Occurrence and spatial distribution of neutral perfluoroalkyl substances and cyclic volatile methylsiloxanes in the atmosphere of the Tibetan Plateau

Abstract

Abstract. Due to their properties of bioaccumulation, toxicity, and long-range atmospheric transport, polyfluoroalkyl and perfluoroalkyl substances (PFASs) and cyclic volatile methylsiloxanes (cVMSs) are currently being considered as emerging persistent organic pollutants (POPs) for regulation. To date, there are limited data on PFASs and cVMSs in the atmosphere of the Tibetan Plateau (TP), a remote environment which can provide information on global background conditions. Sorbent-impregnated polyurethane foam (SIP) disc passive air samplers were therefore deployed for 3 months (May to July 2011 and 2013) at 16 locations across the TP. Using previously reported methods for estimating the air volume sampled by SIP discs, the derived atmospheric concentrations ranged as follows: 18-565 ng m −3 for cVMS (including D3, D4, D5, and D6); 65-223 pg m −3 for fluorotelomer alcohols ( FTOHs); 1.2-12.8 pg m −3 for fluorinated sulfonamides ( FOSA); and 0.29-1.02 pg m −3 for fluorinated sulfonamidoethanols ( FOSE). The highest cVMS occurred at Lhasa, the capital city of the TP, indicating the local contribution to the emerging pollutants. Higher levels of FTOHs were observed at sites close to the transport channel of the Yarlung Tsangpo Grand Canyon, indicating possible long-range atmospheric transport (LRAT). Elevated concentrations of shorter-chain volatile PFAS precursors (4 : 2 FTOH and fluorobutane sulfonamidoethanol) were found in most air samples, reflecting the shift in production from long-to short-chain PFASs in Asia. Overall, concentrations of emerging POPs at background sites of the TP were 1-3 orders of magnitude higher than those reported for legacy POPs.

Occurrence and source apportionment of perfluoroalkyl acids (PFAAs) in the atmosphere in China

“…Specifically, PFOA was the dominant PFAA (accounting 20.6 %), and was detected in all atmospheric samples with an average value of 8.19 ± 8.03 pg m −3 . This phenomenon could occur since PFOA is widely used in the manufacturing of polytetrafluoroethylene (PTFE), perfluorinated ethylene propolymer (FEP), and perfluoroalkoxy polymers (PFA; Wang et al, 2014). The domestic demand for and the industrial production of PFOA-based products have been increasing in China since the late 1990s (Wang et al, 2014), and direct emissions of perfluorooctane sulfonamide (FOSA)-based products may contribute to the relative high level of PFOA.…”

“…This phenomenon could occur since PFOA is widely used in the manufacturing of polytetrafluoroethylene (PTFE), perfluorinated ethylene propolymer (FEP), and perfluoroalkoxy polymers (PFA; Wang et al, 2014). The domestic demand for and the industrial production of PFOA-based products have been increasing in China since the late 1990s (Wang et al, 2014), and direct emissions of perfluorooctane sulfonamide (FOSA)-based products may contribute to the relative high level of PFOA. Meanwhile, one major variation of a PFOA precursor, 8 : 2 FTOH, was reported to rank as the highest concentration among neural PFASs in the air of China (De Silva, 2004;Martin et al, 2006).…”

“…PFAAs can originate from direct sources of products' emissions as well as indirect sources of incomplete degradation of their precursors. It is estimated that the global historical emission quantities of C 4 -C 14 PFCAs were 2610-21 400 t in the period of 1951-2015, of which products based on PFOA and perfluorononanoic acid (PFNA) contributed the most (Wang et al, 2014). A trend of geographical distribution of major fluorochemical manufacturing sites has shifted from Western Europe, USA, and Japan to the emerging economies in the Asia Pacific area over the past decades.…”

“…In general, three pathways/hypotheses for the transport of PFAAs have been suggested: transport associated with particles, degradation from precursors, and sea salts from current bursting in coastal areas. The PFAAs precursors such as fluorotelomer alcohols (FTOHs), which can form the corresponding PFAAs through oxidation reactions initiated by hydroxyl radicals (OH q ) in the atmosphere (Thackray and Selin, 2017), are more volatile than PFAAs and can reach remote areas via long-range transport (Martin et al, 2006;Wang et al, 2018). Due to the lower acid dissociation coefficient (pK A ), 0-3.8 for PFCAs and −3.3 for PFSAs, PFAAs are expected to be mainly associated with aerosols in the non-volatile anionic form (Lai et al, 2018;Karásková et al, 2018).…”

Field‐testing polyethylene passive samplers for the detection of neutral polyfluorinated alkyl substances in air and water

“…Several studies have relied on passive sampling for the detection of neutral, volatile PFASs. In particular polyurethane foam (PUF) discs, often sorbent-impregnated, have been used repeatedly (Genualdi et al 2010; Kim et al 2012; Ahrens et al 2013; Wang et al 2018), but also, activated carbon felts (S Oono et al 2008; Liu et al 2013), and semi-permeable membrane devices (SPMDs) (Fiedler et al 2010). In contrast, the use of single phase polymers, such as silicone-rubber based samplers or polyethylene sheets (PE) has not been explored for neutral, volatile PFASs.…”