In situ benthic flow-through chambers to determine sediment-to-water fluxes of legacy hydrophobic organic contaminants

Abstract

Contaminated sediment can release hydrophobic organic contaminants (HOCs) and thereby act as a secondary source of primarily legacy hazardous substances to the water column. There is therefore a need for assessments of the release of HOCs from contaminated sediment for prioritization of management actions. In situ assessment of HOC sediment-to-water flux is currently done with (closed) benthic flux chambers, which have a sampling time exceeding one month. During this time, the water inside the chamber is depleted of oxygen and the effect of bioturbation on the sediment-to-water release of HOCs is largely ignored. Here we present a novel benthic flux chamber, which measures sediment-to-water flux of legacy HOCs within days, and includes the effect of bioturbation since ambient oxygen levels inside the chamber are maintained by continuous pumping of water through the chamber. This chamber design allows for sediment-to-water flux measurements under more natural conditions. The chamber design was tested in a contaminated Baltic Sea bay. Measured fluxes were 62-2300 ng m d for individual polycyclic aromatic hydrocarbons (PAHs), and 5.5-150 ng m d for polychlorinated biphenyls (PCBs). These fluxes were 3-23 times (PAHs) and 12-74 times (PCBs) higher than fluxes measured with closed benthic chambers deployed in parallel at the same location. We hypothesize that the observed difference in HOC flux between the two chamber designs are partly an effect of bioturbation. This hypothesized effect of bioturbation was in accordance with literature data from experimental studies.

An analytical model for chemical diffusion in layered contaminated sediment systems with bioreactive caps

“…This may be because the effective diffusion coefficient of sand cap is 28 times lower than D bio . The result from the model was in accordance with the experimental studies . Granberg et al also showed that bioturbation can stimulate an augmented release flux of PCBs.…”

“…The result from the model was in accordance with the experimental studies. 77 Granberg et al 78 also showed that bioturbation can stimulate an augmented release flux of PCBs. Figure 8 shows the flux at the surface of system under different combinations of properties of sorbent layer and bioturbation layer.…”

Organic Contaminant Mixture Significantly Changes Microbenthic Community Structure and Increases the Expression of PAH Degradation Genes

“…Dimethyl formamide (DMF) was used for sample cleanup, followed by 1 cm ø silica columns (10% deactivated). The cleanup method is described in detail by Mustajärvi et al (2017a). Following clean-up, the samples were reduced in volume (200 µL), and internal recovery standards (PCB53 and aldrin) were added prior to GCMS analysis.…”

Transferring mixtures of chemicals from sediment to a bioassay using silicone-based passive sampling and dosing

“…Labeled internal surrogate standards (15 PAHs and 7 PCBs, see the Chemicals and materials section, Text ESI S1 †) were added to the combined extract (containing the rst and second extracts) and separately to the third extract. Clean up was done with dimethylformamide and a SiO 2 /H 2 O (10% Milli-Q water w/ w) column as described by Mandalakis et al 40 following the modications described by Mustajärvi et al 41 to include both PAHs and PCBs in the analysis. The extracts were reduced in volume prior to instrumental analysis and the recovery standards (PCB 53 and acenaphthylene) were added.…”