Abstract. We examine the street-scale variation of NOx, NO2,
O3 and PM2.5 concentrations in Beijing during the Atmospheric
Pollution and Human Health in a Chinese Megacity (APHH-China) winter
measurement campaign in November–December 2016. Simulations are performed
using the urban air pollution dispersion and chemistry model ADMS-Urban and
an explicit network of road source emissions. Two versions of the gridded
Multi-resolution Emission Inventory for China (MEIC v1.3) are used: the
standard MEIC v1.3 emissions and an optimised version, both at 3 km
resolution. We construct a new traffic emissions inventory by apportioning
the transport sector onto a detailed spatial road map. Agreement between
mean simulated and measured pollutant concentrations from Beijing's air
quality monitoring network and the Institute of Atmospheric Physics (IAP)
field site is improved when using the optimised emissions inventory. The
inclusion of fast NOx–O3 chemistry and explicit traffic emissions
enables the sharp concentration gradients adjacent to major roads to be
resolved with the model. However, NO2 concentrations are overestimated
close to roads, likely due to the assumption of uniform traffic activity
across the study domain. Differences between measured and simulated diurnal
NO2 cycles suggest that an additional evening NOx emission source,
likely related to heavy-duty diesel trucks, is not fully accounted for in
the emissions inventory. Overestimates in simulated early evening NO2
are reduced by delaying the formation of stable boundary layer conditions in
the model to replicate Beijing's urban heat island. The simulated campaign
period mean PM2.5 concentration range across the monitoring network
(∼15 µg m−3) is much lower than the measured range
(∼40 µg m−3). This is likely a consequence of
insufficient PM2.5 emissions and spatial variability, neglect of
explicit point sources, and assumption of a homogeneous background
PM2.5 level. Sensitivity studies highlight that the use of explicit
road source emissions, modified diurnal emission profiles, and inclusion of
urban heat island effects permit closer agreement between simulated and
measured NO2 concentrations. This work lays the foundations for future
studies of human exposure to ambient air pollution across complex urban
areas, with the APHH-China campaign measurements providing a valuable means
of evaluating the impact of key processes on street-scale air quality.
Secondary effects of urban heat island mitigation measures on air quality