Time filter

Source Type

Stout S.A.,NewFields Environmental Forensics Practice LLC | Graan T.P.,Weston Solutions
Environmental Science and Technology | Year: 2010

Polycyclic aromatic hydrocarbons (PAHs) in urban environments are often derived from point and nonpoint sources, the latter collectively considered as urban background. Quantifying the contributions of point sources and urban background is important for managing and remediating urban sediments. In this work, the sources of PAHs in 350 sediments from a 1.5-mile portion of the Little Menomonee River (Milwaukee, WI) were determined using principal component analysis (PCA), chemical fingerprinting, and positive matrix factorization (PMF), the combination of which mitigates weaknesses of any one method. At issue was quantifying the contributions of a creosote point-source formerly located 3.5 to 5.0 miles upstream versus urban background-derived PAHs in the sediments. In total, creosote and urban background contributed 27 and 73% (±14%) of eight carcinogenic PAHs (CPAHs), respectively, in this part of the River. The concentrations of CPAHs derived from urban background were highest in surface sediments (0?6 in.; 20 ± 17 mg/kg), particularly near major roadway crossings, increased in the downstream direction, and (on average) exceeded the 15 mg/kg regulatory cleanup threshold. Weathered creosote-derived CPAHs were widespread at low concentrations (4.8 ± 8.1 mg/kg) although some discrete sediments, mostly at depths below 6 in., contained elevated CPAHs derived from creosote. This work demonstrates the value of combining multiple techniques in source apportionment studies in urban sediments. It further demonstrates a means to determine the concentration of PAHs attributable to nonpoint sourced background in urban sediments without the need to identify, collect, and analyze (assumedly) "representative" background samples, which may not even exist in heterogeneous urban watersheds. © 2010 American Chemical Society.

Stout S.A.,NewFields Environmental Forensics Practice LLC | Payne J.R.,Payne Environmental Consultants Inc.
Marine Pollution Bulletin | Year: 2016

. In-situ burning during the . Deepwater Horizon oil spill generated tens of thousands of barrels of . in-situ burn (ISB) residues in the northern Gulf of Mexico (GoM), most or all of which eventually sank to the seafloor. Chemical analyses showed that floating and sunken (~. 1400. m deep) ISB residues (1) exhibited distinct . n-alkanes and UCM profiles inconsistent with vapor-pressure driven evaporation, (2) were relatively enriched in pyrogenic PAHs, particularly less stable (mostly) linear PAH isomers formed during burning, and (3) had lost petroleum biomarkers, relative to their volatility. PAH concentrations in ISB residues indicate that between 26,800 and 37,800. kg of total PAHs (TPAH51) and 2880 and 4060. kg of 16 Priority Pollutant PAHs were potentially deposited on the seafloor in discrete ISB residue particles. Despite this additional benthic impact, ISB reduced the total mass loadings of PAH from the burned oil to the GoM by 89% (ignoring any re-deposition from atmospheric emissions). © 2016 Elsevier Ltd.

Stout S.A.,NewFields Environmental Forensics Practice LLC | Douglas G.S.,NewFields Environmental Forensics Practice LLC | Uhler A.D.,NewFields Environmental Forensics Practice LLC
Environmental Forensics | Year: 2010

The release of gasoline at retail service station sites can result in the presence of gasoline-derived constituents dissolved in ground water. Due to regulatory requirements or remediation objectives the concentrations of these constituents often are monitored regularly for several years or decades. This study aims to demonstrate the utility of a large historic dataset for gasoline-impacted groundwater through the evaluation of spatial and temporal trends over 8 years of quarterly benzene, toluene, ethylbenzene, and o, m, and pxylene polymers (BTEX) data from a plume emanating from a service station site. A novel aspect explored herein was to convert the historic, time-series BTEX concentration data into relative mole fractions in a corresponding four-component (BTEX), hypothetical non-aqueous phase liquid (NAPL), i.e., "NAPL-GW fingerprints", in order to: 1) minimize the influence of factors affecting absolute BTEX concentrations over the 8 years of data collection (e.g., groundwater elevation in relation to smear zone), and 2) allow for the comparison of the NAPL-GW fingerprints of groundwater to fresh gasoline as a means of recognizing the impact of new releases on groundwater. More clearly than with using absolute concentration profiles, the NAPL-GW fingerprints revealed that gasoline impacted groundwater on-site during two separate time intervals. These impacts also could be recognized in off-site locations, albeit to different degrees at different downgradient locations. Specifically, an earlier release(s) appears to have impacted the entire study area whereas a later (apparently smaller volume) release only had impacted groundwater on-site and immediately off-site before attenuating. The historic dataset evaluation was supplemented by a survey of current groundwater using conventional paraffin, isoparaffin, aromatic, naphthene, and olefin (PIANO) fingerprinting that focused on the utility of C3- and C4-alkylbenzenes in fingerprinting different types of dissolved gasoline. PIANO fingerprinting revealed molecular differences reflecting two types of gasoline impacting different locations - as revealed by distinct solubility-based ratios among C3- and C4-alkylbenzenes. Collectively, the study demonstrates a means by which the timing and type of gasoline impacting groundwater may be determined using dissolved phase data only. © Taylor & Francis Group, LLC.

Stout S.A.,NewFields Environmental Forensics Practice LLC | Emsbo-Mattingly S.D.,NewFields Environmental Forensics Practice LLC | Douglas G.S.,NewFields Environmental Forensics Practice LLC | Uhler A.D.,NewFields Environmental Forensics Practice LLC | McCarthy K.J.,NewFields Environmental Forensics Practice LLC
Polycyclic Aromatic Compounds | Year: 2015

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soils and sediments, particularly in urbanized environments in which the concentrations of 16 (or so) PAHs are regulated. Distinguishing among the numerous PAH sources is of practical and legal concern and thereby is often an objective of environmental forensic chemistry studies. Studies of prospective sources and impacted soils and sediments that rely upon the 16 U.S. EPA Priority Pollutant PAHs are disadvantaged, as these few compounds generally lack the specificity to distinguish among different PAH sources in the environment. Advances in analytical and interpretive methods over several decades have shown that different PAH sources can be more defensibly distinguished using modified EPA Method 8270 that, among other improvements, measure many other polycyclic aromatic compounds (PACs) that co-occur with the Priority Pollutant PAHs in different sources and in the environment. The PACs include variously-alkylated PAHs and polycyclic aromatic sulfur heterocyclics (PASHs) homologs and individual isomers, which are herein reviewed. Collectively, these PACs provide a higher degree of specificity among PAC sources and can be used to understand the effects of weathering on PAH assemblages. Despite their diagnostic capacity, PACs should not be relied upon at the exclusion of other compound groups (e.g., petroleum biomarkers) in most environmental forensic chemistry studies. In light of these advances, source characterization studies that rely only upon the 16 (or so) Priority Pollutant PAHs warrant considerable caution. © 2015, Copyright © Taylor & Francis Group, LLC.

Discover hidden collaborations