SETAC Globe - Environmental Quality Through Science
 
  21 January 2011
Volume 12 Issue 1
 

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PAHs in Sediment: Blame it on the Rain? Session Summary from the SETAC North American 2010 Annual Meeting

Judy Crane (Minnesota Pollution Control Agency), Greg Durell (Battelle); and Alison Watts (University of New Hampshire)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants formed by the incomplete combustion of organic materials, such as wood, oil, and coal, as well as occurring naturally in crude oil and coal. Most of the PAHs present in the environment today come from human activities, and the large variety of potential sources has complicated efforts to control releases of PAHs to the environment. The relative importance of point and nonpoint sources and fluvial and atmospheric transport processes varies greatly spatially and probably between countries. In addition, long-range atmospheric transport of PAHs can occur between regions, countries, and continents, for example from Asia to North America. Due to their low solubility and high partitioning to particulate matter, aquatic sediments are often enriched in PAHs, especially in urban waterways. Scavenging of airborne PAHs by rain, as well as stormwater runoff of urban nonpervious surfaces provide two transport pathways for PAHs to enter aquatic systems. Dry deposition of atmospheric particles and snowmelt runoff also contribute PAHs to aquatic systems. Biotic enrichment or degradation of PAHs in sediment is another factor influencing the fate of PAHs in sediment.

This session at the SETAC North America meeting in Portland, OR was coordinated by the PAH Work Group of the SETAC Sediment Advisory Group (SEDAG). Of particular interest in this session was the use of PAH forensic, as well as statistical and modeling techniques to elucidate sources and distribution patterns of PAHs in sediment and other environmental media. These techniques dovetail with SETAC’s mission by providing better tools for making management decisions on how to effectively address PAH contamination of aquatic sediments and nearshore soils.

The session opened with two talks characterizing the fate and distribution of PAHs in shoreline sediments associated with the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska. David Page (Bowdoin College) discussed the accessibility of remaining subsurface oil residues that he and his collaborators studied, and Gregory Pope (the University of Texas at Austin) presented column studies and modeling results quantitatively explaining low levels of dissolved PAHs at sites where oil is known to persist. Judy Crane (Minnesota Pollution Control Agency) gave two talks showing new PAH data collected on a statewide basis in a random set of Minnesota lakes from different ecoregions, as well as in urban stormwater ponds from three different land uses in a major metropolitan area; PAH source ratio profiles and the U.S. Environmental Protection Agency’s contaminant mass balance model were used to apportion sources of PAHs in surficial sediment samples. David Mauro (META Environmental) gave two presentations. One involved a large soil data set used to differentiate background from manufactured gas plant (MGP)-derived PAH sources, and the other discussed the use of carbon isotope ratios to identify PAHs in urban background soils and sediment. Kirk O’Reilly (Exponent) compared PAH source ratios from a range of sources to PAH ratios in several environmental media samples, including lake and stormwater pond sediments, and concluded that it is difficult to definitively distinguish between them. Jana Klanova (Masaryk University) travelled from the Czech Republic to give a very interesting, comprehensive presentation on the spatial and temporal distribution of PAHs in the Morava River, Czech Republic. Lizanne Meloche (Golder Associates) provided the sole poster for the session, which provided an assessment of the bioavailability of coal-derived and petroleum-derived PAHs in a marine harbor in coastal British Columbia.

The session was well attended and provided stimulating conversations about how to determine sources of PAHs in sediment and soils.  

Authors’ contact information: judy.crane@state.mn.us, durell@battelle.org and Alison.Watts@unh.edu

Please contact Judy Crane at judy.crane@state.mn.us to join the SEDAG PAH Work Group.  General information about SEDAG is available on the SETAC Web page at  http://ww2.setac.org/node/35.  The SEDAG Communities portal is open to all SETAC members and guests who select SEDAG in their SETAC User Profile.  Information on accessing the portal is available at  http://ww2.setac.org/node/156

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