Assessing the disparities of urban–rural
air quality response
to changes in emissions is essential for the development of effective
air pollution mitigation strategies in megacities. However, meteorology
and nonlinear atmospheric chemistry complicate the determination of
emission–air quality responses. Here, we established a machine
learning (ML)-based air quality simulator based on hourly air quality,
meteorology, traffic activity, and other relevant indicators for Chengdu,
a megacity in Southwest China. The ML-based simulator exhibits high
fidelity in reproducing hourly pollutant concentrations (with cross
validation R2 > 0.6 for NO2, O3,
and PM2.5). The results indicated similar trends of meteorological
impacts but various effects from traffic activities on air quality
between urban and rural areas. Truck restriction policies have significantly
reduced the impacts of truck traffic on air quality in the urban area.
Repartitioning between NO2 and O3 is observed
in both urban and rural areas, indicating a VOC-limited regime in
winter across Chengdu. Total gaseous oxidant (i.e., OX =
NO2 + O3) and PM2.5 concentrations
are more sensitive to changes in nontruck (which emit more VOC) traffic
than truck (which emit more NOX) traffic. We suggest that
effective mitigation policies of OX should be developed
according to local features to improve and alleviate winter haze simultaneously.