Influence of Environmental Factors and Epiphytic Bacteria on Arsenic Accumulation and Biotransformation in Hydrilla verticillata (L.f.) Royle

Submerged aquatic plants have potential applications in the phytoremediation of aquatic environments contaminated with arsenic (As). However, the role of epiphytic bacteria that grow on the surface of plants in As uptake and metabolism in plants has often been overlooked. An orthogonal experimental design with nine treatments, four factors, and three levels was conducted to inspect the effects of nitrogen (N, KNO3, 2, 4, 10 mg/L), phosphorus (P, NaH2PO4<middle dot>2H2O, 0.02, 0.2, 1 mg/L), pH (6, 7, 9), and arsenate (As(V), Na3AsO4<middle dot>12H2O, 15, 75, 375 mu g/L) on As accumulation and biotransformation in sterilized plants and to further explore the role of epiphytic bacteria in the metabolism of As by Hydrilla verticillata (L.f.) Royle. The results indicate that low N, intermediate P, and intermediate pH were beneficial for As accumulation (117.2 +/- 62.2 mu g/g DW) in sterilized plants, and epiphytic bacteria exhibited promotion (68%) in plants. High N promoted As absorption and transformation in non-sterilized plants but reduced As absorption in sterilized plants. Epiphytic bacteria in the medium showed significant As(III) oxidation, which was affected by environmental factors. These findings can promote remediation efficiency by regulating environmental factors for the phytoremediation of As-contaminated waters.