Determination of Henry's law constants of organochlorine pesticides in deionized and saline water as a function of temperature

The Henry's law constant (H) is an important parameter that is required to estimate the air-water exchange of semi-volatile organic compounds. Henry's law constants for 17 banned/restricted/currently used organochlorine pesticides (OCPs) were experimentally determined using a gas-stripping technique in deionized and saline water (3%) over a temperature range of 5-35 degrees C. H values (at 25 degrees C) ranged between 0.066 +/- 0.037 Pa m(3) mol(-1) (endosulfan II) and 62.0 +/- 24.2 Pa m(3) mol(-1) (heptachlor) in deionized water while the range in saline water was 0.28 +/- 0.03 Pa m(3) mol(-1) (gamma-HCH) and 135.2 +/- 31.3 Pa m(3) mol(-1) (heptachlor). The increase in dimensionless Henry's law constants (H') for OCPs over the studied temperature range was between 3 (gamma-HCH)-19 times (chlorpyrifos) and 3 (endosulfan II)-80 times (transnonachlor) in deionized and saline water, respectively. The calculated enthalpies of phase change (Delta H-H) were within the ranges previously reported for OCPs and other organic compounds (23.8-100.2 kJ mol(-1)). The salting-out constant, k(s), ranged between 0.04 (gamma-HCH) and 1.80 L mol(-1) (endosulfan II) indicating the importance of assessing the H values of OCPs in saline water to accurately determine their partitioning and fate in seawater. (c) 2006 Elsevier Ltd. All rights reserved.