Dual Role of Microbe–Fe_xS_y Interaction to Drive Perfluorooctanoic Acid Multipath Chain Reaction Decay Cycles and Secondary Minerals-Ions (Fe²⁺/Fe³⁺) Transformation Cycles

Abstract

The coexistence of iron−sulfur minerals (Fe x S y ) and microorganisms is a common phenomenon, often leading to intricate interactions. Perfluorooctanoic acid (PFOA) presents extensive spatial−temporal attenuation characteristics. However, the mechanism governing PFOA in relevant diverse PFOA-ion occurrence environments remains unclear. In this study, the effects difference between microbe/Fe x S y and microbe−Fe x S y , and specific effects of four PFOA-ions environments on PFOA were investigated. Results showed a remarkable 277% increase in PFOA attenuation rate (λ) in microbe−Fe x S y media (0.343 h −1 ) than in Fe x S y (0.091 h −1 ) alone. The ion inhibiting effect on PFOA attenuation was demonstrated (λ from 0.343 to 0.159 h −1 ), with the maximum effect in HCO 3 − . It can be attributed to the occupation of sites by HCO 3− which led to a greater repulsion. More PFOA was dispersed into distant regions (low reaction zone). Moreover, SO 4 2− or NO 3 − with microbe−Fe x S y interaction exhibited pronounced retardation effects (on PFOA). Notably, enhanced formations of2− and PFOA-NO 3 − environments. Pseudomonas reduced Fe 3+ to Fe 2+ , and Rhizobiales contributed to producing 3 Fe 2+ after consuming 2 Fe 2+ . Fe 2+ and Pseudomonas combined to drive PFOA multipath chain reaction. This provided a theoretical basis for understanding PFOA cross-media transport and fate in microbe−mineral−ions interaction environments.