Plant Bioaccumulation

Plant Bioaccumulation

9.1 General Considerations

In the context of the UTM, plant uptake refers to the bioaccumulation of COC

from dredged material in the tissues of plants growing on the dredged material.

Depending on its design and management, different portions of a CDF may

consist of terrestrial, wetland, or aquatic habitats at any one time, and these

habitats may occur in any portion of a CDF at different times during the design

life of the CDF. The UTM addresses bioaccumulation by terrestrial plants of

COC from the dredged material under terrestrial (wetland and upland) habitat

conditions.

Metals are the most common class of COC for which plant uptake is of

concern. Only a limited number of organics are of concern for plant uptake, e.g.,

certain energetics (RDX), certain solvents (e.g., TCE).

9.1.1 Plant Bioaccumulation Processes

Plants may bioaccumulate COC from dredged material in terrestrial, wetland,

and aquatic habitats in a CDF. Once a COC is in the tissues of a plant, it can be

passed along to other species in the food web that feed on it. This trophic transfer

can create complete exposure routes by which COC from the dredged material can

come into direct physiological contact with organisms that do not live or feed in

direct contact with the dredged material. These complete exposure routes may

include organisms such as foxes that prey on rodents that eat plants from

terrestrial habitats in CDFs, numerous species that prey on herbivores in wetland

habitats in CDFs, and birds, animals, or humans that eat fish caught from aquatic

habitats in CDFs.

9.1.2 Regulatory Considerations

As explained in Chapter 1, there are no regulatory standards for contaminant

uptake by plants and animals at CDFs. Land application of sludge and waste soils

regulatory protocols are not designed to address the unique characteristics that

occur as sediments dry and colonize with wetland or terrestrial plants and animals.

Also, the plant and animal routes of exposure are different and are treated

differently in this manual. It is USACE policy that the procedures used in this

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Chapter 9

Plant Bioaccumulation