Applications of Equilibrium Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 130

acids (extracted from soil) on the aqueous solubility of several chlorinated organics
(1,2,4,-trichlorobenzene, lindane, and several polychlorinated biphenyls). Haas and
Kaplan (1985) reported a similar study on the solubility of toluene in water containing
humic acids. Carter and Suffett (1982) determined the effect of humic acids on the
aqueous solubility of several polyaromatic hydrocarbons. Boehm and Quinn (1973)
reported the enhanced solubility of several hydrocarbons in seawater brought about by
the presence of DOCs. The effects were observed to be specific to the type of DOCs.
Commercial humic acids behaved differently from marine or soil humic acids.
In general, a larger solubility was always noted in the presence of DOCs in water.
Chiouetal.(1986)showedthatif C i representsthesolubilityoftheorganiccompound
in pure water and C app
i

is the apparent solubility in DOC-rich water, then

C app
i

C i =

1 + C C K cw , (4.10)

where C C is the DOC concentration (g/mL) in water and K cw is the equilibrium
partition constant for the organic solute between DOC and water (expressed in mL/g).
The values of K cw for several compounds are given in Table 4.5.
Since K aw isinverselyproportionaltotheaqueoussolubility,theair-waterpartition
constant in the presence of DOCs will be given by

K aw

K aw =

C C K cw .

(4.11)

1 +

Itcanthereforebeseenthattheeffectsonair-waterpartitionconstantsforacompound
of relatively high aqueous solubility will be less than that for one with a very low
aqueous solubility.
Mackay et al. (1982) noted that when commercially available humic acid or fulvic
acid was used in the aqueous solutions, up to concentrations of 54 mg/L, the air-
water partition constant for naphthalene showed a reduction of about 7 10 − 5 for

every 1 mg/L of the colloid added. It was concluded that although natural organic

×

TABLE 4.5
Partition Constants for Pollutants between DOC and Water

Compound Type of DOC Log K C Reference

p , p -DDT

Soil humic 5.06 Chiou et al. (1986)

p , p -DDT Aldrich humic acid 5.56 Chiou et al. (1987)

1,2,3-Trichlorobenzene Soil humic 3.00 Chiou et al. (1987)

Toluene Aldrich humic acid 3.3 Haas and Kaplan (1985)

Lindane Soil humic 2.7 Chiou et al. (1986)

Pyrene Soil humic 4.9-5.5 Gauthier et al. (1986)

2,4,4 -PCB Soil humic 4.24 Chiou et al. (1987)

Anthracene Soil humic 4.92 Carter and Suffett (1982)

Fluoranthene Soil humic 5.32 Acha and Rehbun (1992)