Technical Approach

Three main hypotheses will be tested: (1) enhancing humification reactions by supplementing appropriate enzymes and cofactors can facilitate transformation of PFCs in an aquifer; (2) calcium peroxide can be used as a source of oxidants for humification enzymes in anaerobic aqueous systems; and (3) humification enzymes immobilized on quartz sand remain stable and active in typical groundwater hydraulic conditions and mediate effective PFC degradation. Two representative PFCs, PFOS and PFOA, which have been included in the list of priority pollutants recently, will be investigated. In addition, three model catalysts will be studied, including a laccase isolated from the fungus Trametes versicolor, a lignin peroxidase (LiP) from the fungus Phanerochaete chrysosporium, and horseradish peroxidase (HRP). All these enzymes have been demonstrated in previous studies to catalyze effective oxidative coupling reactions. Three humic monomers--catechol, 4-methoxyphenol, and guaiacol--will be tested as co-substrates. These humic monomers contain functionalities that are frequently present in natural organic matter (NOM) and have often been used in earlier studies to mimic NOM reactivity. Two types of extracted NOM species (Suwannee River fulvic acid and humic acid) that can be obtained from the International Humic Substance Society (IHSS) will also be studied as co-substrates in the reaction systems. The molecular characteristics of these NOM species have been well characterized and the data are available.