Black Carbon Trends and Source Apportionment in Berlin: A Multi-Year Analysis

Black Carbon (BC) is a key component of fine particulate matter that impacts air quality, climate, and public health. Understanding its sources is essential for effective mitigation strategies. This study analyses 5+ years of continuous BC observations in Berlin using Aethalometer AE33 measurements, alongside co-located Particulate Matter (PM₂.₅, PM₁₀), Nitrogen Oxides (NOx), Carbon Monoxide (CO) concentrations, and ultrafine particle (UFP) data. BC source contributions are assessed, with NOx and CO serving as traffic-combustion markers, while biomass burning contributions are examined through seasonalBC variability and its relative contribution is validated with levoglucosan, potassium K+ and/or Elemental Carbon/Organic Carbon (EC/OC) measurements. This study is part of the Net4Cities project, contributing to a broader understanding of urban air pollution dynamics and policy interventions, with a focus on transport sources. Aethalometer wavelength-dependent absorption analysis will be used to to apportion relative contribution of liquid fuel and solid fuel BC, with NOx and CO correlations used to evaluate liquid fuel BC estimates. Multiple assumptions and approaches for source apportionment will be tested to quantify uncertainties and the implications evaluated. Relationships between BC and UFP data are investigated for the final year of data to link BC emissions and particle number concentrations in an urban environment.This work is co-funded by the European Union under Project: 101138405 — Net4Cities, the UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee (grant no. 10107404), and the Swiss Secretariat for Education, Research and Innovation (SERI) (grant no. 23.00622).