From online engagement to offline action: how social media environmental engagement shapes university students' pro-environmental citizenship through intrinsic motivation and personal norms.

Introduction: In the context of intensifying global ecological crises, leveraging social media platforms to foster spontaneous pro-environmental behaviors among college students has become a critical issue in sustainability research. This study integrates self-determination theory and the value-belief-norm theory to construct a serial dual-mediator model, with environmental intrinsic motivation and environmental self-accountability as sequential mediators. It examines how social media environmental engagement influences university students' organizational citizenship behavior for the environment and the underlying psychological mechanisms. Methods: Based on survey data from a sample of Chinese university students, this study employs regression analysis and the bootstrap method for mediation testing. Results: The results support three coexisting mediation pathways: the separate mediating role of environmental intrinsic motivation, the separate mediating role of environmental self-accountability, and the serial mediating role of environmental intrinsic motivation followed by environmental self-accountability. Discussion: These findings reveal a deep alignment between the motivational internalization mechanism of self-determination theory and the norm-activation mechanism of the value-belief-norm theory. Specifically, the deep internalization of intrinsic motivation systematically amplifies the effect of norm activation. Practically, these insights provide a basis for designing digital strategies for environmental education in universities and crafting content for environmental communication on social media.