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Project Title: Using passive samplers to detect legacy and emerging organic
PBTs in Lake Superior, and their air-water exchange
Chemicals Studied: PAHs, PCBs, organochlorine pesticides, PBDEs, new chemicals of concern.
Geographic Areas: Lake Superior
Project Start Date: August 2010
Project Status: Completed
The purpose of this project was to enhance the 2011 Coordinated Science and Monitoring Initiative intensive field program in the Lake Superior watershed by deploying passive polyethylene samplers in the atmosphere and surface water along nine coastal stations and mid-lake to: (i) uniquely enhance measurements of the spatial variability of atmospheric concentrations of persistent bioaccumulative toxics around the lake; (ii) assess whether Lake Superior is volatilizing or absorbing gas-phase PBTs to derive fluxes and loading to the lake; and (iii) screen for halogenated emerging contaminants of concern across the lake.
A total of 60 individual passive polyethylene samplers were deployed in surface water and surface air at 16 sites around Lake Superior (6 coastal US, 3 open water/air and 7 coastal Canadian sites) and analyzed for the: 22 polycyclic aromatic hydrocarbons, 25 legacy organochlorine pesticides, 18 polychlorinated biphenyl congeners, 12 polybrominated diphenylethers and screened for emerging persistent, bioaccumulative and toxic compounds.
PAHs: In general, net deposition was observed for Welcome Isle, Sault St Marie, Pt Aux Pins, Ontonagon and Duluth, while evaporation was more prevalent for the open lake sites, Sturgeon Bay, Marquette and Michipicoten Bay. For pyrene, net deposition was observed for most coastal sites, with net evaporation for the open lake sites. For phenanthrene, net deposition was observed for all southern coastal sites, with only few sites displaying net evaporation (Sturgeon Bay, open Lake site 113 and eastern lake site 23).
Organochlorine pesticides (OCPs): Most OCPs displayed net evaporation, particularly a-HCH, HCB, heptachlor-epoxide, trans-chlordane and p,p'-DDE. Cis-chlordane displayed mostly net deposition, same for o,p'-DDT/p,p'-DDD. Endosulfan was the only pesticide for which net deposition was observed, either because it was present only in the atmosphere and below detection limit in the water (n=20), or because the gradient was strongly favoring net deposition
PCBs: The majority of PCBs appear to be evaporating or in equilibrium in Lake Superior, with a few notable exceptions. CB206 has a high air-water ratio, indicating deposition, however, CB206 is also present at some of the lowest concentrations in both air and water samples. Ontonagon and Marquette appear to have the highest deposition gradients, especially for CB18, 28, 44, 52, 105, and 118.
PBDEs: Air-water exchange gradients of the freely dissolved BDE congeners were generally favoring net deposition and increased with increasing molecular weight of the BDEs. For BDE 47 and higher, even smallest gradients were still favoring net deposition.
Emerging PBTs: This study was not able to confirm the presence of the following in any of the samples: bromopentafluorobenzene; 3,5-dichlorotrifluoropyridine; 3,4-dichlorobenzotrifluoride; pentachloropyridine; 2,4,6-tritertbutylphenol; 1,1-bis-dimethylphenylethane; dibutyl chlorendate; antidechlorane plus.
Publications supported by this award:
1. Lohmann, R. A critical review of low-density polyethylene's partitioning and diffusion coefficients for trace organic contaminants and implications for its use as a passive sampler, Environmental Science & Technology 2012, 46, 606-618.
2. Khairy and Lohmann, Sources and Seasonal Trends of Vapor Phase PAHs in a Major Developing Urban City Using Passive Polyethylene Air Samplers, Environmental Science & Technology 2012, 46, 3990-3998.
3. Khairy, M.A. and Lohmann, R. Field Calibration of Polyethylene Passive Air Samplers for Organochlorine Pesticides, Environmental Science & Technology, submitted August 2012.
Preliminary project results have been presented during the 2012 GLAD webinar series.
Rainer Lohmann, Ph.D.
Graduate School of Oceanography, University of Rhode Island
Phone: (401) 874-6612