U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993, Water-Resources Investigations Report 94-4015

Heavy-Metal Transport in a Sand and Gravel Aquifer with Variable Chemical Conditions, Cape Cod, Massachusetts

Abstract

An overview is presented of a field-based research program that is examining the significance of chemical speciation and variable aquifer chemistry on the transport of toxic metals in ground water. Natural-gradient tracer tests and laboratory experiments with subsurface materials have been used to identify the most important chemical reactions that influence the transport of chromium(VI) and metal-ethylenediaminetetra-acetic acid (EDTA) complexes in the aquifer at the Cape Cod Toxic-Substances Hydrology Research site. The field experiments are being conducted in an uncontaminated, recharge zone and a mildly reducing, sewage-contaminated zone of the shallow, sand and gravel aquifer. The results of several years of research at the site have been used to design a large-scale tracer test at the site (begun in April 1993) involving eight tracers (bromide, chromium, zinc, copper, lead, nickel, EDTA, and potassium). The new experiment will be the most complex and detailed investigation of multispecies, multireaction transport ever conducted in the field. The pertinent results of previous small-scale tracer tests are reviewed, and the objectives and expected results of the new tracer test are discussed.