The ionic liquids (ILs) are often denominated as “green fluids”, because they are considered as innocuous due to their negligible volatility. Due to this apparent innocuousness, the ILs are attracted a great attention as an alternative to traditional organic solvents, highly contaminant. However, the problem of contamination is not limited to the atmosphere, since also aquatic and terrestrial environments can be affected. Therefore, and because the toxic effects of ILs on the environment are largely unknown, research studies are needed to deepen this aspect before to assign them the appellation of “green fluids”. Nevertheless, and despite the increased number in the last few years of studies on different aspects of ILs, the toxicity of these compounds to the environment in general, and to the soils in particular, only rarely is investigated. One of the most used ILs in different applications is 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). Among all the soil properties, those determining the edaphic metabolism, and especially the enzymatic activities, are highly sensitive to ascertain the disturbance caused by any external agent. Given the lack of studies investigating the effect of ILs on the edaphic environment, before the use of enzymatic activities as indicators of the toxicity for soils of any given IL, it is necessary to test if classical methods to determine the soil enzymatic activities are adequate for their use in soils spiked with that given IL.

In this study we investigated the suitability of dehydrogenase method to determine the activity of this enzyme in soils with spiked BMIMBF4, modifying the method according to the problems identified.

Acknowledgments. This research was financed by the Spanish Ministerio de Economía y Competitividad (Project No. CGL2015-66857-C2-1-R). The authors thank Ana I. Iglesias-Tojo for assistance in carrying out the analyses.