Water-to-air transfer of branched and linear PFOA : Influence of pH, concentration and water type

• The volatilisation of perfluorooctanoic acid (PFOA) was measured experimentally at a range of pH valuesusing a previously published laboratory method. Water-to-air transfer was studied for five structuralisomers, namely: the linear isomer (n-PFOA) and the four most commonly occurring branched isomers(3-, 4-, 5- and 6-PFOA). The influence of water concentration and water type on the pH-dependent waterto-air transfer was also investigated for n-PFOA. The water-to-air transfer was studied over the course of 48 h at pH values ranging from 0.2 to 5.5. Under all experimental conditions tested, the volatilisation ofPFOA was negligible at pH > 2.5. In experiments performed with MilliQ water, volatilisation increasedwith decreasing water pH. In experiments performed with tap water and lake water, maximum volatilisationwas observed at pH 1. The concentration of PFOA in water had no influence on the pH value atwhich water-to-air transfer was observed (i.e. at pH < 2.5) for the concentration range tested (0.1e50 mg/L PFOA in deionised water). Although the percentage of PFOA volatilised was significantly different forthe four branched isomers at low pH, volatilisation was not observed above pH 2.5 for any branchedisomer suggesting that all PFOA isomers have a low pKa. Overall, these laboratory results demonstratethat volatilisation of any structural isomer of PFOA from water is negligible at environmentally-relevantconditions. It is unlikely that PFOA isomers will be fractionated in the environment as a result of volatilisationbecause it is a process of negligible environmental relevance.

Ämnesord

NATURVETENSKAP  -- Kemi -- Analytisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Analytical Chemistry (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

Nyckelord

PFOA

Isomer

Branched

Acid dissociation

pKa

Applied Environmental Science

tillämpad miljövetenskap

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