Long-term environmental impact of an artificial island of solidified dredged marine silt

Marine dredging silt that has been solidified is commonly used as a filler material for inland reclamation and artificial island construction. However, determining the long-term environmental safety of artificial islands made of solidified silt is a challenge. A bridge-tunnel conversion artificial island made of solidified silt was the research location of this study. Laboratory tests were conducted to study the effect of cement content on pollutant pore-water concentration and hydraulic conductivity of solidified silt. The results showed that after solidification treatment, the concentration of heavy-metal concentration in the pore water of dredged silt reduced by 60%–85%, whereas the concentration of OH− increased 106–1070 times, and the hydraulic conductivity decreased by approximately three orders of magnitude. On the basis of the test results, the finite element method was used for simulating the long-term transport of heavy metal Ni2+ and OH− artificial islands. When the cement content increased from 60 to 100 kg/m3, the Ni2+ concentration in the dam around the solidified silt decreased by approximately 68%, whereas the OH− concentration increased approximately 10-fold. However, none of them exceeded the seawater water quality standard. This indicates that the long-term environmental safety of the artificial island could be ensured.