## 4 Discussion
### Environmental Implications and Practical Applications  
The comprehensive performance analysis reveals significant implications for environmental remediation applications. The system's demonstrated ability to maintain >80% removal efficiency across 100-fold concentration ranges represents a significant advancement over conventional treatments [36]. This consistent performance across scales and concentrations suggests broad applicability in various environmental scenarios. From a cost-effectiveness perspective, the design optimizes material usage while maximizing treatment capacity. Economic analyses indicate material costs of approximately USD 45-60 m\({}^{-3}\), with operational costs 40-60% lower than conventional systems, aligning with recent cost-benefit analyses [28]. The modular design's scalability and consistent performance metrics support theoretical predictions regarding system optimization and scaling laws [23]. These findings represent a significant improvement over conventional treatment systems, which typically show 40-60% efficiency decreases under variable loads [37]. The integration of theoretical frameworks with empirical data supports the system's potential for both acute and chronic contamination scenarios. Future research directions should focus on long-term performance under variable environmental conditions, including temperature fluctuations and varying pH levels. Additionally, investigation of biochar modification strategies could further enhance removal efficiencies, particularly for metals showing lower removal rates. The potential for in situ regeneration of the biochar component through innovative cavity design modifications also warrants exploration. In real-world riparian applications, our system would face complex conditions beyond those tested in controlled laboratory settings. Typical contaminated riparian zones contain multiple heavy metals simultaneously at varying concentrations, with reported levels in industrial areas in the range of 0.01-5.0 mg\(\cdot\)L\({}^{-1}\) for Cd\({}^{2+}\) ions, 0.05-10.0 mg\(\cdot\)L\({}^{-1}\) for Pb\({}^{2+}\) ions, 0.1-20.0 mg\(\cdot\)L\({}^{-1}\) for Cr\({}^{3+}\) ions, 0.5-50.0 mg\(\cdot\)L\({}^{-1}\) for Cu\({}^{2+}\) ions, and 1.0-100.0 mg\(\cdot\)L\({}^{-1}\) for Zn\({}^{2+}\) ions [1]. Additionally, natural pH fluctuations occur in response to rainfall events (typically causing pH decreases of 0.5-1.5 units), seasonal variations, and diurnal cycles influenced by photosynthetic activity (causing pH increases of 0.5-2.0 units in productive waters). Our modular design offers inherent resilience to these variations through that (1) the concrete matrix's buffering capacity, which helps stabilize localized pH within the biochar cavity; (2) the system's ability to maintain >75% removal efficiency across a broad concentration range, as demonstrated in our multi-concentration experiments; and (3) the potential for field adjustments by replacing or regenerating individual modules as needed. The long-term stability of our modular system was assessed through accelerated weathering tests simulating 3 years of environmental exposure. The concrete matrix maintained >90% of its initial compressive strength and >85% of original permeability after equivalent to 3 years of weathering cycles. Regarding biochar stability, the cavity design effectively contains the biochar while allowing water contact, with less than 2% biochar mass loss observed after 50 simulated high-flow events (equivalent to major storm surges). The concrete cavity functions as an effective confinement material, preventing biochar dispersion while maintaining treatment functionality. Based on these results and extrapolation models, we estimate a minimum functional lifespan of 5-7 years for the complete module before significant performance degradation occurs, with biochar replacement or regeneration possible without replacing the entire concrete structure.