A Study of Leachate from Dredged Material in Upland Areas and/or in Productive Uses

A laboratory lysimeter study was conducted to determine the composition of subsurface leachates generated from each of the five different dredged materials, each combined with one of two different subsurface soil properties. Sixteen 30-cm diam Plexiglas lysimeter columns were consecutively filled with equal depths of homogeneous, oxidized native soil and anoxic dredged material (total profile of 60 cm). The dredged materials were obtained from land disposal area located near Mobile, Ala. (saline silty clay), Sayreville, N.J. (saline silty loam) , Grand Haven, Mich. (freshwater sandy clay loam), Seattle, Wash. (saline silty loam), and Houston, Tex. (saline silty clay). The native soils included a low organic, moderately permeable semiarid soil (Perkins loam) obtained from arable land near Hemet, Cal., and a highly organic upland sand loam soil, obtained from a temperate coniferous forest near Lake Arrowhead, Cal. The primary leaching solution wad distilled water (rainwater leach), which was added in pulses to simulate alternate wet-dry cycling prevalent in most land containment areas. Other leaching fluids consisted of distilled water acidified to pH 4.5 with sulfur dioxide (acid rainfall leach), hard water buffered with bicarbonate (alkaline groundwater simulation), and leaching fluids containing high organic contents (a leachate obtained from a solid waste landfill site and a characterized fulvic acid solution, to represent conditions at a solid waste disposal site or in a marsh or swamp environment). Leaching tests were performed for periods of 3, 6, and 9 months for different columns. Parameters analyzed included major elements, trace metals, PCB's, chlorinated pesticides, nutrients (nitrogen and phosphorus compounds, organic carbon), chloride, sulfides, and various gross physiochemical parameters (alkalinity, Eh, pH, conductivity). The results from this study indicate that leachate quality may be governed by both the dredged material and underlying soil. The leachate (interstitial water) from the dredged material tended to show slight time-dependent increases in pH, Eh, total organic carbon, alkalinity, and manganese....