| Seawater gas research has become the forefront subject of the current ocean resources exploration and scientific research. The abnormal distributions of the symbolic gases, such as CH4, H2S, CO2and H2, are important tracers to find deep-sea hydrothermal fluids, cold springs and gas hydrate. Utilizing the abnormal information of the symbolic gases to find the active mineralogenetic area is one of the important prospects on the current ocean floor resource exploration. The question is how to quickly and accurately collect the seawater samples and make sure those samples truly reflect the in-situ information of the gas compositions has therefore become a hot but difficult topic in the field of ocean technology in recent years.In non gas-tight sampling, some gas in seawater will leak, which leads in the distortion in the results of analysis. The intensive ocean science research needs more accurate and abundant information of seawater, and the non gas-tight sampling can't meet the requirement obviously. The common feature of the existing gas-tight sampler is complex in construction, and is carried by submersible, ROV or AUV with high cost.In present dissertation, a novel deep-sea gas-tight sampling system is studied. A method of discrete gas-tight seawater sampling is introduced. Based on self-adaptive pressure equalizing, a piston type deep-sea gas-tight water sampler with simple structure is presented, which can be carried by CTD water sampler. Using the deep-sea gas-tight water sampler, the appointed gas-tight water sampler can be sampled rapidly and accurately, and the gas remains integrity.By applying fluid mechanics, the volume of self-adaptive pressure equalizer is calculated, and the dynamic model of deep-sea gas-tight water sampler is set up. The simulating results show that the self-adaption pressure equalizer is feasible and reliable.The prototype of deep-sea gas-tight water sampler is developed, whose material is UPVC or 316 stainless steel, which can prevent eroding and polluting during the sampling and storing process. Some problems were found in the pool test and primary sea trial, the optimal design was thus carried out in order to improve the reliability and operability.Based on Lab VIEW the measurement and control system for deep-sea gas-tight water sampler is developed. The data are sampled, analyzed, logged and stored in real time, and the water sampler is monitored and controlled rapidly and accurately. All the operation is controlled automatically. In order to solve the distortion problem, a non-pollution and non-leakage sampler transferring method is presented by interface design.Two sea trials were carried out respectively in South China Sea and hydrothermal area off Kueishantao Island of Taiwan. For the first time, in South China Sea the gas-tight seawater samplers at 3930m were obtained and the sectional gas-tight seawater samplers at 1194m were also obtained in the gas hydrate potential region.The study of the dissertation shows that it's essential to sample the discrete gas-tight seawater, the deep-sea gas-tight water sampler based on on self-adaptive pressure equalizing is feasible, effective, reliable and successful, and the non-pollution and non-leakage sampler transferring method is also effective and reliable.It's certain that the results of present research provide instructive theory and experimental data for engineering application of deep-sea gas-tight sampling system, and also present important academic and technical support to survey,evaluate and delimit the ocean resource's potential region such as gas hydrate.
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