Implications of observed PBDE diffusion coefficients in low density polyethylene and silicone rubber

Abstract

A film-stacking technique was used to estimate diffusion coefficients of polybrominated diphenyl ethers (PBDEs) in low density polyethylene (LDPE) and silicone rubber. Substantially higher PBDE diffusion coefficients were observed for silicone rubber (AlteSil™) than for LDPE. A much steeper decrease in LDPE diffusion coefficients was found with increasing PBDE molecular weight than that for silicone rubber. From a passive sampling point-of-view, this means that for equivalent polymer-water partition coefficients for these two materials, the mass transfer resistance for these substances in the LDPE will be significantly higher than that for silicone rubber. Boundary layer control of the uptake process for silicone rubber can be expected for PBDEs. With a microplastic perspective, the low diffusion coefficients of PBDEs and in particular of decabromo diphenyl ether (BDE 209) in LDPE imply that the polymer diffusion coefficients for these plastic additives used as flame retardants need to be taken into account when considering the risk posed by microplastic particle ingestion by marine organisms.

Understanding and predicting the diffusivity of organic compounds in polydimethylsiloxane material for passive sampler applications using a simple quantitative structure–property relationship model

“…The D PDMS values we obtained were combined with the literature data (Rusina et al ; Narváez Valderramaet al ; Pintado‐Herrera et al ), with the aim of improving the significance of the subsequent interpretations and for use in the model (Supplemental Data, Table S1). The different data sets have a significant number of overlapping compounds.…”

“…The D PDMS values of the selected penetrants (Table 1) were determined using the film stacking technique (Rusina et al 2010;Thompson et al 2015;Pintado-Herrera et al 2016;Narv aez Valderrama et al 2016;Belles et al 2017). A stack of 3 cleaned PDMS sheets was brought into contact with 1 contaminated sheet on the top for periods of 0.5, 1, 5, 18, 98, 600, and 1200 h, during which the compound is allowed to diffuse from the spiked sheet to the clean ones.…”

Calibration of silicone rubber rods as passive samplers for pesticides at two different flow velocities: Modeling of sampling rates under water boundary layer and polymer control

“…The application of Equation 6 required knowledge of diffusion parameters (D w and D s ) for the pesticides studied. Experimental D s values in silicone rubber are scarce in the literature, and have been estimated for only a few classes of contaminants (PCBs and PAHs [20], polybrominated diphenyl ethers [PBDEs] [18], and emerging contaminants [19]) and unfortunately not for pesticides. We chose this method according to the recommendation of the US Environmental Protection Agency and the conclusions of Pintado-Herrera et al [19].…”

“…We chose this method according to the recommendation of the US Environmental Protection Agency and the conclusions of Pintado-Herrera et al [19]. Experimental D s values in silicone rubber are scarce in the literature, and have been estimated for only a few classes of contaminants (PCBs and PAHs [20], polybrominated diphenyl ethers [PBDEs] [18], and emerging contaminants [19]) and unfortunately not for pesticides. We therefore opted to estimate D s values for pesticides by simultaneously fitting the data at the 2 flow velocities to the overall resistance to mass transfer model.…”

“…Although silicone rubbers are strongly hydrophobic [12], they can extract organic compounds with a broad range of polarities (octanol/water partition coefficient [log K OW ] > 1-2) from water; however, only a few studies have focused on pesticides [13][14][15][16][17]. Sorption properties of silicone rubbers for polar contaminants have mainly been assessed by determining partition coefficients between the silicone rubber and water at equilibrium (K sw ), but if equilibrium is not attained, the determination of representative time-weighted average concentrations in water requires the determination of uptake kinetic parameters such as sampling rates (R s ) or diffusion coefficients (D s ) in the silicone rubber for every compound studied [18][19][20]. The uptake kinetic parameters depend on the variation in environmental factors including water flow velocity [5,7,8], temperature, salinity [21], and biofouling [22,23].…”