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Title: Assessing the efficacy of dredged materials from Lake Panasoffkee, Florida: Implication to environment and agriculture. Part 1-Soil and environmental quality aspect

Author
item Sigua, Gilbert
item HOLTKAMP, M. - SWFMD- SWIM, TAMPA, FL.
item Coleman, Samuel

Submitted to: Environmental Science and Pollution Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2004
Publication Date: 10/1/2004
Citation: Sigua, G.C., Holtkamp, M.L., Coleman, S.W. 2004. Assessing the efficacy of dredged materials from Lake Panasoffkee, Florida: Implication to environment and agriculture. Part 1-Soil and environmental quality aspect. ESPR - Environmental Science and Pollution Research. 11(5):321-326.

Interpretive Summary: Dredged materials are often viewed by society and regulators as pollutants, but many have used these materials in coastal nourishment, land or wetland creation, construction materials, and for soil improvement as a soil amendment. Environmental impact assessment is an important pre-requisite to many dredging initiatives. The ability to reuse lake-dredge materials for agricultural purposes is important because it reduces the need for offshore disposal and provides an alternative to disposal of the materials in landfills. Often these materials can be obtained at little or no cost to the farmers or landowners. For this reason, we conducted this study to quantify the effect of applied lake dredged materials on soil physico-chemical properties (soil quality) at the disposal site. The experimental treatments that were evaluated consisted of different proportions of lake dredged materials at 0, 25, 50, 75, and 100%. We have demonstrated that when lake dredged materials were incorporated into existing topsoil they would have the same favorable effects as liming the field. Application of lake dredged materials have improved the soil physical and chemical conditions, and likewise may have had improved soil structure and soil tilth, which can promote better water holding capacity, sufficient aeration, and creates soils that are more friable in subtropical sandy pastures. Soil compaction was lowered significantly by the application of lake dredged materials. The compaction of agricultural soils can become a serious problem because the productive capacity of the land could be seriously reduced. Furthermore, the heavy and trace metal contents of these materials were below the levels that will cause significant hazards to aquatic organism, therefore the agricultural or livestock industry could utilize these lake dredged materials to produce forages.

Technical Abstract: The ability to reuse lake-dredge materials (LDM) for agricultural purposes is important because it reduces the need for offshore disposal and provides an alternative to disposal of the materials in landfills. Additional research on disposal options of dredged materials are much needed to supply information on criteria testing and evaluation of the physical and chemical impacts of dredged materials at a disposal site, as well as information on many other aspects of dredging and dredged material disposal. The objective of this study (Part 1) was to quantify the effect of applied LDM on soil physico-chemical properties (soil quality) at the disposal site. The experimental treatments that were evaluated consisted of different ratios of natural soil (NS) to LDM: LDM0 (100% NS:0% LDM); LDM25 (75% NS:25% LDM); LDM50 (50% NS:50% LDM); LDM75 (25% NS:75% LDM); and LDM100 (0% NS:100% LDM). Field layout was based on the principle of a completely randomized block design with four replications. The heavy and trace metal contents of LDM were below the probable effect levels (PEL) and threshold effect levels (TEL). Average values for Pb, Zn, As, Cu, Hg, Se, Cd, and Ni of 5.2, 7.0, 4.4, 8.7, 0.01, 0.02, 2.5, and 14.6 mg/kg, respectively, were below the TEL and the PEL. As such, the agricultural or livestock industry could utilize these LDM to produce forages. LDM should be regarded as a beneficial resource, as a part of the ecological system. Addition of LDM had significant (p ' 0.001) effects on soil physico-chemical properties and soil quality. Compared with the control plots, the soils in plots amended with LDM exhibited: (1) lower degree of soil compaction; (2) an increase in soil pH, Ca, and Mg; (3) decrease in the levels of soil Mn, Cu, Fe, Zn, and Si; and (4) no significant change in the level of Na in the soil. Results have shown the favorable influence that LDM had on soil compaction. The treatment x year interaction effect was not significant, but the average soil compaction varied widely (p < 0.001) with LDM application. In 2002 and 2003, soil compaction of plots was lowered significantly as a result of LDM additions. The least compacted soils in 2002 and 2003 were observed from plots with LDM75 with mean soil compaction of 300 x 103 and 350 x 103 Pa, respectively.