect due to the lack of concurrent measurements of the aerosol scattering coefficient.…”

“…Besides the uneven spatial distribution of stations, shortfalls are very frequent due to the lack of maintenance, spare parts and technical expertise (Instituto de Energia e Meio Ambiente, 2014). Thus, the air quality in small and mid-sized Brazilian cities is usually unknown, except for a few dedicated short-term field works conducted to investigate specific aspects of atmospheric processes and pollutants (e.g., Targino and Krecl, 2016;Krecl et al, 2015a, b;Tavares et al, 2004).…”

“…Londrina is considered mid-sized for Brazilian standards, however there is no air monitoring network in the city. Targino and Krecl (2016) showed that BC concentrations across the city have a large spatial variability and are due to local and remote sources, such as traffic and long-rang transport (LRT) of smoke, respectively. This study focuses on BC and O 3 concentrations within a busy street canyon and uses ancillary measurements of traffic data and meteorology to help characterize their patterns, as well as BC data at a rooftop site.…”

Seasonal Characteristics of Black Carbon Aerosol and its Potential Source Regions in Baoji, China

“…BC is chemically inert and is mainly concentrated in the accumulation mode with diameters of 0.01-1.0 µm (Bond et al, 2013). These physicochemical characteristics cause BC to have an atmospheric lifetime of approximately one week, making it amenable to long-range transport to other regions (Liu et al, 2011;Wang et al, 2015;Targino and Krecl, 2016). Moreover, BC is an important component of air pollution in urban areas, exacerbating the degradation of visibility (Zhou et al, 2012;Wang et al, 2013).…”