Urban Pollutant Transport and Infiltration into Buildings Using Perfluorocarbon Tracers

Abstract

People spend the majority of their time indoors and therefore the quality of indoor air is worthy of investigation; indoor air quality is affected by indoor sources of pollutants and from pollutants entering buildings from outdoors. In this study, unique perfluorocarbon tracers were released in five experiments at a 100 m and ~2 km distance from a large university building in Manchester, UK and tracer was also released inside the building to measure the amount of outdoor material penetrating into buildings and the flow of material within the building itself. Air samples of the tracer were taken in several rooms within the building, and a CO2 tracer was used within the building to estimate air-exchange rates. Air-exchange rates were found to vary between 0.57 and 10.90 per hour. Indoor perfluorocarbon tracer concentrations were paired to outdoor tracer concentrations, and in-out ratios were found to vary between 0.01 and 3.6. The largest room with the lowest air-exchange rate exhibited elevated tracer concentrations for over 60 min after the release had finished, but generally had the lowest concentrations, the room with the highest ventilation rates had the highest concentration over 30 min, but the peak decayed more rapidly. Tracer concentrations indoors compared to outdoors imply that pollutants remain within buildings after they have cleared outside, which must be considered when evaluating human exposure to outdoor pollutants.

Urban Tracer Dispersion and Infiltration into Buildings Over a 2-km Scale

“…Results showing elevated tracer concentration indoors 30 min to 1 h after tracer has returned to background levels outside is consistent with subsequent measurements undertaken in the same building (Matthews et al 2017) and measurements taken in a separate study in London (Martin et al 2010b).…”

“…However, the movement of traffic along streets can act as both a source and cause of pollutant movement (Patra et al 2008). Infiltration of material into buildings can alter tracer concentrations downwind (Martin et al 2010b) with tracer campaigns showing tracers remaining within buildings long after they have cleared outside (Matthews et al 2017). Infiltration into buildings may lead to wind-tunnel predictions overestimating concentrations as buildings are often considered impervious.…”

“…Ventilation conditions within the Simon Building were investigated for a follow-up study on tracer infiltration (Matthews et al 2017). The CO 2 decay rate showed good correlation with that of PFC tracers, and rooms with the lowest ventilation rate had elevated tracer concentration for the longest.…”

Local Scale Exposure and Fate of Engineered Nanomaterials

“…The method can be advantageous particularly for exposure assessment at large production plants that include outdoor processes and work operations in open air. Furthermore, within the factory, the pollutants could be transported from outdoor air to indoor office spaces via general ventilation [ 67 , 68 ], which presents another possible occupational exposure scenario. A further application stands at construction sites at which bed rock drilling and blasting can produce substantial amount of dust [ 69 ].…”

Indoor Air Quality and Health

“…The manuscript of Batterman [ 10 ] reviews the use of CO 2 as a “natural” tracer gas for estimating VRs in school classrooms, and provides details and guidance for the steady-state, build-up, decay, and transient mass balance methods. The CO 2 tracer approach was also used by Matthews et al [ 11 ] within a large university building in Manchester to estimate air-exchange rates. The same authors presented an innovative approach based on the use of perfluorocarbon tracers to trace the amount of outdoor material penetrating into the university building and the flow of material within the building itself.…”