Distribution of PCDDs and PCDFs in Soils Collected from the Denver Front Range - Principal Components Analysis of Diffuse Dioxin Sources (10 pp) |
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Authors: | Email author" target="_blank">Paul?JonesEmail author John?Newsted Gerry?Henningsen John?Slocomb Email author" target="_blank">John?GiesyEmail author |
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Institution: | (1) Paul D. Jones, PhD Zoology Department National Food Safety and Toxicology Center Center for Integrative Toxicology Michigan State University East Lansing Michigan 48824 USA,;(2) John L. Newsted ENTRIX, Inc. 4295 Science Drive Okemos, MI. 48864 USA,;(3) Gerry Henningsen H & H Scientific Services Littleton, CO. 80122 USA,;(4) John Slocomb ENTRIX, Inc. 5252 Westchester, Suite 250 Houston, TX 77005 USA,;(5) Prof. John P. Giesy, Ph.D. Dept. of Zoology Michigan State University East Lansing, MI 48824 USA, |
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Abstract: | Background, Aims and Scope The Rocky Mountain Arsenal (RMA) is a US Army facility located northeast of Denver, Colorado that has been listed on the
National Priorities List (NPL). It is currently being re-mediated under the authority of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA) and the Superfund Amendments and Reauthorization Act of 1986 (SARA). As part
of the remediation activities at RMA, indications were found that a source of polychlorinated dibenzo-p-dioxins (PCDDs) and
polychlorinated dibenzofurans (PCDFs) had existed on the RMA. As a result, investigations were undertaken to assess the possible
nature and extent of any potential sources of PCDDs and PCDFs on the RMA site. In addition, other studies were conducted that
examined PCDD/PCDF contamination in the Denver area. The goal of these studies was to examine nature and extent of PCDD/PCDF
contamination both on the RMA as well as in the surrounding Denver area. The intent of this study was to characterize sources
of dioxins (PCDDs) and dibenzofurans (PCDFs) at low environmental concentrations which might have originated from diffuse
sources in the Denver Colorado area and in particular, the Rocky Mountain Arsenal (RMA) using Principal Component Analysis
(PCA).
Methods Over 200 soil samples were collected from the RMA and the Denver area. From the RMA, soil was collected as part of three
studies that included a (1) random site-wide sampling of the RMA, (2) soils from the Western Tier Parcel (WTP), and (3) soils
from Historic Use areas. Denver area soil samples were collected from five different land use categories: Residential, Agricultural,
Open Space, Commercial, and Industrial. PCA was conducted on concentrations of 17 2,3,7,8-substuituted PCDD and PCDF congeners
in 220 soil samples collected from the RMA and the Denver Front Range region.
Results and Discussion PCA demonstrated the presence of possible minor sources of dioxins on the RMA. Current remediation efforts on RMA will result
in the removal of these sources. Samples from the RMA were identified by the presence of a congener profile containing higher
chlorinated PCDFs while the Denver Front Range areas were characterized by the presence of higher chlorinated PCDD congeners.
The presence of a PCDF signature for the RMA samples does not necessarily indicate a major source of these contaminants on-site.
Indeed, the relatively diffuse nature of the sample clusters would argue strongly against the presence of a single large source.
Instead, the predominance of the PCDF congeners probably indicates the mixed industrial activities that took place on and
near the site.
Conclusion PCA results indicate that PCDD/PCDF profiles in soils collected from the RMA differed from those collected from the outlying
Denver areas but that a major source of these contaminants was not present. Rather, the diffuse nature of sample clusters
from the PCA indicated that the congener profile of RMA samples was most likely a result of the mixed industrial activities
that historically have taken place on and near the site. PCA also indicated that many of the 'open area' (peripheral site-wide)
RMA soils samples did not differ from Denver are reference congener profiles. This finding was also true for samples collected
from the WTP that were essentially indistinguishable from Off-RMA reference samples. In addition, total TEQ concentrations
in soils collected from WTP were similar to those measured in soils collected from the Denver Front Range areas indicating
that lack of a major source of PCDD/PCDF within the WTP zones of the RMA.
Recommendation and Outlook Analytical as well as statistical results of the soil congener data indicate that the WTP soils are indistinguishable from
soils collected from non-industrial areas in the Denver area. This finding would support the recent 'de-listing' of the WTP
from the other RMA areas and its' transfer to other authorities in the Denver area. |
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Keywords: | superfund amendments and reauthorization act (SARA) distribution of PCDDs and PCDFs in soils polychlorinated dibenzofurans (PCDFs) polychlorinated dibenzo-p-dioxins (PCDDs) national priorities list (NPL) diffuse dioxin principal component analysis (PCA) soils Rocky Mountain Arsenal (RMA) |
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