Effects of Irrigation Water Sources on Heavy Metal Distribution and Dynamics in Soil–Corn Systems

The rational use of reclaimed water for irrigation is a vital strategy to alleviate water scarcity in arid and semi-arid regions. Assessing its impact on heavy metal behavior in soil–plant systems is crucial for ensuring agricultural safety. This study evaluated the effects of four irrigation water sources—well water (CK, control), river water (R0), a 1:1 mixture of river and reclaimed water (R1), and reclaimed water (R2)—on the distribution of heavy metals (Mn, Zn, Cu) in soil profiles and their accumulation in corn organs across growth stages. Results indicated that soil Mn content increased over time, whereas Zn and Cu levels generally decreased, with the smallest reduction observed in the R2 treatment at deeper soil layers. In corn, Mn and Cu were primarily concentrated in roots and leaves, while Zn accumulated notably in grains. Plant heavy metal content was generally lower under R2 than CK. Risk assessment indicated slight Mn pollution in soil, whereas Zn and Cu remained within safe limits. Health risk indices (THQ) for R1 and R2 were lower than CK. Overall, the mixed water treatment (R1) showed the strongest potential for controlling heavy metal contamination, suggesting that blended reclaimed water can support sustainable irrigation with long-term Mn monitoring recommended.