title: Aquatic acute toxicity assessments of molybdenum (+VI) to Daphnia magna.
abstract: Generally, molybdenum (Mo) metals in the environment are very rare, but wastewater discharges from industrial processes may contain high concentrations of Mo, which has the potential to contaminate water or soil if not handled properly. In this study, the impact of three common compounds of hexavalent Mo (sodium molybdate (Na2MoO4‧2H2O), ammonium molybdate ((NH4)6Mo7O24‧4H2O) and molybdenum trioxide (MoO3)) in an aquatic system were assessed based on 48-h exposure acute toxicity to Daphnia magna (D. magna). The LC50 toxicities for associated conjugate ions including Na(+), Cl(-), SO4(2-), and NH4(+) were determined. Furthermore, the LC50 values for the three forms of hexavalent Mo were determined, and the acute toxicities of the Mo forms were found to follow the order: (NH4)6Mo7O24‧4H2O > MoO3 > Na2MoO4‧2H2O in solution. (NH4)6Mo7O24‧4H2O exhibited the lowest LC50 of 43.3 mg L(-1) (corresponding to 23.5 mg Mo L(-1)) among the three molybdenum salts. The research confirmed that the toxicity of molybdenum in the aquatic system is highly dependent on the form of molybdenum salts used, and is also associated with the influence of the background water quality.
authors.affiliation: Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-kuang Road, Taichung 402, Taiwan.
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Wang
authors.affiliation: Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-kuang Road, Taichung 402, Taiwan. Electronic address: cliang@nchu.edu.tw.
authors.forename: Chenju
authors.initials: C
authors.lastname: Liang
authors.affiliation: Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-kuang Road, Taichung 402, Taiwan.
authors.forename: Hui-Ju
authors.initials: HJ
authors.lastname: Yeh
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects*; D007928:Lethal Dose 50; D008982:Molybdenum / Q000633:toxicity*; D010087:Oxides / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D010087:Oxides; D014874:Water Pollutants, Chemical; C082290:molybdenum trioxide; D008982:Molybdenum; C024687:sodium molybdate(VI); C022175:ammonium molybdate
keywords: Ammonium molybdate; Daphnia magna; Industrial wastewater; Median lethal concentration; Semiconductor