Impact of Atmospheric Flow Conditions on Fine Aerosols in Sydney, Australia

Abstract

We apply a simple objective measure of an airshed's degree of ventilation and determine the impact on PM 2.5 observations at Lucas Heights, Sydney, Australia. We extend the analysis of previous studies, which considered total PM 2.5 , by: using positive matrix factorisation to split the aerosol mass by source type; and using Radon-222 measurements as an independent indicator of ventilation and mixing. For this coastal airshed we found that for 64% of the time, conditions could be classified into four categories: local recirculation (LRC; 15%), stagnation (19.5%), regional recirculation (RRC; 10.9%), or ventilation (18.6%). Mean PM 2.5 concentrations under recirculation (in this study separated into; LRC and RRC) were 33% higher than under stagnation and can be double that of concentrations under ventilation. Since the combination of LRC and RRC events account for around 26% of all events, recirculation effects on PM 2.5 concentrations are significant. However, we found that airshed ventilation doesn't affect PM 2.5 concentrations from all sources evenly. Considering the three main sources of total PM 2.5 at this site (vehicle exhaust 26.3%, secondary sulfate 23.7% and aged industrial sulfur 20.6%), conditions leading to the highest concentrations differ. The highest vehicle exhaust concentrations occur under LRC, the highest aged-industrial-sulphur concentrations occur under RRC, and secondary sulfur had similarly high concentrations under LRC and RRC. Under LRC the concentration from vehicle exhaust can be up to a factor of 3.9 greater than under ventilation. On a seasonal basis, RRC flow is most likely to occur in summer and spring (the warmer months of the year when sea breezes are more likely), whereas LRC conditions are more likely to occur in autumn and winter. These findings support those of previous studies, indicating that re-circulation can have a significant effect on PM 2.5 concentrations in coastal airsheds, and the degree of impact can vary by source type.

A Clean Air Plan for Sydney: An Overview of the Special Issue on Air Quality in New South Wales

“…Although Sydney's most extreme pollution events are often associated with fires and dust storms (e.g., [28,[50][51][52]), studies analysing the sources of PM 2.5 and NO X in NSW concluded that motor vehicle exhaust was the largest contributor to total NO X [53] and the largest anthropogenic contributor to total PM 2.5 [54]. Power stations are also implicated as a major source of atmospheric fine particles [18].…”

Aerosol variability induced by atmospheric dynamics in a coastal area of Senegal, North-Western Africa

“…Recently, few studies show that SB events are associated with an increase of PM1 and PM2.5 concentrations (Babu et al, 2016;Crawford et al, 2017;Piazzola et al, 2012;Rodríguez et al, 2008) most probably due to the production of new ultrafine particle formation events, that seem to take place over the sea, being transported back to the coast.…”

Combined effect of boundary layer recirculation factor and stable energy on local air quality in the Pearl River Delta over southern China

“…RF was developed to characterize the characteristics of horizontal transportation in the atmosphere (Allwine and Whiteman 1994), which has been used to quantify coastal recirculation over the Mediterranean basin and the results showed that O 3 concentrations are high for both high and low recirculation (Levy, Dayan, and Mahrer 2008). Many studies showed that the air quality was poor when significant recirculation was observed (Chen et al 2016;Crawford et al 2017;Russo et al 2016;Wu et al 2013). SE was first used to depict the atmospheric vertical diffusion ability and has been proved to be a useful tool for prediction of air quality (Shang et al 2001).…”