Biogenic emissions, chemistry and impacts in the Metropolitan Area of São Paulo: BIOMASP+

Abstract

In the last 50 years, the number of megacities has increased more than ten times, housing more than half of the world population, whose challenges have air pollution at the top of the list, representing more than 5 million deaths per year worldwide, mainly, due to PM2.5. While the anthropogenic nature of air pollution has been considered for a long time, there are evidence that the mixing among emissions by humans and those from the biosphere would modify, and even, exacerbate the effect of anthropogenic pollution on the environment and health. The effect of biosphere-atmosphere would gain importance in the context of emission reduction from traditional mobile sources and global warming that should enhance biogenic emissions at global scale. MASP in South-Eastern Brazil is emblematic of those interactions and threats: it is among the ten megacities worldwide and despite the advance of pollutant emission control, it is experiencing air quality problems due to both O3 and particulate matter (PM10 and PM2.5). Despite the emission control of Anthropogenic Volatile Organic Compounds (AVOC), the maximum O3 concentrations have remained constant over the last 15 years, raising the question of the Biogenic VOCs (BVOCs) role as one of its major precursors. Green urban forest inside the city and also the Atlantic Forest surrounding it, totalize ~30% of the total MASP territory and it has subtropical climate, favoring biogenic emissions and photochemical processes. Taking MASP as a natural laboratory target, the Franco-Brazilian project BIOMASP+ is a unique opportunity to reduce gaps in our understanding of the atmospheric processes, resulting from the complex anthropogenic and biogenic urban mixing. This is needed to properly quantify the impact of pollutants on air quality, health and climate change. The main objective of BIOMASP+ is to evaluate the impact of biosphere-atmosphere interactions on gaseous and particulate urban pollution in a changing climate by addressing the following questions: how does the biosphere-atmosphere interaction affect the ozone production? how does this alter the Secondary Organic Aerosol (SOA) formation and aging? How does this affect health and in return, the biosphere? The above-mentioned questions require a full knowledge of the nature and intensity of chemical and biological compounds emitted by the Atlantic Forest. While there have been lots of efforts towards BVOC from the Amazonian rainforest, the emissions of Atlantic forest trees, which are the native trees present in São Paulo state and in MASP have been completely neglected. The quantification of the Atlantic Forest tree emissions will be one of the original prerequisites of the BIOMASP+ project, divided into one coordination (task 0) workgroup and more four main work-groups: 1- meteorology and VOC fluxes; 2- characterization and quantification of biogenic emission sources; 3- bio-physico-chemical processes and ambient composition and 4 - extended observations, forecast and impacts. To achieve its main objectives, BIOMASP+ has been designed as (I) an integrative project combining new in-situ observations (two experimental sites, RMG and Matão-IAG-USP) on both gaseous and aerosol phases, laboratory experiments and modeling; (II) a multidisciplinary project which is the study of the biosphere-atmosphere interactions, implying shared expertise in biogenic emissions, atmospheric chemistry, biology and meteorology from Brazil and France. Moreover, the study of the biosphere-atmosphere interactions involves multiple nested spatial and temporal scales: from the leaf level to the above-canopy level (fluxes), short time to multi-year scale. BIOMASP+ addresses fundamental science and provides a scientific basis for air quality, health and urban climate mitigation purposes. In-depth knowledge of these processes is necessary to implement the most effective strategies which will lead to sustainable benefits for society. (AU)