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The East-West Divide
<br /> Regional Product Use Translates to Large Differences in PAH Concentrations
<br /> Does product type really matter?PAH concentra- Seattle
<br /> tions in the coal-tar-based sealcoat product are about n -
<br /> 1,000 times higher than in the asphalt-based product Portland 3` 'o,• Minneapolis%A` \,'"
<br /> (more than 50,000 milligrams per kilogram [mg/kg] co , '',3,400 1,300
<br /> in coal-tar-based products and 50 mg/kg in asphalt- Chicago 0 Detroit New Haven
<br /> based products [City of Austin, 2005]). Anecdotal Salt Lake City v 3,20Q ' 3,200
<br /> reports, such as Web sites, blogs, and comments '' ':� -_ _ =- ,gton,D.C.
<br /> by industry representatives, indicate that the coal- 1 f
<br /> tar-based product is used predominantly east of the
<br /> Austin 2 `:000;,, ,-.;.,,
<br /> Continental Divide and the asphalt-based product is ® ,
<br /> used predominantly west of the Continental Divide.
<br /> During 2007-08, the USGS swept dust from seal-
<br /> coated and unsealcoated parking lots in nine cities Concentrations of PAHs in dust swept from sealed parking lots in
<br /> central and eastern U.S.cities,where coal-tar-based-sealcoat
<br /> across the United States and analyzed the dust for use dominates,were about 1,000 times higher than in western
<br /> PAHs. For six cities in the central and eastern United U.S.cities,where asphalt-based-sealcoat use dominates.
<br /> States,the median PAH concentration in dust from Concentrations shown on the map are the sum of 12 PAHs,in
<br /> sealcoated parking lots was 2,200 mg/kg, about 1,000 milligrams per kilogram(Van Metre and others,2009).
<br /> times higher than in dust from sealcoated parking
<br /> lots in the western United States, where the median AP
<br /> concentration was 2.1 mg/kg. Although both product .,
<br /> types are available nationally,these results confirm
<br /> the regional difference in use patterns (Van Metre and / . 0
<br /> others, 2009).
<br /> "Fingerprinting" Shows that Coal-Tar Sealant is the Largest Source of PAHs to
<br /> Urban Lakes
<br /> PAHs are increasing in urban lakes across the
<br /> United States.To better understand why this might
<br /> be happening,USGS scientists collected sedi-
<br /> gg
<br /> 100 _ Coal-tar-based sealcoat ment cores from 40 lakes in cities from Anchorage,
<br /> 1=0 80 —4-- Vehicle-related sources Alaska, to Orlando, Florida, analyzed the cores for
<br /> 9 --®— Wood combustion
<br /> z Y 60 �— Fuel oil combustion PAHs, and determined the contribution of PAHs from
<br /> Lu w �— Coal combustion i many different sources by using a chemical mass-
<br /> o40 I balance model. The model is based on differences in
<br /> a 20 \ ,� the chemical "fingerprint" of PAHs from each source.
<br /> a J/ ,� Coal-tar-based sealcoat accounted for one-half of all
<br /> o 0 PAHs in the lakes, on average, while vehicle-related
<br /> 1930 1950 1970 1990 2010 sources accounted for about one-fourth. Lakes with
<br /> DATE SEDIMENT DEPOSITED a large contribution of PAHs from sealcoat tended
<br /> to have high PAH concentrations; in many cases, at
<br /> Coal-tar-based sealcoat(orange symbol)is the largest contributor levels that can be harmful to aquatic life. Analysis
<br /> to increasing concentrations of PAHs in Lake Killarney,Orlando, of historical trends in PAH sources to 8 of the 40
<br /> Florida,as determined by chemical fingerprinting.Similar patterns lakes indicates that sealcoat use is the primary cause
<br /> were seen in lakes across the central and eastern United States
<br /> (Van Metre and Mahler,2010). of increases in PAH concentrations since the 1960s.
<br /> Identifying where PAHs are coming from is essential
<br /> for developing environmental management strategies
<br /> (Van Metre and Mahler, 2010).
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