Henryʹs law constants measurements of the nonylphenol isomer 4(3′,5′-dimethyl-3′-heptyl)-phenol, tertiary octylphenol and γ-hexachlorocyclohexane between 278 and 298 K

Henryʹs Law Constants (HLC, M atm−1) were determined for the diastereomeric mixture of the nonylphenol isomer 4(3′,5′-dimethyl-3′-heptyl)-phenol diastereomers (NP353(+) and NP353(−)), tertiary octylphenol (t-OP) and γ-hexachlorocyclohexane (γ-HCH) in artificial seawater over a temperature range 278–298 K using a dynamic equilibrium system. Trace organic substances present in the gas phase were trapped by tandem XAD-2 cartridges and extracted with a soxhlet extractor. The extracts were derivatived with N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA), and then analyzed with GC-MS in the selective ion mode. At 293 K and in artificial seawater, HLC (M atm−1) were found to be equal to: NP353(+), HLC=(483±169); NP353(−), HLC=(551±193); t-OP, HLC=(400±140); γ-HCH, HLC=(876±307). The obtained data were used to derive the following Van’t Hoff expressions: ln HLC (NP353(+))=8.73 (±0.95)×(1000/T) –23.61 (±3.30); ln HLC (NP353(–))=8.61 (±0.91)×(1000/T)−23.08 (±3.18); ln HLC (t-OP)=9.03 (±1.40)×(1000/T)−24.83 (±4.86); ln HLC (γ-HCH)=6.17 (±1.08)×(1000/T)−14.28 (±3.75). The derived enthalpies of solvation for NP353(+), NP353(−), t-OP and γ-HCH are −72.6±7.9, −71.6±7.6, −75.1±11.5 and −51.3±9.0 kJ mol−1, respectively. The HLC measurements of γ-HCH, which was used as reference substance, were in good agreement with literature values and its corresponding derived enthalpy of solvation agrees well to the previous values reported in the literature. A reassessment of the air/water gas exchange based on experimentally derived HLC was made for the nonylphenol (NP) in the Lower Hudson River estuary (New York/New Jersey, USA) that was previously reported by Van Ry. A net atmospheric deposition was calculated for the gas exchange of NP in the Lower Bay (Ffw=0.13), and it nearly reaches the condition of equilibrium in the Upper Bay (Ffw=0.46).