Honors Theses

Date of Award

2019

Document Type

Undergraduate Thesis

Department

Chemistry and Biochemistry

First Advisor

James Cizdziel

Relational Format

Dissertation/Thesis

Abstract

This research focuses on two studies: a development towards a DART-mass spectral database for 3D-printed firearm polymers, and a test for airborne mercury concentrations at three lakes in North Mississippi. With the relatively recent developments in 3D-printing technology, 3D-printed firearms have become increasingly prevalent as they have become more accessible to the public. Despite its growing popularity, little research has been done regarding the forensic analysis of evidence from 3D-printed firearms. Using DART-MS in conjunction with thermal desorption techniques, we obtained the mass spectra for 50 different commercially available 3D-printing polymers. Chemometric analysis was done to account for the high variance among DART-MS data for polymer samples. By generating multiple principal component analysis plots, the high dimensionality of the DART-MS data was greatly reduced, allowing us to successfully classify the samples by polymer type. Samples were then further classified by manufacturer and by color. By doing this, we have made the first contribution toward a database of polymer spectra, which can be used to help identify and find the source of unknown 3D-printed firearm-related crime evidence. The second portion of this research was done in response to an advisory from the Mississippi State Department of Health suggesting that fish in Grenada and Enid Lakes held high concentrations of mercury, a toxic heavy metal. In this study, we measured the atmospheric mercury concentrations at Grenada, Enid, and Sardis Lakes using Mercury Passive Air Samplers, each containing an activated carbon powder to adsorb gaseous mercury. After deploying the samplers and allowing atmospheric mercury to accumulate over time, the samplers were taken back to the lab, where the mercury concentration for each sample was obtained using a Direct Mercury Analyzer. This was done for one-week, two-week, three-week, and four-week intervals. Though we hypothesized that point sources near Grenada Lake would result in it having the highest atmospheric mercury concentrations, with Enid Lake having the second highest and Sardis Lake having the lowest, our results suggested the opposite. While we suspect this to have been a result of the proximity to industrial areas north of the lakes, the reasons remain unclear, and further research is needed.

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