Mineral precipitation and dissolution at two slag-disposal sites in northwestern Indiana, USA

Environmental Geology
By:  and 



Slag is a ubiquitous byproduct of the iron- and steel-refining industries. In northwestern Indiana and northeastern Illinois, slag has been deposited over more than 52 km2 of land surface. Despite the widespread use of slag for fill and construction purposes, little is known about its chemical effects on the environment. Two slagdisposal sites were examined in northwestern Indiana where slag was deposited over the native glacial deposits. At a third site, where slag was not present, background conditions were defined. Samples were collected from cores and drill cuttings and described with scanning electron microscopy and electron microprobe analysis. Ground-water samples were collected and used to assess thermodynamic equilibria between authigenic minerals and existing conditions. Differences in the mineralogy at background and slag-affected sites were apparent. Calcite, dolomite, gypsum, iron oxides, and clay minerals were abundant in native sediments immediately beneath the slag. Mineral features indicated that these minerals precipitated rapidly from slag drainage and co-precipitated minor amounts of non-calcium metals and trace elements. Quartz fragments immediately beneath the slag showed extensive pitting that was not apparent in sediments from the background site, indicating chemical weathering by the hyperalkaline slag drainage. The environmental impacts of slag-related mineral precipitation include disruption of natural ground-water flow patterns and bed-sediment armoring in adjacent surface-water systems. Dissolution of native quartz by the hyperalkaline drainage may cause instability in structures situated over slag fill or in roadways comprised of slag aggregates.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Mineral precipitation and dissolution at two slag-disposal sites in northwestern Indiana, USA
Series title Environmental Geology
DOI 10.1007/s00254-003-0875-1
Volume 45
Issue 2
Year Published 2003
Language English
Publisher Springer
Contributing office(s) Indiana Water Science Center, Toxic Substances Hydrology Program
Description 10 p.
First page 252
Last page 261
Country United States
State Indiana
County Lake, Porter, LaPorte
City Gary
Other Geospatial Indiana Dunes National Lakeshore
Online Only (Y/N) N
Additional Online Files (Y/N) N
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