Section Ten
PHYSICAL-CHEMICAL:
METALS PRESENCE, FATE, AND IMPACT
38    LEACHING PROCESS FOR REMOVAL OF HEAVY
METALS IN SOIL
Alton Day Stone, Senior Environmental Scientist
Pennoni Associates Inc.
Hopkinton, Massachusetts 01748
James C. O'Shaughnessy, Professor
Department of Civil & Environmental Engineering
Worcester Polytechnic Institute
Worcester, Massachusetts 01609
ABSTRACT
This paper presents the results of bench-scale experiments conducted to evaluate heavy metals
sorption and desorption phenomena for soils common to New England, and the suitability of soil
leaching (flushing) for in-situ remediation of soils contaminated with heavy metals. The results
of the investigations indicated that the soil physical parameters mass fines/unit mass soil, bulk
density, coefficient of uniformity, and coefficient of concavity were not good predictors of soil
sorptive or desorption capacity.
INTRODUCTION
Environmental contamination by heavy metals is relatively common. Lead, often in high concentrations is ubiquitous in urban soils due to the past use of leaded gasolines and paints. Formerly, arsenic was widely used as a general pesticide. The majority of sites contaminated with
concentrated heavy metals are associated with industrial processes such as mining, smelting,
plating, coating, machining and manufacturing, and locations where disposal of associated
wastes has occurred. The Environmental Protection Agency (EPA)1 estimates that approximately
10% of the Superfund sites involve heavy metal contamination. Concentration ranges of metals
reported in soil at EPA sites are included in Table I. In recognition of the hazard posed by exposures to heavy metals, federal and state agencies have established regulations to limit environmental contamination and reduce human and environmental exposures. The EPA currently lists
13 heavy metals as "priority pollutants" under the Comprehensive Environmental Recovery,
Compensation and Liability Act (CERCLA) commonly known as "Superfund": antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium,
zinc. Each of these metals, except barium and copper, is listed as a "hazardous material" in the
Massachusetts Contingency Plan (MCP, 310 CMR 40.0000), promulgated under M.G.L. c. 21e
the "Oil and Hazardous Materials Act."
Industrial solid wastes which contain sufficient leachable amounts of certain metals (Table I),
as determined by the Toxicity Characteristic Leaching Procedure (TCLP) chemical analytical
procedure, are listed "hazardous wastes" which are regulated under the Resource Conservation
and Recovery Act (RCRA). The TCLP extraction (leaching) analysis is intended to duplicate
leaching of the waste by rainwater in the open environment. If the extract contains a metal concentration above an established criteria, the waste exhibits the characteristic of "toxicity," and is
classified as hazardous. These wastes are considered to be potential sources of environmental
52nd Purdue Industrial Waste Conference Proceedings. 1997. Ann Arbor Press. Chelsea, Michigan 48118. Printed in
U.S.A.
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