A device and method for in-situ online measurement of seawater turbidity and CDOM content

Abstract

The application discloses a kind of seawater turbidity and CDOM content in-situ online measuring device and method, according to the characteristic wavelength of the characteristic difference of seawater turbidity and CDOM to light absorption or fluorescence generation, with multiple ultraviolet light tubes and infrared light tubes comprising multiple light source arrays as the driving light source of measurement system, the light emitted by light source enters the measured water sample containing CDOM after a series of optical lens combination, light is partially absorbed while exciting the characteristic wavelength related to the fluorescence of CDOM component, select narrow-band coated lens with wavelength selective transmittance to cooperate with photon counting detector to realize the detection of excited fluorescence, select wide-band coated lens to cooperate with high-sensitivity photoelectric detector to realize the detection of infrared light absorption coefficient and ultraviolet light absorption coefficient, the output signal of each detector is analyzed and processed by signal processing circuit system circuit board, obtain seawater turbidity and CDOM content information, and use turbidity information for online compensation of CDOM measurement.

Description

Technical Field

[0001] This invention relates to the technical field of measuring physical and chemical elements and biological elements in water bodies, and in particular to an in-situ online measurement device and method for seawater turbidity and CDOM content. Background Technology

[0002] In recent years, research in marine environmental monitoring, intelligent marine sensors and equipment, and marine big data has become an international hot topic. Maintaining a healthy marine environment and ecosystem is crucial for human sustainable development. In the field of marine environmental monitoring, traditional methods for measuring the physicochemical and biological elements of water bodies often involve sampling followed by chemical or spectroscopic analysis in specialized laboratories. This approach has drawbacks such as high specialization requirements, demanding equipment conditions, and poor timeliness. Developing in-situ online marine sensors and related equipment is a prerequisite for constructing a marine sensor network and building a smart ocean.

[0003] The content of colored dissolved organic matter (CDOM) in seawater has a significant impact on ocean color remote sensing, primary productivity of marine phytoplankton, and ecosystem structure and function. The geochemical processes of marine dissolved organic matter are also an important part of global carbon flux and the marine carbon cycle. As a major factor in the carbon cycle system, CDOM affects the stability of the carbon system and also influences the migration and transformation of heavy metals and organic pollutants. CDOM has strong absorption in the ultraviolet band, limiting the penetration of shortwave ultraviolet light, thus protecting the habitat of phytoplankton and other biological communities in the water.

[0004] Developing rapid, accurate, in-situ online CDOM content detection instruments and equipment is of great significance for carbon cycling, aquatic ecosystem stability, and environmental protection. However, existing in-situ CDOM sensors suffer from complex structures, poor mobile measurement performance, and high costs, which are key limitations. Existing in-situ CDOM sensors mainly employ methods such as laser-induced breakdown spectroscopy, absorption spectroscopy, and fluorescence measurement. Laser-induced breakdown spectroscopy for CDOM measurement suffers from low sensitivity, significant matrix effects, and low repeatability; for absorption spectroscopy, error compensation is difficult due to the similarity of CDOM and chlorophyll absorption spectra; fluorescence spectroscopy offers advantages such as high sensitivity and strong selectivity, but is easily affected by other factors such as water turbidity. Solving the problems of stability, reliability, and accuracy of CDOM sensors under actual sea conditions is the core issue for the practical engineering application of in-situ online CDOM sensors. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an in-situ online measurement device and method for seawater turbidity and CDOM content. The method uses a multi-wavelength combined light source array and multiple photoelectric detection devices to simultaneously realize the in-situ online measurement of seawater turbidity and CDOM content, and solves the problems of stability, reliability and accuracy of CDOM sensor under actual sea conditions.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an in-situ online measurement device for seawater turbidity and CDOM content, comprising a housing for a light source array and a signal processing circuit system. A fluorescence excitation and photodetector housing is connected below the housing for the light source array and signal processing circuit system via a first hollow titanium alloy tube and a second hollow titanium alloy tube. A light source array is disposed inside the housing for the light source array and signal processing circuit system. The light source array includes one infrared light-emitting diode and at least two ultraviolet light-emitting diodes of different wavelengths. An upper optical lens assembly is disposed below the light source array, and a first high-sensitivity photodetector is disposed on the side of the upper optical lens assembly. A signal processing circuit system circuit board is disposed above the light source array. The first high-sensitivity photodetector is connected to the signal processing circuit system circuit board. The fluorescence excitation and photodetector... The detection housing has a water tank at its center, with the water sample being tested directly in contact with the tank. The fluorescence excitation and light detection housing contains a lower optical lens assembly, a second high-sensitivity photodetector positioned in front of the lower optical lens assembly, a first silicon photon counting detector positioned on one side of the lower optical lens assembly, and a second silicon photon counting detector positioned on the other side of the lower optical lens assembly. The output electronic signal connection lines of the first silicon photon counting detector, the second silicon photon counting detector, and the second high-sensitivity photodetector pass through a second hollow titanium alloy tube and enter the housing of the light source array and signal processing circuit system, connecting to the circuit board of the signal processing circuit system. A carrier for the sensor is fixedly connected to the top of the housing of the light source array and signal processing circuit system. The circuit board of the signal processing circuit system is connected to the carrier for the sensor via waterproof terminals.

[0007] A further improvement of the technical solution of the present invention is that the housing of the light source array and signal processing circuit system and the housing of the fluorescence excitation and photodetection are both made of titanium alloy.

[0008] A further improvement of the technical solution of the present invention is that: the upper optical lens assembly includes a first focusing lens and a proportional reflector placed horizontally below the light source array, and a second focusing lens and a first high-sensitivity photodetector are arranged vertically on the side of the proportional reflector.

[0009] A further improvement of the technical solution of the present invention is that: the lower optical lens assembly includes a total reflection mirror symmetrically arranged with the proportional reflection mirror; a vertically placed incident light window, a broadband coated lens, and a second high-sensitivity photodetector are arranged horizontally on the side of the total reflection mirror; the incident light window and the broadband coated lens are respectively arranged on the rear and front sides of the water tank wall of the fluorescence excitation and photodetection housing; a first narrow-band coated lens and a second narrow-band coated lens are respectively arranged on the right and left sides of the water tank wall of the fluorescence excitation and photodetection housing; the first silicon photon counting detector is arranged on the side of the first narrow-band coated lens; and the second silicon photon counting detector is arranged on the side of the second narrow-band coated lens.

[0010] A further improvement to the technical solution of the present invention is that: a carrier for supporting the sensor is fixedly connected above the housing of the light source array and signal processing circuit system via a flange.

[0011] A further improvement to the technical solution of this invention lies in: a method for in-situ online measurement of seawater turbidity and CDOM content, comprising the following steps:

[0012] Step S1: The light emitted by the light source array under the control of the electronic drive circuit is converted into parallel light after passing through the first focusing lens and reaches the proportional reflector. Part of the light is reflected and passes through the second focusing lens to form reference light, which is then converted into photoelectric light by the first high-sensitivity photodetector and used as a reference to eliminate light source intensity fluctuations in the signal processing system. Another part of the light propagates in the first hollow titanium alloy tube and reaches the total reflection mirror fixed in the fluorescence excitation and photodetection shell, and then enters the water sample to be tested through the incident light window.

[0013] Step S2: Infrared light entering the water sample is partially absorbed, forming attenuated transmitted light. Simultaneously, the intensity of the incident infrared light and the intensity of the transmitted light are measured, and the obtained data are fitted to obtain turbidity information. At least two different wavelengths of ultraviolet light entering the water sample are partially absorbed, forming attenuated transmitted light, while simultaneously exciting CDOM in the water sample to produce at least two different wavelengths of fluorescence. The partially absorbed ultraviolet light continues to propagate in the water sample, and after passing through a broadband coated lens, it reaches a second high-sensitivity photodetector for photoelectric conversion. The at least two different wavelengths of fluorescence excited pass through a first narrowband coated lens and a second narrowband coated lens respectively to a first silicon photon counting detector and a second silicon photon counting detector for photoelectric conversion. The absorption coefficient of ultraviolet light and the intensity of excited fluorescence reflect the CDOM content information of the water sample.

[0014] Step S3: The output electronic signal connection lines of the first silicon photon counting detector, the second silicon photon counting detector, and the second high-sensitivity photodetector enter the housing of the light source array and signal processing circuit system through the second titanium metal tube, and are connected to the circuit board of the signal processing circuit system to complete the comprehensive processing and analysis of reference light information, absorption spectrum information, and fluorescence spectrum information.

[0015] Step S4: Establish a linear model of the turbidity and fluorescence spectral intensity of the water sample being tested, and reversely eliminate the influence of turbidity on the fluorescence spectrum;

[0016] Step S5: Upload the data processed by the signal processing circuit system circuit board to the carrier carrying the sensor through the waterproof terminal block and output it in digital form.

[0017] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0018] 1. In this invention, the optical path system and signal processing system are arranged in a titanium alloy shell. The light source array, each mirror group, high-sensitivity photodetector, silicon photon counting detector and signal processing circuit system that make up the measurement system are precisely fixed in the appropriate position according to the signal flow path, while giving full consideration to the ease of operation of mechanical structure processing and component assembly.

[0019] 2. Based on the inherent differences in light absorption or fluorescence characteristics of seawater turbidity and CDOM (Chemical Oxygen Demand) at specific wavelengths, this invention uses a multi-source array composed of multiple ultraviolet and infrared LEDs as the driving light source for the measurement system. The light emitted from this source passes through a series of optical lenses and enters the water sample containing CDOM. While the light is partially absorbed, it also excites fluorescence with a characteristic wavelength related to the CDOM composition. To improve detection sensitivity and accuracy, reduce ambient light interference, and avoid mutual interference among multiple wavelengths, a narrow-band coated lens with wavelength selective transmittance is used in conjunction with a photon counting detector to detect the excitation fluorescence. A broadband coated lens is used in conjunction with a high-sensitivity photodetector to detect the infrared and ultraviolet absorption coefficients. The output signals from each detector are analyzed and processed by the signal processing circuit board to ultimately obtain seawater turbidity and CDOM content information. The turbidity information is then used for online compensation in CDOM measurement. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the working principle of the optical path system of the present invention;

[0021] Figure 2 This is a diagram illustrating the overall structural layout of the present invention;

[0022] Among them, 1. Light source array, 2. First focusing lens, 3. First high-sensitivity photodetector, 4. Second focusing lens, 5. Proportional reflector, 6. Total reflection mirror, 7. Entrance window, 8. Water sample to be tested, 9. First narrowband coated lens, 10. First silicon photon counting detector, 11. Second high-sensitivity photodetector, 12. Broadband coated lens, 13. Second narrowband coated lens, 14. Second silicon photon counting detector, 15. First hollow titanium alloy tube, 16. Fluorescence excitation and photodetection housing, 17. Second hollow titanium alloy tube, 18. Light source array and signal processing circuit system housing, 19. Signal processing circuit system circuit board, 20. Flange, 21. Waterproof terminal block. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to embodiments:

[0024] like Figures 1 to 2 As shown, an in-situ online measurement device for seawater turbidity and CDOM content includes a housing 18 for a light source array and signal processing circuit system. Below the housing 18, a fluorescence excitation and light detection housing 16 is connected via a first hollow titanium alloy tube 15 and a second hollow titanium alloy tube 17. Considering the waterproof and corrosion-resistant requirements of marine environmental sensors, both the housing 18 and the housing 16 are made of titanium alloy.

[0025] A light source array 1 is housed within the housing 18 of the light source array and signal processing circuit system. The light source array 1 includes one infrared LED and at least two ultraviolet LEDs of different wavelengths. Below the light source array 1 is an upper optical lens assembly, which includes a first focusing lens 2 horizontally positioned below the light source array 1 and a tilted proportional reflector 5. A second focusing lens 4 and a first high-sensitivity photodetector 3 are horizontally positioned horizontally on the side of the proportional reflector 5. Above the light source array 1 is a signal processing circuit system circuit board 19, and the first high-sensitivity photodetector 3 is connected to the signal processing circuit system circuit board 19.

[0026] A water tank is centrally located within the fluorescence excitation and light detection housing 16, directly contacting the water sample 8 to be tested. A lower optical lens assembly is located within the fluorescence excitation and light detection housing 16. This assembly includes a total reflection mirror 6 symmetrically positioned with the proportional reflector 5. A vertically placed incident light window 7, a broadband coated lens 12, and a second high-sensitivity photodetector 11 are sequentially arranged horizontally on the side of the total reflection mirror 6. The incident light window 7 and the broadband coated lens 12 are respectively located on the rear and front sides of the water tank wall of the fluorescence excitation and light detection housing 16. A first narrow-band coated lens 9 and a second narrow-band coated lens 13 are respectively located on the right and left sides of the water tank wall of the fluorescence excitation and light detection housing 16. A first silicon photon counting detector 10 is located on the side of the first narrow-band coated lens 9, and a second silicon photon counting detector 14 is located on the side of the second narrow-band coated lens 13.

[0027] The output electronic signal connection lines of the first silicon photon counting detector 10, the second silicon photon counting detector 14, and the second high-sensitivity photodetector 11 enter the housing 18 of the light source array and signal processing circuit system through the second hollow titanium alloy tube 17 and connect to the circuit board 19 of the signal processing circuit system. The carrier of the sensor is fixedly connected to the top of the housing 18 of the light source array and signal processing circuit system via a flange 20. The circuit board 19 of the signal processing circuit system is connected to the carrier of the sensor via a waterproof terminal 21. The in-situ online measurement device for seawater turbidity and CDOM content provided by the present invention is small and low-power, and needs to be installed on the carrier of the sensor. The carrier of the sensor provides both power and measurement environment. The carrier of the sensor can be an unmanned boat, submarine, or a laboratory platform for water quality detection.

[0028] A method for in-situ online measurement of seawater turbidity and CDOM content includes the following steps:

[0029] Step S1: The light emitted by the light source array 1 under the control of the electronic drive circuit becomes parallel light after passing through the first focusing lens 2 and reaches the proportional reflector 5. After being reflected, part of the light passes through the second focusing lens 4 to form reference light, which is then converted by the first high-sensitivity photodetector 3 as a reference for eliminating light source intensity fluctuations in the signal processing system. Another part of the light propagates in the first hollow titanium alloy tube 15 and reaches the total reflection mirror 6 fixed in the fluorescence excitation and photodetection shell (16), and then enters the water sample 8 to be tested through the incident light window 7.

[0030] Step S2: Infrared light entering the water sample is partially absorbed, forming attenuated transmitted light. Simultaneously, the intensity of the incident infrared light and the intensity of the transmitted light are measured, and the obtained data are fitted to obtain turbidity information. At least two different wavelengths of ultraviolet light entering the water sample 8 are partially absorbed, forming attenuated transmitted light, which at the same time excites CDOM in the water sample 8 to produce at least two different wavelengths of fluorescence. The partially absorbed ultraviolet light continues to propagate in the water sample 8, and after passing through the broadband coated lens 12, it reaches the second high-sensitivity photodetector 11 for photoelectric conversion. The at least two different wavelengths of fluorescence excited pass through the first narrowband coated lens 9 and the second narrowband coated lens 13 respectively to the first silicon photon counting detector 10 and the second silicon photon counting detector 14 for photoelectric conversion. The absorption coefficient of ultraviolet light and the intensity of excited fluorescence reflect the CDOM content information of the water sample.

[0031] When incident light passes through the water sample 8, the intensity of the transmitted light is weakened due to the absorption and scattering effects of suspended solids and impurities in the water sample 8. According to Lambert-Beer's law:

[0032] C = A / KL

[0033] Where C is the concentration of the absorbing substance; A is the absorbance; K is the absorption coefficient; and L is the thickness of the absorption layer.

[0034] The intensity of excitation fluorescence is positively correlated with CDOM content. A model was established based on fluorescence quantum yield and fluorescence intensity to obtain the CDOM content.

[0035]

[0036] Where y f k represents the fluorescence quantum yield. f k is the rate constant for fluorescence emission; i is the rate constant for nonradiative transition processes.

[0037] Step S3: The output electronic signal connection lines of the first silicon photon counting detector 10, the second silicon photon counting detector 14, and the second high-sensitivity photodetector 11 enter the housing 18 of the light source array and signal processing circuit system through the second titanium metal tube 17, and are connected to the circuit board 19 of the signal processing circuit system to complete the comprehensive processing and analysis of reference light information, absorption spectrum information and fluorescence spectrum information.

[0038] Step S4: Establish a linear model of turbidity and fluorescence spectral intensity of the water sample being tested, and reverse the influence of turbidity on fluorescence spectrum.

[0039] Step S5: Upload the data processed by the signal processing circuit system circuit board 19 to the carrier carrying the sensor through the waterproof terminal 21 and output it in digital form.

[0040] Example 1

[0041] The light source array 1 consists of one infrared LED and two ultraviolet LEDs with different wavelengths. The center wavelength of the infrared LED is 780 nm, and the center wavelengths of the two ultraviolet LEDs are 275 nm and 370 nm, respectively. The 275 nm wavelength (corresponding to tryptophan as the main component of dissolved organic matter in water) and the 370 nm wavelength (corresponding to humic substances as the main component of dissolved organic matter in water) are used to excite CDOM in the water sample to produce fluorescence, while the 780 nm wavelength is used for turbidity measurement. The light emitted by the light source array 1 under the control of the electronic drive circuit (each LED can be time-division multiplexed or frequency-division multiplexed) is converted into parallel light by the first focusing lens 2 and reaches the proportional reflector 5. Part of the light is reflected and passes through the second focusing lens 4 to form reference light, which is then converted into photoelectric light by the first high-sensitivity photodetector 3 and used as a reference to eliminate light intensity fluctuations during signal processing. Another part of the light propagates in the first hollow titanium alloy tube 15 and reaches the total reflection mirror 6 fixed in the fluorescence excitation and photodetection housing 16, before entering the water sample 8 through the incident light window 7. The ultraviolet light (275nm, 370nm) entering the water sample is absorbed by the CDOM in the water sample and also excites fluorescence in the water sample (the center wavelength of the fluorescence excited by the 275nm light source is 340nm, and the center wavelength of the fluorescence excited by the 370nm light source is 460nm). The partially absorbed ultraviolet light continues to propagate in the water sample 8, passes through the broadband coated lens 12, and reaches the second high-sensitivity photodetector 11 for photoelectric conversion. The excited fluorescence passes through the first narrowband coated lens 9 and the second narrowband coated lens 13 to the first silicon photon counting detector 10 and the second silicon photon counting detector 14 for photoelectric conversion. The first narrowband coated lens 9 and the second narrowband coated lens 13 transmit wavelengths centered at 340nm and 460nm, respectively. The output electronic signal connection lines of the first silicon photon counting detector 10, the second silicon photon counting detector 14, and the second high-sensitivity photodetector 11 enter the housing 18 of the light source array and signal processing circuit system through the second hollow titanium alloy tube 17, and are connected to the circuit board 19 of the signal processing circuit system. This completes the comprehensive processing and analysis of reference light information, absorption spectrum information, and fluorescence spectrum information, achieving simultaneous measurement of the turbidity and CDOM of the tested water sample. The turbidity information is used to compensate for the CDOM measurement results, eliminating interference to improve the CDOM measurement accuracy. Finally, the main body of the in-situ online measurement device for seawater turbidity and CDOM content of this invention is fixed to the carrier that carries the sensor during application via flange 20, and provides digital data output through waterproof terminals 21. In the above description, the light emitted by the 780nm light source used for turbidity measurement has the same optical path as the partially absorbed ultraviolet light.

[0042] This invention uses an array of one infrared light source and two (or more) ultraviolet light sources of different wavelengths. The positions and angles of each light source are precisely adjusted so that the central emission point is focused at the focal point of a lens. The light emitted from the array is converted into parallel light by the lens and then split into two paths—a reference light and an excitation light—by a proportional reflector (the reflected part is the reference light, and the transmitted part is the excitation light). The reference light is converged by the lens and then photoelectrically converted by a photodetector, serving as a reference for compensating for light intensity fluctuations in the signal processing system. The excitation light passes through the reflector again to the incident light window and enters the water sample to be tested. The excitation light entering the water sample is partially absorbed and, on the other hand, excites the CDOM in the water sample to produce fluorescence with a wavelength related to the CDOM composition. The partially absorbed excitation light continues to propagate and is detected by a high-sensitivity photodetector through the light window lens. The fluorescence generated in the water sample is detected as a weak fluorescence signal by a silicon photon counting detector after passing through a narrow-band coated lens. Based on the fluorescence characteristics of CDOM, different ultraviolet excitation wavelengths will excite fluorescence with different center wavelengths. To effectively suppress interfering light and fluorescence of other wavelengths entering the detector and improve the signal-to-noise ratio of weak fluorescence signals, this invention sets up a separate silicon photon counting detector for each excitation fluorescence center wavelength, and performs narrowband coating on the optical window lens corresponding to each silicon photon counting detector for a specific fluorescence center wavelength. This ensures that each silicon photon counting detector precisely corresponds to a specific fluorescence wavelength, thereby effectively suppressing other light interferences besides non-characteristic fluorescence wavelengths and significantly improving the sensor's detection limit and measurement accuracy. The output signals of the aforementioned reference photodetector, transmission photodetector, and silicon photon counting detector are processed and analyzed by the signal processing circuit board to achieve real-time measurement of the turbidity and CDOM content of the tested water sample. The algorithm uses turbidity information to compensate for the CDOM measurement results, eliminating the influence of water sample turbidity on the CDOM measurement accuracy. The aforementioned optical path system and signal processing system are housed in a titanium alloy casing. The light source array, various mirror groups, high-sensitivity photodetectors, silicon photon counting detectors, and signal processing circuit system that make up the measurement system are precisely fixed in appropriate positions according to the signal flow path, while fully considering the ease of operation in mechanical structure processing and component assembly.

Claims

1. An in-situ online measurement device for seawater turbidity and CDOM content, characterized in that: The system includes a housing (18) for a light source array and a signal processing circuit system. A fluorescence excitation and light detection housing (16) is connected below the housing (18) via a first hollow titanium alloy tube (15) and a second hollow titanium alloy tube (17). A light source array (1) is housed inside the housing (18). The light source array (1) includes one infrared LED and at least two ultraviolet LEDs of different wavelengths. An upper optical lens assembly is located below the light source array (1), and a first high-sensitivity photodetector (3) is located on the side of the upper optical lens assembly. A signal processing circuit system circuit board (19) is located above the light source array (1), and the first high-sensitivity photodetector (3) is connected to the signal processing circuit system circuit board (19). A water tank is located at the center of the fluorescence excitation and light detection housing (16), and the water in the tank is in direct contact with the water being tested. Example (8), the fluorescence excitation and light detection housing (16) is provided with a lower optical lens assembly, a second high-sensitivity photodetector (11) in front of the lower optical lens assembly, a first silicon photon counting detector (10) on one side of the lower optical lens assembly, and a second silicon photon counting detector (14) on the other side of the lower optical lens assembly. The output electronic signal connection lines of the first silicon photon counting detector (10), the second silicon photon counting detector (14), and the second high-sensitivity photodetector (11) enter the light source array and signal processing circuit system housing (18) through the second hollow titanium alloy tube (17) and connect to the signal processing circuit system circuit board (19). The carrier carrying the sensor is fixedly connected above the light source array and signal processing circuit system housing (18). The signal processing circuit system circuit board (19) is connected to the carrier carrying the sensor through a waterproof terminal (21).

2. The in-situ online measurement device for seawater turbidity and CDOM content according to claim 1, characterized in that: The housing (18) of the light source array and signal processing circuit system and the housing (16) of the fluorescence excitation and photodetection system are both made of titanium alloy.

3. The in-situ online measurement device for seawater turbidity and CDOM content according to claim 1, characterized in that: The upper optical lens assembly includes a first focusing lens (2) horizontally placed below the light source array (1) and a proportional reflector (5) placed at an angle. The side of the proportional reflector (5) is horizontally arranged with a second focusing lens (4) and a first high-sensitivity photodetector (3) placed vertically.

4. The in-situ online measurement device for seawater turbidity and CDOM content according to claim 1, characterized in that: The lower optical lens assembly includes a total reflection mirror (6) symmetrically arranged with the proportional reflector (5). The side of the total reflection mirror (6) is horizontally arranged with a vertically placed incident light window (7), a broadband coated lens (12), and a second high-sensitivity photodetector (11). The incident light window (7) and the broadband coated lens (12) are respectively arranged on the rear and front sides of the water tank wall of the fluorescence excitation and photodetector housing (16). The right and left sides of the water tank wall of the fluorescence excitation and photodetector housing (16) are respectively arranged with a first narrow-band coated lens (9) and a second narrow-band coated lens (13). The first silicon photon counting detector (10) is arranged on the side of the first narrow-band coated lens (9), and the second silicon photon counting detector (14) is arranged on the side of the second narrow-band coated lens (13).

5. The in-situ online measurement device for seawater turbidity and CDOM content according to claim 1, characterized in that: The carrier that carries the sensor is fixedly connected to the housing (18) of the light source array and signal processing circuit system via a flange (20).

6. A method for in-situ online measurement of seawater turbidity and CDOM content, characterized in that: Includes the following steps: Step S1: The light emitted by the light source array (1) under the control of the electronic drive circuit becomes parallel light after passing through the first focusing lens (2) and reaches the proportional reflector (5). After being reflected, part of the light passes through the second focusing lens (4) to form reference light, which is then converted by the first high-sensitivity photodetector (3) as a reference for eliminating light source intensity fluctuations in the signal processing system. Another part of the light propagates in the first hollow titanium alloy tube (15) and reaches the total reflection mirror (6) fixed in the fluorescence excitation and photodetector shell (16), and then enters the water sample (8) to be tested through the incident light window (7). Step S2: Infrared light entering the water sample to be tested will be partially absorbed to form transmitted light with reduced intensity. At the same time, the intensity of the incident infrared light and the intensity of the transmitted light are measured, and the obtained data are fitted to obtain turbidity information. At least two different wavelengths of ultraviolet light entering the water sample (8) to be tested will be partially absorbed to form transmitted light with reduced intensity. At the same time, they will excite CDOM in the water sample (8) to produce fluorescence of at least two different wavelengths. The partially absorbed ultraviolet light continues to propagate in the water sample (8). After passing through the broadband coated lens (12), it reaches the second high-sensitivity photodetector (11) for photoelectric conversion. The at least two different wavelengths of fluorescence excited will pass through the first narrowband coated lens (9) and the second narrowband coated lens (13) to reach the first silicon photon counting detector (10) and the second silicon photon counting detector (14) for photoelectric conversion. The absorption coefficient of ultraviolet light and the intensity of the excited fluorescence reflect the CDOM content information of the water sample. Step S3: The output electronic signal connection lines of the first silicon photon counting detector (10), the second silicon photon counting detector (14), and the second high-sensitivity photodetector (11) enter the housing (18) of the light source array and signal processing circuit system through the second hollow titanium alloy tube (17), and are connected to the circuit board (19) of the signal processing circuit system to complete the comprehensive processing and analysis of reference light information, absorption spectrum information and fluorescence spectrum information. Step S4: Establish a linear model of the turbidity and fluorescence spectral intensity of the water sample (8) to eliminate the influence of turbidity on the fluorescence spectrum. Step S5: Upload the data processed by the signal processing circuit system circuit board (19) to the carrier carrying the sensor via the waterproof terminal (21) and output it in digital form.

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