Aqueous Solubility, n-Octanol–Water Partition Coefficient, and Sorption of Five Selective Serotonin Reuptake Inhibitors to Sediments and Soils

Abstract

Aqueous solubilities (S (w)) and n-octanol-water partition coefficients (K (ow)) of five selective serotonin reuptake inhibitors (SSRIs) were measured and sorption to two sediments and three soils with organic matter contents ranging from 0.16% to 1.77% and pH ranging between 5.0 and 7.8 was investigated using a batch equilibrium method. SSRIs had high S (w) (3,022-15,460 mg/l) and relatively low log K (ow) (1.12-1.39). Sorption isotherms followed the Freundlich equation. All SSRIs had sorption capacities of greater than 91% except fluvoxamine with a minimum capacity of 73%. Organic matter contents partly affected sorption, however no correlation between sorption characteristics and cation exchange capacity (CEC) or clay content was observed for any SSRI or adsorbent. Values of K (f), K (d), and log K (oc) ranged from 39 to 18,342, from 60 to 42,579, and 3.35 to 6.02 for the SSRIs. SSRIs likely exhibit mixed mechanisms of sorption such as ionic binding in addition to hydrophobic interactions.