Black carbon (BC) is an air pollutant that contributes to climate forcing, reduced crop yields and impacts on our health. Produced by incomplete combustion of transport and other fossil fuels, air quality networks have been set-up to monitor its mass concentration and legally binding procedures are in place to identify and treat emission sources. Networks measure equivalent Black Carbon (eBC) mass concentrations in real time with light absorption photometers, but traceability is incomplete, uncertainties are poorly understood, and robust documentary standards are lacking. This project will address these needs and via input into normative standards aims to generate greater reliability for measurements of this important air pollutant.

Carbonaceous particles continue to receive high levels of attention from the scientific community and policy makers, because of their role in both climate change and health effects. The dominant sources of Black Carbon have changed over the decades, with modern emissions arising from vehicle combustion emissions, forest fires, wood and biomass burning. Black Carbon has been identified as an important climate-forcing agent, contributing to atmospheric warming due to its much shorter atmospheric lifetime than CO2. Mitigation strategies for BC could rapidly slow the rate of climate change. Without a reliable measurement infrastructure from the NMI level to field-based measurements supported by underpinning CEN standards upon which legislation can rely, the European vision for a toxic-free environment and climate neutrality will not be put into practice. This project will contribute to the developments of such standards (Objective 4).

The mass concentration of airborne particles loosely described as black carbon has been widely measured by various optical methods since the early 20th century, with hundreds of filter-based optical absorption photometers now installed at European aerosol-monitoring sites due to their portable and robust design. However, these are notorious for their high measurement uncertainties, estimated to be up to 400 % for eBC mass concentration. These uncertainties depend on the aerosol properties at the measurement location. As a result, field measurements at different monitoring sites are often not comparable and it is difficult to extract meaningful long-term data. To overcome these limitations, there is need to determine methods for calibrating filter-based light absorption photometers (Objective 3) using the in-situ reference methods developed in Objective 1 and the parameters for conversion of the optical measurements into mass (Objective 2).