At present, contamination due to toxic metals is a global concern. The management of problems caused by heavy metals relies on stabilization/solidification, which is the most effective technique for the control of metal pollution in soil. This study examined the immobilization efficiency of various phosphate-based binders (Na₃PO₄, Na₂HPO₄, NaH₂PO₄), in addition to ordinary Portland cement (OPC), MgO, and CaO, for the stabilization of multi-metal-contaminated soils. Moreover, this study focused on the leachability of copper, nickel, zinc, lead, cadmium, and manganese (Cu, Ni, Zn, Pb, Cd, Mn, respectively) over different time periods and with different concentrations. Batch leaching experiments were conducted to determine the leaching ratios and percentages of the various metal concentrations, along with measuring the pH values of the leachates. Our results indicate that the use of OPC was validated due to its superior immobilization performance across all metals present in the soil, but particularly with regard to metals in high concentrations. This was due to the formation of stable hydroxides and the high pH values, which assisted in abating the metals’ solubility. Additionally, phosphate-based binders, despite being environmentally favorable, were found to be less effective, particularly for Pb and Cu, and the leaching results exceeded non-hazardous waste limits. MgO showed reasonable immobilization results but was less effective compared to OPC; on the other hand, CaO exhibited increased leaching over time. Therefore, the present research serves primarily to highlight that OPC is more suitable for soil remediation at industrial sites and in the construction of infrastructure. Meanwhile, phosphate-based binders are shown to be more appropriate for eco-friendly, non-load-bearing applications.

The contamination of urban rivers substantially threatens urban ecology, public health, and general progress. Addressing this matter is complex and challenging, particularly in tidal rivers. After investigating the climate conditions, population, and distribution of rivers and pollution in Sanya, China, a hydraulic and water quality model was built for Sanya utilizing InfoWorks ICM, and a comprehensive remediation approach was proposed. The implementation of this scheme led to a substantial decrease in point and non-point sources of pollution. In particular, COD, NH₃-N, and TP were reduced by 87.00%, 84.01%, and 74.24%, respectively, from point source pollution. Point source pollution was well-managed north of the bridge, with a reduction rate close to 40% for non-point source pollution. This research confirmed that pollutants are only temporarily retained in the river at high tide and are discharged as the tide recedes, thus having a limited impact on long-term pollution discharge. This research provides valuable references for applying water environment models and the comprehensive treatment of tidal river pollution. The final plan scheme is to significantly improve the water quality of Sanya’s rivers by effectively controlling the discharge of pollutants while achieving considerable cost savings of approximately CNY 1.7 billion.

Contamination by heavy metals is the global concern now-a-days. But the management of these heavy metals problems by stabilization/solidification is the most effective technique for controlling metal pollution in the soil. However, this research studies the immobilization efficiency of various phosphates-based binders (Na₃PO₄, Na₂HPO₄, NaH₂PO₄), which also includes Ordinary Portland Cement (OPC), MgO, and CaO for stabilizing multi-metal contaminated soils. Moreover, the current study focused on the leachability of heavy metals (Cu, Ni, Zn, Pb, Cd, Mn) over different time periods and with different concentrations. Therefore, batch leaching tests experiment were conducted to determine the leaching ratio and percentage of various metal concentrations along with measuring the pH values of the leachates. Our study results indicate that OPC validates because of its superior immobilization across all metals present in the soil, but more specifically the metals with high concentrations and also owing to the formation of stable hydroxides and high pH which assists in abating metal solubility. Additionally, phosphate-based binders, though are environmentally favorable, but disclosed less effectiveness, particularly for Pb and Cu, whereas, leaching beats non-hazardous waste limits. Conversely, MgO also offer a reasonable immobilization but was less effective as compared to OPC, while on the other hand, CaO exhibited and found to be an increased leaching over time. Therefore, this research highlights OPC's as a more suitable for soil remediation wherever structural and contamination control is essential. Despite the fact, phosphate-based binders are found to be more appropriate for eco-friendly, non-load-bearing applications.