Ecotoxicity of nitramines, important transformation products of amines used in carbon capture

Summary

Norway has the world’s largest facility for testing and improving CO2 capture. The aim of carbon capture technology is to minimize greenhouse gas emissions through a reaction between amines and effluents from gas power plants. During the overall process of CO2 capture, amines and their transformation products might escape to the environment through emissions, leakage, and as solid waste. The two main groups of transformation products with the most potential to cause environmental harm have been identified as nitrosamines and nitramines, both of which are considered to be carcinogenic. Recent theoretical modelling as well as laboratory experiments have found nitramine compounds, 2-nitroaminoethanol (CAS: 74386-82-6) and dimethylnitramine (CAS: 4164-28-7) to be present. However, despite the likelihood of these compounds increasing in the environment, no environmental toxicity data for these compounds currently exist. The aim of this project was to provide an environmental risk assessment for the selected nitramine compounds taking into account the key trophic groups within freshwater, marine and terrestrial environments. The toxicity assessment was made using a suite of standardised bioassays for the measure of acute and chronic toxicity. In the soil environment, the most potent compound was 2-nitroaminoethanol, which impaired the reproduction of earthworms and the seedling emergence of sunflower and ryegrass. The opposite was found in the aquatic environment, with freshwater and marine species consistently more affected by dimethylnitramine. All the tested freshwater species were more sensitive to nitramines than marine species. The selected amines were not acutely toxic to aquatic and soil species, with EC50 in the mg/L range. Both nitramines increased the nitrogen and carbon transformation activity of soil microorganisms.