Capping efficiency of various carbonaceous and mineral materials for in situ remediation of marine sediments contaminated with PCDD/Fs, OCS and HCB

• The efficiency of various thin-layer capping materials in reducing the sediment-to-water flux and benthic organism bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), hexachlorobenzene (HCB) and octachlorostyrene (OCS) was investigated in a boxcosm experiment. The influence of cap layer thickness (0.5-5 cm) and different cap materials were tested using a three-factor experimental design. The capping materials consisted of a passive carrier (coarse or fine limestone material, or a marine clay sediment), and an active material (activated carbon (AC) or kraft lignin) to sequester the contaminants and decrease their bioavailability. Macrofauna was added to the boxes to get a semi-natural bioturbation. The sediment-to-water flux was measured using passive (SPMD) samplers, and the bioaccumulation by the surface-dwelling gastropod Hinia reticulata and the deep-burrowing polychaetes Nereis spp. was determined. Results showed substantial decreases in both flux and bioaccumulation as a result of thin-layer capping. The thickness of the capping layer and the choice of active material were important factors, while the use of different types of passive materials was not statistically significant for any of the observed endpoints. Flux and bioaccumulation decreased with increased cap thickness, and could be further decreased with addition of active material. Activated carbon was more efficient than lignin, and a ~90% reduction of the flux and bioaccumulation, compared to uncapped control sediment, could be achieved with 3 cm caps with 3.3% AC (g C/g ww clay). The reduction was generally larger in the surface-dwelling H. reticulata than in Nereis spp., and the magnitude of the reduction was frequently similar between Nereis spp. and sediment-to-water fluxes. The latter was interpreted to indicate a link between Nereis spp. bioirrigation and sediment-to-water fluxes. Furthermore, the reduction in sediment-to-water flux was dependent on the hydrophobicity of the congeners, with less hydrophobic congeners achieving a larger reduction than more hydrophobic congeners.      

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Annan naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Other Environmental Engineering (hsv//eng)

Nyckelord

sediment-to-water fluxes

benthic bioaccumulation

thin-layer capping

cap thickness

Environmental chemistry

Miljökemi

Persistent organic compounds

Persistenta organiska föreningar

Environmental engineering

Miljöteknik

Environmental Science

miljövetenskap

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