Monthly Total Nitrogen Concentration Dataset for Seaward Rivers in Qingdao, China: Insights into Piston Flow and Environmental Debt (2020-2025)

This dataset provides raw monthly Total Nitrogen (TN) concentrations (mg/L) for key seaward rivers in Qingdao, China, including Licun River (urban), Dagu River (agricultural), and Baisha River (mixed-use), from January 2020 to December 2025. Data were sourced from the China National Environmental Monitoring Centre and Shandong Provincial Environmental Monitoring Network, analyzed via GB 11894-89 method. The dataset supports the study "Unlocking the Environmental Debt: Piston Flow Mechanisms and Systemic Nitrate Toxicity in Coastal Agricultural Watersheds under Climate Extremes" (manuscript under review). It highlights a catastrophic TN rebound in 2025 (+168% in Dagu River) due to piston flow mobilization under extreme precipitation (+25.3%).Funding: National Natural Science Foundation of China (No. U1806214); Laoshan Laboratory (No. LSKJ202203900, LSKJ202203600).