Groundwater Transport of Perfluorooctane Sulfonate (PFOS) and Volatile Organic Compounds (VOCs) from a Former Fire Fighter Training Site
Abstract
Per- and polyfluoroalkyl substances (PFAS) are widespread in the environment, and represent a significant risk to human health when present in groundwater used as a drinking water source. Laboratory studies have documented PFAS sorption behavior for a range of soil and rock matrix compositions, but the applicability of these sorption results to field-scale fate and transport problems remains less known. Firefighter training sites are commonly long-term point sources of PFAS to underlying aquifers, and can serve as case studies to illuminate transport at the field scale. In the 1970s, activities at a fire fighter training site in University Park, Pennsylvania introduced perfluorooctane sulfonate (PFOS) and volatile organic compounds (VOCs) to the underlying dolomite aquifer. The present close correlation between PFOS and VOC concentrations across the site is unexpected given the difference in Koc ranges for the two compound classes. Additionally, both plumes have two sperate concentration maxima: one immediately down-gradient of the training site, and one approximately 200 m down-gradient. We used 2D MODFLOW and MT3D models to history-match the contaminant data and determine the physical and chemical aquifer properties likely responsible for the observed plume shape. Although site-specific Kd values should ideally be used to model field-scale PFOS transport, Koc values reported in the literature for generic cases may adequately describe PFOS transport in this shallow aquifer. We determined that heterogeneity in aquifer total organic carbon content (% TOC) is most likely responsible for the observed shape of the plumes. This highlights an important consideration for modeling PFOS transport in aquifers that may have discrete layers of higher and lower TOC; models that use a homogenous site-average TOC instead of variable TOC zones can significantly underestimate PFOS transport distances and therefore misrepresent exposure risks.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGH11B1036J
- Keywords:
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- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0486 Soils/pedology;
- BIOGEOSCIENCES;
- 0496 Water quality;
- BIOGEOSCIENCES;
- 0240 Public health;
- GEOHEALTH