Walkaway Points

1.  HR-ICP-MS data indicate that road sediment samples investigated show extensive pollution consistent with being derived from the steel plant as well as likely traffic sources. Results are consistent overall with the findings of Dietrich et al. (2019). Cr and V are interpreted to be largely from steel pollution, whereas Pb and Zn are likely from traffic or other sources. Pollution is extensive and quantitative indices will be used to make refined data interpretations. 

2. TEM investigation indicates that technogenic spherules are common, if not prolific in road sediment with an average diameter of 0.23 micrometers. These particles appear to be enriched in siderophile elements that are known to be or may be toxic.  The size distribution of the population and the chemical elements observed combine to open questions of concern for human and environmental health broadly. 

3. XRF data overestimates Pb concentrations by one to two orders of magnitude generally. Pb concentrations are still of concern in several samples and are generally consistent with SEM—EDS data observed in Dietrich et al. (2019).  XRF overestimates Cu and Zn, and thus XRF data, and may overestimate these elements in general in similar matrixes. 

4. This investigation provides additional constraints on the nature of pollution in Gary, Indiana and may be useful for health professionals to assess pulmonary and other diseases in the region.  This investigation opens additional questions regarding the nature and distribution of metal pollution throughout the region. 

Future Work

High resolution inductively coupled plasma mass spectroscopy (HR-ICP-MS) has yielded data indicating variability between samples, which will be investigated using statistical analysis. Variability of metals will be accounted for in part by supporting microscopy work looking for Pb, Zn, and Cu pollutant particles, and USEPA total release inventories (TRIs) inventories will be explored.  Pollution will be assessed using multiple quantitative indices. Additionally, the HR-ICP-MS data will be compared to Dietrich’s initial data in a more detailed and thorough manner. The spatial relationships of metal concentrations of the samples will be explored using GIS approaches including inverted weight distance. If warranted additional samples will be collected to test or verify spatial trends or predictions.