Abstract
CO2 enrichment in the marine environment caused by leakages from carbon capture and storage technologies may occur over operational procedures. An integrated approach using weight-of-evidence was applied to assess the environmental risk associated with the acidification caused by CO2 enrichment in coastal sediments from Santos (Brazil). Chemical analyses (metal(loid)s and organic contaminant (e.g., hydrocarbons), toxicity tests (amphipods mortality, sea-urchin embryo-larval development) and macro-benthic community structure alteration assessment were performed with different acidified scenarios (pH 8.0–6.0) for two stations with different contamination degrees. These lines of evidence were statistically analyzed and integrated (multivariate analysis and ANOVA). Results of toxicity showed significant chronic effects starting at pH 7.0 while acute effects were observed starting at pH 6.5. The macro-benthic community integrity showed significant differences for all treatments at the Piaçaguera channel station, considered to be moderately contaminated. Results from the multivariate analysis correlated toxic effects and increase in the mobility of some elements with acidification. Also, the biological indexes were correlated with concentrations of dissolved Zn in seawater. The pH of 6.0 was extremely toxic for marine life due to its high acidification and metal bioavailability. The approach herein identified and discriminated the origin of the degradation caused by the acidification related to the enrichment of CO2.
Highlights
The increasing of anthropogenic activities since the pre-industrial era produced a series of changes in the ecosystems due to the CO2 increase in the atmosphere and high anthropogenic emissions such as the use of fossil fuel, electric power plants, and automobiles, among others [1]
The weight-of-evidence approach was successfully applied in this study using different lines-of-evidence that allows an environmental risk characterization related to the enrichment of CO2 in the studied coastal zones
The results showed chronic biological adverse effects associated with values of pH 7.0, significantly differenced to the reference case (PAI station, pH 8.0) using a sediment with low contamination levels (PAI station)
Summary
The increasing of anthropogenic activities since the pre-industrial era produced a series of changes in the ecosystems due to the CO2 increase in the atmosphere and high anthropogenic emissions such as the use of fossil fuel, electric power plants, and automobiles, among others [1]. Previous studies estimated that CO2 concentrations in the atmosphere have been raised from 280 ppm, dated in the pre-industrial era, to current concentrations higher than 415 ppm (Mauna Loa–Hawaii–observatory 2021 [2]) In this way, mitigation strategies to combat the impact caused from the increase of greenhouse gases (such as carbon dioxide) and the climate change phenomena have been considered in the last few years [3]. Among the strategies to reduce the CO2 atmosphere levels, some consist of large-scale carbon capture and storage (CCS) in geological formations, which might contribute to a 19% reduction of CO2 emissions by 2050 [4] Despite of this current practice, there are some gaps in the environmental risk assessment of the technique; it still remains largely unexplored hampered by complex ecological relationships and different ecosystems [5,6]. Many studies have been performed in the last few years in order to analyze the potential effects from CO2 enrichment in the ocean caused by both increases in CO2 atmosphere concentrations and natural uptake on seawater surface, and by CO2 leakages during the CCS process (e.g., [7,8,9,10]), as well as in combination with harmful substances [11,12]
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