Occurrence and Fate of Perfluorochemicals in Soil Following the Land Application of Municipal Biosolids

TLDR

EPA guidance values for PFOA and PFOS underscore growing concerns about these persistent chemicals, yet risk assessments for municipal biosolid land application remain scarce. The study aimed to investigate the occurrence and fate of PFCs in soils receiving land‑applied municipal biosolids. Researchers evaluated PFC levels, mass balance, desorption, and transport across varying biosolid loading rates, used the data to build a predictive model, and performed desorption experiments showing leaching potential decreases with chain length and that existing partition coefficients may be inaccurate for long‑chain PFCs. This first report found PFOS dominated PFCs in municipal biosolids and amended soils, with concentrations rising linearly with loading rate, evidence of precursor transformation, and trace PFCs detected to 120 cm depth, indicating potential vertical movement and higher transport for short‑chain PFCs.

Abstract

The recent implementation of soil and drinking water screening guidance values for two perfluorochemicals (PFCs), perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) by the U.S. Environmental Protection Agency (EPA), reflects the growing concerns regarding the presence of these persistent and bioaccumulative chemicals in the natural environment. Previous work has established the potential risk to the environment from the land application of industrially contaminated biosolids, but studies focusing on environmental risk from land application of typical municipal biosolids are lacking. Thus, the present study investigated the occurrence and fate of PFCs from land-applied municipal biosolids by evaluating the levels, mass balance, desorption, and transport of PFCs in soils receiving application of municipal biosolids at various loading rates. This study is the first to report levels of PFCs in agricultural soils amended with typical municipal biosolids. PFOS was the dominant PFC in both biosolids (80−219 ng/g) and biosolids-amended soil (2−483 ng/g). Concentrations of all PFCs in soil increased linearly with increasing biosolids loading rate. These data were used to develop a model for predicting PFC soil concentrations in soils amended with typical municipal biosolids using cumulative biosolids loading rates. Mass balance calculations comparing PFCs applied vs those recovered in the surface soil interval indicated the potential transformation of PFC precursors. Laboratory desorption experiments indicated that the leaching potential of PFCs decreases with increasing chain length and that previously derived organic-carbon normalized partition coefficients may not be accurate predictors of the desorption of long-chain PFCs from biosolids-amended soils. Trace levels of PFCs were also detected in soil cores from biosolids-amended soils to depths of 120 cm, suggesting potential movement of these compounds within the soil profile over time and confirming the higher transport potential for short-chain PFCs in soils amended with municipal biosolids.