Aerobic Bioaugmentation to Decrease Polychlorinated Biphenyl (PCB) Emissions from Contaminated Sediments to Air

Abstract

We conducted experiments to determine whether bioaugmentation with aerobic, polychlorinated biphenyl (PCB)-degrading microorganisms can mitigate polychlorinated biphenyl (PCB) emissions from contaminated sediment to air. Paraburkholderia xenovorans strain LB400 was added to bioreactors containing PCB-contaminated site sediment. PCB mass in both the headspace and aqueous bioreactor compartments was measured using passive samplers over 35 days. Time-series measurements of all 209 PCB congeners revealed a 57% decrease in total PCB mass accumulated in the vapor phase of bioaugmented treatments relative to non-bioaugmented controls, on average. A comparative congener-specific analysis revealed preferential biodegradation of lower-chlorinated PCBs (LC-PCBs) by LB400. Release of the most abundant congener (PCB 4 [2,2′-dichlorobiphenyl]) decreased by over 90%. Simulations with a PCB reactive transport model closely aligned with experimental observations. We also evaluated the effect of the phytogenic biosurfactant, saponin, on PCB bioavailability and biodegradation by LB400. Time-series qPCR measurements of biphenyl dioxygenase (bphA) genes showed that saponin better maintained bphA abundance, compared to the saponin-free treatment. These findings indicate that an active population of bioaugmented, aerobic PCB-degrading microorganisms can effectively lower PCB emissions and may therefore contribute to minimizing PCB inhalation exposure in communities surrounding PCB-contaminated sites.

Lab-scale biodegradation assay using passive samplers to determine microorganisms’ ability to reduce polychlorinated biphenyl (PCB) volatilization from contaminated sediment

“…Two types of passive sampling media are used: [1] polyurethane foam (PUF) plugs as flask stoppers and [2] solid phase microextraction fibers coated with polydimethylsiloxane (SPME-PDMS) directly immersed in sediment slurry. This methodological protocol refers to results and procedures and data from a companion study [10] , [11] , [12] where necessary or helpful.…”

“…The sediment used in the companion study [10] , [11] , [12] was gathered from a PCB-contaminated field site in Altavista, VA [8] . We thoroughly homogenized the sediment by mixing for approximately 20 min with a Masterforce® Tornado Power Mixer (paddle mixer accessory) attached to a DeWalt® DW235G 1/2″ Heavy Duty Side Handle Drill inside a standard-size (20 gal) solid PCB-waste container provided by University of Iowa Environmental Health and Safety (UI EHS; Fig.…”

“…Record the exact mass of sediment added to the bioreactors so that measured PCB mass can be normalized to that value. To make appropriate pairwise comparisons in the companion study, sterile liquid microbiological medium was used as aqueous solution in the control group (instead of sterile water) because the bioaugmentation strain added to treatment group was also suspended in the same liquid medium [10] . The order in which the various components of the bioreactor were added to the flasks was as follows: [1] liquid microbiological medium [2], ∼10 g PCB-contaminated sediment [3], SPME passive samplers [4], bioaugmentation solution containing live cells (treatment only), and [5] PUF passive samplers (see Detailed Protocol section for step-by-step instructions).…”

“…PCB congener mass can be measured in two separate bioreactor compartments using this protocol: [1] the air phase (headspace) and [2] the freely dissolved aqueous phase. To measure airborne PCBs, cut 3″ h × 1.5″d PUF cylinders ( TE-1015 ; Tisch Environmental Inc., Ohio) to desired dimensions ( h ≈ 1″ in the companion study) [10] , [11] , [12] and place them in the neck of the flasks to measure PCB congeners that volatilize to the headspace of the bioreactor, over time. In the companion study [10] , [11] , [12] , SPME fibers manufactured by Fiberguide Industries, Inc. (Stirling, NJ) with a 210 µm inner diameter and a 10 µm-thick layer of PDMS coating were directly immersed in the sediment slurry to measure freely dissolved PCB congeners that readily desorbed from sediment particles [2] .…”

“…To measure airborne PCBs, cut 3″ h × 1.5″d PUF cylinders ( TE-1015 ; Tisch Environmental Inc., Ohio) to desired dimensions ( h ≈ 1″ in the companion study) [10] , [11] , [12] and place them in the neck of the flasks to measure PCB congeners that volatilize to the headspace of the bioreactor, over time. In the companion study [10] , [11] , [12] , SPME fibers manufactured by Fiberguide Industries, Inc. (Stirling, NJ) with a 210 µm inner diameter and a 10 µm-thick layer of PDMS coating were directly immersed in the sediment slurry to measure freely dissolved PCB congeners that readily desorbed from sediment particles [2] . PDMS coating volume on the fibers used in the companion study [10] , [11] , [12] was 6.9 × 10 −8 L/cm-fiber, but specifications can vary between manufacturers.…”