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Abstract
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 nano spherules 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.
Introduction
Introduction
Lead (Pb) is incredibly harmful to humans when ingested because of its classification as a toxic metal and a neurotoxin (ATSDR,2020). For children, it is commonly asserted that there are no safe levels of Pb exposure because even relatively low-level Pb exposure in the environment has proven to be detrimental (e.g., Lanphear et al., 2005; Grandjean, 2010; Grandjean and Landrigan, 2014; Zheng et al., 2023). It can affect almost every organ in the body and has no confirmed safe level of exposure. Part of the problem is that it’s known that Pb is present, but the concentrations, nature, and distribution of Pb in particles have not been quantified. Road sediment is an under-utilized medium to analyze pollutants and elemental concentrations to determine the effects of certain activities within an area and can be used to ascertain the extent to which Pb (and other harmful pollutants) has permeated an environment. Particulate matter is also a major pollution concern as they can introduce toxic metals into the respiratory system (USEPA, 2024). Technogenic spherules are a particular concern. Because of their size, nanospherules (technogenic spherules < 0.5 micrometers) have a high probability of being ingested and absorbed through the lungs (e.g., Plumlee, 2006; USEPA 2024). This can have significant drawbacks to human health depending on the elemental composition of the particles. Dietrich et al. (2019) investigated road sediment in Gary Indiana to assess the general nature of pollution, however only limited information regarding the nature of lead particles was presented and technogenic spherules were investigated by scanning electron microscopy only. This poster presents the first concentrations of lead and new characterization of nanospherules from Gary, IN road sediment. Dietrich et. Al, (2019) analyzed several metals with ICP-MS but did not determine concentrations of Pb. However, data in their paper shows Pb is clearly present within the samples based on previous scanning electron microscopy (SEM) / energy dispersive X-ray spectroscopy (EDS) (FIGURE X). Limited X-ray fluorescence (XRF) data of the samples indicates that lead levels occur at concentrations below detection to 5,375 ppm, however XRF data can be prone to error. Thus the concentrations, nature, and distribution Pb within Gary road sediment is an open question. Furthermore, SEM/EDS data from Dietrich et al. (2019) indicates that microspherule and nanospherule technogenic particles are present in the road sediment, but the nature of chemical composition and size constraints on nanospherule particles was not investigated. Thus there are open questions regarding the nature and composition of nanospherules in Gary road sediment.
Geologic Setting
Geologic Setting
Gary, IN is located in the northwestern corner of Indiana in Lake County (far left reference map below) near Gary Works steel mill and is ~1.5 miles from the shore of Lake Michigan. It has a population of ~67,199 as of 2024. The steel mill has been in operation since 1908 and is the largest integrated mill in North America. Steel mills are a source of metal pollution, which means the continued operation of a large steel mill in a city will drastically affect the environment and the health of its citizens (USEPA TRI, 2025).
The image immediately above is a historic photograph from Wikipedia from 1973 showing the nature of pollution from the mill. Such extensive pollution likely persists to some degree in the surrounding environment and can be mixed and re-introduced in road sediment.
The image above shows the sample map of road sediment from Dietrich et al (2019), the same numbers were used for this study.
Methods
Methods
Samples:
Samples:
Materials used were archived and are from Dietrich et al. (2019) to enable direct comparisons of data. Samples used were unmodified sediment samples. Powdered samples were milled using a SPEX 8000 mini mill with a tungsten carbide ball and vial.
X-ray Fluorescence (XRF):
X-ray Fluorescence (XRF):
Samples were prepared for XRF by first milling sands in a SPEX 8000 mini mill using a tungsten carbide ball and vial. Approximately 1.00–1.10 g of powder was used for loss on ignition (LOI) calculations at 950 °C. Sample powders were then prepared by first mixing 0.50 g of sample with 7.75 g of lithium borate bromide flux and fused pellets were produced. X-ray fluorescence analyses were performed using a Rigaku Supermini 200 wavelength-dispersive XRF spectrometer at the University of Cincinnati. More methods details can be found in Oglesbee et al. (2020). The XRF data is a data set acquired by Krekeler in the Summer of 2019.
High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS):
High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS):
Samples were prepared for HR-ICP-MS using in house methods available on request and similar to that used by Wudke et al. (2024) Trace elements were determined by solution High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS); Table 2 using a Nu Instruments Attom ES in the Department of Geology and Environmental
Transmission Electron Microscopy (TEM):
Transmission Electron Microscopy (TEM):
Samples were prepared from ethanol suspensions as simple grain mounts on holey carbon gold copper grids. For transmission electron microscopy (TEM) investigation data was acquired at the University of Cincinnati’s Advanced Materials Characterization Center using a Talos F200i (Thermo Fisher) instrument equipped with a 200 kV field emission gun. The instrument was operated in scanning transmission electron microscopy (STEM) mode and high-angle annular dark-field (HAADF), and was equipped with EDS. STEM elemental mapping shown was acquired using a JEOL 2100 transmission electron microscope at Miami University.
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