Unveiling airborne threats: Vertical profiles of multiple emerging pollutants in PM_2.5 across the urban atmosphere of Southern China

PM_2.5 has a detrimental impact on human health and has become a focus of widespread concern. The tempo-spatial distribution of emerging pollutants has been extensively studied, while there is a scarcity of understanding their vertical distribution in atmospheric environment. Here we investigated the vertical profiles of phthalate esters (PAEs), organophosphate esters (OPEs), neonicotinoids (NEOs), and per-and polyfluorinated substances (PFASs) in PM_2.5 at ground level (4.5 m), 118 m, and 488 m in an urban environment. Results reveal that the PAEs in PM_2.5 had higher concentrations than OPEs, NEOs, and PFASs. Vertical pollutant distribution generally exhibits a decline in concentration with increasing altitude. However, the opposite pattern also occurs, especially for NEOs and PFASs. The underlying mechanisms are multifaceted, encompassing the physicochemical characteristics of pollutants, meteorological parameters, and air-mass trajectories, each contributing to the vertical profile in varying degree. Additionally, the indoor health risks posed by outdoor pollutants at 118 m and 488 m were evaluated and found to be comparable to the outdoor risks at the ground. To our knowledge, this is the first exploration of the vertical characteristics of emerging pollutants at heights exceeding 100 meters, which provides a crucial reference for the prevention and control of emerging pollutants.