Acetic Acid

CAS RN: 64-19-7

Soil Adsorption / Mobility

A log Koc of 0.00 (Koc = 1), which was derived from experimental measurements, has been reported for acetic acid(1,2). According to a classification scheme(3), this Koc value suggests that acetic acid is expected to have very high mobility in soil. No detectable sorption was measured for acetic acid using the OECD Guideline 106 method employing an acidic forest soil, pH 2.8, an agricultural soil, pH 6.7, and a lake sediment, pH 7.1(4). Adsorption of acetic acid to 3 nearshore marine sediments collected from three different locations resulted in Kd values of 0.65 (Koc = 228), 0.085 (Koc = 6.5) and 0.046 (Koc = 27) using clastic mud (3.5% organic carbon, pH 7.0), muddy sand (1.3% organic carbon, pH 7.7), and carbonate sand (0.17% organic carbon, pH 8.1), respectively(5). The pKa of acetic acid is 4.76(6), indicating that this compound will exist partially 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(7).
In 24 hr aqueous adsorption studies using montmorillonite and kaolinite clay adsorbents, 2.4-30.4% of added acetic acid was observed to be in the adsorbed phase(1). In adsorption studies using the adsorbent hydroxyapatite (a mineral which occurs in the environment as a result of the diagenesis of skeletal apatite), only 5% of added acetic acid (in aqueous solution, pH 8.0) became adsorbed to the hydroxyapatite(2). Acetic acid has been noted to leach from biological disposal areas(3).
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