A sediment sampling system for monitoring plume redeposition from deep-sea polymetallic nodule mining

The spatiotemporal characterization of plume sedimentation and microorganisms is critical for developing plume ecological monitoring model. To address the limitations of traditional methods in obtaining high-quality sediment, a novel sampling system with 6000 m operational capability and three-month endurance was developed. It is equipped with three sediment samplers, a set of formaldehyde preservation solution injection devices. The system is controlled by a low-power, timing-triggered controllers. To investigate low-disturbance rheological mechanisms, gap controlled rheological tests were conducted to optimize the structural design of the sampling and sealing assembly. Stress-controlled shear rheological tests were employed to investigate the mechanisms governing yield stress in sediments under varying temperature conditions and boundary roughness. Additionally, the coupled Eulerian-Lagrangian (CEL) method and sediment rheological constitutive models were employed to simulate tube-soil interaction dynamics and sediment disturbance. The radial heterogeneity of sediment disturbance and friction variation of the sampling tube were revealed. The tube was completely “plugged” at a penetration depth of 261 mm, providing critical data support to the penetration depth parameters. The deep-sea pressure test and South China Sea field trials demonstrated the system’s capability to collect and preserve quantitative time-series sediment samples with high fidelity.