HENRYS LAW CONSTANT, VOLATILIZATION RATE, AND AQUATIC HALF-LIFE OF OCTAMETHYLCYCLOTETRASILOXANE

The undimensioned Henry's law constant (H-c) and volatilization rate c onstant (k(v)(c)) of the silicone fluid octamethylcyclotetrasiloxane ( OMCTS) were determined experimentally. The grand mean H-c for five exp eriments conducted under dynamic conditions with initial concentration s ranging from 4 to 50 mu g/L (20 degrees C; 48-h equilibration period ) was 3.4 +/- 1.37. An H-c of > 17 was observed under kinetic ally lim ited, static conditions where equilibrium was not reached in 96 h. H-c increased about 10-fold when humic acids were added to OMCTS test sol utions, suggesting typical environmental cosolutes will increase the H enry's law constant for OMCTS. The measured volatilization/re-aeration ratio (k(v)(c)/K-v(o)) fdr OMCTS was 0.57, a value similar to that me asured for trichloroethylene (0.57) and benzene (0.56), indicating tha t OMCTS will readily volatilize from water.