  Deep street canyons are characterized by weak ventilation and recirculation
of air. In such environment, the exposure to particulate matter and other air
pollutants is enhanced, with a consequent worsening of both safety and health.
The main solution adopted by the international community is aimed at the
reduction of the emissions. In this theoretical study, we test a new solution:
the removal of air pollutants close to their sources by a network of Air
Pollution Abatement (APA) devices. The APA technology depletes gaseous and
particulate air pollutants by a portable and low-consuming scrubbing system,
that mimics the processes of wet and dry deposition. We estimate the potential
pollutant abatement efficacy of a single absorber by Computational Fluid
Dynamics (CFD) method. The presence of the scrubber effectively creates an
additional sink at the bottom of the canyon, accelerating its cleaning process
by up to 70%, when an almost perfect scrubber (90% efficiency) is simulated.
The efficacy of absorber is not proportional to its internal abatement
efficiency, but it increases rapidly at low efficiencies, then tends to
saturate. In the particular configuration of the canyon we choose (aspect ratio
of 3) the upwind corner is the most favourable for the absorber application. In
the downwind corner the maximum pollutant abatement is -24%, while in the
upwind corner the maximum abatement is twice as much at -51%. The efficacy of
the absorber increases much faster at low efficiencies: at 25% efficiency, the
abatement is already about half that obtained with the 90% efficiency. These
first results, suggest strategies for the real-world application of a network
of absorbers, and motivates further theoretical study to better characterize
the details of the air flow inside and around the absorber.

Physics and Society;Atmospheric and Oceanic Physics