Elemental Characterization of PM2.5 at an Urban Traffic Site in Central Europe

Laurence Windell, Jaroslav Schwarz, Radek Lhotka, Petra Pokorná, Jakub Ondráček, Vladimír Ždímal, PHILIP K. HOPKE, ICPF CAS, Prague, Czech Republic

     Abstract Number: 319
     Working Group: Urban Aerosols

Abstract
Metal content in traffic emissions is often overlooked during regulation and policy making. Exhaust and non-exhaust traffic emissions, including tire, brake wear and re-suspended dust, contribute greatly to particulate matter and pose significant adverse health effects to humans in urban areas (Johansson et al., 2009). The current lack of strict regulations on these metal emissions draws attention to the need for controls and monitoring, as reflected in the recent Euro 7 standards proposal for research on traffic emissions. This work aims to quantify metal emissions from traffic at an urban traffic site in Prague, Czech Republic, identify key tracers of emissions, and investigate exhaust and non-exhaust emissions observable in fine particulate matter (PM2.5). This project signifies the first high-time resolution metal analysis in Prague.
Two one-month long measurement campaigns were conducted from February to March and November to December 2020 at an urban traffic site in Prague. Elemental data were obtained from the Xact625i Ambient Metals Monitor (analytical method nondestructive energy dispersive X-ray fluorescence – EDXRF) equipped with a PM2.5 sampling head at a two-hour time resolution. Enrichment factors were calculated, and correlations of key tracers (e.g. Cu, Ba, Zn, Mn) were identified. Source apportionment was carried out using Positive Matrix Factorization (US EPA PMF 5.0). Four factors were identified: dust, traffic, local heating, and coal burning. Metallic elemental concentrations were observed in decreasing order: Fe > Zn > Cu > Ti > Mn > Ba > Cr > As > Cd > Ni. The most abundant metal, Fe, was found in the range of 10 – 2933 ng/m3, followed by Zn (1 – 144 ng/m3), Cu (1 – 104 ng/m3), Ba (0.1 – 41 ng/m3) and Cr (0.2 – 16 ng/m3). Enrichment factors of Mn, Cr, and Cu and Zn were found to be up to 71, 113, 1066, and 1937, respectively.

References:
[1] Johansson, C., Norman, M. & Burman, L. 2009. Road traffic emission factors for heavy metals. Atmospheric Environment - ATMOS ENVIRON, 43, 4681-4688.