PM₁₀ Contributions from Construction, Biomass Burning, and Non-Exhaust Traffic Emissions at the UK Urban Background Site, Based on Online Metals Data

Atmospheric trace metals in particulate matter (PM) pose significant environmental and health risks, making their study crucial for understanding urban air quality. These metals originate from various sources, including traffic emissions, industrial activities, and natural processes, and can have detrimental effects on human health and ecosystems. Investigating their concentrations and sources provides valuable insights into pollution dynamics and informs mitigation strategies. In this study, PM<i>10</i> trace metal concentrations were investigated at an urban background site in Manchester, assessing the influence of different sources, including the effect of the COVID-19 lockdown. Utilising an Xact <i>625i </i>ambient metal analyser and applying Positive Matrix Factorisation (PMF), four sources of PM₁₀metals were identified: vehicle non-exhaust emissions (NEE), biomass burning, sea salt, and construction dust. The study the used Multiple Linear Regression to quantify the contributions of the factors’ time series to the variations in concentrations of PM₁, PM_2.5and PM₁₀ measured using a FIDAS. Surprisingly, while the sea salt, construction dust and biomass burning all made appreciable contributions to the variances of the expected size fraction, the NEE contribution was small, implying that its influence on measured PM concentrations was low. This may be because the particles were large and were not transported efficiently away from the nearby roads. Analysis also showed during lockdown decreases in concentrations of NEE, NOx, and optical absorption from traffic measured by an aethalometer (Babs950 (traffic)) by 37%, 66%, and 41%, respectively. While a decrease associated with a reduction in traffic is expected, the disparity between the different metrics may be due to the average speed of vehicles increasing, changing the emissions factors.