OH-initiated heterogeneous oxidation of tris-2-butoxyethyl phosphate: implications for its fate in the atmosphere

Abstract

Abstract. A particle-phase relative rates technique is used to investigate the heterogeneous reaction between OH radicals and tris-2-butoxyethyl phosphate (TBEP) at 298 K by combining aerosol time-of-flight mass spectrometry (C-ToF-MS) data and positive matrix factor (PMF) analysis. The derived second-order rate constants (k2) for the heterogeneous loss of TBEP is (4.44 ± 0.45) × 10−12 cm3 molecule−1 s−1, from which an approximate particle-phase lifetime was estimated to be 2.6 (2.3–2.9) days. However, large differences in the rate constants for TBEP relative to a reference compound were observed when comparing internally and externally mixed TBEP/organic particles, and upon changes in the RH. The heterogeneous degradation of TBEP was found to be depressed or enhanced depending upon the particle mixing state and phase, highlighting the complexity of heterogeneous oxidation in the atmosphere. The effect of gas-particle partitioning on the estimated overall lifetime (gas + particle) for several organophosphate esters (OPEs) was also examined through the explicit modeling of this process. The overall atmospheric lifetimes of TBEP, tris-2-ethylhexyl phosphate (TEHP) and tris-1,3-dichloro-2-propyl phosphate (TDCPP) were estimated to be 1.9, 1.9 and 2.4 days respectively, and are highly dependent upon particle size. These results demonstrate that modeling the atmospheric fate of particle-phase toxic compounds for the purpose of risk assessment must include the gas-particle partitioning process, and in the future include the effect of other particulate components on the evaporation kinetics and/or the heterogeneous loss rates.

Seasonal variation and influence factors of organophosphate esters in air particulate matter of a northeastern Chinese test home

“…Furthermore, Li et al have revealed that RH could retard the reaction rate of •OH initiated heterogeneous oxidation of gaseous TCIPP and subsequently hindered the gaseous TCIPP degradation, implying the varied concentrations upon different humidity conditions (Li et al, 2017a). A significant negative correlation was observed between RH and particulate TBOEP (p b 0.05, Table S9), which is consistent with the finding that increased RH promotes TBOEP degradation via decreasing the viscosity of particle (Liu et al, 2014a;Liu et al, 2019). However, other hydrophilic OPEs including TCIPP and TCEP, the two important chlorinated OPEs with higher detection rates and measured concentrations in this study, did not possess a similar trend, indicating that the effect of RH may be obscured by other influence factors such as a more significant positive correlation with temperature of TCEP.…”

“…Water (i.e., RH) can influence the OH-initiated heterogeneous oxidation of TBOEP via influencing the phase of particles, subsequently influence the mixing state and reactivity (Liu et al, 2014a;Liu et al, 2019). Furthermore, Li et al have revealed that RH could retard the reaction rate of •OH initiated heterogeneous oxidation of gaseous TCIPP and subsequently hindered the gaseous TCIPP degradation, implying the varied concentrations upon different humidity conditions (Li et al, 2017a).…”

Rate constant and secondary organic aerosol formation from the gas-phase reaction of eugenol with hydroxyl radicals

“…S1 and S2 in the Supplement. The gas-phase reactions were conducted in the OFR, a detailed description of which has been presented elsewhere (Liu et al, 2014b). Before entering into the OFR, gasphase species were mixed thoroughly in the mixing tube.…”

Laboratory study on OH-initiated degradation kinetics of dehydroabietic acid

“…It has been found that RH can positively or negatively influence reactions between OH and the organic particles. Some researchers have observed that increased RH will lower the viscosity of the amorphous aerosol particles and subsequently enhance OH uptake because particle-phase diffusion is feasible, [78][79][80] whereas other results show that the OH uptake was suppressed at higher RH because of competitive co-adsorption of water, which will take up the reactive sites. 52 Based on our previous study, degradation of levoglucosan by OH was influenced significantly by RH because of different layers of water cover on the surface of levoglucosan under different relative humidities.…”