Non-equilibrium passive sampling of hydrophobic organic contaminants in sediment pore-water: PCB exchange kinetics

Abstract

This study investigates the isotropic exchange kinetics of PCBs for polyethylene (PE) passive samplers in quiescent sediment and develops a novel non-equilibrium passive sampling method using PE with multiple thicknesses. The release and uptake kinetics of PCBs in quiescent sediment are reproduced by a 1-D diffusion model using sediment diffusion parameters fitted with the data from actual measurements. From the sediment diffusion parameters observed for uptake and release kinetics, it is seen that the uptake kinetics are distinctly slower than the release kinetics, most likely because of the sorption-desorption hysteresis of PCBs in the study sediment. Despite the presence of the anisotropic PCB exchange kinetics, a performance reference compound (PRC)-based method, which is grounded on the assumption of isotropic exchange kinetics, estimated the freely dissolved aqueous concentrations (Cfree) of PCBs in sediment pore-water with less than a factor of two error for the study sediment. The novel method developed in this study using PE with multiple thicknesses also gives reasonable estimates of Cfree, demonstrating its potential as another option for non-equilibrium passive sampling for hydrophobic organic contaminants in sediment pore-water.

Microplastics as a Vector for HOC Bioaccumulation in Earthworm Eisenia fetida in Soil: Importance of Chemical Diffusion and Particle Size

“…For instance, Rochman et al (2013) reported that LDPE required at least 6 months to reach sorption equilibrium of PCBs or polycyclic aromatic hydrocarbons (PAHs) in San Diego Bay under field conditions . Choi et al (2016) observed only 11% of the preloaded PCB192 desorbed from 102 μm PE after 264 d of deployment in sediment . Therefore, given that the clean or precontaminated microplastics were deployed in the soil for only 28 d in this study, it was unlikely that the sorption in the S1 scenario and the desorption in the S2 scenario can reach phase equilibrium.…”

“…40 Choi et al ( 2016) observed only 11% of the preloaded PCB192 desorbed from 102 μm PE after 264 d of deployment in sediment. 41 Therefore, given that the clean or precontaminated microplastics were deployed in the soil for only 28 d in this study, it was unlikely that the sorption in the S1 scenario and the desorption in the S2 scenario can reach phase equilibrium. For the S1 scenario, PCBs on microplastics may be in the state of "underequilibrium", suggesting that PCBs in soil porewater or earthworm gut fluid preferred to sorb on microplastics, thus leading to lower accumulation.…”

Accumulation of HOCs via Precontaminated Microplastics by Earthworm Eisenia fetida in Soil

“…For example, for the strongly hydrophobic DDT compounds, equilibrium was not achieved for a 51 μm PE film even after one year under field conditions. 36 Choi et al (2016) reported that only 20% of PCB192 preloaded onto a 17 μm PE film was desorbed after 265 d in a sediment. 51 Several studies further showed slow mass transfer from microplastics to the surrounding environments under static conditions.…”

“…36 Choi et al (2016) reported that only 20% of PCB192 preloaded onto a 17 μm PE film was desorbed after 265 d in a sediment. 51 Several studies further showed slow mass transfer from microplastics to the surrounding environments under static conditions. For instance, Endo et al (2013) evaluated desorption of PCBs from field-collected PE pellets via long-term desorption and diffusion modeling, and estimated that the time to reach equilibrium spanned from 2.8 yr for PCB8 and up to 3500 yr for PCB209 under near static conditions.…”

In Situ Investigation of Performance Reference Compound‐Based Estimates of PCB Equilibrated Passive Sampler Concentrations and Cfree in the Marine Water Column

“…The C free estimated using and PRC results can then be compared to measured or extrapolated from the uptake curve. Recent temporal studies using PRC‐loaded passive samplers in quiescent sediments showed mixed results and indicate caution in the use of PRCs in field applications (Bao et al 2016; Choi et al 2016). To the best of our knowledge, this type of study has not been conducted in surface waters, where the sampling kinetics are more easily modeled.…”