Metal mobility and toxicity to microalgae associated with acidification of sediments: CO2 and acid comparison

• The paper analyses the potential impacts of CO2 leakage from CCS activities.
• CO2 injection system is developed to perform experiments with contaminated sediments.
• Toxicity tests are performed with marine microalgae.
• Mobility of metals from sediment to elutriates is increased due to acidification.
• Microalgae growth is inhibited due to acidification and presence of metals.

The injection and storage of CO2 into marine geological formations has been suggested as a mitigation measure to prevent global warming. However, storage leaks are possible resulting in several effects in the ecosystem. Laboratory-scale experiments were performed to evaluate the effects of CO2 leakage on the fate of metals and on the growth of the microalgae Phaeodactylum tricornutum. Metal contaminated sediments were collected and submitted to acidification by means of CO2 injection or by adding HCl. Sediments elutriate were prepared to perform toxicity tests. The results showed that sediment acidification enhanced the release of metals to elutriates. Iron and zinc were the metals most influenced by this process and their concentration increased greatly with pH decreases. Diatom growth was inhibited by both processes: acidification and the presence of metals. Data obtained is this study is useful to calculate the potential risk of CCS activities to the marine environment.