Quantification and occurrence of 39 tire-related chemicals in urban and rural aerosol from Saxony, Germany
Volkwin Kuntz, Daniel Zahn, Thorsten Reemtsma
Abstract
• More than 30 tire-related chemicals determined in urban PM 10 . • Concentration of single compounds in urban PM 10 from 0.022 to 950 pg/m 3 . • Distribution of tire-related chemicals was not uniform between PM 10-2.5 and PM 2.5 . • Compounds significantly higher in PM 10-2.5 may the most selective ones for TRWP. • Many compounds up to two orders of magnitude lower in rural PM 10 . Tire and road wear particles (TRWP) are a major contributor to non-exhaust traffic emissions, but their contribution to and dynamics in urban aerosol is not well known. Urban particulate matter (PM) in the size fraction below 10 µm (PM 10 ) from two German cities was collected over 2 weeks and analysed for 39 tire-related chemicals, including amines, guanidines, ureas, benzothiazoles, p -phenylenediamines, quinolines and several transformation products (TPs). Of these, 37 compounds were determined in PM 10 at median concentrations of 212 pg/m 3 for 1,3-diphenylguanidine (DPG) and 132 pg/m 3 for benzothiazole-2-sulfonic acid (BTSA); 10 of the compounds have not been reported in urban aerosol before. Median concentrations of N-(1,3-dimethylbutyl)-N′-phenyl- p -phenylenediamine (6-PPD), 6-PPD quinone (6-PPDQ), and 1,2-dihydro-2,2,4-trimethylquinoline (TMQ) were 1.0, 4.1, and 8.1 pg/m 3 , respectively. Some parent compounds showed positive correlation with their TPs, e.g. 6-PPD with 4-aminodiphenylamine (4-ADPA), N,N’-diphenyl- p -phenylenediamine (DPPD) with DPPD quinone (DPPDQ), and DPG with phenylguanidine (PG). The concentration pattern of the compounds in PM 10 did not agree to the pattern found for cryo-milled tire tread (CMTT mix ), likely reflecting transformation processes in tires or the aerosol and the influence from other sources than TRWP. Concentrations in PM 2.5 were determined from one of the sites and were by a factor of 4 – 10 lower than in PM 10-2.5 for 9 compounds, but a few others, mostly benzothiazoles showed similar or higher concentrations. Many of the tire-related chemicals were also determined in PM 10 of one rural site, although at median concentrations up to two orders of magnitude lower. A large number of tire chemicals with a wide concentration range is present in urban PM 10 and PM 2.5 aerosol and requires scrutiny with respect to its relevance for human exposure.