Partitioning and removal of perfluorooctanoate during rain events: the importance of physical-chemical properties

Abstract

The potential for airborne emissions to undergo long-range transport or to be removed from the atmosphere is influenced by their physical-chemical properties. When perfluorooctanate (PFO) enters the environment, its physical-chemical properties can vary significantly, depending on whether it exists as an acid, a salt, or a dissociated ion. A summary of the physical-chemical properties of the three most likely environmental states: ammonium perfluorooctanoate (APFO), perfluorooctanoic acid (PFOA) and the dissociated perfluorooctanoate anion (PFO(-)) is presented to illustrate the distinct environmental properties of each. The most volatile species, PFOA, is shown to have a pH-dependent air-water partitioning coefficient (K(aw)). The variability of K(aw) with pH influences the potential for vapor formation from aqueous environments, including rain events. Using the pH-dependent K(aw) and measured rain and air concentrations, it is shown that vapor-phase PFOA is not likely to be present above measurable levels of 0.2 ng m(-3) (12 parts per quadrillion v/v) during a rain event. Because rain concentrations determined in this work are comparable to measurements in other parts of North America, it is unlikely that rain events are a significant source of vapor-phase PFOA for the general North American region. It is shown that PFOA exists primarily in the particle phase in ambient air near direct sources of emissions and is efficiently scavenged by rain droplets, making wet deposition an important removal mechanism for emissions originating as either PFOA or APFO. Washout ratios of particle-associated PFO were determined to range between 1 x 10(5) and 5 x 10(5), in the same range as other semi-volatile compounds for which wet deposition is an important mechanism for atmospheric removal and deposition onto soils and water bodies.

Emissions of Per- and Polyfluoroalkyl Substances in a Textile Manufacturing Plant in China and Their Relevance for Workers’ Exposure

“…65,67,68 PFCAs might be released as impurities from textile finishes that are based on fluorinated polymers both associated with particles or unassociated followed by a rapid adsorption to particles. 69 Additionally, PFCAs may be formed during the degradation of FTOHs, 17,70 which can easily volatize because of their high vapor pressure from fluorinated polymerbased textile finishes.…”

“…64 The vapor pressure of the anionic form of PFOA is assumed as negligible. 65 The lower the vapor pressure of a compound, the higher the tendency to adsorb to surfaces and particles. 66 Assuming that the vapor pressure is negligible for all anionic conjugate bases of PFCAs and considering that the vapor pressure decreases with increasing chain-length, PFCAs should…”

Air concentrations and particle–gas partitioning of polyfluoroalkyl compounds at a wastewater treatment plant

“…[20] PFCAs and PFSAs have been detected in the particle-phase in the atmosphere; however, only a few studies have reported their presence in the gas-phase. [19,22] The aim of this study was to generate more information on aerosol-mediated sources of PFCs by investigating the air concentrations and particle-gas partitioning of PFCs emitted at two locations in a WWTP -the aeration tank and the secondary clarifier. A secondary aim was to compare measurements conducted using the active high volume air sampler with time-integrated measurements using a sorbent-impregnated polyurethane foam (SIP) disk passive air sampler.…”

Wet Deposition and Photodegradation of Perfluoroalkyl Carboxylates and Fluorotelomer Alcohols: Distribution Pathways from Air to Water Environment

“…Perfluoroalkyl carboxylates concentrations and profiles in rainwater can be influenced by many factors such as their presence and half-life in the atmosphere, physicochemical properties i.e. solubility and sorption onto particle, amount of rainfall and also meteorological conditions (Barton et al, 2007;Rayne and Forest, 2009;Dreyer et al, 2010;Taniyasu et al, 2013a). …”