Atmospheric contamination from ionic liquids (ILs) is very improbable due to the low vapour pressure of these compounds. Nevertheless many ILs are water soluble and they can generate harmful effects on aquatic organisms, soils and plants.

Inhibition of bioluminescence of Vibrio fischeri bacteria is one of the most used tests to determine the toxicity of ILs, however these results cannot be extrapolated to other trophic levels. Germination and early growth tests are very commonly used in ecotoxicology studies because of their sensitivity to environmental contamination.

This work presents the main conclusions of a study of early growth of Eucalyptus globulus Labill plants on two forest soils with different pH (one acidic and one calcareous) and spiked with five different amounts of aqueous solutions of [BMIM][BF₄] (0, 1.2, 3, 12 and 30 g·kg^-1 dry soil). Six plants of E. globulus were slightly introduced into the soil surface. Quadruplicate samples for each soil and [BMIM][BF₄] dose were prepared, and the pots with soils were placed in a growth chamber with photoperiod at 25 °C, ambient humidity of 60% and light/dark cycles of 16/8 h for 2 weeks. The stems and roots length, the leaf number and the dry weight were determined in every case.

The addition of [BMIM][BF₄] had important effects on the survival and early growth of plants characterized by a decrease with the increasing IL concentration, and for doses higher than 10% the total mortality was observed for both soils. The decrease observed on the survival and early growth of E. globulus plants was lower in the calcareous soil than in the acidic soil.