A device and method for turbidity correction of phytoplankton photosynthetic activity

Abstract

The application discloses a kind of phytoplankton photosynthetic activity turbidity correction device and method, belong to phytoplankton monitoring technical field, the device includes excitation emission optical structure, light source driving module, signal detection module and main control module;The application constructs water turbidity scattering and initial fluorescence relative increment relationship by measuring 750nm water turbidity scattering and combined light-induced fluorescence kinetics curve, by calculating the correlation coefficient of both, the influence of water turbidity scattering on phytoplankton photosynthetic activity detection is corrected into photosynthetic activity correction model.The device structure is simple, and the measurement period is short, and it is non-invasive, and the underwater in-situ detection of phytoplankton photosynthetic activity of turbid water can be carried out, which provides a new way for rapid and accurate measurement of phytoplankton photosynthetic activity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of monitoring of planktonic algae, and particularly relates to a device and method for correcting turbidity of photosynthetic activity of planktonic algae. BACKGROUND

[0002] Planktonic algae play an important role in aquatic ecosystems, and their photosynthetic activity is crucial for assessing the health and function of the ecosystem. However, the turbidity in natural water bodies can significantly interfere with the measurement of planktonic algae photosynthetic activity. Existing measurement techniques often result in large deviations in measurement results due to the inability to effectively remove the influence of turbidity, affecting subsequent analysis and research of the ecosystem, and there is an urgent need for a device and method that can accurately correct the influence of turbidity. SUMMARY

[0003] To solve the above technical problems, the application provides a device and method for correcting turbidity of photosynthetic activity of planktonic algae.

[0004] The purpose of the application is achieved by the following technical solutions:

[0005] In a first aspect, the application provides a device for correcting turbidity of photosynthetic activity of planktonic algae, comprising an excitation emission optical structure, a light source driving module, a signal detection module, and a main control module.

[0006] The excitation emission optical structure comprises a light-shielded sample chamber, a light source, and a photomultiplier tube. The light source is vertically arranged above the light-shielded sample chamber. The light source is arranged around the photomultiplier tube and forms an angle with the photomultiplier tube. A narrow-band filter, a long-wave pass filter, a focusing mirror, and a collimating mirror are sequentially arranged at the front end of the photomultiplier tube. The light source comprises a lamp bead, a first laser diode, and a second laser diode. Light source focusing lenses are arranged at the front end of the lamp bead, the first laser diode, and the second laser diode, respectively.

[0007] The light source driving module comprises an operational amplifier, a linear voltage regulator, a MOS tube driver, and a MOS tube. A 16-bit digital-to-analog converter, an operational amplifier, a linear voltage regulator, and a laser diode are sequentially connected. A general-purpose input / output interface, a MOS tube driver, a MOS tube, and a laser diode are sequentially connected. The laser diode comprises a first laser diode and a second laser diode. The 16-bit digital-to-analog converter of the main control module outputs an adjustable voltage through the operational amplifier to adjust the voltage of the linear voltage regulator, thereby achieving dynamic control of the excitation light intensity. The GPIO port of the main control module outputs a pulse signal to control the switch circuit composed of the MOS tube driver and the MOS tube to drive the excitation light source to generate a variable light pulse signal.

[0008] The signal detection module comprises a double-channel analog switch, a scattered light signal detection channel and a fluorescence kinetics signal detection channel; the scattered light signal detection channel comprises an operational amplifier and an integral amplifier; the fluorescence kinetics signal detection channel comprises a USB communication circuit, an FPGA circuit, a fluorescence 16-bit digital-to-analog converter and a fluorescence preamplifier; the 16-bit digital-to-analog converter, the operational amplifier, the integral amplifier and the double-channel analog switch are sequentially connected; the UART communication interface, the USB communication circuit, the FPGA circuit, the fluorescence 16-bit digital-to-analog converter, the fluorescence preamplifier and the double-channel analog switch are sequentially connected; and the double-channel analog switch is connected with the photomultiplier tube.

[0009] The main control module comprises a Cortex-M8 processor, a 16-bit digital-to-analog converter, a 16-bit analog-to-digital converter, a general input and output interface, a UART communication interface, a touch liquid crystal display and a peripheral circuit, and realizes light source control, signal detection module data acquisition, data analysis and processing and device input and output control.

[0010] Further, the lamp bead is a 750nm LED lamp bead, the first laser diode is a 445nm laser diode, the second laser diode is a 632nm laser diode, the long-wave pass filter is a 670nm long-wave pass filter, and the narrowband filter is a 685nm narrowband filter.

[0011] Further, the included angle between the lamp bead, the first laser diode and the second laser diode and the photomultiplier tube is 45 degrees.

[0012] Further, the lamp bead, the first laser diode and the second laser diode are arranged at equal intervals in the circumferential direction.

[0013] Further, the power of the first laser diode is 1.6W, and the power of the second laser diode is 1.2W.

[0014] Further, the light-shielded sample chamber is made of black nylon material, has an open upper end and a hollowed-out lower end, and avoids external environmental light irradiation while not affecting water sample flowability.

[0015] Further, the long-wave pass filter is an HB670 material filter, and the narrowband filter is a BP685 interference filter.

[0016] Further, the signal detection is divided into two parts of scattered light signal detection and fluorescence kinetics signal detection.

[0017] In a second aspect, the present application further provides a method for correcting the turbidity of the photosynthetic activity of planktonic algae, and the specific steps are as follows:

[0018] Step 1: Collect water samples with different spatial distributions in the study area. The water samples with the same spatial distribution are divided into an experimental group and a control group. The experimental group is the original water sample containing water turbidity information, and the control group is the water sample that does not contain or contains a small amount of water turbidity information after sedimentation, stratification and filtration enrichment.

[0019] Step 2: Use the device to measure the turbidity scattering information of the experimental group at 750nm and construct a scattering matrix;

[0020] Step 3: Use the device to measure the single-turnover fluorescence kinetic curves of the experimental group and the control group, perform maximum normalization on the fluorescence kinetic curves, obtain the initial fluorescence by fitting and inversion, and construct the initial fluorescence relative increment matrix;

[0021] Step 4: Input the scattering matrix and the relative increment matrix into the correlation coefficient model to calculate the correlation coefficient;

[0022] Step 5: Input the correlation coefficient into the photosynthetic activity turbidity correction model to correct the effect of water turbidity scattering on the photosynthetic activity of phytoplankton.

[0023] Furthermore, the experimental group and the control group have the same chlorophyll content;

[0024] Furthermore, the scattering matrix is ​​Turb=[t1,…t i …,t N ], where Turb is the scattering matrix, t i is the scattering of experimental group i, N is the total number of experimental groups;

[0025] Furthermore, the maximum fluorescence F M The turbidity scattering of water will raise the base value of the initial fluorescence F0, thereby affecting the photosynthetic activity F V / F M Measurement results;

[0026] Furthermore, the initial fluorescence relative increment matrix is , where ΔF0 is the initial fluorescence relative increment matrix, is the initial fluorescence of experimental group i, is the initial fluorescence of control group i;

[0027] Furthermore, the correlation coefficient model is A=[a1 … a i … a N ] T =ΔF0·Turb T ·(Turb·Turb T ) -1 , where A is the correlation coefficient matrix, a iis the correlation coefficient of the experimental group i and the control group i;

[0028] Further, the correlation coefficient is , wherein alpha is the correlation coefficient;

[0029] Further, the photosynthetic activity turbidity correction model is F V / F M =1-F'0 / F M ·(1-α·Turb), wherein F V / F M is the turbidity-corrected photosynthetic activity, F'0 is the initial fluorescence before turbidity correction, F M is the maximum fluorescence.

[0030] Beneficial effects:

[0031] The present application measures the 750nm water turbidity scattering and the combined light-induced fluorescence kinetic curve, constructs the relationship between the water turbidity scattering and the initial fluorescence relative increment, and corrects the influence of the water turbidity scattering on the detection of the photosynthetic activity of the planktonic algae by calculating the correlation coefficient and bringing it into the photosynthetic activity correction model. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a schematic diagram of a photosynthetic activity turbidity correction method for planktonic algae;

[0033] Figure 2 is a schematic diagram of a measuring device of the present application;

[0034] Figure 3 is a schematic diagram of the connection of the excitation and emission optical structure, the light source driving module, the signal detection module and the main control module;

[0035] Figure 4 is a schematic diagram of the excitation and emission optical structure (one);

[0036] Figure 5 is a schematic diagram of the excitation and emission optical structure (two);

[0037] Figure 6 is a schematic diagram of the excitation and emission optical structure (three);

[0038] Figure 7 is a schematic diagram of the excitation and emission optical structure (four);

[0039] Figure 8 is a schematic diagram of the optical simulation of the excitation and emission optical structure;

[0040] Figure 9A correlation coefficient a and 750nm relationship diagram;

[0041] Figure 10 F V / F M A comparison chart.

[0042] Wherein, 10 is an excitation emission optical structure, 10a is a light shielding sample chamber, 10b is a light source focusing lens, 10c is a lamp bead, 10d is a light source fixing plate, 10e is a photomultiplier tube, 10f is a narrow-band optical filter, 10g is a first laser diode, 10h is a long-wave pass filter, 10i is a focusing mirror, 10j is a collimating mirror, and 10k is a second laser diode;

[0043] 20 is a light source driving module, 20a is a linear voltage regulator, 20b is an operational amplifier, 20c is a MOS tube, and 20d is a MOS tube driver;

[0044] 30 is a signal detection module, 30a is a dual-channel analog switch, 30b is an integrating amplifier, 30c is an operational amplifier, 30d is a fluorescence preamplifier, 30e is a fluorescence 16-bit digital / analog converter, 30f is an FPGA circuit, and 30g is a USB communication circuit;

[0045] 40 is a main control module, 40a is a 16-bit digital / analog converter, 40b is a general-purpose input / output interface, 40c is a 16-bit analog / digital converter, and 40d is a UART communication interface. DETAILED DESCRIPTION

[0046] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only used to explain the present application, and the protection scope of the present application should include the entire content of the claims. Furthermore, through the description of the following embodiments, those skilled in the art can fully realize the entire content of the claims of the present application.

[0047] EMBODIMENT

[0048] As Figure 1 shown, a phytoplankton photosynthetic activity turbidity correction method, the specific steps are as follows:

[0049] 1. Measure the 750nm water body turbidity scattering of N experimental groups, and construct a 1xN order scattering matrix Turb;

[0050] 2. Measure the fluorescence kinetic curves of N experimental groups within 0-200us, and obtain N groups of initial fluorescence by curve fitting inversion;

[0051] 3. Measure the fluorescence kinetic curves of N control groups within 0-200us, and obtain N groups of initial fluorescence by curve fitting inversion;​ ;

[0052] 4. Calculate the relative increment matrix of initial fluorescence of 1×N order ΔF0 according to the initial fluorescence of experimental group and the initial fluorescence of control group ;

[0053] 5. Calculate the correlation coefficient matrix A of N×1 order according to the scattering matrix Turb and the initial fluorescence increment matrix ΔF0, and average all elements of the matrix A to obtain the correlation coefficient α

[0054] 6. Input the correlation coefficient α into the photosynthetic activity turbidity correction model to correct the influence of water turbidity scattering in the study area on the photosynthetic activity of phytoplankton.

[0055] As shown in Figure 2 , a phytoplankton photosynthetic activity turbidity correction device includes an excitation and emission optical structure 10, a light source driving module 20, a signal detection module 30 and a main control module 40, the excitation and emission optical structure 10 (as shown in Figure 4 、 Figure 5 、 Figure 6 and Figure 7 ) includes a light-shielded sample chamber 10a, a light source fixing plate 10d, a lamp bead 10c, a first laser diode 10g, a second laser diode 10k, a light source focusing lens 10b, a photomultiplier tube 10e, a narrow-band filter 10f, a long-wave pass filter 10h, a focusing mirror 10i and a collimating mirror 10j. Figure 8 It is an optical simulation schematic diagram of the excitation and emission optical structure.

[0056] The light source driving module 20, the signal detection module 30 and the main control module 40 are as shown in Figure 3 , wherein the light source driving module 20 includes an operational amplifier 20b, a linear voltage stabilizer 20a, a MOS tube driver 20d, a MOS tube 20c and other peripheral circuits.

[0057] ​The signal detection module 30 includes a double-channel analog switch 30a, an integral amplifier 30b and an operational amplifier 30c, a fluorescence preamplifier 30d, a 16-bit digital / analog converter (sampling rate 1 MSPS) 30e, an FPGA circuit 30f and a USB communication circuit 30g and other peripheral circuits. When the scattered light signal is detected, the double-channel analog switch 30a is switched to the scattered light signal detection channel. The main control module 40 controls the light source driving module 20 to light the lamp bead 10c. The excitation light is converged into a light spot by the focusing lens 10b and irradiates the water sample in the light-shielded sample chamber 10a to form scattered light. The scattered light is received by the photomultiplier tube 10e through the collimating lens 10j, the focusing lens 10i, the long-wave pass filter 10h and the narrow-band filter 10f and is converted into an electrical signal. The electrical signal is amplified by the double-channel analog switch 30a and is received by the 16-bit analog / digital converter 40c of the main control module 40. When the fluorescence dynamic signal is detected, the main control module 40 controls the light source driving module 20 to light the first laser diode and the second laser diode. The excitation light is converged into a light spot by the light source focusing lens 10b and induces the water sample in the light-shielded sample chamber 10a to generate fluorescence. The fluorescence is converged by the collimating lens 10j and the focusing lens 10i, and then the stray light is filtered out by the long-wave pass filter 10h and the narrow-band filter 10f. The fluorescence is converted into an electrical signal by the photomultiplier tube 10e. The signal is input into the fluorescence dynamic signal detection channel through the double-channel analog switch 30a. The fluorescence signal is pre-filtered and amplified by the fluorescence preamplifier 30d, and then is collected by the high-speed data collection circuit. The collected data is output to the main control module through DMA. The fluorescence dynamic rising process in a single cycle within 200 us can be accurately measured.

[0058] The main control module 40 takes a Cortex-M8 processor as the core, combines a 16-bit digital / analog converter 40a, a 16-bit analog / digital converter 40c, a general input / output interface 40b, a UART communication interface 40d, a touch liquid crystal display and peripheral circuits, and realizes light source control, signal detection module data collection, data analysis and processing, and device input / output control.

[0059] When the scattered light signal is detected, the main control module 40 turns on the 750nm LED through the light source driving module 20, and the photomultiplier tube 10e detects the scattered light signal of the water sample in the light-shielded sample chamber 10a and converts it into an electric signal, which enters the scattered light signal detection channel through the double-channel analog switch 30a, and the integral amplifier 30b integrates and amplifies the current signal, and then the voltage follower buffers and isolates, and is received by the 16-bit analog-to-digital converter 40a of the main control module, and the scattered light signal detection is completed; when the fluorescence kinetic signal is detected, the main control module 40 turns on the first laser diode 10g and the second laser diode 10k through the light source driving module 20, and the excitation light converges into a spot through the light source focusing lens 10b to induce the water sample in the light-shielded sample chamber 10a to produce fluorescence. The fluorescence is converged through the collimating mirror 10j and the focusing mirror 10i, and then the scattered light is removed through the long-wave pass filter 10h and the narrow-band filter 10f, and the fluorescence is converted into an electric signal by the photomultiplier tube 10e. The signal enters the fluorescence kinetic signal detection channel through the double-channel analog switch 30a, and the fluorescence preamplifier 30d pre-filters and amplifies the fluorescence signal, which is then collected by the high-speed data acquisition circuit. The collected data is output to the main control module 40 through DMA, and the precise measurement of the fluorescence kinetic rising process within a single cycle of 200us can be realized.

[0060] Specifically, the turbidity correction effect of the photosynthetic activity of the planktonic algae is:

[0061] The wetland park of Tongling West Lake is selected as the research area, and water samples with different spatial distributions are collected. The original water sample is used as the experimental group, and the original water sample treated by sedimentation, layering and filtration enrichment is used as the control group. First, the device is used to measure the 750nm scattering of the experimental group to obtain a scattering matrix. Then, the device is used to measure the fluorescence kinetic curves of the experimental group and the control group to obtain the initial fluorescence by fitting and inversion. The relative increment matrix of the initial fluorescence is calculated. According to the scattering matrix and the relative increment matrix of the initial fluorescence, the correlation coefficient is calculated, as shown in the formula (1). The correlation coefficient α is 0.001. The correlation coefficient α is input into the photosynthetic activity turbidity correction model to measure the photosynthetic activity of the water samples with different spatial distributions in the research area. The results are shown in the formula (2). After correction, the photosynthetic activity is basically consistent with that of the control group, indicating that the accuracy of the photosynthetic activity measurement results is high. Figure 9 Figure 10

[0062] The above description is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.​​

Claims

1. A method for correcting turbidity of phytoplankton photosynthetic activity, characterized in that: The steps include: Step 1: Collect water samples with different spatial distributions in the study area. The water samples with the same spatial distribution are divided into an experimental group and a control group. The experimental group is the original water sample containing water turbidity information, and the control group is the water sample that does not contain or contains a small amount of water turbidity information after sedimentation, stratification and filtration enrichment. Step 2: Use the device to measure the turbidity scattering information of the experimental group at 750nm and construct a scattering matrix; Step 3: Use the device to measure the single-turnover fluorescence kinetic curves of the experimental group and the control group, perform maximum normalization on the fluorescence kinetic curves, obtain the initial fluorescence by fitting and inversion, and construct the initial fluorescence relative increment matrix; Step 4: Input the scattering matrix and the relative increment matrix into the correlation coefficient model to calculate the correlation coefficient; the correlation coefficient model is A=[a1 … a i … a N ] T =ΔF0·Turb T ·(Turb·Turb T ) -1 , where A is the correlation coefficient matrix, a i is the correlation coefficient between experimental group i and control group i; Step 5: Input the correlation coefficient into the photosynthetic activity turbidity correction model to correct the effect of water turbidity scattering on the photosynthetic activity of phytoplankton; The above method uses a turbidity correction device for photosynthetic activity of phytoplankton, which includes an excitation and emission optical structure, a light source driving module, a signal detection module and a main control module; The excitation emission optical structure includes a light-shielding sample chamber, a light source and a photomultiplier tube. The light source is vertically arranged above the light-shielding sample chamber, and is arranged around the photomultiplier tube and forms an angle with the photomultiplier tube. A narrowband filter, a long-wave pass filter, a focusing lens and a collimating lens are sequentially arranged at the front end of the photomultiplier tube. The light source includes a lamp bead, a first laser diode and a second laser diode. Light source focusing lenses are respectively arranged at the front ends of the lamp bead, the first laser diode and the second laser diode. The light source driving module includes an operational amplifier, a linear voltage regulator, a MOS transistor driver, and a MOS transistor; a 16-bit digital-to-analog converter, an operational amplifier, a linear voltage regulator, and a laser diode are connected in sequence; a universal input / output interface, a MOS transistor driver, a MOS transistor, and a laser diode are connected in sequence; the laser diode includes a first laser diode and a second laser diode; the 16-bit digital-to-analog converter of the main control module outputs an amplitude-adjustable voltage through the operational amplifier, which regulates the voltage of the linear voltage regulator to achieve dynamic control of the excitation light intensity; a GPIO port of the main control module outputs a pulse signal to control a switching circuit composed of the MOS transistor driver and the MOS transistor to drive the excitation light source to generate a variable light pulse signal; The signal detection module includes a dual-channel analog switch, a scattered light signal detection channel, and a fluorescence kinetics signal detection channel; the scattered light signal detection channel includes an operational amplifier and an integrating amplifier; the fluorescence kinetics signal detection channel includes a USB communication circuit, an FPGA circuit, a fluorescence 16-bit digital / analog converter, and a fluorescence preamplifier; the 16-bit analog / digital converter, the operational amplifier, the integrating amplifier, and the dual-channel analog switch are connected in sequence; the UART communication interface, the USB communication circuit, the FPGA circuit, the fluorescence 16-bit digital / analog converter, the fluorescence preamplifier, and the dual-channel analog switch are connected in sequence; and the dual-channel analog switch is connected to a photomultiplier tube; The main control module includes a Cortex-M8 processor, a 16-bit digital / analog converter, a 16-bit analog / digital converter, a universal input and output interface and a UART communication interface to realize light source control and signal detection module data acquisition.

2. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, characterized in that: The scattering matrix is ​​Turb=[t1,…t i …,t N ], where Turb is the scattering matrix, t i is the scattering of experimental group i, and N is the total number of experimental groups.

3. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, characterized in that: The initial fluorescence relative increment matrix is: , where ΔF0 is the initial fluorescence relative increment matrix, is the initial fluorescence of experimental group i, is the initial fluorescence of control group i.

4. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, wherein: The photosynthetic activity turbidity correction model is , where F V / F M is the photosynthetic activity after turbidity correction, is the initial fluorescence before turbidity correction, F M is the maximum fluorescence.

5. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, characterized in that: The lamp bead is a 750nm LED lamp bead, the first laser diode is a 445nm laser diode, the second laser diode is a 632nm laser diode, the long-wave pass filter is a 670nm long-wave pass filter, and the narrow-band filter is a 685nm narrow-band filter.

6. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, characterized in that: The angle between the lamp bead, the first laser diode, the second laser diode and the photomultiplier tube is 45 degrees; the lamp bead, the first laser diode and the second laser diode are arranged at equal intervals along the circumferential direction; the power of the first laser diode is 1.6W, and the power of the second laser diode is 1.2W.

7. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, characterized in that: The light-shielding sample chamber is made of black nylon, with an open top and a hollow bottom.

8. The method for correcting turbidity of phytoplankton photosynthetic activity according to claim 1, characterized in that: The long-wave pass filter is a filter made of HB670 material, and the narrow-band filter is a BP685 interference filter.

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