Speech title "Simultaneous Stabilization of Arsenic and Lead in Contaminated Soil Using a Composite Amendment of Fishery By-Product-Derived Partially Calcined Oyster Shell and Biochar"
Abstract-In the Republic of Korea, the enactment of the Act on the Promotion of Recycling of Fishery By-products has established a legislative framework for promoting the recycling of shell waste as a substitute for industrial limestone. However, conventional in situ stabilization/solidification (S/S) using quicklime (CaO) derived from limestone is associated with substantial CO₂emissions during high-temperature calcination and may adversely affect soil health by excessively increasing soil pH. Therefore, the development of low-carbon amendments that support the circular use of fishery by-products while minimizing adverse effects on soil ecosystems is needed. In this study, discarded oyster shells were converted into partially calcined oyster shells (PCOS) and combined with rice husk biochar (RHB) to stabilize soil co-contaminated with arsenic (As) and lead (Pb). This approach was designed to address the potential limitation of pristine biochar, which may promote As mobilization under alkaline conditions. PCOS, calcined at 750 °C for 2 h, and RHB, pyrolyzed at 750 °C for 2 h, were mixed at mass ratios of 1:0.5, 1:1, and 1:2. The resulting amendments were applied to the contaminated soil at rates of 5 and 10 wt%. Following moist curing for 1 week at a moisture content of 35 wt%, the environmental availability of As and Pb was evaluated using 0.1 M HCl extraction. Increasing the PCOS mixing ratio and amendment application rate consistently increased soil pH from 8.37 to 9.34 and improved the stabilization performance. Among the tested treatments, the 10 wt% RHB–PCOS amendment with a mixing ratio of 1:2 exhibited the highest stabilization efficiency, reducing the HCl-extractable concentrations of As and Pb by 37.3% and 43.4%, respectively. These results indicate that PCOS derived from fishery by-products can supply Ca²⁺ and moderate the increase in soil alkalinity, thereby mitigating biochar-associated As mobilization while maintaining effective Pb immobilization. The combined use of PCOS and RHB provides a promising strategy for the valorization of marine waste and the development of low-carbon remediation technologies for As/Pb co-contaminated soils.
Speech title "Eco-Engineered Coastal Infrastructure for Marine Biodiversity Enhancement: Insights from Hong Kong"
Abstract-Rapid coastal urbanization has resulted in widespread shoreline hardening, replacing natural habitats with artificial coastal infrastructure. In Hong Kong, seawalls constructed from concrete and granite are common but typically provide limited structural complexity, reducing the availability of suitable habitats for intertidal marine organisms and contributing to biodiversity loss. To address this issue, a range of eco-engineered panels, tiles, and armour units were developed and tested on existing seawalls over periods of up to two years. These innovations incorporated habitat-enhancing features and environmentally friendly construction materials to increase ecological value while maintaining engineering performance. The results demonstrated that eco-engineered additions can significantly improve intertidal biodiversity by creating diverse microhabitats that help organisms withstand extreme environmental conditions, particularly heat and desiccation stress during the summer. The study also found that sustainable concrete mixtures containing locally sourced waste materials, including incineration ash and dredged marine sediments, are suitable for producing these eco-engineered structures. By combining habitat enhancement with resource recycling, these approaches support both biodiversity conservation and sustainable coastal development. The findings provide valuable guidance for the future planning, design, and implementation of eco-engineered shorelines in Hong Kong and other rapidly urbanizing coastal regions across Asia.
Speech title "Intelligent compaction on detecting dam construction defect beneath the surface"
Abstract-The objective of this study was to analyze and percieve the dam compaction defects relying on the intelligent compaction (IC) technology during the construction process. The dynamic response of a vibratory roller was investigated under different depth defects in the dam-subgrade. Four vibratory roller compaction models were created using the finite element method (FEM) to compare their dynamic responses. The results revealed that when the drum-soil interaction was in full contact, the dynamic response could be approximated as a harmonic excitation with a damped system. However, once the interaction was lost, the dynamic response became more complex. Deeper defects exhibited dynamic responses that closely resembled those of an intact dam-subgrade. The time required for the transition from transient to steady state depended on the soil stiffness. The harmonic ratio index Compaction Meter Value (CMV) was found to be closely related to the drum-soil interaction. Additionally, a novel method for assessing acceleration attenuation from the drum to a specified region was proposed and validated. These findings provide valuable references for the application of dectecting defects beneath the surface by IC methods.