Analysis of Measurement Errors in Passive Sampling of Porewater PCB Concentrations under Static and Periodically Vibrated Conditions

Abstract

Although the field of passive sampling to measure freely dissolved concentrations in sediment porewater has been sufficiently advanced for organic compounds in the low- to midrange of hydrophobicity, in situ passive sampling of strongly hydrophobic polychlorinated biphenyls (PCBs) is still challenged by slow approach to equilibrium. Periodic vibration of polyethylene (PE) passive samplers during exposure has been previously shown to enhance the mass transfer of polycyclic aromatic hydrocarbons (PAHs) from sediment into PE. Herein, we used a new vibrating platform, developed based on our earlier platform design, to demonstrate the effectiveness of periodic vibration for strongly hydrophobic compounds such as hexa-, hepta-, and octachloro-PCBs. Uptake of PCBs in PE after 7, 14, 28, and 56 days under different vibration modes was compared to that under static and mixed laboratory deployments. All PCBs reached within 95-100% of equilibrium after 56 days of deployment in the system vibrated briefly every 2 min, while none of the congeners achieved more than 50% of equilibrium in static deployment for the same period. Periodic vibration also increased the dissipation rate of four performance reference compounds (PRCs) from passive samplers. Higher fractional loss of PRCs and closer approach to equilibrium in the vibrated deployment resulted in estimation of corrected porewater concentrations that were statistically indistinguishable from the true equilibrium values even after a short 7-day deployment. Porewater concentrations of the strongly hydrophobic PCB congeners were overestimated by up to an order of magnitude in the static passive sampler after the same deployment time.

Kinetics of PCB Microbial Dechlorination Explained by Freely Dissolved Concentration in Sediment Microcosms

“…Assumptions made in this model are that the microbial population remains constant and that the mass transfer between the polymer and water is faster than the microbial dechlorination rate, as observed by Lombard et al To maintain a high rate of mass transfer between the solids and water phase, the microcosms were continuously stirred on a rotary shaker throughout the experiment. Past work modeling uptake of PCBs in PE passive samplers in a well-mixed system shows that the polymer comes to equilibrium within a few hours . In comparison, the time scale for degradation in the present experiments was about 21 days.…”

“…shows that the polymer comes to equilibrium within a few hours. 27 In comparison, the time scale for degradation in the present experiments was about 21 days.…”

Assessing Benthic Bioaccumulation of Polychlorinated Dioxins/Furans and Polychlorinated Biphenyls in the Lower Passaic River (NJ, USA) Based on In Situ Passive Sampling

“…Freely dissolved concentrations of HOCs in porewater have been previously measured either in situ (field deployment by inserting samplers in sediments for a sufficient period of time; Fernandez et al 2009; Oen et al 2011; Beckingham and Ghosh 2013; Jalalizadeh and Ghosh 2016, 2017) or ex situ (equilibrating sediment–water slurry with passive sampler in the laboratory for a period of time usually sufficient to attain equilibrium; Adams et al 2007; Khairy et al 2016; Khairy and Lohmann 2017; Jonker et al 2018). Polychlorinated biphenyls (PCBs), chlorinated hydrocarbons, and polyaromatic hydrocarbons (PAHs) were the most widely investigated HOCs in porewater using the in situ approach, whereas PCDD/Fs were rarely investigated.…”

Expanded Application of the Passive Flux Meter: In-Situ Measurements of 1,4-Dioxane, Sulfate, Cr(VI) and RDX

“…Examples of diffusion-based samplers currently used include ceramic dosimeters, bag samplers, dialysis membrane samplers, polyethene samplers, peepers and polymer-based samplers [3][4][5][6][7][8][9]. However, such samplers have difficulty reaching equilibrium between the pore water and sorbent material due to mass transfer limitations through the depletion layer and the absence of active mixing [10][11][12]. Permeation-based passive samplers rely on groundwater flow to control advective transport processes as it passes through the sampler, while Passive Flux Meters (PFMs) have proven to be the only sampler that is able to effectively measure mass fluxes near source groundwater [2].…”

“…Lysimeters and capillary passive samplers are more qualitative than quantitative, as they sample an undefined volume, do not provide flux data and macroporous flow can cause mass transfer issues with the devices [62,64]. Depending on the environmental conditions, the NALGENE ® passive sampler may only provide semi-quantitative results, as the equilibrium between the sampler and aqueous phase may never be reached [10]. Box-aquifer tests were previously conducted, and average measurement errors for Cr(VI) mass flux of 12% were measured, suggesting that this permeation-based passive sampler can overcome the limitation of the diffusion-based samplers, as previously described [24].…”