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. 2020 Oct 20:740:140017.
doi: 10.1016/j.scitotenv.2020.140017. Epub 2020 Jun 6.

PFAS concentrations in soils: Background levels versus contaminated sites

Mark L Brusseau  1 , R Hunter Anderson  2 , Bo Guo  3
Affiliations

PFAS concentrations in soils: Background levels versus contaminated sites

Mark L Brusseau et al. Sci Total Environ. .

Abstract

Per- and polyfluoroalkyl substances (PFAS) are contaminants of critical concern due to their persistence, widespread distribution in the environment, and potential human-health impacts. In this work, published studies of PFAS concentrations in soils were compiled from the literature. These data were combined with results obtained from a large curated database of PFAS soil concentrations for contaminated sites. In aggregate, the compiled data set comprises >30,000 samples collected from >2500 sites distributed throughout the world. Data were collected for three types of sites- background sites, primary-source sites (fire-training areas, manufacturing plants), and secondary-source sites (biosolids application, irrigation water use). The aggregated soil-survey reports comprise samples collected from all continents, and from a large variety of locations in both urban and rural regions. PFAS were present in soil at almost every site tested. Low but measurable concentrations were observed even in remote regions far from potential PFOS sources. Concentrations reported for PFAS-contaminated sites were generally orders-of-magnitude greater than background levels, particularly for PFOS. Maximum reported PFOS concentrations ranged upwards of several hundred mg/kg. Analysis of depth profiles indicates significant retention of PFAS in the vadose zone over decadal timeframes and the occurrence of leaching to groundwater. It is noteworthy that soil concentrations reported for PFAS at contaminated sites are often orders-of-magnitude higher than typical groundwater concentrations. The results of this study demonstrate that PFAS are present in soils across the globe, and indicate that soil is a significant reservoir for PFAS. A critical question of concern is the long-term migration potential to surface water, groundwater, and the atmosphere. This warrants increased focus on the transport and fate behavior of PFAS in soil and the vadose zone, in regards to both research and site investigations.

Keywords: AFFF; PFOA; PFOS; Sources.

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Conflict of interest statement

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1.
Figure 1.
Numbers of publications reporting PFAS concentrations in soil samples for surveys of background concentrations and contaminated sites. For some years the two types have identical numbers of publications, which shows as the filled circle residing within the open square.
Figure 2.
Figure 2.
Example depth profiles of PFOS soil concentrations developed using data from the U.S. Air Force AFFF Impacted-Site database.
Figure 3.
Figure 3.
Depth distribution of total PFAS in soil as a function of chain length. The data represent 124 boreholes across 30 sites for which at least 8 depth-discrete samples were collected, tracked in the U.S. Air Force AFFF Impacted-Site database. Since the actual sample depths differed from location to location, depths were normalized by sequential rank, and generally reflect the interval from the ground surface to the water table. Similarly, total PFAS concentrations were normalized by the computation of standard normal (Z) scores for each borehole, and are summarized as the mean among all boreholes for short- and long-chain PFAS, respectively. Long-chain (≥C7) and short-chain are used as defined in Buck et al. (2011).
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