Bio-based dispersants for oil spill response in estuarine environments: development strategy, mechanism exploration and impact evaluation

Oil spills pose a significant ecological threat to aquatic ecosystems due to the persistent toxic hydrocarbons, necessitating continuous efforts to improve the associated spill response. Chemical dispersants (i.e., chemical surfactants mixed with solvents) are widely used to mitigate the effects of oil spills by breaking oil into smaller droplets that dilute the oil in the water column below toxicity threshold levels and facilitate biodegradation. However, increasing concerns regarding the environmental effects of chemical dispersants and their limited performance across varying salinity levels, particularly in estuarine environments, highlight the need for sustainable and adaptable alternatives. Bio-based dispersants have emerged as promising solutions, yet the potential of mixing various biosurfactants with other components for enhanced oil dispersion remains largely unexplored. Moreover, limited research exists on evaluating bio-based dispersant performance, interfacial properties, underlying interaction mechanisms, and ecological implications across different salinity conditions. The role of such dispersants in enhancing the biodegradation of oil components also requires further investigation. To address these challenges, this thesis work aims to: 1) develop bio-aided dispersants by mixing biosurfactants with other components and investigate the mechanisms governing the interactions between dispersant components during blending; 2) examine how salinity variations influence bio-based dispersant performance and elucidate the salinity-dependent mechanisms involved; 3) assess the interfacial properties of bio-based dispersants across different salinity conditions; 4) evaluate the molecular mechanisms by which bio-based dispersants facilitate oil component biodegradation using computational tools (e.g., molecular docking and molecular dynamics simulation). The results showed that developed bio-based dispersants achieved effective oil dispersion with reduced interfacial tension and lower acute toxicity compared to conventional chemical dispersants. Molecular dynamic simulations revealed synergistic surfactant interactions that explain the salinity-dependent performance and indicated that bio-based dispersants can influence enzyme–hydrocarbons interactions relevant to biodegradation. The findings from this thesis research help provide critical insights into the development and optimization of bio-based dispersants, promoting sustainable and effective oil spill response strategies in sensitive and dynamic aquatic environments such as estuaries and coastal waters.