Research on In-situ Timing Sampling Device of Pore Water in Deep-Sea Sediments

The pore water of seafloor sediments is affected by biogeochemistry and geological processes. The study of deep-sea sediment pore water sampling is of great significance to the exploration and development of marine oil and gas resources, especially in the exploration of submarine gas hydrates, which can provide effective geochemical characteristic information. For example, through continuous monitoring of the chemical composition of the deep-sea hydrothermal vent water (such as the concentration of chlorine, calcium, magnesium, iron oxide, pH value, etc.), the changes in the local seafloor crust can be assessed. Therefore, deep-sea sediment pore water is important in marine engineering geology research. In recent years, the new in-situ pore water sampling technology based on osmotic pumps has been developed significantly. The principle of this technology is that the upper part of the sampling device chamber is filled with NaCl and deionized water to form supersaturated brine. The reverse osmosis membrane doesn’t allow dissolved salts to pass through, and the salinity difference between the two sides of the membrane encourages water flow from the side with a lower concentration to the side with a higher concentration. Under this osmotic pressure, the pore water flows into the storage pipe. It is a sampler that can work continuously without power and moving parts. It can collect pore water samples independently and reliably. However, because the specific location of the pore water sample collected by the osmotic pump sampler is estimated based on the flow rate and sampling time of the osmotic pump, the equipment has the defect of insufficient time resolution when sampling for a long time. To make up for the lack of insufficient time resolution caused by long sampling time, the final pore water sample with high time resolution can be obtained more accurately. Based on previous work, this study researches the pore water sampling device of osmotic pumps. When sampling the device for a long time, simulate the diffusion process of pore water and discuss its stability. Finally, a timing marking device that can be used in the osmotic pump sampler is designed so that it can be applied to complex deep-sea environments, to can collect comprehensive, long-term, continuous deep-sea pore water data.