Degassing-free underwater dissolved carbon dioxide detection device and method

Abstract

The invention belongs to the technical field of ocean dissolved gas detection, and discloses a degassing-free underwater dissolved carbon dioxide detection device and method. The degassing-free underwater dissolved carbon dioxide detection device is provided with a computer used for providing power tuning driving signals for a power tuning unit and controlling tuning parameters of the power tuning unit;lo the computer is respectively connected with the laser driving control module and the power tuning unit; the laser driving control module is connected with the laser, and the laser is connected with the optical isolator; the optical isolator is connected with a thulium-doped optical fiber straight-cavity laser light source system, and the thulium-doped optical fiber straight-cavity laser light source system is connected with a photoacoustic cell system through the optical fiber collimator; and the photoacoustic cell system is sequentially connected with a pre-amplification circuit and a lock-in amplifier, and the lock-in amplifier is connected with the computer. According to the invention, degassing-free detection can be realized, bright field in-situ detection is realized, and the response speed and the detection sensitivity of the system are improved.

Description

technical field [0001] The invention belongs to the technical field of marine dissolved gas detection, and in particular relates to a degassing-free underwater dissolved carbon dioxide detection device and a detection method. Background technique [0002] At present, since the industrial revolution, the emission of carbon dioxide has been increasing, causing a series of climate problems such as global warming, sea level rise, and frequent extreme weather. The ocean is the largest active carbon pool on the earth, absorbing about 30% of the carbon dioxide produced by human activities. Carbon dioxide, the increase of dissolved carbon dioxide in the ocean will bring about problems such as ocean acidification, marine mineral dissolution, and marine anoxic dead zone. Therefore, the development of ocean dissolved carbon dioxide detection technology is very important. [0003] At present, marine dissolved carbon dioxide detection technology includes on-site sampling detection method...

AI Technical Summary

Problems solved by technology

Among them, TDLAS technology has the advantages of strong environmental adaptability, high sensitivity, and no consumption of sample gas, but it still needs to be degassed before detection in practical applications, and there are problems such as low degassing efficiency and slow response speed; secondly, if you want to improve detection Sensitivity requires a multi-reflection long optical path absorption cell design, which leads to an increase in the volume of the absorption cell and more gas needs to be released. At present, there is an irreconcilable contradiction between the response time and the improvement of measurement sensitivity under this scheme.

[0007] Through the above analysis, the common problems and defects in the existing technology are: need to degas first, then measure

Especially for the relatively reliable TDLAS detection technology at present, in order to improve the measurement sensitivity, a large amount of gas to be measured needs to be extracted from the seawater to fill the long optical path absorption cell, which greatly increases the measurement time of the system, and the long degassing time will bring A series of negative effects, such as reducing the temporal and spatial resolution of seawater measurement, reducing measurement accuracy

[0008] The difficulty in solving the above problems and defects is: currently there is no advanced technology that can support the degassing-free measurement of dissolved gases in seawater. The infrared light source used in TDLAS technology has extremely high transmission loss and short transmission distance in seawater, which will inevitably lead to The technology is directly used for underwater measurement accuracy, and the stability is difficult to guarantee

However, other traditional methods such as electrochemistry are limited by the reaction mechanism, and sensitive probes cannot be in direct contact with seawater.

[0009] The significance of solving the above problems and defects is: the present invention proposes a degassing-free underwater dissolved gas detection scheme based on photoacoustic spectroscopy, which solves the difficult problem of "degassing first, then measuring" in the field, and gets rid of the degassing link. The direct detection of dissolved gas in water greatly improves the response speed of the system, and the problems of low measurement accuracy and difficult gas concentration inversion caused by the long degassing time are also greatly alleviated.

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