Aerosolisation of “forever chemicals” from contaminated water

Introduction

Poly- and perfluoro alkyl substances (PFASs), also known as “forever chemicals”, are persistent in the environment and are challenging to eliminate. There is a growing concern over their widespread presence in the environment and potential adverse effects on human health and ecosystems. Most of the current studies on PFAS pollution are related to aqueous and soil matrices while less emphasis has been given to their relevance to air quality. Several recent studies reported presence of PFASs in atmosphere; however, their atmospheric sources, especially for restricted for more than a decade perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are not well understood (e.g. Kourtchev et al., 2022; Zhou et al., 2021). Wastewater treatment (WWT) plants are repositories of 1000s of pollutants including PFASs (Barisci & Suri, 2021). Aerosolisation/volatilisation during WWT processes (e.g., aeration, trickling filtration) is suggested as one of the potential sources of PFASs in the atmosphere. However, to the best of our knowledge, aerosolisation potential of PFASs was conducted on a very small number of molecules from that class and under relevant to other than WWT processes conditions e.g., seaspray. 

The aim of this work is to investigate, for the first time, the aerosolisation potential of the extensive number of PFASs from contaminated waters under relevant to WWT plant conditions.

Method and results

Aerosolisation potential of PFASs, covering short-, medium- and long-chain compounds and including legacy PFOA, PFOS and perfluorononanoic acid (PFNA), was examined by aerating PFAS-fortified aqueous solutions at relevant to wastewater effluent concentrations and pHs in an aeration chamber. The generated PFAS-enriched aerosol was collected onto a prebaked glass fiber filter and methanolic solution using a filter pack, and an impinger. The samples were extracted and analysed using an on-line solid phase extraction (SPE) liquid chromatography (LC)-Orbitrap-Mass spectrometry (MS). The PFAS decay from the fortified aqueous solutions were also monitored to understand the extent of PFAS partitioning onto aerosol.

Our study indicates that a significant fraction of PFASs can be aerosolised from the contaminated water. This effect was more pronounced for long-chain PFASs irrespective of the pH of the contaminated water. Perfluorocarboxylic acids showed an increase in aerosol phase enrichment with increasing carbon chain length. Short chain PFASs showed lowest aerosol phase enrichment and losses from the contaminated water.

Conclusions

This study, for the first time, establishes the liquid-to-air transfer potential of 15 persistent semi-volatile PFASs including new generation replacements for legacy PFASs such as 4:2 fluorotelomer sulfonate (4:2 FTS) and 8:2 fluorotelomer sulfonate (8:2 FTS) via aerosolisation. The aerosolisation tendency of PFASs was found to increase with increasing carbon chain length. Legacy PFOS and PFOA were detected in the aerosol phase at alarming concentrations suggesting that the contaminated with PFAS waters exposed to aeration can be responsible for  observation of “forever chemicals” in the atmosphere.

 Reference:

Barisci and Suri, Water Sci.Technol., 84(12), 3442-3468. https://doi.org/10.2166/wst.2021.484

Kourtchev et al.  Sci. Total Environ., 835, 155496. https://doi.org/10.1016/j.scitotenv.2022.155496

Zhou et al. Environ.Sci.: Processes Impacts, 23(4), 580-587. https://doi.org/10.1039/D0EM00497A