# High-Resolution Mass Spectrometry Analysis of Legacy and Emerging PFAS in Oilfield Environments: Occurrence, Source, and Toxicity Assessment

## TL;DR

This study uses advanced mass spectrometry to detect and assess the environmental and health risks of PFAS compounds, including a PFOS substitute, in oilfield environments.

## Contribution

The study introduces an optimized HPLC–Q-Orbitrap HRMS method for detecting 32 PFAS compounds and identifies a PFOS substitute with high toxicity and bioaccumulation potential.

## Key findings

- PFAS concentrations in groundwater and soil at the oilfield site exceeded background levels by 10-fold.
- OBS, a PFOS substitute, showed higher toxicity and bioaccumulation potential than PFOS in zebrafish embryos.
- Short-chain PFAS are more mobile in soil, while long-chain compounds adsorb more readily to surface layers.

## Abstract

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic chemicals used in daily life and industrial production. Due to their widespread use, these compounds are frequently detected in environmental samples. Many studies have shown that PFAS pose a significant threat to both ecological environments and human health, leading to widespread public concern. This study developed and optimized an analytical method for the detection of 32 common PFAS compounds in chemical additives and environmental samples, including oil displacement agents, groundwater and soil, utilizing High-Performance Liquid Chromatography–Quadrupole-Orbitrap High-Resolution Mass Spectrometry (HPLC–Q-Orbitrap HRMS) technology. Applications in an eastern Chinese oilfield revealed significant PFAS accumulation, with ∑PFAS concentrations in groundwater and soil at the well site ranging from 212.29 to 262.80 ng/L and from 23.70 to 71.65 ng/g, respectively, exceeding background levels by 10-fold. The oil displacement agents used in oilfields are one of the important sources of PFAS, particularly p-perfluorous nonenoxybenzenesulfonate (OBS), a perfluorooctanesulfonic acid (PFOS) substitute. Soil analysis indicated greater mobility of short-chain PFAS, while long-chain compounds adsorbed more readily to surface layers. Molecular docking and quantitative structure–property relationship (QSPR) modeling suggest that the bioaccumulation potential of OBS is high and comparable to that of PFOS. Zebrafish embryo assays demonstrated that OBS induced significant concentration-dependent cardiac developmental toxicity, including pericardial edema and apoptosis, showing 1.5–2.4 times greater toxicity than PFOS across multiple endpoints. These findings reveal OBS as a pervasive contaminant with elevated environmental and health risks, necessitating urgent re-evaluation of its use as a PFOS substitute.