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hours at 22 0C at a speed of 29 rpm. After mixing, the jar was allowed to settle for
5 min. An aqueous sample was then extracted by vacuum filtering through a
0.45-Lm glass fiber filter. The extract was acidified below pH 2 for preservation
using nitric acid.
The aqueous samples were analyzed within 24 hrs using inductively
coupled plasma mass spectrometry (ICP-MS) at the Soil and Plant Laboratory at
the University of Wisconsin-Madison.
3.2.2 Total Elemental Analyses
3.2.2.1 Inorganic Analyses
An acid digestion was conducted on each foundry sand following USEPA
Method 3051 to measure the total concentration of metals. A 0.5-g sample of
foundry sand was digested in 10 mL of concentrated nitric acid for 10 min using a
microwave oven. Fluorocarbon digestion vessels were used. Calibration of the
microwave equipment is described in Appendix A.
Groups of six vessels were evenly located on the turntable in the
microwave oven. When less than six vessels were used for digestion, the
remaining vessels were filled with nitric acid to ensure that the energy delivered
was similar to that applied when six specimens were digested. The vessels were
irridated at 574 W for 10 m.in
Concentrations of heavy metals in the digestions were measured by
atomic adsorption using a Varian® SpectrAA 800 following USEPA Method SW