Over -application of nitrogen fertilizer induces soil acidification, which activates heavy metals availability and poses significant challenge to crop production and food safety. In this study, we prepared a clay-based material by ball-milling bentonite with NH4Cl (NH4Cl@bentonite) and assessed its synergistic performance in enhancing nitrogen fertilizer utilization efficiency, immobilizing heavy metals, and improving crop yield and safety. The results showed that the optimal performance of NH4Cl@bentonite was achieved by milling bentonite with NH4Cl at a 4:1 mass ratio for 9 h. NH4Cl@bentonite significantly improved soil water holding and retention capacity by 1.6 and 4.3 times, respectively. In comparison to NH4Cl alone, NH4Cl@bentonite led to a 22.3% increase in N -use efficiency and a 1.5 times enhancement in crop yield. The Pb and Cd content in water spinach shoots decreased by 55.3% and 57.5%, respectively, attributed to the transformation of heavy metals into lower bioavailability states by NH4Cl@bentonite. Experiments and Density Functional Theory (DFT) calculations indicated that NH4Cl@bentonite could immobilize Pb and Cd through processes such as cation exchange, surface adsorption, complexation, and enhancement of soil pH. This work proposes a simple and efficient method for improving cropland fertilizer utilization while ensuring healthy and sustainable development. Environmental implication: Soil acidification, caused using chemical fertilizers, especially nitrogen -based ones, threatens crop production and food safety by damaging soil structure, speeding up nutrient loss, and increasing the solubility of heavy metals. To tackle this problem, we made a clay material by mixing bentonite with NH4Cl (NH4Cl@bentonite) in a ball mill. NH4Cl@bentonite increased N -use efficiency by 22.3%, boosted crop yield by 1.5 times, and reduced the Pb and Cd levels in water spinach shoots by 55.3% and 57.5%, respectively. This work suggests a simple and effective way to enhance fertilizer use in croplands while ensuring healthy and sustainable development.

The nanoscale zerovalent iron (nZVI) was successfully modified with sulfidation and loaded by kaolin (K@SnZVI) for enhanced persulfate (PS) activation. K@S-nZVI was characterized by SEM-EDS, TEM, XPS, BET and XRD. The better degradation performance of BDE209 was in the following order: K@S-nZVI/PS> S-nZVI/PS> nZVI/PS> > systems without PS activation. The maximum removal of BDE209 was 88.32% under PS concentration of 0.2 mol/L, soil-water ratio of 1:2.5 and the molar ratio of K@S-nZVI/PS of 2:1. The reactive oxygen species in the K@S-nZVI/PS system were identified by EPR and quenching experiments as SO4- & sdot;,& sdot;OH,& sdot;O(2)(- )and the nonracial of 1 O2. SO4-& sdot; and & sdot;O-2(-) dominated the degradation of BDE209 and & sdot;OH and 1 O2 were involved. According to gas chromatography-mass spectrometer (GC-MS) and density functional theory (DFT) calculations, BDE209 could be degraded to BDE7 by gradual debromination and further degraded into Br- and short-chain acids by ring opening reaction of benzene ring. The coexistence of SO42-, Cl- , CO32-, NO3- and HA reduced the degradation of BDE209. The soil pH did not change significantly during the remediation process. At the beginning of remediation process, soil catalase activities were enhanced while phosphatase and urease activities were weakened but they all recovered finally, exhibiting less damage to microbial cells. The K@S-nZVI/PS system is expected to be practically applied to the remediation of BDE209 contaminated soil.