Room-temperature ionic liquids (RTILs) recently have generated great interest as a result of their potential commercial applications. In particular, because of their negligible vapor pressure and low inflammability, they have been suggested as green alternatives to traditional organic solvents. The toxicity and potential environmental risk of this heterogeneous class of chemicals, however, are poorly understood. An alkyl-substituted RTIL, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]), is one of the most widely used cations of RTILs, and information regarding its toxicity is relatively extensive. On the other hand, oxygenated chain-substituted ionic liquids, 1-methoxyethyl-3-methylimidazolium salts (moemims), are a new class of RTILs that have been poorly studied. Here, we compared the acute toxicity of [bmim][BF(4)] and moemims to the crustacean Daphnia magna (end point, 48-h immobilization) and the bacterium Vibrio fischeri (end point, 15-min inhibition of bioluminescence). The concentrations of [bmim][BF(4)] resulting in 50% of the maximum adverse effect (EC50s) for D. magna and V. fischeri were 5.18 and 300 mg/L, respectively, and were consistent with previously published values. The EC50s of the two moemims for D. magna are very similar, ranging from 209 to 222 mg/L in different experimental trials, and are higher by two orders of magnitude than the EC50 of [bmim][BF(4)]. The EC50s of 1-methoxyethyl-3-methylimidazolium tetrafluoroborate ([moemim][BF(4)]) and 1-methoxyethyl-3-methylimidazolium dicyanamide ([moemim][dca]) for V. fischeri are 3,196 and 2,406 mg/L, respectively. Results indicate that introduction of an oxygenated side chain in the imidazolium cation can greatly reduce the toxicity of RTILs and that these RTILs are less toxic than commonly used chlorinated solvents, such as tricloromethane, but are more toxic than nonchlorinated solvent, such as methanol and acetone.
Lake Orta (N. Italy) was severely polluted from 1927 by an effluent from a rayon factory, which discharged great amounts of ammonium nitrogen and copper into the lake. In the mid nineteen fifties, some plating factories also started dumping chromium and aluminum. As a result of ammonium oxidation, the lake became very acid and the concentration of metals in the waters reached very high values. Phytoplankton, zooplankton and fish disappeared suddenly from the lake which was by 1930 classified as “sterile”. Later on, about the fifties, a small population of Cyclops abyssorum re-colonised the lake together with some rotifers, in particular Hexarthra fennica. In mid eighties following the introduction of anti-pollution legislation, ammonium loads were greatly reduced and Daphnia obtusa was recorded. The lake waters however were still very acid, prompting the proposal of the Istituto Italiano di Idrobiologia to lime the lake with calcium carbonate to neutralise the excess acidity and reconstruct the alkaline reserve. This was done successfully from May 1989 to June 1990. pH values began to rise and in the same time the metal concentrations decreased, so that at present the lake waters are almost “normal”. In the meantime, due to the increased pH values, D. obtusa was replaced by D. longispina and, as toxic metal concentrations became lower, Megacyclops viridis, Bosmina longirostris, Diaphanosoma brachyurum, Keratella quadrata, Asplanchna priodonta. and other Brachionidae species appeared. Diaptomidae are still absent, except for some specimens of Arctodiaptomus wierzejskii
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