Response of marine benthic fauna to thin-layer capping with activated carbon in a large-scale field experiment in the Grenland fjords, Norway

Göran S Samuelsson,Caroline Raymond,Gerard Cornelissen,Stefan Agrenius,Morten Schaanning,Jonas S Gunnarsson

doi:10.1007/s11356-017-8851-6

Abstract

A field experiment with thin-layer capping was conducted in the Grenland fjords, Norway, for remediation in situ of mercury and dioxin-contaminated sediments. Experimental fields at 30 and 95 m depth were capped with (i) powdered activated carbon (AC) mixed with clay (AC+cla`y), (ii) clay, and (iii) crushed limestone. Ecological effects on the benthic community and species-feeding guilds were studied 1 and 14 months after capping, and a total of 158 species were included in the analyses. The results show that clay and limestone had only minor effects on the benthic community, while AC+clay caused severe perturbations. AC+clay reduced the abundance, biomass, and number of species by up to 90% at both 30 and 95 m depth, and few indications of recovery were found during the period of this investigation. The negative effects of AC+clay were observed on a wide range of species with different feeding strategies, although the suspension feeding brittle star Amphiura filiformis was particularly affected. Even though activated carbon is effective in reducing sediment-to-water fluxes of dioxins and other organic pollutants, this study shows that capping with powdered AC can lead to substantial disturbances to the benthic community.

Highlights

Thin-layer capping (1–10 cm) in situ with active sorbents, such as activated carbon (AC), has been proposed as an alternative method to dredging or conventional capping for sediment remediation (Ghosh et al 2011)
A total of 4437 specimens from 158 different species were included in the analyses, with 1253 specimens belonging to the 116 species obtained from the 18 van Veen grab samples collected 1 month after capping, and 3184 specimens belonging to the 123 species obtained from the 35 van Veen grab samples collected 14 months after capping
There were a smaller subset of overlapping species between AC mixed with clay (AC+clay)-95 and reference field at 80 m depth (Ref80) (37–41%) compared to the larger overlap of species between Ref-80 and reference field at 95 m depth (Ref-95) (56%)

Summary

Introduction

Thin-layer capping (1–10 cm) in situ with active sorbents, such as activated carbon (AC), has been proposed as an alternative method to dredging or conventional capping for sediment remediation (Ghosh et al 2011). Activated carbon has a strong sorption capacity for hydrophobic organic contaminants (HOCs) (Cornelissen et al 2005; Grathwohl and Kleineidam 2000; Luthy et al 1997), and thin-layer capping with AC has proven to be an efficient method to decrease the bioavailability and the sediment-to-water fluxes of HOCs such as PCBs, PAHs, dioxins, and furans (Beckingham and Ghosh 2011; Cho et al 2009, 2007; Cornelissen et al 2012, 2011; Josefsson et al 2012; Kupryianchyk et al 2013b; Lin et al 2014; McLeod et al 2007; Millward et al 2005; Samuelsson et al 2015; Zimmerman et al 2004, 2005). Negative effects on abundance and number of species were documented in a mesocosm experiment, where an intact marine benthic community was exposed to thin-layer capping with powdered AC (Näslund et al 2012)

Methods

Results

Discussion

Conclusion