The atmospheric fate of di-2-ethylhexyl-phthalate, adsorbed on various metal oxide model aerosols and on coal fly ash

The atmospheric fate of a plasticiser, Di-(2-ethylhexyl-)phthalate (DEHP), is simulated in an aerosol smog chamber. DEHP is adsorbed on various metal oxide model aerosols, on NaCl and on fly ash from a coal power plant. Rapid evaporation loss is observed to occur from NaCl aerosol, from fly ash to a minor extent and from other aerosols only at surface densities exceeding one monolayer. The coating of DEHP is observed to be inert against ozone, leading to an upper limit of the rate constant of 10 E-18 cm -3s E-1. Exposed to a simulated photochemical smog, the decay of DEHP is observed to be governed by reaction with OH radicals. The decay is observed to obey a pseudo-first order rate law, proportional to the concentration of OH in the gas-phase. Rate constants, k +- 2 sigma, of 1.36 +- 0.2, 1.4 +- 0.2, 1.28 +- 0.3, and 0.8 +- 0.3 are obtained for SiO2, Al2O3, Fe2O3 and fly ash aerosol, respectively (in units of 10 E-11 cm E3 s E-1). Adopting 5 x 10 E5 cm E-3 as the average global tropos pheric concentration of OH, the mean tropospheric residence time of DEHP is calculated to be about one day. (ITA)