Figure 2. Average growth response (N = 4) of C. esculentus plants cultivated on test dredged material and control soil in 2-L pots, with a small (S, 0.0167 m2 ) and large (L, 0.0238 m2) surface area

ERDC TN-DOER-C22

September 2001

metals using Inductively Coupled Plasma Analysis (ICP) (USEPA Method 3050 (USEPA 1996)),

or cold-vapor determination for mercury (USEPA Method 7471A (USEPA 1994)).

Toxicity. Analysis of variance (ANOVA) of the complete data set indicated that the effect of

substrate on growth response (i.e., total biomass) was not statistically significant, but the effects of

plant species and test duration were significant (P < 0.001). The data are graphically represented in

Figures 2 and 3. This means that the differences in growth responses of both plant species could

not be attributed to differences in substrate type alone, i.e., test dredged material being phytotoxic

compared to control soil, but that they depended on plant species and on test duration. The effect

of pot size on the belowground plant biomass of C. esculentus was significant, with more biomass

being produced in the relatively deeper pots with the smallest surface area (P < 0.05). The effect of

pot size on total biomass of C. dactylon (roots were so small that belowground and aboveground

biomass was not distinguishable) was also significant, with more biomass being produced in the

pots with the largest surface area (P < 0.05).

Figure 2. Average growth response (N = 4) of C. esculentus plants cultivated on test dredged material

and control soil in 2-L pots, with a small (S, 0.0167 m2 ) and large (L, 0.0238 m2) surface area

(top left). Bioaccumulation of lead, nickel, and zinc was also measured; of the bioaccumulation

data, only those pertaining to pots with a small surface area are shown