Environmental Engineering Reference
In-Depth Information
(Table
5
). ENPs have a positive zeta potential, whereas nematodes have an even
distribution of net negative charges on their membranes. Net negative charges on the
surfaceofthenematodesattractENPs.ThebulkandnanoENPformscanaffectthe
growthandreproductioncapabilityofnematodes(Wangetal.
2009
).Growthinhi-
bition in both wild type and mutant nematode species are known to occur from
exposuretoandinternalizationofAgNPs(Table
5
)(Meyeretal.
2010
). AgNPs also
decrease the reproduction potential and increase expression of Sod-3 in
C. elegans
throughaoxidativepathway(Table
5
)(Rohetal.
2009
).
Earthworms
Exposure tests were performed on earthworms (
Lumbricus rubellus
) with C
60
at
concentrationsof0,15.4and154mg/kginsoil,withthegoalofmeasuringmortality,
growth and reproduction effects. Dose-dependent effects were observed in both
adultandjuvenilegrowthafter4weeksofexposure(Table
5
). Juveniles were more
sensitive to C
60
thanwereadults(VanderPloegetal.
2011
).Earthworms(
Eisenia
veneta
) were given food spiked with double-walled nanotubes (DWNTs) (outer
diameter10-30nm)andC
60
fullerene(11nm)atlevelsofviz.,0,50,100,300and
495mg/kg(Scott-Fordsmandetal.
2008
).Theearthwormswerekeptin500gof
soil for 28 days at 20 ﾰC. No signiicant growth effect resulted from exposure to the
lower concentrations; however a 20% reduction in growth occurred at the highest
concentration of C
60
(Table
5
). Cocoon production and reproduction was severely
impairedatconcentrationsabove37mgDWNT/kg.Noeffectswereobservedon
earthwormhatchabilityforanydose(Scott-Fordsmandetal.
2008
).
Recently,Courtisetal.(
2012
)studiedthebioavailabilityofcobalt(CoNPs)and
AgNPsinearthworms(
Eisenia fetida
).ItwasobservedthattheseNPsweretaken
upbythetestedearthworms,andwasexcretedandbio-distributed.After4weeksof
exposuresigniicantamountofCoions(88%)andCoNPs(69%)werefoundinthe
blood samples of earthworm, whereas Ag ions and AgNPs were found to be 2.3%
and 0.4%, respectively (Table
5
). The authors of this study concluded that most
absorbedsilverwasexcretedfromtheearthworms,whereas32%ofthecobalttaken
upremainedinbloodandthedigestivetract(Courtisetal.
2012
).
AlimittestdesignwasusedbyHeckmannetal.(
2011
) to assess the toxicity in
earthworms(
Eisenia fetida
)ofthreepuremetal-basednanoparticles(Ag,Cuand
Ni), four metal oxide nanoparticles (Al
2
O
3
, SiO
2
, TiO
2
, and ZrO
2
) and their bulk
counterparts(i.e.,metalandmetaloxides)(Table
5
). All treatments carried out were
atasoillevelof1,000mg/kgandtestswereconductedfor28daysat20ﾰC.The
AgNPs, AgNO
3
, CuNPs, TiO
2
NPs and their metal salts all induced reproductive
toxicity(Heckmannetal.
2011
).
Lietal.studiedtheeffectofDOMonearthworm(
Eisenia fetida
) toxicity for sev-
eralsaltsofZnONPs(0,50,100,200,500and1,000mg/kg).Testswereconducted
inagarandonilterpaperspikedwithasoilextractandtheintendedamountofthe
nanoparticles. Accumulation of nanoparticle in organelles and in cytosol of earth-
worms was observed after feeding with the agar medium that had been impregnated
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