Soil enzyme dynamics under PFAS contamination in arid and Mediterranean soils

Area of Science:

• Environmental Chemistry
• Soil Science
• Biogeochemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants found in agricultural soils.
• Their impact on soil extracellular enzyme activities is not well understood.
• Understanding these effects is crucial for assessing agricultural soil health.

Purpose of the Study:

• To investigate the short- and long-term effects of PFOA and 6:2 FTSA on Mediterranean and arid agricultural soil biochemical functioning.
• To determine the sensitivity of different soil types to PFAS contamination.
• To assess the risk posed by PFAS to agricultural ecosystems.

Main Methods:

• Soils were spiked with environmentally relevant concentrations of PFOA and 6:2 FTSA.
• Incubation for 210 days to assess short- and long-term effects.
• Enzyme activities and eco-enzymatic stoichiometry were analyzed.
• PFAS stability and transformation products were monitored.

Main Results:

• Arid soils showed significant impairment of biochemical functioning, with Treated-Soil Quality Index values dropping below 70% of control levels.
• 6:2 FTSA strongly inhibited key enzymes like β-glucosidase and alkaline phosphomonoesterase (up to 81.7%) in arid soils.
• Mediterranean soils exhibited minimal enzymatic response to PFAS exposure.
• Eco-enzymatic stoichiometric modeling indicated PFAS-induced shifts in microbial enzyme allocation, especially in arid soils.
• PFOA was stable, while 6:2 FTSA dissipated, forming perfluoroheptanoic acid.

Conclusions:

• Arid agricultural soils are more biochemically sensitive to PFAS contamination than Mediterranean soils.
• PFAS contamination poses a significant biochemical risk to dryland agricultural systems.
• Repeated application of PFAS-contaminated materials could exacerbate soil degradation in arid environments.