Placing reclamation covers is an effective method to mitigate nitrate (NO3-) release from coal gangue. This study considered the impacts of different reclamation covers on the contributions and release of NO3-from explosive and exchangeable NH4+ (NH4+-ex) sources in coal gangue using column experiments. The delta 18O-NO3-values were measured to identify the sources of NO3-in coal gangue, and the calibrated and validated hydraulic and solute parameters were used to simulate NO3-release for all treatments (without cover, CK; 30-cm sandy loess, T1; 30-cm Pisha sandstone, T2; 30-cm mixed soil, T3; 15-cm Pisha sandstone overlying 15-cm sandy loess, T4; and 15-cm sandy loess overlying 15-cm Pisha sandstone, T5). Results indicated that SEEP/W and CTRAN/W with optimized parameters accurately simulated water movement and NO3-transport. The contribution of the explosive source was 80, 81, 86, 82, 84, and 84 % and of the NH4+-ex source was 20, 19, 14, 18, 16, and 16 % for CK, T1, T2, T3, T4, and T5, respectively. Compared to CK, the five covered treatments reduced total NO3-cumulative mass released from the coal gangue by 5.59, 20.95, 7.41, 14.61, and 14.36 %, respectively. Reclamation covers significantly reduced NO3-release primarily by decreasing NO3-derived from the NH4+-ex source, with the most significant effect noted for the 30-cm Pisha sandstone cover. This reduction was attributed to limited oxygen diffusion under the cover, which decreased nitrifying bacterial activity and thus NO3-production. Future studies should further validate these findings under real-world field conditions through the optimization of model parameters.