Sorption of estrogens, triclosan, and caffeine in a sandy loam and a silt loam soil

Purpose: Recently, pharmaceuticals and personal care products (PPCPs) have been identified in the environment. Concerns on the occurrence and fate of these compounds in soil and sediment have significantly increased. It is believed that these PPCPs sorb to soil and sediment; however, information on sorption of PPCPs is still limited. In this study, the sorption of estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2), triclosan, and caffeine to two loam soils and Ottawa sand was assessed. Materials and methods: Sorption was determined using the batch equilibrium method. Freundlich and linear equations were applied to the sorption data in order to obtain sorption isotherms for each test compound and the respective sorption coefficients (K_f, K_d, and log K_oc). Results and discussion: The results indicated that isotherms were generally linear over the range of concentrations tested. Sorption capacity was directly related to organic carbon content such that partition coefficients for silt loam soil > sandy loam soil > sand. Triclosan had the highest values of K_f (231 in the sandy loam and 344 in the silt loam) and K_d (256 in the sandy loam and 282 in the silt loam). The log K_oc values for the PPCPs tested varied from 1.85 to 4.30. Desorption tests over 24 h indicated that caffeine had the greatest desorption capacity (>15%) among the compounds in sandy loam soil, while triclosan had the lowest desorption capacity (<1%) in both soil types. Conclusions: Data indicated that E1, E2, EE2, and triclosan have a strong tendency to sorb to both soils, and their corresponding mobility in these soils would be minimal. If persistent enough, E3 and caffeine would have the best potential for groundwater contamination; however, soil conditions would also have to favor leaching for this to occur. The sorption capacity for sorbents was in an order directly related to organic carbon content: silt loam soil > sandy loam soil > sand.