Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/47125
Title: Long-term release of contaminants from dredged material
Authors: Brannon, James M.
Plumb, Russell H.
Smith, Isaac
Keywords: Water quality bioassay--Methods
Marine pollution
Marine sediments
Dredging spoil
Dredged material
Water--Pollution
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Dredged Material Research Program (U.S.)) ; no. D-78-49
Abstract: Man’s activities in the Nation’s coastal zones and waterways have served to contaminate sediments in these areas, generating concern that dredging and disposal may exert adverse effects on water quality and aquatic organisms. The long-term effects of dredged material on water quality at the disposal site remain an area of particular concern. To study the magnitude and predictability of long-term releases from dredged material, an 8-month aerobic leaching study was conducted in the laboratory. A large number of sediments (32) representing broad geographical and pollutional variation were used to ensure wide applicability of study results. Under the aerobic chemical conditions likely to prevail at aquatic disposal sites, total organic carbon, orthophosphate-P, and zinc exhibited the most consistent net releases to the water column. Very little net mass release of mercury (Hg), lead (Pb), cadmium (Cd), or arsenic (As) into the water column was observed regardless of the composition of the sediments. Worst case evaluation of the potential effects of contaminant releases, conducted by comparing results of this study with the most stringent water quality criteria available, indicated that sediments used in this study would not be expected to cause significant long-term water quality problems. The Elutriate Test procedure (modified for aeration) and interstitial water analyses demonstrated considerable utility as predictors of potential long-term net mass releases of contaminants from sediments. The Elutriate Test was related to long-term net mass release of copper (Cu), total organic carbon, phosphorus (P), As, Cd, Pb, and Hg after 4 months. Interstitial water analyses were related to net mass release of zinc (Zn), As, Hg, and ammonium-nitrogen (NH₄-N) after 4 months of leaching and Hg, total organic carbon, and NH₄-N after 8 months of leaching. The ability of the Elutriate Test and interstitial water analyses to predict release decreased slightly as time after initial mixing increased, apparently due to the increased significance of the aquatic chemistry of each constituent. Results from limited sediments incubated under both agitated and quiescent conditions indicated that mechanical agitation did not appreciably enhance long-term net mass release of most constituents. However, one sediment suspension from Oakland Inner Harbor, California, when incubated under aerobic, agitated conditions, exhibited a marked drop in pH from near 8.0 to 3.6. The acidic condition was accompanied by a high net release of trace metals. The same sediment, incubated under aerobic, quiescent conditions did not lower the overlying water pH and did not release significant amounts of trace metals. If disposed of in an upland and drained disposal site, such a sediment could oxidize, become acidic, and pose a potentially severe environmental problem. Manganese (Mn) and NH₄-N exerted no long-term effects on water quality. Large amounts of Mn and NH₄-N were released during the Elutriate Test and presumably when the leaching columns were prepared. However, at the end of a 4-month incubation both constituents were usually present in lower concentrations than in the initial disposal site waters. These results indicate that Mn and NH₄-N were being actively removed from the water column. Consideration of net mass release during the Elutriate Test procedure and other short-term extractants can provide useful information on the probable direction (i.e., sediment to water, to sediment) of long-term net mass release when concern exists over possible contaminant releases at aquatic disposal sites. However, because the relationships are based on laboratory observations and have not been field verified, caution in their use is recommended.
Description: Technical Report
Gov't Doc #: Technical Report D-78-49
Rights: Approved for Public Release; Distribution is Unlimited
URI: https://hdl.handle.net/11681/47125
Appears in Collections:Technical Report

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