The blocking between terrestrial and riverine ecosystems by impermeable concrete can cause negative impacts on plant growth, water quality, and biodiversity in riparian zones. Herein, pursuing a balance among mechanical, planting, and water purification property, chitosan/biochar-modified eco-concrete (CBEC) was prepared as a new sustainable alternative for riparian protection, ecological restoration and water quality improvement. Compressive strength of CBEC with an optimized chitosan/biochar content of 6% could reach up to 14.05 MPa, meeting the requirements for stabilizing riparian slopes. Micromorphology characterization and porosity measurement (29.63%) confirmed the abundantly porous structure of CBEC, facilitating the soil-water nutrient exchange, plant growth and microbial attachment. The 30-d water tank cultivation observed that the physiological parameters of T. orientalis planted in CBEC, including biomass, chlorophyll, protein and starch, were greatly improved compared to unmodified eco-concrete (EC). Moreover, compared to EC, biochar-modified EC and chitosan-modified EC, the planting CBEC could most effectively decrease the levels of TN, NH4+-N, TP, and COD by 53.82%, 62.50%, 88.31%, and 57.95%, respectively. Specially, the planting CBEC could degrade a common but recalcitrant pesticide nitenpyram (NTP) by 32.83% into low-toxic substances, recognized by LC-MS analysis. Microbiological analysis revealed that CBEC greatly promoted the proliferation of both nutrient-transforming bacteria (e.g., Nitrospira and Pseudomonas) and some specific species dominating NTP degradation (e.g., Rhodococcus and Bacillus). Also, PICRUSt2 prediction results identified the enrichment of functional genes related to nitrogen and phosphorus transformation. Our findings can not only develop a superior multi-performance ecoconcrete material but also provide a promising strategy for sustainable riparian restoration.
