Influence of residence time on the particle-gas partitioning of phthalates onto airborne inorganic particle

In indoor environments, the presence of particulate matter promotes SVOCs volatilization, increasing their overall concentration in the air. This effect arises from the partition of SVOCs between the gas and particulate phases. The particle-gas partition ratio ( K p ) is a critical parameter influencing the fate, transport, and human exposure to indoor SVOCs. Air exchange rate (AER) is a pivotal factor in closed spaces as it regulates the residence time of airborne SVOCs in an indoor environment. It has been reported that AER (or residence time) can affect particle-gas partitioning behavior for organic particles when equilibrium between gas and particle phases is not reached; however, its effect on inorganic particles has not been thoroughly investigated. This study develops an experimental procedure to measure K p of Di-n-butyl phthalate (DnBP) and Diethyl phthalate (DEP) with inorganic sodium chloride (NaCl) particles. Results shows that DnBP had higher K p values than DEP. Positive correlation of K p values and mixing time was observed. These findings are consistent with model predictions. Further experiments were carried out to study the impact of AER on K p , and the results shown that higher air exchange rates (lower residence time) result in lower particle-phase concentrations of SVOCs due to increased dilution and reduced interaction time with particles. These findings have important implications for indoor air quality assessments, highlighting the influence of ventilation strategies on SVOCs behavior in indoor environments. • The gaseous DnBP and DEP were generated in a quasi-stable system. • DnBP possessed higher K p than DEP due to its lower vapor pressure. • Higher AER led to lower SVOCs particle-phase concentration.