The exceptional thermophysical properties of ionic liquids (ILs) make these compounds very attractive solvents for different applications, e.g. as the electrolyte in high-voltage batteries, advanced supercapacitors and next-generation fuel cells (owing to the wide electrochemical window and high levels of ionic conductivity and chemical and thermal stability). Thus, research on the electrochemical response of mixtures of ILs with relevant inorganic salts (such as Li, Mg, Ca and Al salts) is currently under way. The negligible vapour pressure of ILs constitutes a further advantage as it means that these materials do not contaminate the atmosphere. Nevertheless, this does not imply that they are not toxic to aquatic or terrestrial environments, and this possibility must be investigated in depth.

This study aimed to assess the toxicity of the IL ethylammonium nitrate (EAN) and of the mixture of EAN and lithium nitrate salt (EAN-LiNO₃) by evaluating the impact of different amounts of these materials on soil basal respiration, in two soils of similar texture and pH, but differing in organic matter content. The impact of both EAN and EAN-LiNO₃ mixture was more intense in the soil with the low organic matter content than in the soil rich in organic matter. The effects of EAN and EAN-LiNO₃ on soil respiration kinetics also differed between both soils. The presence of lithium intensified the toxicity of EAN, especially in the organic matter-poor soil. In addition, soil respiration decreased in a dose-dependent manner in the organic matter poor soil spiked with the highest amounts of EAN-LiNO₃.