Consolidated report based on D1 to D7 submitted to CEN/TC 264, CEN/TC 264/WG 35 and ISO/TC 146/SC 3 with evidence of its submission for consideration for incorporation into new standards for determining aerosol light absorption coefficients (i.e. at multiple wavelengths) and materials and methods for calibrating filter-based photometers against the reference method(s) by these committees

The STANBC project successfully established a comprehensive measurement framework for aerosol light absorption coefficient and its conversion to equivalent black carbon (eBC) mass concentration, bringing unprecedented traceability and consistency to air quality monitoring across European and internationalnetworks. The project has delivered a calibration guide for the calibration of in-situ reference methods for measuring aerosol light absorption coefficient such as extinction minus scattering and photo-thermal interferometry techniques (Deliverable D1). These methods achieved target measurement uncertainties of ≤10% across multiple light wavelengths and ambient aerosol properties. Comprehensive guidelines were provided to end users detailing specifications, limitations, and application ranges for each reference method. Additionally, the project delivered a report on transferring the SI-traceable calibration to photoacoustic spectrometers that could be potentially deployed in the field as a transfer standard (Deliverable D2). Traceable measurement methods for determining aerosol mass absorption cross-section with rigorous uncertainty budgeting at various wavelengths were studied in two measurement campaigns. Inter-comparison studies successfully determined the relationships between eBC mass, refractory blackcarbon (rBC) mass, and elemental carbon (EC) mass according to EN 16909:2017 standards. Seedeliverables D3 and D4. A systematic calibration method for filter-based light absorption photometers using the reference methods and laboratory-generated synthetic aerosols spanning the complete Single Scattering Albedo (SSA) range (0.5 to almost 1.0) was developed. SSA-dependent calibration factors and multiple scattering factors weredetermined with measurement uncertainties < 15% at the 95% confidence level. See deliverables D5 and D6. A New Work Item (NWI) has been proposed by the STANBC consortium following contact with CEN/TC 264. The proposal on Methods for the determination of black carbon mass concentration, aerosol light absorption coefficient and derived optical parameters in ambient air has been already voted and assigned as a project to be carried out by CEN/TC 264/WG 35. The standardisation strategy proposed here comprises a set of three European Standards. The STANBC project successfully facilitated technology adoption across the measurement supply chain, including accredited laboratories, standards organizations, and end users. Dissemination occurred through the European Metrology Network (EMN) for Climate and Ocean Observation, EMN Pollution Monitoring, and major air quality monitoring networks. By establishing sound metrological foundations and standardised methods, the STANBC project has enhanced the accuracy and comparability of aerosol measurements globally, strengthening scientific evidence for air quality monitoring and climate research initiatives. In this report we outline the standardisation strategy recommended by the STANBC consortium.