Technical note: Dispersion of cooking-generated aerosols from an urban street canyon

The dispersion of cooking-generated aerosols from an urban street canyon is examined with building-resolving computational fluid dynamics (CFD). Using a comprehensive urban CFD model (PALM) with a sectional aerosol module (SALSA), emissions from deep frying and boiling are considered for near-ground and elevated sources. It is found that, with representative choices of the source flux, the inclusion of aerosol dynamic processes decreases the mean canyon-averaged number concentration by 15–40 % for cooking emissions, whereas the effect is significantly weaker for traffic-generated aerosols. The effects of deposition and coagulation are comparable for boiling, but coagulation dominates for deep frying. Deposition is maximised inside the leeward corner vortices, while coagulation increases away from the source. The characteristic timescales are invoked to explain the spatial structure of deposition and coagulation. In particular, the relative difference between number concentrations for simulations with and without coagulation are strongly correlated with the ageing of particles along fluid trajectories or the mean tracer age.

Urban Obstacles Influence on Street Canyon Ventilation: A Brief Review

Many research articles explore new designs and how to arrange barriers/obstacles to improve roadside air quality and ventilation within the urban street canyon. These obstacles are generally categorized into porous, non-porous and mixed type. Porous barriers include vegetated shrubs and trees; non-porous barriers include parked cars, low boundary walls, etc., while mixed barriers combine both porous and non-porous barriers. Moreover, new developments can benefit from added design flexibility using lift-up building design and building porosity as a promising way of improving ventilation. This short paper reviews the different research studies conducted on obstacles/barriers in an urban canyon which helps improve air quality and also highlights potential future research.

Vertical Distribution of Polycyclic Aromatic Hydrocarbons in Window Organic Films Formed in an Urban Street Canyon

Polycyclic Aromatic Hydrocarbon (PAHs) were determined in outdoor organic films formed on window glasses inside a street canyon at four different heights. The vertical distribution of PAHs in the organic film and the factors responsible for this have been studied. Significant changes of the concentration levels depending on the height and on the season were observed. The concentrations were elevated in the organic film at the street level and during the cold period. This work provides evidences that window organic film may pose an additional risk for human health in such locations through the accumulation of PAHs near the street level.