Date of Award

Fall 2009

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Kevin Gardner

Abstract

Contaminated sediments are a significant problem that has adverse effects on human, animal and plant health. Heavy metal contamination, with dissolved metals being the most bioavailable form, has been occurring since man first started living in communities around water bodies. Pore water provides contaminated metals a medium for transport from the sediment to the water body. Determining the toxic metal concentration in pore water is essential to any remediation plan. In-situ dialysis samplers or peepers were investigated in this thesis as a tool for evaluating metal contamination in sediments. Peeper performance was compared to direct suction samplers. Both samplers were evaluated for effectiveness in determining geotextile reactive cap efficacy.

The industry standard, as defined by Richard Carignan from the University of Quebec at Montreal, is to eliminate oxygen in peeper material, preparation and sample removal. Studies preformed by Carignan indicated oxygen caused redox sensitive metals to precipitate, resulting in lower concentrations. Oxygen in peeper material resulted in an orange tint on the peeper and membrane. It should be noted that the majority of his studies were performed at the bottom of freshwater lakes. Deoxygenating peepers is a time consuming and complicated operation. The theory evaluated in this thesis is that oxygen effects are mitigated during peeper equilibration. Equilibration time allows oxygen to be dissipated into the surrounding sediment or consumed by microbial activity.

The effects of oxygen introduced during preparation were evaluated by comparing peepers assembled with makeup water purged with air and nitrogen. These effects were examined in field studies in the intertidal zone and in tub in laboratory studies. Sample removal compared filtering with unfiltered samples to evaluate whether colloidal phases could form in the chambers and affect measured concentrations. Samples removed with the use of a nitrogen purged glove box were compared with the standard removal procedure. Analysis of redox sensitive metals, anions and the selected heavy metals indicated oxygen was not a problem in the preparation or sample removal. Results indicated orange tint was dependent on sediment type and not peeper material.

The push point sampling device yields a sample with a minimum of effort and training but it is only effective in loose, sandy sediment. The prevailing evidence is that push point yields a higher concentration than those obtained with peepers. The difference is not so great that it does not preclude using the devices together as part of the overall sampling plan.

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