Street-scale black carbon modelling over the West Midlands, United Kingdom: Sensitivity test of traffic emission factor adjustments

Black carbon is harmful for climate, environment, and human health. Road traffic is one of the major sources for black carbon in urban areas. This study develops a street scale air quality model configuration for the dispersion of black carbon concentrations across the West Midlands, UK, incorporating updated road traffic emission factors. A range of modelling cases accounting for traffic emission factor adjustments was conducted and evaluated against measurements at three monitoring sites within the region. The model overall has good performance. With unadjusted traffic emission factors, the model can capture black carbon annual concentrations at urban background sites. However, an adjustment (factor of 3) for the traffic emission factors is needed to better represent the roadside site (although with a slight overestimation of 3 % in annual concentration). There are near-linear relationships between black carbon concentrations and the adjustment ratio for the traffic emission factor. Black carbon concentration maps have been generated at 10 m × 10 m resolution, which were then aggregated into health-related electoral ward and local authority levels.