Effects of Polyacrylamide Application on Runoff, Sediment Yield, and Nutrient Loss on Spoil Heap Slopes With Different Gravel Contents

ABSTRACT Earth‐rock mixed accumulation bodies formed during land development and construction projects are highly susceptible to water erosion and may trigger secondary hazards. Polyacrylamide (PAM) can enhance soil structural stability, reduce erosion, and improve water and nutrient retention. However, its effects on soil and water loss in spoil heaps remain unclear. In this study, simulated rainfall experiments were conducted on spoil heaps with three gravel contents (20%, 40%, and 60%) and three PAM application rates (0, 1, and 2 g m −2 ) to evaluate runoff, sediment yield, and nitrogen and phosphorus losses. The results showed that PAM application reduced runoff and sediment production and improved erosion resistance of spoil heap materials. The erosion mitigation effect of PAM increased with increasing gravel content, whereas further increases in PAM application rate produced limited additional benefits. PAM consistently reduced nitrogen loss, whereas its effect on phosphorus loss was weaker and more variable, indicating that PAM was more effective in controlling nitrogen than phosphorus loss. Moreover, the strong coupling between runoff, sediment yield, and nutrient losses demonstrated the dominant role of runoff in controlling material transport from spoil heap slopes. Overall, this study highlights the importance of gravel‐induced structural heterogeneity in optimizing PAM application strategies for erosion and nutrient loss management in disturbed earth‐rock environments.