Abstract
The in situ remediation of aquatic sediments with activated carbon (AC)-based thin layer capping is a promising alternative to traditional methods, such as sediment dredging. Applying a strong sorbent like AC directly to the sediment can greatly reduce the bioavailability of organic pollutants. To evaluate the method under realistic field conditions, a 300 m2 plot in the PCB-contaminated Lake Kernaalanjärvi, Finland, was amended with an AC cap (1.6 kgAC/m2). The study lake showed highly dynamic sediment movements over the monitoring period of 14 months. This led to poor retention and rapid burial of the AC cap under a layer of contaminated sediment from adjacent sites. As a result, the measured impact of the AC amendment was low: Both the benthic community structure and PCB bioaccumulation were similar on the plot and in surrounding reference sites. Corresponding follow-up laboratory studies using Lumbriculus variegatus and Chironomus riparius showed that long-term remediation success is possible, even when an AC cap is covered with contaminated sediment. To retain a measurable effectiveness (reduction in contaminant bioaccumulation), a sufficient intensity and depth of bioturbation is required. On the other hand, the magnitude of the adverse effect induced by AC correlated positively with the measured remediation success.
Highlights
Thin layer capping with activated carbon (AC) and other sorbents is a promising method for the in situ remediation of contaminated sediments
The remediation potential of AC thin layer caps has been clearly demonstrated in a wide range of laboratory trials, with reductions in hydrophobic organic contaminants (HOCs) bioaccumulation and sediment to water fluxes reaching over 90%.4−6 Field trials on the remediation method have been focusing mostly on the release of contaminants into the water column, which has been shown to be significantly reduced.[7]
The aim of this study is to evaluate the applicability of AC thin layer caps for sediment remediation under suboptimal environmental conditions, such as the aforementioned frequent dynamic sediment movements
Summary
Thin layer capping with activated carbon (AC) and other sorbents is a promising method for the in situ remediation of contaminated sediments. The resulting adsorption is strong enough to lower the pollutant’s bioavailability and mobility significantly, limiting its uptake into organisms and release from the sediment into the water phase.[1] The costs and labor requirements of AC-based remediation are generally lower compared to traditional remediation methods, such as dredging or capping with nonactive materials like sand or clay. These conventional methods can cause major disruptions, leading to the deterioration of the local benthic ecosystem.[2,3]. Samuelsson et al.[9] reported a reduction of HOC uptake by benthic invertebrates of 40%−97% in fieldcollected sediment cores amended with AC thin layer caps
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