Work

Long-term efficiency of biochar amendment in PFAS-contaminated soil under unsaturated field conditions

Year: 2026

Type: article

Abstract: Long-term experiments under environmentally relevant conditions are critically needed to explore and validate the longevity of biochar immobilization of per- and polyfluoroalkyl substances (PFAS) in contaminated soils. The present study investigates the remediation efficiency of three sewage sludge-based biochars on target PFAS and precursors in well-drained soils contaminated by aqueous film-forming foam (AFFF) (ƩPFAS27 = 1624±276 µg/kg). Initial target PFAS concentrations increased by a factor of 2 in the soil following the total oxidizable precursor (TOP) assay, indicating presence of precursors. Fifteen field-scale columns were operated outdoors for a time span of 2 years. Amendment (1%) with the best-performing biochar immobilized long-chain PFAS by 91.0% and short-chain PFAS by 96.7%. The temporal variations in PFAS concentration observed in the control columns became negligible after amendment with the best-performing biochar, but the immobilization efficiency of short-chain PFAS dropped after one year (from 97.8 to 74.2% for the best-performing biochar). Applying biochar as a barrier was two times more efficient than mixing it homogenously into the soil, and the effect was most pronounced for long-chain PFAS. Our findings suggest that biochar may immobilize precursors to the same extent or better than typical target perfluoroalkyl acids. Notably CF3-CF6 precursors exhibited greater immobilization than their transformation products, but more research is needed to confirm the observed trends. Going beyond simple lab experiments, this long-term outdoor field-scale study suggests that biochar is a promising solution for PFAS remediation and brings the technology closer to field application.

Source: Journal of Hazardous Materials

DOI: 10.1016/j.jhazmat.2026.142119

Authors: Karen Ane Skjennum, Jan Mulder, Gijs D. Breedveld, Thomas Hartnik, Nicolas Estoppey, Erlend Sørmo

Institutions: Norwegian University of Life Sciences, Norwegian Geotechnical Institute, University Centre in Svalbard, Norwegian Institute of Bioeconomy Research

Language: English

Topic: Per- and polyfluoroalkyl substances research

Subfield: Environmental Chemistry

Field: Environmental Science

Domain: Physical Sciences

SDGs: Responsible consumption and production, Life on land, Clean water and sanitation, Climate action

Open Access status: hybrid

Estimated APC paid: $4,340