Influence of Fungal Low Molecular Weight Organic Acids on Extraction and Speciation of Runoff Particulate-Associated Phosphorus: Implications for Nonpoint Phosphorus Recovery and Beneficial Reuse

摘要

Massive nonpoint particulate-bound phosphorus (P) losses in runoff and erosion streams cause eutrophication and toxic algal blooms in surface water bodies that receive these streams. On the other hand, runoff particulates can be regarded as a "new" sustainable source of P that can be recovered and reused in agriculture to minimize dependence on mined P sources. In this study, the effects of low molecular weight organic acids (LMWOA) generated by P-solubilizing fungi (PSF) on bound P extraction efficiency and inorganic P speciation from intercepted runoff sediments discharging into a eutrophic lake were investigated. Runoff sediments were processed using model aqueous LMWOA solutions and cell-free PSF culture broths containing oxalate and citrate. Up to 61% of total bound P were extracted from runoff sediments using 2:1 and 1:1 (by molarity) oxalate-citrate mixtures. Equilibrium soluble P levels were reached within 120 min of extraction. Majority of the extracted P originated from potentially bioavail-able Fe-bound P pools whereas some desorbed P appeared to reform as Ca-P phases when using oxalate-dominant extrac-tant mixtures. Extractions using cell-free fungal culture broth demonstrated higher P mobilization rates than using pure aqueous LMWOA solutions, indicating the relevance of other non-LMWOA-related chelating and dissolution mecha-nisms.