W11 AM Environmental Chemical Forensics|
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 343-344
493 (VAN-1117-822607) Parking lot sealcoat: an unrecognized source of urban PAHs.
Start time: 8:00 AM
Van Metre, P1, Mahler, B1, 1 U.S. Geological Survey, Austin, Texas, USA
Polycyclic aromatic hydrocarbons (PAHs) are a ubiquitous contaminant in urban environments and are increasing in concentration in a majority of urban lakes sampled by the USGS National Water-Quality Assessment Program. Although numerous sources of PAHs to urban runoff have been identified, their relative importance remains uncertain. We show that a previously unidentified source of PAHs in urban environments, parking lot sealcoat, might dominate loading of PAHs to urban water bodies in the United States. Particles in runoff from six parking lots with coal-tar emulsion sealcoat had a mean concentration of PAHs of 3,500 mg/kg, 65 times higher than the mean concentration from four unsealed asphalt and cement lots. Contaminant yields projected to the watershed scale for four urban watersheds indicate that runoff from sealed parking lots could account for the major part of PAH loads in streams. Diagnostic ratios of individual PAHs indicate similar sources for particles from coal-tar emulsion sealed lots and suspended sediment from the four urban streams. PAH ratios in sediment cores from lakes undergoing rapid urbanization and coincident increases in PAH concentrations also indicate sealcoat as an important source of PAHs.
494 (BOC-1117-813031) Fingerprinting of polycyclic aromatic hydrocarbons in environmental samples, a weight of evidence approach.
Start time: 8:20 AM
Bock, M1, Barber, T2, 1 ARCADIS, Portland, ME, USA2 ENVIRON, Burton, OH, USA
Polycyclic aromatic compounds (PAHs) are ubiquitous in urban settings as a result of their presence in petroleum hydrocarbons and their formation during the combustion of organic materials. Although thousands of different PAHs exist, in most environmental investigations only the 16 priority pollutant PAHs are quantified. Methods such as high resolution gas chromatography mass spectrometry analysis (HR GCMS), quantify many more PAHs, including parent and alkylated isomers. Many of these additional PAHs are resistant to weathering and are present in proportions diagnostic of the original source or alternatively non-point source urban background. Forensic analysis or "fingerprinting" can be used to differentiate multiple potential sources of PAHs in environmental samples (e.g., urban runoff, manufactured gas plant residues, lubricating oils, fuel oils). Differentiating PAH sources requires a mixture of graphical and statistical methods including: simple comparisons of the total priority pollutant or benzo[a]pyrene equivalent concentrations, the PAH composition, an examination of the levels of alkylation of the homologue groups, correlation analysis, double-ratio plots, hierarchal tree clustering analysis, and principal components analysis (PCA). The valid application of some these techniques requires careful normalization of the data, for example the use of the proportion of the total concentration rather than the raw concentration of individual isomers. This paper describes the application and interpretation of multiple techniques using a weight of evidence approach. The weighting is based on the power of the various lines of evidence to resolved differences in the PAH composition. If there is general concordance among multiple lines of evidence then there is a high confidence in the determination of sources. We will present cases studies illustrating how the results of a weight of evidence evaluation can be used differential multiple sources of PAHs and used to support environmental management decisions.
495 (BOE-1118-031311) Determining the Sources of Polycyclic Aromatic Hydrocarbons in the Hylebos Waterway.
Start time: 8:40 AM
Boehm, Paul1, Stout, Scott2, Wyatt, Glen3, 1 Exponent, Inc, Maynard, MA, USA2 NewFields, LLC, Norwell, MA, USA3 Weyerhaeuser Company, Federal Way, WA, USA
One of the drivers for cleanup of sediment contamination in the Hylebos Waterway, Commencement Bay, WA is the presence of polycyclic aromatic hydrocarbons (PAHs) at levels triggering environmental concern. In any multiuse, urban, waterway contaminant sources have numerous origins - both point sources from specific industrial properties, and non-point sources from urban runoff and atmospheric fallout. Potential source types are both petrogenic (petroleum sources) and pyrogenic (high temperature combustion-derived). Our investigation focused on one segment of the Waterway, the "Turning Basin" to determine the nature and specific source(s) of the PAHs in sediments. The major focus of the investigation were sediments from a contaminated ditch adjacent to several properties, which in turn represented a major potential pathway of PAHs to the Waterway. Other areas of foci were the shoreline of the Waterway; a log sort yard bordering on the Waterway; and an adjacent aluminum smelter facility. Additional potential source samples were obtained from stormsewer (runoff) manholes and from ambient particulate air samples. Using detailed measurements of parent and alkylated PAHs and other supportive chemical measurements, combined with principal components analyses (PCA), a PAH source allocation model was developed. This model was supported by a mass balance approach, wherein the PAH content of various source materials was developed to support the allocation model. Results indicated that the vast majority of the PAHs were of a pyrogenic origin and were sourced from the aluminum smelter (e.g., potliner effluents and fugative particulate emissions ) and that the petrogenic or pyrogenic PAH inputs to the Waterway from the log sort yard machinery, wood debris, and its associated piling dock were negligible.
496 (COS-1117-650979) Differentiating HMW PAHs in sediments from coal tar, creosote, and combustion-related background sources.
Start time: 9:00 AM
Costa, H1, Sauer, T1, 1 Blasland, Bouck and Lee, Inc., New Bedford, MA, 02740
Former manufactured gas plant (MGP) and wood-treating site remedial investigations frequently require delineating site-related wastes and dense non-aqueous-phase liquid (DNAPL) residues in adjacent rivers and streams. Natural physical-chemical weathering and biodegradation in surficial sediments alters the composition of pyrogenic tars (e.g., coal tar, carburetted water gas tar, creosote) by depleting the 2- and 3-ring polycyclic aromatic hydrocarbons (PAHs) relatively rapidly, and the high-molecular-weight (HMW) 4- through 6-ring PAHs slowly. As a result, weathered/biodegraded pyrogenic tar residues are compositionally similar to typical urban/industrial background PAH residues, which originate primarily from incomplete combustion of fuel, coal and wood. The presence of these pyrogenic PAHs, which can accumulate from background sources at concentrations on the order of up to 100 mg/kg total PAHs in sediments, is frequently mistaken for site releases. Because background determinations are a key component common to all sediment remedial investigations, it is necessary to distinguish site-related HMW PAHs from background, especially in rivers and streams with high background PAH concentrations. Resolving the compositional similarity of weathered/biodegraded pyrogenic tar residues and pyrogenic background PAH residues calls for a fingerprinting approach directed at the HMW PAH components of these residues. A forensic interpretation approach is presented using multiple double ratios of HMW PAH pairs (non-alkylated constituents) of similar physical properties to establish a weight of evidence in source differentiation. Case study results are presented for several DNAPL tar sites where this approach has successfully distinguished residuals in sediments from elevated background PAH concentrations. The case study results include validation of double ratios from conventional PAH delineation data (Method 8270) by comparison with comprehensive alkylated PAH analytical data.
(58097) COFFEE BREAK.
Start time: 9:20 AM
498 (JOH-1117-822088) Distinguishing Between Two Types of Aroclor 1254: Considerations for Environmental Forensics Investigations.
Start time: 10:20 AM
Johnson, G1, Hansen, L2, Hamilton, M3, Hermanson, M4, Horsak, R5, O'Keefe, P6, 1 University of Utah, Salt Lake City, UT, USA2 University of Illinois, Urbana, IL, USA3 Axys Analytical Services, Ltd., Sidney, BC, Canada4 University of Pennsylvania, Philadelphia, PA, USA5 3TM International, Inc., Houston, TX, USA6 NY State Dept. Health, Albany, NY, USA
Two distinct variants of Arolcor 1254 (A1254) were produced by Monsanto. The "typical" variant was produced through the early 1970s and accounts for the vast majority of A1254 production. It has been reported in the literature that the "late-production" variant was sold from 1974 through 1976. In this paper, we present information that pushes that estimated production start-date back to at least 1972. It may predate 1972, but if so, it is unlikely to have been produced before 1971 because its production was linked to the Aroclor 1016 production process which began that year. Late production A1254 is also notable because it has higher proportions of both coplanar (dioxin-like) PCBs and polychlorinated dibenzofurans, as compared to the more typical A1254 variant. The congener patterns of the two A1254 variants are distinct, and are readily recognizable when encountered in environmental media. While late-production A1254 accounts for a small percentage of total production, it can be and has been encountered in environmental forensics field investigations. We present a litigation related case study where the late-production variant was recognized in industrial site soils, residential soil, and tree bark.
499 (GIN-1118-239671) Statistical tools for the analysis of PCB and dioxin profile data.
Start time: 10:40 AM
Ginevan, Michael1, Shields, Walt 2, Benton, Laurie 2, 1 Exponent, Washington, DC, USA2 Exponent, Bellevue, WA, USA
When addressing the question of source attribution PCB and dioxin contamination it is common to look at the relative composition of congeners across a set of samples, commonly referred to as "evaluation congener profiles." While one can often often get a good idea of the relative similarities across samples using procedures like principal components analysis (PCA) or by simple visual examination of graphs of profiles, it is more difficult to say which samples are statistically most similar to one another or whether two samples are statistically different. Our presentation shows that log-transformed ratios of scaled concentrations will generally be expected to follow a normal distribution and uses this fact to construct difference metrics that have defined statistical properties. We then use this result to develop hypothesis tests of whether the profiles of two samples or two groups of samples are statistically different.
500 (LIE-1117-836137) Multivariate analysis of PCB congeners found in Maryland fish: PCB advection and dispersal of fishes.
Start time: 11:00 AM
Liebert, D1, Baker, J1, 1 University of Maryland Chesapeake Biological Laboratory, Solomons, MD, USA
Fish tissues from Maryland were monitored for polychlorinated biphenyl (PCB) contamination beginning in 1999. Levels of PCBs in fish supported consumption advisories of no more than two meals per month in four primary areas, Patapsco River, Northern Chesapeake Bay, Back River, and Potomac River. We used PCB congener patterns in these fish and associated sediments to differentiate among the sources of PCBs to the fish. Principal components analysis showed that PCB congener patterns varied spatially. Cluster analysis was used to demonstrate that fish collected at adjacent sites had the most similar congener patterns. A source apportionment model, Positive Matrix Factorization, was used to assess the influence of each source of PCBs to the fish. This study focused on three species of varying mobility. These included anadromous striped bass, semi-anadromous white perch, and residential catfish. Application of the multivariate analysis to the three datasets revealed that mobility is a factor in the strength of the spatial signals. Specifically, the smaller a species' home range, the greater the influence of the local PCB source on a fish's PCB congener signature. This work demonstrates the utility of such monitoring data for the investigation of contaminant dispersal patterns as well as revealing ecological behavior.
501 (MUR-1118-171018) Forensic Methods for Chlorinated Solvents.
Start time: 11:20 AM
Murphy, B1, Mohsen, F2, 1 Exponent, Sarasota, FL, USA2 Exponent, Cranbury, NJ, USA
This presentation describes several ways of age-dating and identifying sources of chlorinated solvents such as 1,1,1-trichloroethane (TCA), trichloroethene (TCE) or perchloroethene (PCE). Examples of the methods and use including complicating factors and uncertainties are also given. Age dating methods include the following. (1) Using the position of a ground water plume front together with a contaminant velocity estimate and an adjustment for longitudinal dispersion. (2) Using the observed ratio of TCA to its hydrolysis product, 1,1-dichloroethene, together with a groundwater temperature estimate and a laboratory evaluation of the hydrolysis rate at this temperature. Source identification methods include the following. (3) Plotting parent-daughter ratios in ground water, such as TCE /1,2-dichloroethylene, versus distance to identify additional chlorinated solvent sources. (4) Source identification using isotopes.