A pKa of 4.31(1) indicates phenylacetic acid will exist almost entirely in the anion form at pH values of 5 to 9(2) and therefore volatilization from water surfaces is not expected to be an important fate process. Phenylacetic acid is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3).
Literature: (1) Dean JA; Lange's Handbook of Chemistry 13th ed NY, NY: McGraw-Hill, Inc p. 5-53 (1985) (2) Doucette WJ; pp. 141-188 in Handbook of Property Estimation Methods for Chemicals. Boethling RS, Mackay D, eds. Boca Raton, FL: Lewis Publ (2000) (3) Perry RH, Green D; Perry's Chemical Engineer's Handbook 6th ed NY, NY: McGraw-Hill, Inc p. 3-59 (1984)
Koc values of 31, 26, and 28 were experimentally determined for phenylacetic acid in three specific soils: a Podzol (pH = 2.8, sand = 89.2%, silt = 8.2%, and clay = 2.6%), an alfisol (pH = 6.7, sand = 69.7%, silt = 14.4%, and clay = 15.9%) and sediment from Lake Constance (pH = 7.1, sand = 5.5%, silt = 58.8%, and clay = 35.7%), respectively(1). According to a recommended classification scheme(2), these Koc values suggest that phenylacetic acid is expected to have very high mobility in soil(SRC). The pKa of phenylacetic acid is 4.31(3), indicating that this compound will primarily exist in anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4).
Literature: (1) von Oepen B et al; Chemosphere 22: 285-304 (1991) (2) Swann RL et al; Res Rev 85: 23 (1983) (3) Dean JA; Lange's Handbook of Chemistry 13th ed NY, NY: McGraw-Hill, Inc p. 5-53 (1985) (4) Doucette WJ; pp. 141-188 in Handbook of Property Estimation Methods for Chemicals. Boethling RS, Mackay D, eds. Boca Raton, FL: Lewis Publ (2000)