Measurement report: Seasonality, distribution and sources of organophosphate esters in PM2.5 from an inland urban city in Southwest China

Organophosphate esters (OPEs) are contaminants of emerging concern, and studies have concluded that urban areas are a significant source of OPEs. Samples were collected from six ground-based sites located in Chengdu, a typical rapidly developing metropolitan area in Southwest China, and were analyzed for seven OPEs in atmospheric PM2.5 (Sigma(7) OPEs). The concentrations of Sigma(7) OPEs in PM2.5 ranged from 5.83 to 6.91 ng m(-3), with a mean of 6.6 +/- 3.3 ng m(-3), and the primary pollutants were tris-(2-butoxyethyl) phosphate (TBEP), tri-n-butyl phosphate (TnBP), tris-(2-chloroethyl) phosphate (TCEP) and tris-(2-chloroisopropyl) phosphate (TCPP), which together made up more than 80 % of the Sigma(7) OPEs. The concentrations of Sigma(7) OPEs were higher in autumn and winter than in summer. Nonparametric tests showed that there was no significant difference in Sigma 7 OPE concentrations among the six sampling sites, but the occurrence of unexpectedly high levels of individual OPEs at different sites in autumn might indicate noteworthy emissions. A very strong correlation (R-2 = 0.98, p < 0.01) between the OPEs in soil and in PM2.5 was observed. Backward trajectory analysis indicated that the OPEs in PM2.5 were mainly affected by local sources. Principal component analysis (PCA) revealed that the OPEs in PM2.5 were largely sourced from the plastics industry, interior decoration and traffic emission (34.5 %) and the chemical, mechanical and electrical industries (27.8 %), while the positive matrix factorization (PMF) model revealed that the main sources were the plastics industry and indoor source emissions, the food and cosmetics industry and industrial emissions. In contrast to coastal cities, sustained and stable high local emissions in the studied inland city were identified, which is particularly noteworthy. Chlorinated phosphates, especially TCPP and TCEP, had a high content, and their usage and source emissions should be controlled.