Research — Dr. Imari Walker-Franklin

Research Objectives at RTI International

Imari Walker-Franklin is a Research Chemist with RTI’s Discovery Science Division. As an environmental engineer, she contributes to the development of suspect screening, non-targeted chemical analysis and other research interests of the Analytical Sciences group, including understanding the effects of PFAS chemicals. Dr. Walker-Franklin is a subject matter expert with practical experience with operating and maintaining liquid chromography with tandem/high-resolution accurate mass spectrometry systems (LC-MS/MS and LC-HRAMS). Dr. Walker-Franklin’s research interests include microplastics, environmental analytical chemistry, environmental justice, and non-target analysis workflow development.

Expertise

Environmental Chemistry

Mass Spectrometry
Microplastic Analysis
Data Analysis
Science Communication

Imari’s PhD Dissertation

The release, transformation, and effects of polymer-associated chemicals in the aquatic environment [Full Dissertation Here]

Question 1: What is the leaching behavior of polymer associated chemicals (PACs) within various simulated aqueous environments?

Findings:

Processes that weather epoxy and polycarbonate polymers exacerbate the release of phenolic additives.
- Temperature, pH, UV light, microplastic formation
Carbon nanotubes decrease the release of these compounds by potentially acting as a secondary sorbent.
This study has implications for understanding other monomeric additive release.
[Read the article here.]

Question 2: How are polymer associated chemicals (PACs) chemically transformed in simulated aqueous environments?

Findings:

Polypropylene microplastics leached more PACs into water than polyurethane
UV inhibitors, monomers, surfactants and degradation products were important leachable chemicals in PU and PP microplastics
- Some compounds are likely UV-labile or transformed by UV exposure
Loss of polymer associated chemicals over time in the mesocosm water may indicate degradation or removal by sorption
Non-targeted analysis is a powerful tool to structurally annotate and identify PACs and their transformation products

Question 3: To what extent do released PACs contribute to the estrogenic activity in a leachate?

Findings:

Fifteen extractable and leachable polymer associated chemicals were structurally annotated and functioned as catalysts, colorants, intermediates, antioxidants, plasticizers, and lubricants.
Further structural annotation and chemical classification highlights organosulfur-based compounds as a dominant chemical class released from PS foams.
Mixtures of phenols and phthalates representing the chemical composition of the PE bag after simulated seabird digestion demonstrated significant estrogenic response that were not significantly different from the biological activity of the gastric digest.