9.3.3 Tier II - Plant Uptake Program (PUP)

effectively occurs only after the salts have been leached from the surface layer by

precipitation. Therefore the DTPA can be applied to saltwater dredged material

after the material has been prepared in the laboratory to reflect salt leached

conditions.

Guidance for the DTPA extraction procedures is provided in Appendix H.

Although DTPA extraction can only be used for evaluation of potential plant

bioaccumulation of metals from freshwater dredged material, it is a useful

procedure because metals are the most common COC for plant bioaccumulation.

Because the DTPA is limited to metals, evaluation in a subsequent tier is

necessary for plant bioaccumulation of all other COC. If there are COC other

than metals, the DTPA should not be conducted and the plant bioaccumulation

evaluation may proceed to Tier III.

9.3.3 Tier II - Plant Uptake Program (PUP)

A computerized program, the Plant Uptake Program (PUP) uses the results of

the DTPA extraction procedure to predict bioaccumulation of metals from

freshwater dredged material by freshwater plants and compare the results to a

background or reference sediment or soil (Folsom and Houck 1990). The model

requires total sediment metals concentrations, DTPA extraction data, sediment

organic matter content, and the sediment pH in the condition of placement

(wetland or terrestrial). The PUP program statistically compares the DTPA

prediction of plant bioaccumulation from the dredged material to the prediction

from the reference material to determine whether there is an indication of greater

bioaccumulation from the dredged material than from the reference. Because the

reference material is carefully selected to represent acceptable conditions,

whatever bioaccumulation it may cause is an acceptable level of plant

bioaccumulation. Although statistical significance, per se, cannot indicate

environmental importance, a statistically significant increase above reference

bioaccumulation has previously been considered to indicate a potential for effects,

and that convention is followed in the Tiers II and III plant bioaccumulation in the

UTM. The PUP program is described in http://www.wes.army.mil/el/elmodels/

pdf/ee-04-12.pdf and the program can be downloaded from http://www.wes.army.

mil/el/elmodels/index.html.

9.3.4 Tier II - Plant Bioaccumulation DTPA Decision

After consideration of the Tier II plant bioaccumulation information in the

context of the conceptual site model and the complete exposure routes to ROC

populations outside the CDF, one of the following conclusions is reached for

nonpolar organic COC.

1. Information is sufficient to reach a decision regarding plant

bioaccumulation. This is the case where the DTPA prediction of plant

bioaccumulation from the dredged material is not statistically greater than

the prediction from the reference material. No further evaluation of plant

bioaccumulation is necessary.

2. Information is not sufficient to reach a decision regarding plant

bioaccumulation. This is the case if the DTPA prediction of plant

bioaccumulation from the dredged material is statistically greater than the

9-8

Chapter 9

Plant Bioaccumulation