T262 Sources, Transport, and Fate of Trace and Toxic Elements in the Environment (Posters)

Wednesday, 3 November 2010
8:00 AM - 6:00 PM
Hall D

THE ROLE OF "FINES" IN THE TRANSPORT OF PHARMACEUTICALS AND PERSONAL-CARE PRODUCTS (PPCPs) THROUGH SEDIMENTS AND SOILS

Paper number: T262-13
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Sorption to sediments and soils can significantly impact the transport and fate of pharmaceuticals and personal-care products (PPCPs) in the environment. Sorption to fine-grained sediments can be particularly important due to their relatively high surface areas. In this study, preliminary batch and column experiments were performed to investigate the relative role of these “fines” on bulk sorption. Seven PPCPs were selected for the study and include anionic acids (salicylic acid, ibuprofen, and diclofenac), neutral acids and bases (bisphenol A, carbamazepine, caffeine) and cationic bases (propranolol) at the experimental pH. In batch experiments, PPCP solutions were mixed with six different substrates: a coarser (0.25-0.5mm grain-size diameter) and finer (<0.044mm) crushed limestone, a coarser filter sand (99.4% quartz; 0.43-0.50mm) and finer dune sand (79% quartz, 0.21-0.30mm), and a bulk natural soil (TOC=2.97%) and the sieved fines (<0.044mm) from that soil. Equilibrium aqueous concentrations were measured after mixing, and sorption coefficients (Kd) were determined using linear isotherms. In the column experiments, PPCP solutions were pumped through a flow cell, collected from the column outlet, and analyzed. Retardation factors determined from PPCP breakthrough curves were used to calculate corresponding sorption coefficients.

Measured Kd values from the batch experiments were nearly identical to those from the column experiments. Propranolol was the most highly sorbed compound on all substrates, with sorption coefficients of 0.8 L/kg (filter sand), 6.5 L/kg (dune sand), 6.5 L/kg (coarse limestone), and 10.6 L/kg (fine limestone). No other compounds readily sorbed to the filter sand (Kd≤0.1 L/kg), though salicylic acid (Kd=0.13 L/kg), bisphenol A (0.23), carbamazepine (0.17) and caffeine (0.46) did sorb to the coarse limestone. All compounds were more highly sorbed to the natural soil, with Kd values ranging from 0.2 L/kg (ibuprofen) to 44 L/kg (propranolol). Compared to the bulk soil, Kd values increased by factors of 10-68 in the sieved, fines-only soil fraction. Four compounds (salicylic acid, bisphenol A, caffeine, and propranolol) also exhibited greater sorption to the fines-only limestone compared to the coarser size fraction, though the increase was much less pronounced.