# Tracking the Spread of PFAS and EOF in Shanghai Soils over a Decade: Insights from 2007, 2012, and 2017

## TL;DR

This study tracks PFAS contamination in Shanghai soils from 2007 to 2017, showing increasing concentrations and shifting pollution hotspots.

## Contribution

The study provides a decade-long analysis of PFAS in Shanghai soils, revealing trends and highlighting the importance of measuring F-53B.

## Key findings

- PFAS concentrations in Shanghai soils increased over the decade, with median levels rising from 1090 to 2390 pg/g.
- Long-chain PFAS dominated, and F-53B was found in significant amounts in 2017 samples.
- Unidentified organofluorine compounds made up over 88% of extractable organofluorine in all years studied.

## Abstract

Per- and polyfluoroalkyl
substances (PFAS) are ubiquitous contaminants
in the soil environment, yet their spatiotemporal distribution and
long-term trends remain poorly understood. This study investigated
the temporal variations and spatial patterns of legacy and emerging
PFAS in soil of Shanghai, China, by analyzing 162 soil samples collected
in 2007, 2012, and 2017. The results revealed that sum PFAS concentrations
ranged from 110 to 18000 pg/g, with an upward trend over the decade
(median levels: 1090, 1190, and 2390 pg/g in 2007, 2012, and 2017,
respectively). Long-chain PFAS dominated the contaminant profile with
perfluoroalkyl carboxylic acids (PFCAs) (1370–2090 pg/g) consistently
exceeding perfluoroalkyl sulfonic acids (PFSAs) (145–466 pg/g).
For soil samples collected in 2017, a significant amount of F-53B
was noted (median: 148 pg/g) as compared to PFOS (median: 95.7 pg/g)
and PFOA (median: 1250 pg/g), highlighting the importance of measuring
this compound in the Chinese environment. Spatially, PFAS contamination
expanded over time, with the pollution center shifting from urban
Shanghai to the southwest, forming a new hotspot in that sector. However,
no significant correlation was observed between the PFAS distribution
and land use. A mass balance analysis indicated that unidentified
organofluorine constituted a substantial proportion of extractable
organofluorine (90.1, 92.7, and 88.2% in 2007 (target PFAS 11), 2012
(target PFAS 11), and 2017 (target PFAS 20), respectively), highlighting
significant gaps in current contaminant identification. These findings
provide critical insights into the long-term dynamics of PFAS in a
soil environment and underscore the need for future research to prioritize
the characterization of unknown fluorine compounds in environmental
monitoring.