PhD Proposal: Oindrila Ghosh

Oindrila Ghosh, PhD Student

Advisor: 

Dr. Upal Ghosh

Title:

Optimization of Passive Sampling for surface-water and sediment porewater measurements. 

Abstract:

Stable chemical structures of hydrophobic organic contaminants (HOCs) like polychlorinated biphenyls (PCBs) are difficult to break down. These contaminants thus, persist in the environment for decades and due to strong bioaccumulation potential, pose threats to human and ecological health even at trace concentrations of ng-pg/L. Polymeric passive sampling allows measurement of the freely dissolved concentrations that control bioavailability of HOCs. Unlike grab sampling that provides a snapshot of the concentration at one point in time, passive samplers provide a time-integrated measurement of concentration. The true nature of this time-integrative property of equilibrium passive samplers under fluctuating ambient concentration is not well understood. Aim 1 of this research is to develop the theoretical and modeling framework of exchange kinetics in passive samplers to understand the impact of the timing of fluctuations, hydrophobicity of the analyte, and sampler physical characteristics on the final measurement. The work will allow improved interpretation of a time-integrated measurement provided by a passive sampler. In Aim 2, I plan to use the modeling framework developed above to explore the feasibility of designing a polymer that can perform short-term measurements.  Such measurements are often critical in assessing inputs from episodic events for which passive sampling is currently not available.  Since the water boundary layer and the membrane thickness are major rate-limiting zones for mass transfer in passive samplers, I will explore the opportunity of manipulating these through the design of the sampler and achieve faster equilibration. This work will involve a combination of mathematical modeling and physical modeling to allow testing under a range of water velocities in the laboratory. Aim 3 of this research is to optimize sampling methods for sediment porewater measurements, by introducing vibration on the passive sampling platform with the vision of faster achievement of equilibrium by expediting mass transfer. A scaled-up version of an early prototype from previous research will be optimized and tested for robustness in field applications and better performance for sampling more hydrophobic PCBs and Dioxins. This research will develop the mathematical framework to describe mass transfer in time-integrated passive sampling and apply the model to optimize long- and short-term deployments in the field for pore-water and surface water measurements.

Agenda:

• 8:45 am: Meeting room will open  
• 9:00 am: 45 min presentation will be open to the public with Q&A.
• Followed by a closed session with the committee and PhD Student.