Great Lakes Air Deposition Program Sponsored Projects
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Project Title: Measurement and Modeling of PBT Transport in Lake Superior

Synopsis: This project will continue the development and application of novel methods for the direct determination of pollutant deposition to the Great Lakes. The micrometeorological methods used collect air samples at multiple heights above the lakes over short timeframes and use temperature differences to determine the rate of pollutant movement to or from the lake. Methods will be fully developed for polybrominated diphenyl ethers, polychlorinated biphenyls, and other chlorinated organic compounds. Preliminary results have indicated that such direct measurements of deposition can differ by 1-2 orders of magnitude from deposition rates calculated from on-shore concentration measurements. These measurements will be used to inform creation of one-dimensional models of pollutant deposition to the lakes. These new methods will be applied to better understand the physical-chemical processes involved in deposition and how parameters such as increasing fetch across the lakes affect deposition rates.

Chemicals Studied: The measurement techniques will be applied to polybrominated diphenyl ethers (PBDEs), a class of currently-used flame retardant chemicals that have caused concern recently due to rapidly increasing concentrations in the Great Lakes environment. In addition, polychlorinated biphenyls (PCBs), a class of chemicals banned from production in North America but still present in the Great Lakes at levels above risk thresholds, will be examined, as will other chlorinated organic compounds.

Geographic Areas: The measurements will take place largely aboard a research vessel on Lakes Superior. Some shore-based measurements will be taken as well, also near Lake Superior.

Project Duration: The project will begin in the Spring of 2006 and extend through the Spring of 2008.

Methods Used: Sampling will be done with newly-developed multi-capillary collection devices (MCCDs). The MCCDs consist of fused silica columns and allow for faster sample collection and improve sample analysis. With the low sampling times achieved by the MCCDs, a direct deposition measurement technique can be used in which concentrations are measured at two heights above the lake and sensible heat flux is used as a surrogate to determine the rate of contaminant transfer. Using these methods, the uncertainty in estimates of deposition are decreased by more than an order of magnitude. Preliminary results show differences in calculated depositions compared to conventional methods of up to or more than an order of magnitude.

Potential Results and Implications: The improved accuracy in deposition estimates obtained by these methods have significant ramifications for further scientific or policy development efforts that depend upon estimates of contaminant deposition to the lake. Improved certainty regarding the amount of chemicals entering the lakes from the atmosphere will significantly increase the ability to establish accurate mass balance models for the lakes, to estimate recovery trajectories of the lakes from chemical impairments, and other efforts.

Project Contact:
Judith Perlinger, Ph.D.
Michigan Technological University
Phone: (906)487-3641
Email: jperl@mtu.edu