Toxicity assessment within the application of in situ contaminated sediment remediation technologies: A review

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Review

Toxicity assessment within the application of in situ contaminated

sediment remediation technologies: A review

Libralato Giovanni

a,

⁎

, Minetto Diego

b

, Lofrano Giusy

c

, Guida Marco

a

, Carotenuto Maurizio

c

,

Aliberti Francesco

a

, Conte Barbara

b

, Notarnicola Michele

b

a

Department of Biology, University of Naples Federico II, Complesso Universitario di Monte S. Angelo, Via Cinthia ed. 7, 80126 Naples, Italy

b

Department of Civil, Environmental, Land, Building Engineering and Chemistry (DICATECh), Technical University of Bari, Via Orabona 4, 70125 Bari, Italy

c

Department of Chemistry and Biology, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Salerno, Italy

H I G H L I G H T S

• Sediment as sink/source of pollution represents a great deal for aquatic eco-systems.

• In situ technologies are a chance for re-mediation but with unknown long-term effect.

• Reviewed toxicity data are fragmentary, incomplete or entirely missing. • Activated carbon is a frequent

amend-ment, but with potential undesired ef-fects.

• Long-term toxicity data are necessary for remediated sites monitoring/ maintenance. G R A P H I C A L A B S T R A C T

a b s t r a c t

a r t i c l e i n f o

Article history: Received 14 September 2017

Received in revised form 19 November 2017 Accepted 20 November 2017

Available online xxxx Editor: F.M. Tack

Polluted sediment represents a great problem for aquantic environments with potential direct acute and chronic effects for the biota and can be tackled with both in situ and ex situ treatments. Once dredging activities are not compulsory, sediment can be kept in place and managed with techniques involving the use of amendment and/or capping. Before their application, the assessment of their potential impact to the target environment cannot ig-nore the safe-by-design approach. The role of toxicity in in situ sediment remediation was reviewed discussing about how it can be used for the selection of amendments and the monitoring of treatment technologies. Results evidenced that capping technology coupled to activated carbon (AC) is the most frequently applied approach with effects varying according to the rate of contamination in treated sediment, the amount of AC used (% v/ v), and target biological models considered. Little data are available for zerovalent iron as well as other minor amending agents such as hematite, natural zeolite, biopolymers and organoclays. Current (eco-)toxicological in-formation for in situ sediment remediation technologies is fragmentary and incomplete or entirely missing, mak-ing also the interpretation of existmak-ing data quite challengmak-ing. In situ sediment remediation represents an interesting potentially effective approach for polluted sediment recovering. As its application in some lab-based andﬁeld studies reported to induce negative effects for target organisms, amendments and capping agents

Keywords: Sediment In situ remediation Amendment Toxicity Capping Activated carbon

Science of the Total Environment 621 (2018) 85–94

Abbreviations: AC, activated carbon; BAF, bioaccumulation factor; BSAF, biota-sediment accumulation factor; DO, dissolved oxygen; EPA, environmental protection agency; GSH, glu-tathione; HOC, hydrophobic organic compound; LDH, lactate dehydrogenase; LPO, lipid peroxidation; NA, naphtenic acid; NP, nano particle; OC, organic carbon; OECD, Organisation for Economic Co-operation and Development; Ox, oxyde; OSPW, oil sands process-affected water; OSWER, ofﬁce of solid waste and emergency response; PAH, polycyclic aromatic hydrocar-bons; PCB, poly chloro biphenyls; PCC, powdered coconut coal; SOD, superoxide dismutase; ZVI, zero-valent iron.

⁎ Corresponding author at: Laboratory of Hygiene: Water, Food and Environment, Department of Biology, University of Naples Federico II, Via Cinthia, Complesso Universitario di Monte Sant'Angelo, Building 7, 80126 Naples, Italy.

E-mail address:giovanni.libralato@unina.it(G. Libralato).

https://doi.org/10.1016/j.scitotenv.2017.11.229

Contents lists available atScienceDirect

Science of the Total Environment

j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v

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must be attentively evaluated for short- and long-term environmental effects, also in the perspective of the remediated site monitoring and maintenance.

Contents

1. Introduction . . . 86

2. Remediation technologies . . . 86

2.1. Amended capping and direct sediment amendment . . . 89

2.1.1. Activated carbons, charcoal and other minor treatments . . . 89

2.1.2. Organoclay, apatite and biopolymers . . . 91

2.1.3. Iron-based and natural zeolite amendments . . . 92

2.2. Toxicity as an added value for in situ treatment selection . . . 92

3. Conclusions. . . 93

References. . . 93

1. Introduction

Sediment toxicity proved to be essential in monitoring studies to characterise the state-of-the-art of aquatic environments and to take decisions about contaminated areas according to the TRIAD approach (Chapman, 1990; Losso and Volpi Ghirardini, 2010; Libralato et al., 2008; Hurel et al., 2017).

Polluted sediment represents a great problem for fresh, brackish and marine ecosystems, especially coastal ones, due to the high human pres-sures (i.e. commercial and industrial port activities, human settlements and tourism) and sedimentation rates caused by solid discharges from catchment basins (Nikolaou et al., 2009a; Lofrano et al., 2016; Hurel et al., 2017).

Sediment drains and temporarily stores pollution with potential di-rect acute and chronic effects for benthic communities. Natural (i.e. bio-turbation) or artificial (i.e. dredging) perturbative events can release the accumulated contamination causing acute concerns to water column populations and the re-allocation of contaminants within the same aquatic environment. Thus, contamination can be scattered in vaster areas or sometimes exported outside from the confined aquatic ecosys-tem (e.g. lake or lagoon) due to sediment loss (e.g.flooding events or tides) (Arizzi Novelli et al., 2006; Nikolaou et al., 2009b; Mamindy-Pajany et al., 2010a).

Currently, commercial and industrial ports must face up to contam-inated sediment management because sedimentation rates can be sub-stantial (Apitz et al., 2007), navigation must be guaranteed and, thus, sediment dredging from sea or riverbed is compulsory. Anyhow, this ac-tivity must be carried out in a highly ef_{ficient and environmentally} friendly manner to reduce and keep impacts to a minimum. Dredged sediment can be treated ex situ“on site” or “off site” and, finally, transported to its destination (e.g. landfill) or second life (e.g. construc-tion materials).

Sometimes the problem of polluted sediment can be tackled without dredging keeping them in place especially when it must not be removed like for assuring drafting ships and if site physical dynamics (i.e. current and wave actions) are not of concern. In this case, in situ sediment treatment(s) can be applied.

Lofrano et al. (2017)reviewed in situ remediation of contaminated marine sediment showing that, apart from the no action option, several methods involve the use of amendment. Amendment composition and combinations, its application techniques and rates, and its potential en-vironmental implications have been only barely investigated. Particu-larly, fragmentary information exists about the role of (eco-)toxicity in assessing the best available in situ technology for sediment remediation (Lofrano et al., 2017) being generally reported as secondary side effects of treatment activities (Libralato et al., 2008; Rakowska et al., 2012).

Several questions remain open about the relative toxicity of amend-ments on their own like as their potential relative contribution to the ﬁnal sediment toxicity. Current literature still does not describe exten-sive in situ applications (ISAs) for contaminated treatments as well as their potential undesired long-term effects.

This review paper stressed on how there is a mutual require by en-vironmental alerts and enen-vironmentally friendly businesses to intro-duce new consistent methods for contaminated sediment treatment and management considering toxicity reduction/removal in the per-spective of the zero-emission approach. The aim of this paper is to re-view the role of toxicity in in situ sediment remediation discussing about how it can be used for the selection of amendments and the mon-itoring of treatment technologies. Information was clustered based on the considered remediation technologies and, sub-grouped them ac-cording to testing organisms.

2. Remediation technologies

The implications of toxicity in sediment remediation were investi-gated considering in situ technologies referring to capping with amend-ments, nanoremediation, solidiﬁcation and stabilisation, chemical oxidation, bioventing, thermal treatment, and sediment washing ac-cording to the review ofLofrano et al. (2017).

Capping can be used to cover submerged sediment by stable layers of natural or synthetic materials. The cap reduces the mobility of con-taminants (i.e. apart when placing theﬁrst layer of capping material that can suspend sediment in the water column) and the subsequent in-teraction with biota. Generally, it can be considered applicable when the pollution source that led to the deposition of contaminants has been halted, the environmental effects of moving/treating contaminated sed-iment are too great and hydrologic conditions are favourable that is not disturbing the site (e.g. strong currents can displace caps). Capping re-quires long-term monitoring and maintenance to ensure that contami-nants are not migrating, and thus cap integrity must be regularly veriﬁed and ad hoc designed to provide containment for as long as the contaminated sediment requires management (USEPA, 2014; Lofrano et al., 2017).

Further remediation methods like nanoremediation and solidi fica-tion and stabilisafica-tion, chemical oxidafica-tion, bioventing, thermal treat-ment, and sediment washing are still in their infancy for in situ treatment and very scarce information is available about the assessment of toxicity and its reduction/removal from treated sediment (Lofrano et al., 2017).

Besides capping, only one case study proposing the in situ chemical oxidation based on ozonation (O3) investigated sediment toxicity (He

et al., 2012).

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Table 1

Contaminated sediment treatment review considering the single species response, sediment main contaminants, exposure media and time, investigated life stage, and the potential bioaccumulation of pollutants; A = apatite; Ad = adult; B = bio-polymers; BAF = bioaccumulation factor; BSAF = biota-sediment accumulation factor; d.w. = dry weight; EC50 = median effect concentration; FW = freshwater; SW = saltwater;– = not available; n.e. = no effect; OC = organoclay; OSPW = oil sand process-affected water; ZVI = zero-valent iron.

Sediment treatment Group of organisms Speciﬁc amendment mix

Species Sediment main

contaminants (μg/g) Exposure media Exposure time (d) Endpoint Exposure concentrations (%) Toxicity effect range (%) EC50 Bioaccumulation or contaminant reduction in organisms References

AC Bacteria – Escherichia coli;

Raoultella terrigena

– Culture

media

30 min Colony mortality – 36–96 – – Van der Mei

et al. (2008) – Microbial community – FW and SW sediment – Community structure

2–20 n.e. – Jonker et al.

(2009)

Annelids – Nereis diversicolor

(Ad)

PAHs SW

sediment

28 BSAF reduction 2 2 – – Cornelissen

et al. (2006) – Limnodrilus spp. (Ad) PCBs (0.09) FW sediment 28 Bioaccumulation; lipid content 1.5 1.5 – Accumulated PCB reduction from 1.5 to 8.5 times Jonker et al. (2004) – Lumbriculus variegatus (Ad) PCBs (6.8) FW sediment 56 Bioaccumulation 2.6 2.6 – Accumulated PCB reduction from 70% to 84% Sun and Ghosh (2007)

– L. variegatus (Ad) PAHs FW

sediment

14 Mortality 100 – 4–60 g/L – Jonker et al.

(2009)

10–112 Mortality; lipid content; egestion rate

1–25 All the range – –

AC in three different particle size fractions, namelyb63 μm (90%, ACp), 63–200 μm (ACm) and 1000 μm (ACg)

L. variegatus (Ad) Uncontaminated sediment (1 natural +1 artiﬁcial) FW sediment 28 Growth, reproduction rate, egestion rate, lipid content, morphological changes in gut microvilli

0.05–15 All the range Worst biomass alteration:

IC50 = 0.11 (ACm) (natural sediment) and IC50 = 0.35 (ACp); worst egestion rate: IC50 = 0.22 (ACp) (natural sediment) and IC50 = 0.60 (ACm)

– Nybom et al. (2012)

AC (63–200 μm) L. variegatus (Ad) Three PCB contaminated sediments applying long AC-sediment contact time FW sediment 28 Growth, reproduction rate, egestion rate, lipid content, morphological changes in gut microvilli

0.25–2.5 All the range Biomasses of the worms

exposed to 2.5% AC amended sediments were signiﬁcantly lower compared to the unamended sediments. – Nybom et al. (2015) Magnetic AC and AC

L. variegatus (Ad) PAHs contaminate sediments FW sediment 28 Egestion rate, growth and reproduction

1.86, 5 and 8.1 All the range Growth, reproduction, and egestion were strongly inhibited – Han et al. (2015) – Neanthes arenaceodentata (Ad) – SW sediment

28 Feeding rate, weight

loss

5–20 n.e. – – Janssen et al.

(2012) – Neanthes arenaceodentata (Ad) PCBs SW sediment 30 min Bioaccumulation, body weight

3.4–8.5 All the range – Accumulated PCB

reduction up to 82%; up to 87% for 6 months

Millward et al. (2005)

Molluscs – Corbiculaﬂuminea

(Ad)

PCBs FW

sediment

28 Bioaccumulation 0.3–3.5 n.e. – Accumulated PCB

reduction from 67% to 95% McLeod et al. (2008) – Hinia reticulata (Ad) PAH SW sediment

28 BSAF reduction 2 n.e. – – Cornelissen

et al. (2006)

– Lymnaea stagnalis

(Ad)

Hg FW

sediment

41 BAF relatively to Hg 1 n.e. – BAF decreased

from 103.1 to 64.6

Lewis et al. (2016)

(continued on next page) 87

G. Li br al at o et al ./ Sc ie nc e of th e Tot al En vi ro n me nt 6 21 (2 01 8 ) 85 – 94

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Table 1 (continued) Sediment treatment Group of organisms Speciﬁc amendment mix

Species Sediment main

contaminants (μg/g) Exposure media Exposure time (d) Endpoint Exposure concentrations (%) Toxicity effect range (%) EC50 Bioaccumulation or contaminant reduction in organisms References ng/g – Macoma balthica (Ad) PCBs SW sediment

28 Bioaccumulation 0.34–3.4 n.e. Accumulated PCB

reduction from 22% to 89%, correlated with concentration and inversely correlated with particle size McLeod et al. (2007)

Crustaceans – Americamysis

ba-hia; Ampelisca abdita (Ad) Ammonia, metals, PAHs, PCBs, endosulfan SW sediment 4 Mortality; contaminant reduction

15 n.e. Endosulfan totally

removed from sediment; no reduction for ammonia and metals Ho et al. (2004) – Asellus aquaticus (Ad) – FW sediment

3 Avoidance 1–25 15–25 – Jonker et al.

(2009) Daphnia magna(Ad) 2 Mortality 100 – 0.5–4% Corophium volutator (Ad) SW sediment 3 Mortality 100 – 4–60 g/L 10 Mortality; avoidance 1–25 n.e. – –

– A. aquaticus (Ad) Metals, PAHs,

PCBs FW sediment 1–28 Avoidance (72 h); locomotion impairment (1–5 d); survival (28 d); growth (28 d) 1–30 n.e. – – Kupryianchyk et al. (2011) Gammarus pulex (Ad) 1–30 – 3.1 g/L (survival) – – Leptocheirus plumulosus (Ad) PCBs FW sediment

30 Bioaccumulation 3.4–8.5 n.e. – Accumulated PCB

increasing by 70% Millward et al. (2005) Arthropods Bituminous coal-based AC Chironomus riparius PCBs FW sediment Up to 10 Growth, developmental stage, of larvae, emergence time, developmental rate, sex ration and egg production in the full life cycle test

0.5 and 2.5% v/v d.w. with 0.63–200 μm grain size Concentration 2.5% AC: induced delayed emergence, and larvae development and morphological changes in larval gut microvilli – Increasing the dose of AC reduced the body residues of PCBs in adult and ladult midges Nybom et al. (2016) Fishes – Pimephales promelas (1 h embryo) OSPW + naphtenic acid

OSPW 7 Eggs' hatching;

survival; spontaneous movement; hemorrhage incidences; pericardial edema; embryos' spine malformation 5 n.e. – Efﬁcient contaminant reduction He et al. (2012)

OC; A; B Annelids OC L. variegatus (Ad) – FW

sediment

28 Survival; growth 25 n.e. – – Paller and

Knox (2010)

A 25 n.e.

B 2.5 All the range

OC Neanthes

arenaceodentata (Ad)

– SW

sediment

28 Survival; growth 2.5 n.e. – – SERDP

(2010) A 5–10 n.e. OC and A 2.5–5 n.e. OC N. arenaceodentata (Ad) – SW sediment

28 Survival; growth 5–10 n.e. – – Rosen et al.

(2011) A 5 n.e. 88 G. Li br al at o et al ./ Sc ie nc e of th e Tot al En vi ro n me nt 6 21 (2 01 8 ) 85 – 94

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De ta il s a bo ut b iol og ic a l m od el s, ex po sur e cond it ion s, lif e st a ge s in -v o lv ed ,t es te d co nc e nt rat io ns ,e ff ec t ran ge an d e nd p o int s w e re re po rte d in Ta bl e 1 . 2. 1. Am end ed ca pp in g an d di rec t sed im ent am en dm ent Ca p pi ng me an s lea v in g the co nt am ina tio n in p la ce iso lat ing it fro m th e pr ox y com pa rt me nt s th us re du cin g po ll ut an t bi o ava il ab il ity to th e fo od we b as wel l a s p ol lu ta nts ' re sus pe ns io n in to th e wa ter colu mn ( USE PA, 201 4 ). Bes ide s cap pin g, sed ime nt ma y als o be dir ec tly mix ed w ith am en d me nt s ( Lo fr an o et al ., 2 01 7 ). Tr ad it io na l cap s d o no t al w ay s ful fi ll the redu ction of risks that can be des tructiv e for huma n healt h, ec os ys tem, a n d ev en na tu ra l re so u rce s. Re cen tl y, a ct iv e ca ps ha ve b ee n d e si g ne d to e mp loy ac ti v e ma te rial s to str e ng th e n the ir ad so rpt io n an d de g rad at io n ca pa ci ty .T he ac ti v e ca p pi ng tec h no lo g y pr o mi ses to be a p er m an e nt an d co st -ef fi ci e nt so lut io n to co nt am ina te d sed ime nt s e s-p ec ia ll y fo r hy dr o ph ob ic or g an ic co nt am ina nt s (H O Cs ), b ut o nl y fe w o f them are used for ISA. The most used amendm ents are carbonace ous materia ls like acti vated carbon (AC) (ISA), soot and charco al/biochar (ISA ) ( Rako wska et al., 2012 ), and bitu minou s coal base d AC ( Nyb om et al ., 20 12 ,20 15 ,20 16 ), ma gn et ic ac ti vat ed ca rb o n ( Ha n et al. ,20 15 ), organoclays ™ (ISA) (i .e. modi fi ed bent onite), clay and crushed lime-st on e ( Sa mue ls so n et al ., 20 17 ), a pa tit e (as p hos p ha te so ur ce) (I SA ) ( Si ngh et al ., 200 1 ), b au xi te (as A l sou rc e) ( Hu re l et a l. , 20 17 ), zer ov al en t ir on (ZVI ) (I SA) ( US EP A, 2 014 ) a nd h ema tit e ( Mam in dy -Pa jan y et a l. , 2 010 b ), na tu ra l zeo li te (NZ ) ( Ma mi n dy -P a ja n y et al ., 20 10b ) a n d b iop ol yme rs (IS A) ( Pa ll er a n d K nox , 2 010 ), b ut ISA a re very limit ed. Ame ndmen ts can cont ribu te to bind meta ls or soil/s edi-me nt p ar ti cl e s an d ac t as p lug g ing ag e nt s to m ak e b ar rie rs iso lat ing co n-ta mi n an ts ( K n ox et al ., 2 008 , 201 2 ). Ex cep t fo r AC , to xi cit y da ta a re qu it e sc ar ce (li ke fo r h em ati te an d NZ ) or un av a il ab le fo r a ll ot h er am en d me nt s. In thi s re v iew ,to xi ci ty d at a w e re pr e se nt ed g ro up ing d at a in sub se c-ti ons in cl ud in g bac ter ia , in ve rte br ate s (ann el id, mo llu sc , cru st ac ea n , an d ar thr o p o d) an d ve rt eb rat es (fi sh ). 2. 1. 1. Ac ti vat ed ca rb on s, ch a rc oa l a nd o th er m in or tr eat m en ts A C s ar e u se d fo r the ir str o ng so rb en t pr o p er ties th at ar e o ft en u p to 10 0 ti m es gr ea ter th an a bs or pt io n to or ga n ic car bo n (O C) ( US EP A, 20 14 ) sh ow ing int er est ing abi li ti es in sor bin g po ly aro mat ic hy dro car -bo ns (P AH s) ,po ly chl or ina ted by ph en yl s (P CBs ), di oxi ns /fu ran s, pe sti -ci de s an d me ta ls /m et al lo id s, ma ki ng th em les s bi o av ai lab le. Ra ko w sk a e t al .(2 01 2) al re ad y cr iti ca lly re v ie w ed the rol e o f al lca rbo na ce o u s m a-te ri als for in si tu re me di at io n of con ta mi nat ed sed ime nt (ma inl y af ter lab ora tor y bas ed act iv ity ) evi den cin g on ly mil d ef fec ts fo r th e ben th ic com mun it y. Mos t stu di es on am end men ts rel y on la b-b ase d a cti vi ty ( Ra kow sk a et al ., 20 12 ), wh il e fi el d da ta ar e sc arc e ( Sam ue ls so n et al ., 20 17 ). Co rn el is se n et al . (2 012 ) st u di ed th e ap pl ic ati on of an in sit u thi n-lay e r ca pp ing ch ar ac ter ise d by th e ap pl ica ti o n at 30 – 10 0 m w at e r depth on 10,000 – 40,000 m 2 ; the use of passive samplers allowe d the de te rm in ati on of con tam in an t conc en tr a ti ons (po ly chl or in at ed di be nz o-di ox in/ fu ra n, PC DD /F ). Th ey com pa red ac ti ve ca ps co nt ai ni ng A C (i .e .cl e an cl ay m ixe d w ith A C (c o al b as e d w ith 20 μmo fa v er a g e p a r-ti cle si ze) dep osi ted on con ta min at ed sed ime nt) , an d cla y wi th out AC an d cru sh ed lim es to ne (i.e . n on-act ive capp in g mat eri al ). Th in -la yer cappin g showed to be ef fi cien t in reduci ng the fl uxes of PCD D/F from se d im en t-to -s ed im en t a n d to wa te r col um n wit h a re la tive st a bi li ty up to 20 mo nt hs af te r th e int er ve nt io n. Th e ma in cr iti ca l po int w as re-lat e d to the lo ss o f th e app lie d A C (~ 7 5% ) and th e lo w e r e ffi ci en cy co m-pa red to lab -b as e d e xp er im e nt (7 0– 90 % ) du e to sl ow se di me nt -to -ca p tr a ns fe r, cap in te gr it y, an d la ter al pa rt ic le tr a n sp or t, bu t n o to xi cit y re la ted -e ff ec ts we re pr es e nte d a nd di scu ss ed . Sa m ue ls son et a l. (2 01 7) ca rri ed o ut a fi e ld e xp er im en t at 30 an d 90 m de pt h w it h th in -la ye r cap pi n g for th e re med ia ti on of mer cur y (Hg) a n d di ox in -p o ll u te d se d ime nt .C ap p ing w as ad mi ni st e re d co ns id e ri ng thr e e sc e na r-ios including powdered AC (Jacobi Carbons , BP2, 20 μ m averag e size)

Molluscs OC Corbiculaﬂuminea

(Ad)

– FW

sediment

28 Survival; weight 25 n.e. – – Paller and

Knox (2010) A 25 n.e. B 2.5 – – – Crustaceans OC Eohaustorius estuarius (Ad) – SW sediment

10 Survival 2.5 n.e. – – SERDP

(2010)

A 5–10 n.e.

OC + A 2.55 n.e.

OC E. estuarius (Ad) – SW

sediment

10 Survival 5–10 n.e. – – Rosen et al.

(2011) A 5 n.e. OC Hyalella azteca (Ad) – FW sediment

10 Survival 5–100 All the range – – Paller and

Knox (2010)

A 50–100

OC L. plumulosus (Ad) 10 Survival 10–25 n.e. – –

Fishes OC Cyprinodon

variegatus (7 d juvenile)

– SW

sediment

96 h Survival 2.5 n.e. – – SERDP

(2010)

A 5–10 n.e.

OC + A 2.5–5 n.e.

OC – SW

sediment

96 h Survival 5–10 n.e. – – Rosen et al.

(2011)

A 5 n.e.

ZVI Molluscs – Lymnaea stagnalis

(Ad)

Hg FW

sediment

41 BAF relatively to Hg 43–269 μM n.e. – BAF decreased

from 103.1 to 41.8 ng/g

Lewis et al. (2016)

Ozonation Fishes – Pimephales

promelas (1 h embryo)

OSPW + naphtenic acid

OSPW 7 Eggs' hatching;

survival; spontaneous movement; hemorrhage incidences; pericardial edema; embryos' spine malformation – n.e. – Efﬁcient contaminant reduction He et al. (2012) 89 G. Li br al at o et al ./ Sc ie nc e of th e Tot al En vi ro n me nt 6 21 (2 01 8 ) 85 – 94

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mixed with clay, clay and crushed limestone. The assessment of benthic community up to 14 months showed minor effects after clay and crushed limestone treatment, while AC mixed with clay reduced the abundance, biomass and amount of species up to 95%.Samuelsson et al. (2017)suggested highly divergent outcomes for AC ISA between ﬁeld and lab-based activities compared to the critical review of

Rakowska et al. (2012).

2.1.1.1. Bacteria.Van der Mei et al. (2008)exposed Escherichia coli and Raoultella terrigena to substrates treated with various wood based ACs (i.e. basic wood-based activated carbon, acidic wood-based AC, coconut-based carbon, and coated with polyvinyl amine) observing their cell viability. After 30 min exposure, the average mortality for both colonies was 83–96%, 54–56%, 76–78% and 32–37% for acid, basic, positively and negatively charged ACs, respectively.Jonker et al. (2009)evidenced no effects on the microbial community structure in bacteria from freshwater and marine sediments treated with AC (Organosorb 200-1 (Desotec Activated Carbon; Roeselare, Belgium), ac-tivated charcoal (C3345; Sigma-Aldrich; Steinheim, Germany), Norit SAE Super (Norit Activated Carbon; Amersfoort, The Netherlands), Carbopal MB 4 (Donau Carbon; Frankfurt, Germany), and Hydrafﬁn P 800 (Donau Carbon)) dosed at 2, 4, 10 and 20% v/v. These contrasting results suggest the need to check each time the characteristics of the ACs because, due to their speciﬁc properties, effects can drastically change.

2.1.1.2. Annelids.Jonker et al. (2004)used the freshwater polichaete Limnodrilus spp. (17 °C for 28 d) to investigate the coal or charcoal ef ﬁ-ciency in reducing annelids PCBs bioaccumulation testing any second-ary effects of the amendment. Sediment was prepared and spiked with PCBs (90μg/kg) and subsequently treated with AC (~1.5%) in the treatment run. Results highlighted a reduction in PCBs bioaccumulation of 1.2 up to 8.5 times compared to treatments. AC induced an average lipid content in the exposed organisms signiﬁcantly lower compared to negative controls independently from PCBs suggesting that AC can be stressful for organisms by itself.

Millward et al. (2005)investigated the AC (type TOG, Calgon Corp., Pittsburgh, PA) effects in the marine polichaete Neanthes arenaceodentata. After 28 d exposure to contaminated sediment, and 30 d to sediment amended only with AC (3.4% and 8.5% v/v) in two size ranges (63–105 μm and 105–250 μm), its average body weight was reduced by 50% by the ingested AC that presents a strong affinity for lipids, carbohydrates and proteins thus interfering with nutrient up-take. In this specific case, the efficacy of AC was not improved by in-creasing dosage, contact time or dein-creasing particle size range. AC reduced PCBs in N. arenaceodentata up to 82% after 1 month and up to 87% after 6 months treatment. Similarly,Janssen et al. (2012)compared three AC grain sizes (Coal-derived virgin AC, Calgon Carbon, F400) (b45 μm; 180–350 μm; 600–1000 μm) exposing N. arenaceodentata for up to 28 d (burrowing, survival and weight cage) at sediment amended with 5% and 20% v/v. No negative effects on feeding were observed with the exception of weight loss in specimens that were not regularly fed. Apart from the fact that AC did not sorb sediment-associated nitrogen, but sorbed nitrogen fromfish food, absolute effects of AC amendments on growth and energy reserves were not significant. Results from

Millward et al. (2005) andJanssen et al. (2012) reported highly constrating data, nevertheless the size of particles was similar, suggest-ing that results are highly dependent on the characteristics of the ACs used.

Sun and Ghosh (2007)assessed the PCBs reduction from contami-nated sediment (6.8μg/g) uptaken by the oligochaete Lumbriculus variegatus considering two main exposure scenarios: i) AC (2.6% v/v) (TOG (Calgon Corp. Pittsburgh, PA) with the size range of 75–300 μm (coarse) and 45–180 μm (ﬁne)) was mixed with PCBs spiked sediment from 2 min up to 1 month; ii) spiked sediment was only covered with a thin layer of AC (2.6% v/v) without mixing. For both scenarios, the

exposure was up to 56 d. The PCB bioaccumulation was reduced from 70% to 84% when AC was mixed for 2 min and 1 month, respectively; whereas a 70% reduction was equally obtained in the second scenario.

Cornelissen et al. (2006)measured the biota-sediment accumula-tion factor (BSAF) of the marine polichate Hediste diversicolor exposed to PAH contaminated sediment. After 28 d exposure (7.2 °C) to sedi-ment amended with 2% v/v of AC (untreated powder 100–400 mesh, 37–149 μm; Sigma-Aldrich, Oslo, Norway), BASF was reduced up to 7 times compared to treatments without AC.

Jonker et al. (2009)assessed the adverse effects of AC alone and mixed with freshwater sediment spiked with PAHs and oil exposing L. variegatus for 28 d. For AC alone, increasing amounts (from 1.5 to 4000 mg) were added to 40 mg of water; for AC spiked sediment, con-centrations were 1, 2, 4, 7, 10, 15 and 25% (v/v dry weight (dw)). For AC alone, results showed a median lethal concentration (LC50) in the range

4 and 60 g/L. Authors suggested various explanations: i) obstruction of the gastrointestinal tract, impediment of movement, or adsorption of skin constituents (e.g. mucus) essential for organism's survival; ii) AC suspension in the water column lead to a change in its chemistry (e.g., by releasing of AC-associated chemicals), thereby inducing ad-verse effects; iii) reduction (up to 92%) of the egestion rate probably due to the slower sediment ingestion. However, no effects were ob-served in AC spiked sediments. L. variegatus reproduction rate, egestion rate and lipid content were used to investigate the potential role of AC size (b63 μm; 63–200 μm; 1000 μm) in toxicity definition (Nybom et al., 2012). Organisms were exposed for 28 d at 20 °C with 16:8 light:dark photoperiod at 0.05–15% v/v of AC. Egestion rate, growth, and reproduction decreased with increasing AC concentration and finer AC particle fractions; adverse effects showed to be stronger after exposure to natural uncontaminated sediment rather than the artificial one. AC toxicity was directly correlated to the exposure concentration and inversely correlated to grain size, presenting hormesis at very low concentrations for growth and reproduction. Polichates and oligo-chaetes are interesting biological models to be considered to assess the potential impact of ACs and other carbonaceous amendments be-cause of both external exposure through sediment and internal expo-sure via ingested particles. Moreover, they are target test species for adverse effects of carbon-based amendments (Silcarbon TH90 Extra; 0.02 mm average particle size; 80%b 0.045 mm) because they can be found in many contaminated areas as sediment-dwellers (Cornelissen et al., 2011).

2.1.1.3. Molluscs.McLeod et al. (2007)studied the AC (TOG, Calgon Cor-poration, Pittsburgh, PA, USA) efﬁciency in removing bioaccumulated PCBs in the marine bivalve Macoma balthica as well as its background toxicity. Clams were exposed for 28 d at 13 °C considering various AC sizes (25–75 μm; 75–180 μm; 180–250 μm) and concentrations (0.34%, 1.7%, 3.4% v/v or at 1.7% v/v for treatment and background ef-fects, respectively). ACs reduced the accumulated PCBs by 22%, 64% and 84% for 0.34%, 1.7% and 3.4% of AC, in that order. Moreover, as a function of its dimension, ACs reduced the accumulated PCBs by 41%, 73% and 89% for 180–250 μm, 75–180 μm and 25–75 μm, respectively.

McLeod et al. (2008)followed the experimental design ofMcLeod et al. (2007)with the freshwater bivalve Corbicula_{fluminea considering} AC exposure at 0.3%, 2.7% and 3.5% v/v for 28 d at 13 °C. Authors estimat-ed that 45% of PCB bioaccumulatestimat-ed in C.fluminea (filter-feeder) from sediment, less than what previously observed with M. balthica (depos-it-feeder) that accumulated 90% of PCB of its body burden through sed-iment ingestion, probably due to their feeding strategy. Results highlighted that bioaccumulated PCBs were reduced by 67%, 86% and 95% considering the addition of 0.7%, 1.3% and 1.5% of AC, respectively.

Cornelissen et al. (2006)replicated the same experimental design mentioned above for anellids using as target organism marine gastro-pod Hinia reticulata. No signiﬁcant changes were observed on BSAF, mainly due to the different physiology of the considered species.

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Lewis et al. (2016)evaluated the AC efﬁciency in Hg removal with the freshwater snail Lymnaea stagnalis. AC (1%) was added to sediment and snails were exposed for 41 d. Authors measured the bioaccumula-tion factor (BAF) values relatively to Hg and they could observe its sig-niﬁcant reduction from 103.1 ng/g (control sediment) to 64.6 ng/g (ZVI treated sediment).

2.1.1.4. Crustaceans.Ho et al. (2004)used the mysid Americamysis bahia and the amphipode Ampelisca abdita to test the efﬁciency of AC pow-dered coconut carbon (PCC) in reducing the toxicity of sediment con-taminated by ammonia, metals, PAHs, PCBs and endosulfan. Crustaceans were exposed to amended sediment (15% v/v AC PCC) for 96 h at 20 °C showing a survival rate of 100%. About pollutants, endosul-fan toxicity was totally removed, whereas no reduction was observed for ammonia and metals.

Millward et al. (2005)investigated the effects of AC (3.4% and 8.5% v/ v) (75–300 μm type TOG, Calgon Corp., Pittsburgh, PA)) towards the freshwater crustacean Leptocheirus plumulosus. After 28 d exposure to PCBs contaminated sediment, followed by 1 month-contact to sediment with AC only, it was observed a PCB bioaccumulation decrease of 70%, but no adverse effect was present despite the toxicity for polychaete N. arenaceodentata probably due to the lack of AC uptake by the crustaceans.

Freshwater crustaceans Asellus aquaticus and Daphnia magna and the marine crustacean Corophium volutator were studied byJonker et al. (2009). Experimental design considered direct exposure to AC only for D. magna (2 d) and C. volutator (3 d) to evaluate their survival. Exposure to sediment amended with 1, 2, 4, 7, 10, 15, 20 and 25% of AC was considered for the avoidance test with A. aquaticus (3 d) and C. volutator (3 d). The same AC concentrations were used for a 10 d sur-vival test with C. volutator. Results showed LC50 values only for AC in the range 0.5–4 g/L for D. magna and 4–60 g/L for C. volutator. A. aquaticus exhibited to avoid AC amended sediment in a concentration range between 15% and 25%, instead, no signiﬁcant avoidance nor mor-tality were observed for C. volutator.

Kupryianchyk et al. (2011)used the freshwater species A. aquaticus and Gammarus pulex to test the effects of AC amendment (1–30%) in remediating freshwater sediment contaminated with metals, PAHs and PCBs. Organisms were exposed to sediment (18 °C, 12:12 light:dark photoperiod) to investigate avoidance (72 h), locomotion impairment (1–5 d), and survival and growth (28 d). No negative effects were de-tected except for the survival decrease in G. pulex (LC50 = 3.1 ± 0.64%). Similarly,Kupryianchyk et al. (2013)assessed A. aquaticus con-sidering for scenarios in PCBs contaminated sediments: no AC addition (control), powdered AC addition, granular AC (GAC) addition, and addi-tion and subsequent removal of GAC (sediment stripping). Results evi-denced that bioturbation can play a major role in contaminant toxicity after AC administration to benthic organisms according to differences in species tolerance (i.e. A. aquaticus more tolerant than L. variegatus) di-rectly affecting massfluxes from sediment to the water column. 2.1.1.5. Arthropods.Nybom et al. (2016)assessed the effects of AC amendments (63–200 μm) on PCB bioaccumulation and secondary re-sponses on Chironomus riparius in twofield-collected sediment samples. Endpoints studied in 10-day larvae and full life cycle over two genera-tions included growth, developmental stage, of larvae, emergence time, developmental rate, sex ration and egg production in the full life cycle test. AC amendments reduced the aquatic and bioaccumulated concentration of PCBs, but secondary effects were observed such as de-layed emergence and dede-layed larvae development as well as changes in the microvilli layer in the gut wall when AC dose was 2.5%. Moreover, ACs are suspected to bind nutritious compounds from the sediment re-ducing their bioavailability.Nybom et al. (2016)stated that the effects of ACs are dependent on sediment properties of the two analysed sedi-ment samples, suggesting site-specific evaluation before a remediating approach is implemented.

2.1.1.6. Fishes.He et al. (2012)studied the effects of untreated, ozone-treated, and activated charcoal-treated oil sand process-affected water (OSPW) towards the early life stage of fathead minnow Pimephales promelas (i.e. success of eggs' hatching, spontaneous movement, inci-dences of hemorrhage, pericardial edema, and malformation of embry-os' spine). OSPWs were contaminated by naphtenic acids (NAs) (19.7 mg/L). Fertilized eggs were collected within 1 h post fertilization and embryos were exposed for 7 d both at OSPW and biochar-OSPW at 25 °C (pH = 8.7) with 16:8 h light:dark. Survival was significantly lower when exposed to not amended OSPW (43.8%). Eggs exposed to untreated OSPW exhibited a significantly greater rate of premature hatching, and embryos exhibited greater spontaneous movement. Inci-dences of hemorrhage (50.0%), pericardial edema (56.3%) and spine malformation (37.5%) were significantly greater in embryos exposed to OSPW compared to negative controls. Results highlighted an efficient removal of dissolved organic constituents by activated charcoal: surviv-al, hemorrhages incidence, pericardial edema and spine malformation percentages were 77.1%, 10.4%, 10.4% and 4.2%, in that order. After ozon-ation, results highlighted an efficient reduction of dissolved organic con-stituents significantly attenuating adverse effects observed in embryos. Compared to negative controls, survival rate significantly decreased (93.8%), as well as hemorrhage incidence (12.5%), pericardial edema (6.3%) and spine malformation (6.3%).

As reported inTable 1, only annelids and crustaceans seem to be sen-sitive to AC; indeed, they manifestated effects within all the exposure ranges. At now, bacteria, molluscs andﬁsh embryos did not evidence signiﬁcant negative effects, apart from the generalised negative effects on the benthic community found bySamuelsson et al. (2017). 2.1.2. Organoclay, apatite and biopolymers

Organoclay is created replacing the surface cation of bentonite or hectorite with quaternary amines (Olsta and Darlington, 2010; Paller and Knox, 2010). They are hydrophobic, permeable, and effective at ab-sorbing dissolved hydrophobic organics and immobilizing metals (Alther, 2002). Other minor amendments are apatite (i.e. facilitating the immobilization of metals including Cu, Pb, and Zn) and biopolymers (i.e. high-weight molecular organic compounds with repeated se-quences that can react with other compounds) that are still at the bench-scale or pilot-testing phase (Lofrano et al., 2017).

Data about the effects towards benthic organisms are limited. Some toxicity data are available for invertebrates (annelid, mollusc and crus-tacean) and vertebrates (ﬁsh).

2.1.2.1. Annelids. Paller and Knox (2010) assessed the toxicity of organoclay, apatite and biopolymers mixed in various percentages using the oligochaete L. variegatus and considering survival, growth and aggregate weight after 28 d exposure. Results showed that organoclay alone (up to 25% v/v) and apatite alone (up to 25% v/v) did not affect polychaetes, as their average recovery efﬁciency from the amended sediment was 90%. Conversely, in presence of biopolymers (2.5% v/v), the recovery was lower and only individuals that remained on or near the substrate surface were able to survive. Further examina-tion conﬁrmed that they were unable to burrow through biopolymers because of their high viscosity.

In the_{ﬁnal report of SERDP Project ER-1551 (}SERDP, 2010), the ef-fects of apatite, organoclay, acetate and chitin (alone or in combination) were investigated onto N. arenaceodentata. Amendments were mixed with uncontaminated sediment according to the following experimen-tal design: i) mat + apatite (10% v/v); ii) mat + apatite (5% v/v) + organoclay (5% v/v); iii) apatite (5% v/v); iv) organoclay (5% v/v); v) apatite + organoclay (2.5 + 2.5% v/v); vi) acetate (5% v/v); vii) chitin (2.5% v/v); and viii) chitin + apatite (2.5 + 2.5% v/v) (i.e. for each treat-ment 150 g of seditreat-ment and 0.75 L ofﬁltered (0.45 μm) natural seawater were added in a jar). Polychaete survival and growth were assessed after 28 d exposure at 20 °C and 30‰. Results showed that mixed apatite and organoclay presented no adverse effects either individually or in

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combination. Organisms' biomasses increased by a factor of approxi-mately 2 in presence of chitin, while survival was statistically lower only in the acetate treatment. Similarly,Rosen et al. (2011)assessed the toxicity of apatite (5% v/v) and organoclay (5–10% v/v) amended sediment to N. arenaceodentata assessing survival and growth rate after 28 d exposure (20 °C). Results con_{ﬁrmed that no negative effects} were present according to the considered experimental design. 2.1.2.2. Molluscs. Considering the same exposure conditions ofSERDP (2010),Paller and Knox (2010)assessed survival and aggregate weight with C.ﬂuminea reporting no negative effects except in presence of biopolymers.

2.1.2.3. Crustaceans. The amphipod Eohaustorius estuarius was exposed toSERDP (2010)experimental design for 10 d at 15 °C and 30‰ in pres-ence of constant light. As for annelids, mixed apatite and organoclay showed no adverse effects both when they were present individually or in combination to sediment; chitin and chitin-apatite decreased E. estuarius survival rate to 12% and 27%, respectively.

Paller and Knox (2010)completed their experimental activities using Hyalella azteca and L. plumulosus. Organoclay and apatite (5– 100%) were assessed unmixed or mixed with sand. Toxicity tests were conducted for 10 d at 23 °C and 16:8 h light:dark photoperiod. Results showed a concentration-response relationship between H. azteca sur-vival and organoclay increase, while 100% apatite had minimal adverse effects on crustaceans. Up to 25% organoclay no toxicity can be detected to L. plumulosus.

Rosen et al. (2011)evaluated the toxicity of apatite and organoclay also with the marine amphipod E. estuarius after 10 d exposure at 15 °C under constant light. As for annelids, no signiﬁcant effects on survival were observed.

2.1.2.4. Fishes. Juveniles of Cyprinodon variegatus (7 d old) were exposed for 96 h at 20 °C and 30‰ according toSERDP (2010)experimental de-sign. Results highlighted that mixed apatite and organoclay presented no adverse effects either added individually or in combination to sedi-ment, but chitin and chitin-apatite decreased C. variegatus survival of 65% and 48%, respectively. The effects of chitin and chitin-apatite seem to be a consequence of the dramatic increase in unionized ammonia concentrations.

With the same species,Rosen et al. (2011)also evaluated the toxicity of apatite and organoclay, exposing 7 d old juveniles of C. variegatus for 96 h at 20 °C. Similarly, no adverse effects on survival and growth were recorded.

As synthesized inTable 1, organoclays presented adverse effects to crustaceans between 5 and 100% v/v, but annelids, molluscs andﬁsh seemed to be unaffected. Current data show that apatite did not cause any negative effects on the investigated biologic models. Biopolymers seemed to be the most toxic among the three amendments, having ef-fects on annelids and molluscs since 2.5% v/v. At now,ﬁsh did not show any adverse effects.

2.1.3. Iron-based and natural zeolite amendments

Elemental iron (i.e. Fe0_{and Fe}2+_{) and hematite showed to reduce}

and immobilize the availability of redox sensitive elements (Cundy et al., 2008; Mamindy-Pajany et al., 2010b; Libralato et al., 2016; Ou et al., 2017). Zerovalent iron (ZVI) is a strong reducing agent for many organics (i.e. halogenated methanes, ethanes, and ethenes and other ha-logenated compounds) at ambient temperatures (Cundy et al., 2008) like as for metals (Ou et al., 2017). Besides these, nano-ZVI is widely used, because efﬁciency of iron is proportional to its available reactive surface area that can be drastically enhanced at the nanoscale (Libralato et al., 2017). Current applications of iron-based technologies can be broadly divided into two groups: technologies which use iron as a sorbent, (co-)precipitant or contaminant immobilizing agent (sorp-tive/stabilisation technologies); and those which use iron as an electron

donor to break down or to convert contaminants into a less toxic or mo-bile forms (reductive technologies) (Cundy et al., 2008). In some cases, iron can be partially removed via magnetic recovery (Ou et al., 2017), but the amount and effects of residuals are still unknown.

Several papers investigated the potential adverse effect of ZVI for land remediation and water treatment (Libralato et al., 2017), but just few focused on sediment and only one on the potential ecotoxicological implication of ZVI in in situ contaminated sediment treatment (Lewis et al., 2016).Lewis et al. (2016)assessed the efficiency of ZVI to remove Hg from contaminated sediment, using the freshwater snail L. stagnalis. Sediment was amended with ZVI ranging from 43 to 269μm. After 41 d exposure, BAF(Hg) values were significantly reduced from 103.1 ng/g (control sediment) up to 41.8 ng/g (ZVI treated sediment). No other po-tential side-effects of the use of ZVI were assessed. Other applications of ZVI for sediment remediation are available considering ex situ applica-tions.Mamindy-Pajany et al. (2010b)compared the ef_{ficiency of 5%} he-matite, ZVI and NZ in stabilising the contamination in four sediment samples from the French Riviera using Crassostrea gigas embryotoxicity test on elutriates produced from sediment after treatment (i.e. dredged sediment specimen were composted for several weeks and conditioned with amendments). Results highlighted that ZVI and NZ had sample-specific abilities to reduce toxicity while hematite can be a potential in-teresting candidate for sediment stabilisation prior to its deposit in a specific site or landfill; but hematite, ZVI and NZ were not assessed for toxicity at the employed concentrations (as stand-alone reagents).

Currently, the use of iron-based amendments for in situ remediation is in its infancy for toxicity monitoring, even if the attention of such ap-plications is constantly increasing.

2.2. Toxicity as an added value for in situ treatment selection

The assessment of sediment toxicity is now compulsory in several national legislations (i.e. USA, Canada, EU countries, etc…) and public risk assessment tools have been introduced to help understand the po-tential role of toxicity in sediment management like Georisk (Ifremer, 2001) or Sediqualsoft_109 (DLgs 173/2016, Italy). Toxicity can be con-sidered as an“all included” parameter stating the potential adverse ef-fects to target biological models referred to speciﬁc sediment matrix-species pairs (i.e. whole sediment-matrix-species#1, pore water-matrix-species#2, and elutriate species#3) within a balanced battery of toxicity tests (i.e. at least three species presenting different trophic levels and phylogenet-ic complexity). Besides sediment toxphylogenet-icity evaluation related to management purposes, toxicity should be considered to check the envi-ronmental suitability of products and technologies to be used within in situ remediation activity as well as to monitor their effectiveness during and after the remedial action took place on a long-term basis (Libralato et al., 2010).

This review highlighted that most papers considered single species rather than batteries of bioassays for the toxicity assessment of amend-ments and sediment remediation. Carbonaceous materials, with a spe-cial focus on AC, are able to effectively limit the mobility of HOCs in aquatic environments, but potentially presenting negative secondary effects, and these outcomes must be held in comparison to traditional remediation approaches as stated byJanssen and Beckingham (2013). Lab-based investigations at the microcosm level were mostly present, and just little examples of in situ sediment assessment were investigat-ed (Cornelissen et al., 2011, 2012;Ghosh et al., 2011; Samuelsson et al., 2017). Generalﬁndings are related to:

- Effects on amendments, especially of AC, are related to sediment characteristics like particle size and nutrient content;

- AC grain size may inﬂuence toxicity effects showing that ﬁner parti-cles are more toxic mostly due to their facilitated ingestion by sedi-ment dwellers;

- AC may indirectly affect the considered biological models reducing the bioavailability of nutritious compounds present in sediment;

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- Sediment grain size can affect sediment dwellers both in presence and absence of AC, but the mechanisms causing adverse effects are still unknown;

- Amendments before their direct ISA need to be carefully investigat-ed on an amendment-by-amendment basis: toxicity may signi ﬁ-cantly change according to AC origin, way of production and administration;

- Within the largest in situ case study of AC application (Cornelissen et al., 2012), slow sediment-to-cap transfer, cap integrity, and lateral particle transport were observed, but no toxicity related-effects were presented and discussed: toxicity should be one of the most “hot” parameter to be considered especially for ﬁeld studies; - Field-experimental studies evidenced that the in situ use of AC

mixed with clay can cause severe perturbations within the benthic community with abundance, biomass and number of species de-crease (Samuelsson et al., 2017) being in contrast with most lab-based results (Rakowska et al., 2012; present review);

- Combination of AC and iron-based amendments into“magnetic AC” presented remediation properties similar to AC, but allowed their magnetic recovery, representing a very interesting future potential-ity for the eco-friendly development of this sector;

- Non-AC-based amendments are still in their infancy and careful at-tention should be paid to their future direct use.

Amendments need to be investigated before real scale applications on a case-by-case basis, meaning that even their origin (i.e. source ma-terial), target sediment characteristics and way of administration can strongly condition their potential intrinsic ecotoxicity, like in the case of carbonaceous materials (Rakowska et al., 2012). Moreover, toxicity may significantly vary from lab-based experiments to field applications, indicating that laboratory activity is only thefirst step of their assess-ment andfield-based experiments are compulsory before real scale ap-plication. The safe-by-design approach should be adopted including safe production and safe use.

3. Conclusions

Apart from the“no action” option, active in situ sediment remedia-tion started to be taken into consideraremedia-tion as potential low impact solu-tions for sediment confinement or/and remediation. Literature review evidenced that the safe-by-design approach failed or was not consid-ered at all. Indeed, scarce information is available about the potential side effects of in situ remediation activities mainly in relation to amend-ments used to carry out the remediation process especially forfield studies. Nevertheless, polluted sediment is not dredged, but confined or treated on site with limited potential resuspension events, adverse effects might be associated to the materials used for the remediation process itself. Currently, only AC technology, with and without capping, have been widely investigated and little data are available for non-AC-based remediating materials. Existing data are fragmentary and incom-plete; several toxicity outcomes are completely missing. Organisms from some biological groups, such as annelids and molluscs, have been investigated more frequently, while others are completely unex-plored like microalgae and rotifers as well as multi-species toxicity tests (i.e. micro- and mesocosms). Freshwater sediment data are more frequent than saltwater ones, even if more sea-basedfield applications are present. Key biological models including bivalves and sea urchins should be taken into consideration for future research activities. Existing data interpretation is quite challenging due to i) the way the various technologies are applied; ii) the use of various species, life stages or exposure conditions presenting different experimental de-signs; iii) the consideration of various endpoints; iv) the lack of established database to refer to.

In situ sediment remediation technologies represent an important and potentially efﬁcient resource to recovery polluted sediment. As their application showed to frequently generate negative effects for tar-get and non-tartar-get organisms, amendments must be attentively evalu-ated for short- and long-term environmental effects, also in the perspective of the remediated site monitoring and maintenance.

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