Black carbon (BC) is a component of Particulate Matter (PM) with a short-term health impact and an active substance that promotes global warming due to its ability to absorb solar radiations. Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds with multiple fused aromatic rings presenting health effect. The heavier ones are in solid form, while those with a small number of rings can be volatile and present in gaseous form in the atmosphere. PM contain a large spectrum of components such as dust, BC, organic compounds, sulphates, nitrates, ammonium, etc… These different components can have a warming or cooling effect on the atmosphere.
To mitigate health risks and climate change, it is therefore necessary to have a good understanding of the physical and chemical properties of particulate pollutants, particularly carbonaceous species, as well as their fate, transport and transformation in the environment. Fossil fuel consumption, whether from stationary or mobile sources, biomass burning (BB), and industrial emissions are the key sources of BC and associated PAHs into the atmosphere. As BC has a short life span, it can be easy to overcome the environmental burden by cutting up or controlling its emissions.
Secondary processes in the atmosphere are also a major source of PM.
The reduction of BC and PAH emissions is linked to the reduction of PM emissions. This report provides an overview of BC, PAH and ultrafine particles (UFP) emissions and the effect of PM emission reduction measures on emissions of these species. The study was extended, as far as possible, to all carbonaceous species such as secondary organic aerosols (SOA) and brown carbon (BrC), which have an impact on the radiative balance and the mass of PM. Three target sectors have been considered, two of them, small combustion sources and road transport, because they are the main sources of BC, and gas flaring (GF), because this activity is a major source of pollutants for both air quality and climate impact in the Artic regions.
This document completes the Guidance document on prioritising reductions of PM so to also achieve reduction of BC (ECE,2020) prepared by TFIAM in collaboration with TFTEI, by providing an in-depth analysis of the capacity of techniques to effectively reduce BC and PAHs. It also provides background information for the process of revision of the Gothenburg Protocol scheduled in 2024 and 2025.