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An assessment of PFAS-contaminated sediment transport in an urban river
Citation:
Cashman, M., M. Morales-Mcdevitt, L. Coiro, T. Boving, M. Cantwell, AND A. Robuck. An assessment of PFAS-contaminated sediment transport in an urban river. SETAC North America, 43rd Annual Meeting, Pittsburgh, PA, November 13 - 17, 2022.
Impact/Purpose:
Existing research for PFAS in riverine systems are mostly focused on water samples, but PFAS are known to aslo accumulate in sediments. In this research, we hypothesized that PFAS contaminated sediments may travel downstream through suspended solids and contribute to overall PFAS loading in an estuarine system. We tested this hypothesis by deploying a sediment trap in a river downstream of a known PFAS contaminated site. Weekly water samples and total suspended solids were analyzed for 24 PFAS compounds on an LC-MS/MS. The results showed that PFAS do transport via suspended solids and contribute to contaminant loading. This research is intended for scientific confrence audience, but it will ultimately be shared with a wide array of state, Federal, and regional partners who are interested in PFAS site characterization and remediation.
Description:
The continuous use and discharge Per- and polyfluoroalkyl substances (PFAS) since the 1950s has resulted in their ubiquitous distribution in aquatic matrices. While PFAS transport mechanisms are well studied in aqueous phase surface waters, little is known about their fate in solid phase or sediment transport. This study focuses on the transport of PFAS via suspended solids (SS) downstream of a site with known PFAS sediment contamination. A sediment trap was deployed in the Pawtuxet River (Rhode Island, USA), 0.5km upstream of the river mouth to Narragansett Bay and swapped out monthly for the duration of a 12-month study. The selected site is downstream of several small wastewater treatment facilities, and 5km downstream of a known site with PFAS contaminated sediments. Weekly water samples were taken alongside the sediment trap to assess PFAS concentrations in the water column. These results were normalized to stream height and volume using a proximal USGS stream gauge to approximate PFAS mass loading via aqueous and SS over the course of one year as part of a time-series analysis. Concentrations of ∑PFAS in the water column ranged from 10-91 ng/L over the course of the year (<m:chr m:val="¿"/><span style='font-family:"Cambria Math",serif;mso-ascii-font-family: "Cambria Math";mso-hansi-font-family:"Cambria Math";mso-bidi-font-family: Calibri;mso-bidi-theme-font:minor-latin;font-style:italic;mso-bidi-font-style: normal'><i style='mso-bidi-font-style: normal'><span style='font-family:"Cambria Math",serif;mso-bidi-font-family: Calibri;mso-bidi-theme-font:minor-latin'>x<i style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif; mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin'>=31 ng/L) <v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f"> <v:shape id="_x0000_i1025" type="#_x0000_t75" style='width:66.6pt; height:13.8pt'> <v:imagedata src="file:///C:/Users/mcashman/AppData/Local/Temp/msohtmlclip1/01/clip_image001.png" o:title="" chromakey="white"/> and showed high variability that were not correlated to changes in flow or season. The ∑PFAS concentrations in SS ranged from 6-24ng/g (<m:chr m:val="¿"/><span style='font-family:"Cambria Math",serif;mso-ascii-font-family: "Cambria Math";mso-hansi-font-family:"Cambria Math";mso-bidi-font-family: Calibri;mso-bidi-theme-font:minor-latin;font-style:italic;mso-bidi-font-style: normal'><i style='mso-bidi-font-style: normal'><span style='font-family:"Cambria Math",serif;mso-bidi-font-family: Calibri;mso-bidi-theme-font:minor-latin'>x<i style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif; mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin'>=15 ng/g<v:shape id="_x0000_i1025" type="#_x0000_t75" style='width:60.6pt;height:13.8pt'> <v:imagedata src="file:///C:/Users/mcashman/AppData/Local/Temp/msohtmlclip1/01/clip_image003.png" o:title="" chromakey="white"/> ). Strong correlations were observed between sediment concentration and SS mass in linear regressions for many PFAA compounds, including PFDoA (R2=0.94), PFOA (R2=0.81), and PFOS (R2=0.93). The correlations between increased PFAA concentrations with increasing SS are evidence of contaminated sediments transporting downstream and contributing to overall PFAS through SS. These results signify the importance of sediment mobilization and transportation when considering PFAS source characterization for riverine environments.
