41 Biogeochemical Cycling of Elements at the Earth’s Surface Across Space and Time (Posters)

Friday, 21 March 2025
1:00 PM - 5:00 PM
Shenandoah ABC

ANALYSIS OF ROAD SEDIMENTS FROM GARY, INDIANA: FOCUS ON LEAD CONCENTRATIONS AND OTHER PARTICULATES AND POLLUTANTS

Paper number: 41-10
Program: Theme Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

Gary, Indiana is well recognized as a municipality that has an extensive and intensive history of steel manufacturing and associated pollution. Road sediment is an environmental medium which can capture pollution in a given community. It can be used to assess the distribution and concentration of particles within an environment. Although some studies have been done, there is a lack of variability studies of the road sediment in the area. Previous inductively coupled plasma - mass spectrometry (ICP-MS) work has found extensive metal pollution in road sediment in Gary, Indiana and this work has been supported by scanning electron microscopy. Aspects of two pollutants that are not well understood are concentrations of Pb and the nature and occurrence of nanoparticulate spherules. Initial powder X-ray diffraction (XRD) indicates dominant minerals present include quartz, calcite and minor feldspars. Initial X-ray fluorescence (XRF) bulk chemistry data on 11 road sediment samples indicate Pb concentration varies. However, the minimum concentration was determined to be below detection, while the maximum concentration was 5,375 ppm and the average concentration was 2,774 ppm. Other metals of environmental concern were observed, including Cu (600 - 6,623 ppm), Zn (1,233 - 6,354 ppm), As (below detection - 1,431 ppm), and Mo (below detection - 684 ppm). Scanning transmission electron microscopy - energy dispersive spectroscopy mapping (STEM-EDS) indicates nanospherules are present. The average diameter of the spherules is 230 nm (0.23 µm), with a minimum diameter of 52 nm (0.05 µm) and a maximum diameter of 830 nm (0.83 µm). Spherules observed are < 2.5 µm and thus if resuspended in air could pose exposure risk. STEM-EDS mapping indicates that the spherules observed are dominated by iron-oxides and other siderophile elements such as Cr, Ni, and Co occur. Lesser amounts of Zn and Pb are also observed in some spherules. Bulk XRF suggests concentrations that warrant high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) analysis on samples to determine a more precise concentration range and better estimate of variation. Road sediment in Gary, Indiana is of significant concern as an environmental media for human exposure and for fate and transport of Pb and other metals into surface water systems.

Geological Society of America Abstracts with Programs. Vol. 57, No. 2

doi: 10.1130/abs/2025SE-407573

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