Poluição atmosférica na área urbana de Manaus: modelagem e aspectos observacionais de traçadores de queimada

Abstract

In the Amazon region, severe droughts associated with climate change occurred in the 21st century, such as the 2005, 2010 and 2015-16 droughts. Recent studies have shown that in extreme drought years there is a significant increase in forest fires. Burning increases the concentration of carbon monoxide (CO), atmospheric methane (CH4) and particulate matter in the Amazonian atmosphere, generating smoke that covers large areas and plays a vital role in environmental systems, air quality and strong adverse impacts. about human health. Thus, at the regional scale, the present study investigated the impact of biomass burning in the Amazon region on the spatiotemporal variability of methane and carbon monoxide, particularly during drought years. In addition, at the local scale, the impact on air quality of the urban area of Manaus was evaluated, focusing on the levoglucosan, a biomass burning tracer, present in the PM2.5 during a period of El Niño (2015) and a period of non-El Niño (2016), as well as, seasonal variability and its possible regions of origin were analyzed during an intensive field experiment of surface PM2.5 sampling, from August 2017 to July 2018. Initially, from CH4, CO and fires satellite data, an analysis of their interrelationships and spatiotemporal variability over the Amazon in the period 2003-2012, focusing on the dry years of 2005, 2007 and 2010, was carried out. Positive peaks were observed in the relationship between the increase in the number of fires, mainly in the southern area of the Amazon, with consequent contributions to the interannual variability of CO and CH4 during the dry years of 2005, 2007 and 2010 and negative during the wet years. Afterwards, we analyzed the spatiotemporal variability of the biomass burning and carbon monoxide during the 2005, 2010 and 2015 drought episodes, in particular over the Amazon. During the dry season, the occurrences of fires were lower in 2015 than in 2005 (-44%) and 2010 (-47%). On the other hand, in the dryto-wet transition season, they were higher in 2015 than in 2005 (+ 192%) and 2010 (+ 332%). The CO concentration showed positive variations (up to + 30%) that occurred in southern Amazonia and central Brazil during the dry seasons of 2005 and 2010, and north of 20 ºS during the dry-to-wet transition season of 2015-16. In 2015 the fires occurred mainly in the central and northern of the Amazon. Also, from the investigation of the influence of biomass burning emissions on urban pollution in the metropolitan region of Manaus during a strong El Niño (2015) and a non-El Niño (2016) period, it was observed that CO concentration was up to 15% higher and levoglucosan concentration up to 500% higher in Manaus metropolitan region during El Niño compared to non-El Niño period. Finally, a well-defined seasonal cycle of levoglucosan was observed in the urban area of Manaus, from August 2017 to July 2018. From these surface measurements combined with the biomass burning satellite data in the Amazon region and combining an ensemble of stochastic back trajectories at the Manaus receptor within the Stochastic Time-Inverted Lagrangian Transport (STILT) model, it was observed that the biomass burning in the cities located east of Manaus, together with the contributions of the biomass burning emissions from the eastern and southeastern regions of Pará State, were identified as the main regions of origin of the biomass burning particles transported at the surface level in the urban area of Manaus. Therefore, these results point to a strong degradation of air quality that may occur in the metropolitan region of Manaus if drought and biomass burning trends continue in the future.