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Reconstructing Temporal PFAS Trends from Sediment Cores with Multiple Approaches
Citation:
Cashman, M., A. Robuck, M. Morales-Mcdevitt, J. Koelmel, AND M. Cantwell. Reconstructing Temporal PFAS Trends from Sediment Cores with Multiple Approaches. International Conference on the Remediation and Management of Contaminated Sediments, Austin, TX, January 09 - 12, 2023.
Impact/Purpose:
Per- and polyfluoroalkyl substances (PFAS) are a diverse suite of fluorinated chemicals found ubiquitously in the environment. This research uses a radiometrically dated sediment core to demonstrate an age-depth model of PFAS contamination over history in an urban mill pond. Initial analyses are constrained to the detection of 24 different PFAS compounds with analytical standards. However, other proxies such as EOF, TOP, and NTA are utilized to indicate the presence of previously undetected PFAS. This research highlights the ability for sediment cores to develop depositional timelines of environmental PFAS release, and also shows the importance of multiple proxies for detection of environmental matricies. This reserach will be presented to a scientific community at the Battelle Sediments Confrence.
Description:
Background/Objectives. The use of Per- and polyfluoroalkyl substances (PFAS) in industrial applications predates analytical techniques for their identification in environmental matrices, leaving a gap in historical contamination records. One way to determine past PFAS contamination is through examining dated sediment cores. In this study, a sediment core was taken from an urban river in Rhode Island, USA. The sediment core was collected in a quiescent depositional area near former textile mills that were suspected of using PFAS containing products. The core was radiometrically dated and analyzed for PFAS using multiple techniques including a Total Oxidizable Precursor Assay (TOP), Extractable Organic Fluorine (EOF), and Nontarget Analysis (NTA). Approach/Activities. A 1.3m sediment core was extracted from an urban river for PFAS analysis. The core was radiometrically dated using 210-Pb and Cs-137 markers to develop an age-depth profile. PFAS were extracted from sediments at verified age-depths and quantified using isotopic dilution on a Waters TQD LC-MS/MS. From there, sediments underwent a novel TOP Assay to oxidize precursor compounds into detectable terminal products. PFAS concentrations pre- and post TOP Assay were compared to identify precursor presence in sediments. A fluorine mass balance was calculated using EOF with combustion ion chromatography. Discrepancies in the fluorine mass balance were further investigated using NTA carried out with a Thermo Fisher Orbitrap Fusion. Novel PFAS were identified using FluoroMatch Software with peak picking and alignment performed in Compound Discoverer. All annotations were manually confirmed using both FluoroMatch Visualizer and FreeStyle based on retention time trends, fragmentation, and mass defect. Results/Lessons Learned. Initial targeted sediment concentrations showed temporal trends of PFAS preserved within the sediment record ranging from <1-55 ng/g sediment (d/w) in 18 unique PFAS compounds. Coupling these data with an age-depth model revealed temporal trends of specific PFAS compounds, with peak ∑PFAS concentrations of 55 ng/g in 1973. Results from TOP and EOF indicated that targeted analysis only accounted for 6% of the total organic fluorine detected in select segments of the core. Further analysis through NTA revealed the presence of additional PFAS, including long-chain (<C19) and fluorotelomer carboxylic acids. This research highlights the utility of a multi-analysis approach to characterize temporal PFAS trends in sediments.
