Black carbon, a by-product of combustion, is an air pollutant affecting human health and the Earth’s climate. Annually, around 300,000 deaths are linked to fine particulate matter like black carbon and there is currently no targeted legislation limiting its concentration outdoors. The pollutant has also been identified as an impactful climate-forcer and mitigating emission could rapidly slow the effects of climate change.

Black carbon mass concentration (BC) can be measured indirectly using filter-based absorption photometers, which measure the light absorption of the sample (b). This value is proportional to BC by a constant called the ‘mass absorption cross-section’ (MAC).

Although standardised photometer methods exist for elemental carbon, there are no standardised methods for black carbon. The method is also impacted by interference caused by the filter itself. These effects are usually counteracted using generic corrections, which incorrectly treat MAC as constant across all aerosols.

New calibration factors are therefore required.

This project will produce standardised in-situ reference methods for measuring b and for calibrating filter-based photometers using synthetic aerosols. It will produce standardised methods for measuring MAC and use inter-comparisons to establish a relationship between black and elemental carbon masses. This will contribute to a new CEN standard, as part of CEN/TC 264 ‘Air quality’, around traceable methods for measuring b and calibrating filter-based photometers.

The work of the project will improve the accuracy of black carbon measurements, allowing the pollutant to be better tracked and its sources better understood.

This will help to reduce its concentration in outdoor air, improving human health and the Earth’s climate.