Contaminants from Aged Dredged Material Using Plants and Worms"">

 

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Page Title: Bioaccumulation and Toxicity in Worms
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ERDC TN-DOER-R3
September 2004
cultivated on the 33-percent IHC DM mixture may have been adsorbed to the tiny roots anchor-
ing the plants to the substrate. These roots were so small that they were not harvested separately.
It may also have been adsorbed through volatilization from the substrate surfaces.
Concentrations in plant roots from dry DM mixtures were far higher than from wet DM
mixtures.
PAHs (sum of 16 PAHs) were recovered from roots and shoots (Table 3). PAH concentrations
were higher in roots than in shoots and they increased with increasing PAH concentration in the
DM mixture. This may indicate that most PAHs were taken up by the plants and translocated
from roots to shoots, since a large part of the volatile PAHs had been lost during drying of the
IHC-DM (Material and Methods Section `Substrates' p. 5). The high PAH concentrations in
plant shoots cultivated on the 33-percent IHC DM mixtures may also have been adsorbed to the
tiny roots anchoring the plants to the substrate, as suggested for the PCBs. PAH concentrations
were far higher in plant roots from dry than from wet DM mixtures. No significant relationships
between organics concentrations in plant tissues and those in DM mixtures, both expressed as
milligrams compound per kilograms dry weight, were found. However, upon further inspection
of the data, significant relationships were identified; these are discussed under "Relationships
between concentrations of individual organics in substrates and tests using plants, animals, and
C18-disks," p. 10.
In the plant material, various metals accumulated up to considerable concentrations (Table 3).
Shoot concentrations of Cr, Pb, and Zn exceeded CSCLs for plants in the dry 20-percent IHC
mixtures, while the concentration of Zn came close to the phytotoxic level recently determined
for another grass species, Cynodon dactylon (bermudagrass; Best et al. 2003).
Plant biomass was significantly affected by percent IHC contribution to the DM-mixture, as
found by ANOVA (p<0.05; Table 3). Substrates with an IHC-DM contribution exceeding
33 percent did not support plant growth. The decrease in plant biomass with increasing IHC-DM
percent was tentatively attributed to the various metals in the DM mixtures, but no single metal
could be identified that explained this biomass decrease using multiple regression techniques.
Biomass was significantly higher in plant material harvested from the wet than from the dry DM
mixtures (p<0.001; Table 3). The biomass of plants exposed to DM mixtures, including the ref-
erence, was always lower than that of the control plants (226 23.45 g DW m-2), indicating that
all DM mixtures provided less than optimal substrates for biomass formation.
Bioaccumulation and Toxicity in Worms: In the worms, both Arochlor1248 and PAHs
accumulated. Arochlor1248 and PAH concentrations in worm tissues were significantly affected
by percent IHC contribution to the DM mixtures, as found by ANOVA, with PAHs accumulating
more gradually than PCBs (Table 4). No significant relationships between organics concentra-
tions in worm tissues and those in DM-mixtures, both expressed as mg compound per kg dry
weight, were found.
In the worms, various metals accumulated up to considerable concentrations (Table 4). In the
DM mixtures containing ≥10 percent IHC-DM, only the zinc concentrations exceeded the CSCL
for worms.
9

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