Effects of activated carbon ageing in three PCB contaminated sediments: Sorption efficiency and secondary effects on Lumbriculus variegatus

Abstract

The sorption efficiency and possible secondary effects of activated carbon (AC) (ø 63-200 μm) was studied with Lumbriculus variegatus in three PCB contaminated sediments applying long AC-sediment contact time (3 years). AC amendment efficiently reduced PCB bioavailability as determined with both, L. variegatus bioaccumulation test and passive samplers. However, dose related secondary effects of AC on egestion rate and biomass were observed (applied doses 0.25% and 2.5% sediment dry weight). The sorption capacity and secondary effects remained similar when the experiments were repeated after three years of AC-sediment contact time. Further, transmission electron microscopy (TEM) samples revealed morphological changes in the L. variegatus gut wall microvilli layer. Sediment properties affected both sorption efficiency and secondary effects, but 2.5% AC addition had significant effects regardless of the sediment. In, conclusion, AC is an efficient and stable sorbent to decrease the bioavailability of PCBs. However, sediment dwelling organisms, such as Oligochaete worms in this study, may be sensitive to the carbon amendments. The secondary effects and possible morphological changes in benthic organisms should not be overlooked as in many cases they form the basis of the aquatic food webs.

Toxicity of sediment-bound lufenuron to benthic arthropods in laboratory bioassays

“…In addition, a decline in bioavailability of persistent chemicals due to ageing processes is reported in the scientific literature (e.g. Landrum et al, 1992;Alexander, 2000;Choi et al, 2012;Nybom et al, 2015). Since a 7-day equilibrium phase after spiking was used in all toxicity tests described in the present paper, the possible decline in bioavailability due to ageing processes was most likely similar in all tests.…”

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

“…Both AC concentration and particle size are important factors for if, and how much, the benthic organisms are affected. In general, higher concentrations of AC (>5%) and smaller particle sizes (<200 μm) have been associated with negative impact on benthic invertebrates (Jonker et al 2004, 2009; Kupryianchyk et al 2013a; Nybom et al 2012, 2015; Rakowska et al 2012). Milder effects can be expected if AC is mixed into a non-active carrier such as clay (Cornelissen et al 2011; Jonker et al 2009; Nybom et al 2012), but this study demonstrates that effects from powdered AC was not eliminated in this habitat, although AC was mixed with clay.…”

“…Powdered AC interferes with the preferable particle size range in feeding activities for many of the exposed organisms. Besides, fine AC particles seem to have sharp edges that can harm the gut of benthic organisms when ingested (Nybom et al 2015). Species with activities at the sediment-water interface would be the ones most exposed to the fine particles of AC used in this study and accordingly, it is primarily the suspension and surface deposit feeding species that were the most affected in our study.…”

“…However, in a review with a compilation of 82 tests performed within a total of 18 species, negative biological effects of AC treatment were recorded in one fifth of the tests (Janssen and Beckingham 2013). The negative effects on single species assays include decrease in growth (Janssen et al 2012; Kupryianchyk et al 2011; Macleod et al 2008; Millward et al 2005; Nybom et al 2012, 2015), lipid content (Janssen et al 2011, 2012; Jonker et al 2009; Nybom et al 2012), and survival (Kupryianchyk et al 2011; McLeod et al 2008) as well as changes in behavior (Jonker et al 2009; Nybom et al 2012, 2015), reproduction (Nybom et al 2012, 2015), and morphology (Nybom et al 2015). Further, a few studies on benthic community level exposed to AC also show contradictory results.…”

Evaluation of strategies to minimize ecotoxic side‐effects of sorbent‐based sediment remediation

“…Compromises can be found between maximizing the treatment benefits of sorbent amendments and minimizing unwanted ecotoxic side-effects: reducing the magnetic sorbent dose from 8.1% in the previous study 28 to 2.5% in the current study, increasing the magnetic AC particle size to just above the ingestible limit of L. variegatus, replacing AC with biochar as the carbonaceous sorbent matrix, and the recovery of magnetic sorbents, all these measures, to a variable extent, alleviated or annulled ecotoxic amendment effects to the sediment worm L. variegatus, which had sensitively responded to even low AC amendment doses in earlier studies with clean 23 and contaminated sediments. 26,28 MagBio appears to present a particularly good candidate material for sediment remediation, considering, in addition to the demonstrated remediation effectiveness, lower ecotoxicity and good magnetic recoverability. Also, biochar is produced from renewable biomass and has lower net environmental impacts compared with fossil coal-derived AC in sediment remediation applications.…”