Partitioning mechanisms and film formations of DEHP on realistic indoor airborne particles and road dust

In order to investigate the key factors resulting in the large deviations of the literature-reported PAE partition coefficients on particles, a direct particle sampling and DEHP partition coefficient-detecting method was developed to analyze realistic indoor airborne particles (AirP), Arizona test dust (ATD) and Beijing road dust (BJD). Mechanistic models were developed to determine the partition coefficients. Our results showed that the AirP partition coefficient (K_ap) of DEHP was 4.03 × 10⁴ m³/g, and the DEHP absorption in AirP organic matters dominates the sorption capacity. We found that the realistic AirP organic matter components varied from the traditional hypothesis that assumes organic matter is similar to octanol. In contrast, the DEHP partition coefficients (K_dust) for ATD and BJD were two orders of magnitude smaller than that of AirP. DEHP adsorption on the inorganic matter was found to be the main sorption mechanism on the surfaces of ATD and BJD. Following an 8-day DEHP exposure, the adhesion forces increased approximately from 4.0 nN to 11.0 nN for AirP and BJD, indicating the formation of organic films. These films could potentially enrich other organic pollutants to generate more hazardous combined pollution. This study provides a direct particle sorption method and more accurate partition coefficients to correctly evaluate DEHP concentrations in airborne particles and settled dust in indoor environments.