This paper proposes the concepts of ESG information flows and a predictable framework of ESG flows based on AR process, and studies how ESG information flows are incorporated into and affect a dynamic portfolio with transaction costs. Two methods, called the ESG factor model and the ESG preference model, are considered to embed ESG information flows into a dynamic mean-variance model. The dynamic optimal portfolio can be expressed as a traditional optimal portfolio without ESG information and a dynamic ESG preference portfolio, and the impact of ESG information on optimal trading is explicitly analyzed. The rich numerical results show that ESG information can improve the out-of-sample performance, and ESG preference portfolio has the best out-of-sample performance including the net returns, Sharpe ratio and cumulative return of portfolios, and contribute to reducing risk and transaction costs. Our dynamic trading strategy provides valuable insights for sustainable investment both in theory and practice.

It has been confirmed that sustainable investments contributing to environmental protection can benefit from the deterioration of air pollution, but this influence mechanism has not been fully discussed. This paper proposes a mediation model to study air pollution's influence on green bonds. Theoretically, air pollution raises public environmental awareness and perceptions of physical health risks, leading to increased public concern. Enhanced public concern drives investors' green preference and environmental responsibility, thus expanding green bond demand. Our studies show air pollution is significantly positive related to public concern. Public concern positively links with green bond investment willingness, resulting in increased volatility. The total positive effect of air pollution on green bond is partly absorbed by the effect of public concern. These findings confirm the mediation role of public concern. In addition, major crisis events (e.g., COVID-19) may hinder the mediation process by generating a negative trend and distracting the public.