Contribuições da queima de biomassa local e regional para o deterioro da qualidade do ar urbano

Abstract

In Brazil, the burning of forest and grass in the agricultural sector occurs mainly in Amazon and Cerrado biomes and, depending on weather conditions, the emitted pollutants can be transported long distances. This study focused on the impact of biomass burning events at the local and regional scales on the air quality in Londrina (PR). The monitoring campaign conducted on the campus of the Federal Technological University of Paraná (UTFPR) measured the concentrations of nitrogen oxides (NOx), ozone (O3), fine particulate matter (PM2,5), particle number (NP) and black carbon (BC) between July and October 2016. Pollutant concentrations were analyzed with descriptive statistics and daily cycles, while the source identification was performed with the Conditional Bivariate Probability Function (CBPF). Local events were characterized by analyzing 2-min pollutant concentrations and the Ångström absorption exponent (Å370/880). On the other hand, regional events were studied based on the time series of pollutants and meteorological variables, the analysis of the air mass back-trajectories, occurrence of fire foci, and modelled concentrations of O3 and burning particles, as well as surface and height analysis of synoptic conditions. It was determined that the study site had a small influence from vehicle emissions, but local burning of solid waste/biomass and regionally transported biomass smoke largely affected the air quality on some occasions. The concentrations of PM2,5, NP and BC370 in the local scale, increased 6.0, 5.3 e 4.5 times, respectively, when compared to a reference period. Moreover, weak winds favored the persistence of relatively high pollutant concentrations for several hours. On the other hand, three regional events were identified with concentrations of PM2,5, BC370 and O3 that were (2.5–2.8), (1.7– 2.8) and (1.4–1.5) time higher, respectively, in relation to the reference period, and the regional contribution of O3 was 61 µg m-3, consistent with previous studies in Brazil. The South American Low-Level Jet favored the transport of smoke from biomass fires in the Cerrado biome and the interior of São Paulo state, contributing to deteriorate the air quality in Londrina. Other synoptic events in the low troposphere also favored the accumulation (a stationary front) or removal (cold front passage with postfrontal precipitation) of pollutants. Therefore, it is essential to eliminate or reduce the anthropogenic burning of biomass in Brazil, since it affects not only the region where it occurs, but also contributes to the deterioration of the air quality in the regions where the pollutants are transported.