<p>Baseline regression results.</p>

Trade liberalization has accelerated export growth in China’s coastal regions, becoming a major driving force behind local economic development. However, this rapid expansion has also imposed severe environmental pressures on marine ecosystems. As a key indicator for assessing the technological content and quality level of export structures, export sophistication warrants in-depth investigation regarding its potential impact on the marine environment. Drawing on panel data from 11 coastal regions in China between 2011 and 2022, this study employs a two-way fixed-effects model to empirically examine the relationship between export sophistication and marine pollution. The baseline regression results show that higher export sophistication significantly reduces marine pollution. The System GMM dynamic panel analysis further confirms a lagged, long-term pollution-reducing effect. Moreover, environmental regulation, port size, and industrial structure weaken this effect, indicating that the environmental benefits of export sophistication diminish under stricter regulatory conditions, larger port scales, or more advanced industrial structures. The mediation analysis reveals that green technological innovation partially transmits the impact of export sophistication on pollution reduction. Robustness checks, including the exclusion of provinces with extreme pollution levels, confirm the stability of the findings. Heterogeneity analysis further shows that the effects vary across different types of marine pollutants. This study enriches the research perspective on the link between export sophistication and environmental pollution, providing theoretical foundations and policy implications for promoting coordinated development between export structure optimization and marine environmental governance.贸易自由化加速了中国沿海地区的出口增长，成为推动当地经济发展的核心动力。然而，这种快速扩张也给海洋生态系统带来了严峻的环境压力。作为衡量出口结构技术含量与质量水平的关键指标，出口复杂度（export sophistication）对海洋环境的潜在影响值得深入探究。本研究基于2011至2022年中国11个沿海地区的面板数据，采用双向固定效应模型实证检验出口复杂度与海洋污染之间的关联。基准回归结果显示，更高的出口复杂度能够显著降低海洋污染水平。系统广义矩估计（System GMM）动态面板分析进一步证实了其滞后性的长期污染减排效应。此外，环境规制、港口规模与产业结构会削弱这一效应，表明在更严格的监管条件、更大的港口规模或更高级的产业结构下，出口复杂度的环境效益会有所减弱。中介效应分析表明，绿色技术创新在出口复杂度影响污染减排的过程中发挥了部分传导作用。剔除极端污染省份等稳健性检验证实了研究结论的稳定性。异质性分析进一步显示，该效应因不同类型的海洋污染物而存在差异。本研究丰富了出口复杂度与环境污染关联的研究视角，为推动出口结构优化与海洋环境治理的协同发展提供了理论基础与政策启示。