RESULTS AND DISCUSSION

ERDC TN-DOER-R3

September 2004

fresh soil-to-liquid ratio of 1:2.5 (w/v). pHKCl was converted to pHwater using a regression equa-

tion of pHwater = 0.677 x pHKCl + 2.35 (ISO 10390; Best and Jacobs 2001).

Dry weight (plants and worms) was determined by drying of the fresh material in a forced-air

oven to constant weight (105 C). PCB and PAH concentrations were determined in the fresh

materials of three of the five replicate plant and animal samples, using a similar approach as for

the DM mixtures. Lipid contents were determined gravimetrically in subsamples of the plant and

worm dichloromethane (DCM; Bligh and Dyer 1959) extracts. Total metal concentrations were

determined in the remaining two replicate plant and animal samples, including As, Cd, Cr, Cu,

Pb, Ni, and Zn, using an approach similar to that used for the DM mixtures, but digesting 0.3 g

DW. These latter determinations in plants and worms allowed exploration of factors contributing

to the untimely demise of the test organisms.

PCB and PAH concentrations were determined in hexane extracts of all C18 disks (Krauss and

Wilcke 2001). Recoveries of the internal standard were on average 40 percent in DM mixtures,

48 percent in DM mixtures, 65 percent in plants, 81 percent in worms, and 48 percent in C18

disks.

Statistics. The STATGRAPHICS Plus for Windows 3 package (Manugistics, Rockville, MD;

1997) was used for statistical analyses.

Effects of treatment on plant and worm responses were tested for statistical significance using

analysis of variance (ANOVA), followed by a multiple range test. The p-value in the ANOVA is

a measure of the significance of the analysis; it was set at a 95-percent confidence level (p value

≤0.05).

Relationships between plant and worm responses and substrate contaminant concentrations were

derived by linear regression. The p-value in the regression model was set at a 95-percent confi-

dence level (p value of ≤0.05) unless stated otherwise. The R2-value of the regression model

indicates the proportion of the variance explained by the model; regressions with R2-values of

0.50 explain 50 percent of the variance in the dataset.

RESULTS AND DISCUSSION

Substrates. The five DM mixtures spanned organics concentration ranges of 0 to 46 mg Aro-

chlor1248 kg-1 DW for PCBs and of 0.32 to 336 mg PAH kg-1 DW (Table 2). The levels of total

As, Cd, Cr, Cu, Pb, Ni, and Zn were far higher in the DM mixtures than in the reference DM,

and the DTPA-extractable metal levels were far lower than the total metal levels. Based on the

published critical stressor concentration levels (CSCL), largely identical with the "No Observed

Adverse Effect Level" (NOAEL) or "Lowest Observed Adverse Effect Level" (LOAEL), it was

expected that the concentrations of Cd and Zn even in the least diluted IHC DM mixture might

be deleterious for plants as well as worms.

Bioaccumulation and Toxicity in Plants: In the plant material, Arochlor1248 was mainly

recovered from the roots. Arochlor1248 concentrations in root tissues increased with those in the

DM mixtures (Table 3). This led to the conclusion that Arochlor1248 was sorbed and/or taken up

by the roots, but not translocated to the shoots. Arochlor1248 recovered from the plant shoots