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Title: Plant bioassay of materials from the Blue River dredging project
Authors: Folsom, Bobby L.
Lee, Charles R.
Preston, Karen M.
Keywords: Biological assay
Chemistry, Analytic
Dredging spoil
Plants (Botany)
Blue River (Mo.)
Publisher: Environmental Laboratory (U.S.)
Series/Report no.: Miscellaneous Paper;EL-81-6
Abstract: Abstract: A plant bioassay and associated chemical analyses were performed on sediment and bank material from the Blue River and soil from a proposed disposal site. The objectives of the tests were to determine the availability and extent of plant uptake of cadmium and zinc that would occur when the dredged material was placed in an upland environment and seeded to grass. In addition, the results of the tests were used to formulate a disposal plan for the materials. Composite samples were taken of each sediment and soil, placed into polyethylene-lined steel drums, and transported by truck to WES. Each of the sediments and soils was air-dried and mixed well before being placed into plastic buckets. Two complete sets of buckets were prepared. One set was unfertilized while the other set was fertilized with an appropriate amount of nitrogen, phosphorus, and potassium for establishing grass. Each of the sediment soil treatment combinations was planted to five plant species: Cynodon dactylon (common bermuda grass), Festuca rubra (red fescue), Festuca arundinacea (tall fescue), Poa pratensis (Kentucky bluegrass), and the index plant, Cyperus esculentus. The experiment was replicated three times. Common bermuda grass and C. esculentus were allowed to grow 45 days before harvest. Tall fescue, red fescue, and Kentucky bluegrass were allowed to grow 63 days before harvest. After the respective plant growth periods, the plants were harvested, dried to constant weight at 70°C, digested in nitric acid--red fuming nitric acid, and analyzed for zinc and cadmium. Samples of the air-dried sediment and soil were subjected to extraction by nitric acid, DTPA, and distilled water. Common bermuda grass had the greatest yield of all the species. Yields of red fescue, tall fescue, and Kentucky bluegrass were low with more than 70 percent of them being less than 0.5 g oven-dry weight. Yield of C. esculentus was somewhat less than common bermuda but much greater than either the fescues or Kentucky bluegrass, Best plant growth for all species was observed on the north bank material. Concentration of cadmium and zinc in the index plant, Cyperus esculentus, was relatively low compared to recent research data collected at the WES. These results indicated that the cadmium and zinc in the river sediments were relatively unavailable: Consequently, concentrations of cadmium and zinc in the other grasses were relatively low. In general, plant concentrations of cadmium and zinc in common bermuda, red fescue, and Kentucky bluegrass varied in the order of river channel No. 2 sediment > river channel No. 1 sediment > north bank soil > disposal site soil. Tall fescue did not show such pronounced differences; however, the highest concentrations of cadmium and zinc were found in plants grown in river channel No. 2 sediment. Suppressed plant growth on river channel No. 2 sediment resulted in elevated plant concentrations of cadmium and zinc. Since common bermuda grass produced the greatest yield of the grasses tested, it had the greatest total uptake of cadmium and zinc. Red fescue showed some of the lowest plant concentrations and total uptake of cadmium and zinc compared to the other grass species grown on soil from north bank and river channel-No. 1 sediment. Based upon the results of the plant bioassay experiment, river channel No. 2 sediment should be placed on the disposal site first, followed by covering with river channel No. 1 sediment, and then topped with soil from the north bank. Plant cover could be established by planting common bermuda grass and then overseeded with red fescue in the fall. This approach to the disposal of these materials will ensure reduced mobility of the cadmium and zinc in the river sediments. Until additional data are obtained for metal uptake by agricultural crops other than the grass tested in this study, use of the disposal site should be limited to grasses.
Appears in Collections:Miscellaneous Paper

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