第九届青年地学论坛

The coexistence of iron-sulfur minerals (Fe_xS_y) and microorganisms is a common phenomenon, often leading to intricate and multifaceted interactions. Perfluorooctanoic acid (PFOA) presents extensive transport and spatial-temporal attenuation characteristics. However, the transport and attenuation mechanism governing PFOA in diverse PFOA-ions occurrence environments, specifically in conjunction with microbe-mineral interaction, remains unclear. In this study, the effects difference between microbe/Fe_xS_y (pyrite (FeS₂) and pyrrhotite (Fe_1−nS)) and microbe-Fe_xS_y interaction media on PFOA, and specific effects of four PFOA-ions occurrence environments on PFOA considering microbe-Fe_xS_y interaction were investigated. A microbe-Fe_xS_y interaction-induced multi-process reaction model was constructed to quantitatively describe influential effects. Results showed a remarkable 277% increase in PFOA attenuation rate (λ) in microbe-Fe_xS_y interaction media (0.343 h^-1) than in alone Fe_xS_y (0.091 h^-1). The ions inhibiting effect on PFOA attenuation was demonstrated (λ from 0.343 to 0.159 h^-1), with the maximum effect in HCO₃^-. It can be attributed to the occupation of sites by HCO₃^- which led to a greater repulsion. More PFOA was dispersed into distant regions (low reaction zone with poor Fe²⁺/microorganism) compared to other ion environments. Moreover, SO₄^2- or NO₃^- with microbe-Fe_xS_y interaction exhibited pronounced retardation effects (K_d from 0.292 to 0.447 cm³·g^-1) on PFOA. Notably, enhanced formations of β-Fe₂O₃·H₂O and α-Fe₂O₃·H₂O regulated PFOA transport behavior in PFOA-SO₄^2- and PFOA-NO₃^- environments. The common attenuation pathway of PFOA was proposed as Deprotonation (A) with the cycle of Activation (B), decarboxylation (C), hydroxylation (D), HF elimination (E), hydrolysis (F), and HF elimination (E). Pseudomonas reduced Fe³⁺ to Fe²⁺, and Rhizobiales contributed to producing 3 Fe²⁺ after consuming 2 Fe²⁺. Fe²⁺ and Pseudomonas combined to drive PFOA multi-path chain reaction decay cycles. This study provided the theoretical basis for understanding PFOA cross-media transport and fate in microbe-mineral-ions interaction environments.

PFOA,iron sulfur mineral,microorganisms,transport and fate,interaction