DGT testing device and testing method for lake water

Abstract

The present invention provides a DGT testing device for lake water, comprising: a float and a plurality of water sampling units; each water sampling unit is provided with a DGT detection device, a water quality multi-parameter probe detection device and a water sample collection device; wherein the water sample collection device comprises: a plurality of sampling bottles, each of which is provided with a sample inlet tube and an exhaust pipe; each sample inlet tube and exhaust pipe is provided with a one-way solenoid valve; a peristaltic pump, the water sample outlet of the peristaltic pump is respectively connected to the sample inlet tubes of a plurality of sampling bottles through a first multi-way connector; at the same time, the exhaust pipes of the plurality of sampling bottles are connected to an exhaust main pipe through a second multi-way connector; a control device is connected to the peristaltic pump and each one-way solenoid valve. The device of the present invention can ensure the circular DGT in-situ test of multiple layers of water depth of lake water, and can simultaneously collect multiple layers of water samples and determine physical and chemical properties, and is suitable for the study of the distribution characteristics of multiple layers of nutrient elements in the profile of deep-water lakes.

Description

Technical Field

[0001] The invention belongs to the research field of lake water eutrophication mechanism and DGT (gradient diffusion film) technology, and specifically relates to a lake water DGT testing device and a testing method. Background Art

[0002] DGT (Diffusion Gradient Film) technology can be used to monitor available metals / nutrients / oxygenated anions in water / sediment / soil. The principle is that DGT measures the amount of solutes that diffuse through the concentration gradient of the diffusion gel and the filter membrane. After the solute passes through the diffusion layer of the DGT device, it is quickly bonded by the fixed gel. The fixed gel is behind the diffusion gel and continuously removes the solute and maintains the concentration gradient during operation (Zhang et al., 1995). Based on Fick's first law, the time-averaged flux (F) of DGT and the time-averaged concentration (C) of the DGT / solution interface can be calculated. DGT ) .

[0003] In the existing technology, circular DGT can usually be used to determine the nutrients (nitrogen / phosphorus) in lake water, thereby revealing the biological effectiveness of nutrients in water. At present, there are two types of DGT testing methods for lake water: the first is to collect lake water samples using sampling bottles, and then conduct DGT ex situ testing of water samples in the laboratory; the second is to install a circular DGT on the test device, place the test device in the lake water, and conduct in situ testing of surface water or sediment overlying water in the water body.

[0004] However, the first method mentioned above has the following problems: the physical and chemical properties of the water sample collected in the laboratory, such as Eh, pH, temperature and conductivity, change, which will affect the water chemical reaction and the form of elements, and distort the form, composition and bioavailability of the elements in the water sample collected in the laboratory. Therefore, the ex situ circular DGT test in the laboratory cannot accurately reflect the on-site element form, bioavailability and physical and chemical properties of the water sample.

[0005] The second method is to make some simple devices to achieve in-situ testing of circular DGT in water. The equipment used in the prior art includes the following: (1) a simple device for installing DGT in a PVC pipe, placing the PVC pipe in the surface water, and completing the DGT test on the surface water; (2) fixing the DGT with a crutch-shaped device, with a circular DGT placed on the upper end of the device and the lower end inserted into the sediment to fix it, to achieve the test of the water overlying the sediment; (3) using a spindle-shaped or flat device, placing the circular DGT in the device for testing the water overlying the sediment.

[0006] Although the above-mentioned test device can complete the DGT test in the surface water or overlying water of the lake, it has the following disadvantages: (1) It does not have the function of accurately collecting water samples in the DGT test area at the same time; it can only collect water samples near the test sample point at the beginning or end of the test. Such a water sampling method has a low sampling frequency, so the water sample analysis results cannot be compared with the time-integrated concentration of DGT, that is, it is impossible to accurately study the biological effectiveness and eutrophication of water elements by comparing the time-averaged concentration of DGT with the test results of multiple water samples collected at different times. (2) The existing device cannot synchronously measure the physical and chemical properties of the DGT test area. It can only use a handheld water quality analyzer to test the physical and chemical properties of the surface water before or at the end of the DGT test. It cannot in situ measure the physical and chemical properties of the middle water and the water overlying the sediment (Eh, pH, DO, salinity and temperature, etc.). The time-averaged concentration of DGT combined with the physical and chemical properties of water samples is an important method for studying the eutrophication mechanism at different water depths.

[0007] How to invent a new type of DGT testing device that can not only realize the in-situ testing of DGT in the three layers of water: the surface layer, the middle layer, and the overlying water of the sediment, but also simultaneously collect water samples from the DGT testing area of ​​the three layers of water and measure the physical and chemical properties of the three layers of water, so as to simultaneously obtain the DGT concentrations of nitrogen and phosphorus in the lake water profile, and the nitrogen and phosphorus concentrations and physical and chemical properties of the water at multiple time points obtained by conventional analysis methods; so that the research results can reflect the eutrophication mechanism of water bodies at different water depths of lake water bodies; this is a difficulty in developing an in-situ DGT testing device for water bodies. Summary of the invention

[0008] The present invention solves the technical problems that the DGT testing device in the prior art cannot realize in-situ DGT testing at multiple water depths, cannot synchronously collect water samples in the DGT testing area, and cannot synchronously determine the physical and chemical properties of the water body. Therefore, a DGT testing device is provided which can simultaneously realize in-situ DGT testing of three water layers, namely, the surface layer, the middle layer, and the water overlying the sediment, synchronously obtain the DGT concentrations of nitrogen and phosphorus in the lake water profile, the water concentrations and physical and chemical properties of the conventional analytical method, and can synchronously sample. The present invention also provides a testing method based on the DGT testing device.

[0009] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0010] A lake water DGT testing device comprises: a float; a plurality of water sampling units, which are arranged in sequence below the float in the vertical direction, and every two adjacent water sampling units and the water sampling device located at the top and the float are connected by ropes; each of the water sampling units is provided with a DGT detection device, a water quality multi-parameter probe detection device and a water sample collection device; wherein the water sample collection device comprises: a plurality of sampling bottles, each of which is provided with an inlet tube and an exhaust pipe; each of the inlet tube and the exhaust pipe is provided with a one-way solenoid valve; a peristaltic pump, the water sample outlets of the peristaltic pump are respectively connected to the inlet tubes of the plurality of sampling bottles through a first multi-way connector; at the same time, the exhaust pipes of the plurality of sampling bottles are connected to an exhaust main pipe through a second multi-way connector; a control device, connected to the peristaltic pump and the one-way solenoid valve on each of the inlet tube and the exhaust pipe.

[0011] The water sample collection device is provided with an integrated sampler, which includes: a fixed plate, on the bottom surface of which a power supply and a control device are fixedly installed; a water pump fixed base, located below the fixed base, fixedly connected to the fixed plate, on which the peristaltic pump is installed; a solenoid valve and joint fixing ring, located below the water pump fixed base, fixedly connected to the water pump fixed base, a connecting seat is installed on the solenoid valve and joint fixing ring, on which the first multi-way connector, the second multi-way connector and the one-way solenoid valve are fixedly installed; a sampling bottle fixing ring, located below the solenoid valve fixing ring, fixedly connected to the solenoid valve fixing ring, and a sampling bottle is installed below the sampling bottle fixing ring; the power supply is connected to the peristaltic pump, the one-way solenoid valve and the control device through wires respectively. The DGT detection device is provided with a DGT fixing ring, and a plurality of placement holes are evenly arranged along the circumferential direction of the DGT fixing ring, and a plurality of DGT probes are respectively installed in the plurality of placement holes.

[0012] The water quality multi-parameter probe detection device includes a base, a mounting hole is provided on the base, a detection electrode is installed in the mounting hole, and the detection electrode is fixedly installed on the mounting hole of the base through an electrode fixing cover plate; a fixing rod is fixedly installed below the base, and the base of the water quality multi-parameter probe detection device is fixedly installed above the DGT detection device through the fixing rod; the bottom probe of the detection electrode passes through the DGT fixing ring of the DGT testing device and extends to the bottom of the DGT fixing ring.

[0013] The integrated sampler is also provided with a data storage device, and the data storage device is fixedly mounted on the fixing plate and connected to the detection electrode.

[0014] There are four sampling bottles, and both the first multi-way connector and the second multi-way connector are five-way connectors; there are three water sample sampling units.

[0015] A sealing cylinder is also provided, in which the integrated sampler is detachably mounted, and the DGT fixing ring of the DGT detection device is sleeved on the outer wall of the sealing cylinder and is located at the upper part of the sealing cylinder.

[0016] The exhaust main pipe and the water suction pipe of the peristaltic pump both pass through the DGT detection device and the water quality multi-parameter probe detection device, and finally reach the base of the water quality multi-parameter probe detection device. The exhaust port of the exhaust main pipe and the water sample inlet of the water suction pipe are both arranged on the upper surface of the base.

[0017] A sampler auxiliary frame is also provided, and the water sample sampling unit is suitable for being installed on the sampler auxiliary frame in a detachable manner.

[0018] The testing method based on the lake water DGT testing device comprises: (1) placing the lake water DGT testing device in the lake water; (2) using the DGT detection device of the water sampling unit located at different depths to perform DGT detection on the water at the depth, and using the water quality multi-parameter probe detection device to detect water quality indicators; opening the one-way solenoid valves on the inlet tube and the exhaust pipe of the sampling bottle of the water sampling device, using the control device to control the peristaltic pump, the one-way solenoid valves on the inlet tube and the exhaust pipe, and pumping water into a sampling bottle at fixed intervals for sampling; (3) taking the lake water DGT testing device out of the lake water, taking out the circular DGT and the water sample in the sampling bottle, and processing and analyzing them.

[0019] The advantages of the lake water DGT testing device described in the present invention are:

[0020] The device described in the present invention can not only ensure the in-situ testing of circular DGT at three water depths of lake water, but also can simultaneously collect three water samples and measure physical and chemical properties (Eh, pH, temperature and conductivity), so as to truly reflect the biological effectiveness of nitrogen, phosphorus or metal elements in water. The device is equipped with multiple split test units, which can detect water bodies at different heights, thereby realizing the multi-layer water body testing task, and is suitable for the study of the distribution characteristics of multi-layer nutrient elements in deep water lake profiles. The device is suitable for the study of the distribution characteristics and eutrophication mechanism of eutrophic elements (nitrogen / phosphorus) in lake water profiles.

[0021] In the lake water DGT testing device described in this embodiment, there are multiple sampling bottles, and the water sample collection device is provided with a first multi-way connector, one of the connectors in the first multi-way connector is a liquid inlet, which is connected to the water sample outlet of the peristaltic pump, and the other multiple connectors of the first multi-way connector are liquid outlets, and the multiple liquid outlets are respectively connected to the injection tubes of the multiple sampling bottles, and the exhaust pipes of the sampling tubes are connected to the exhaust main pipe through the second multi-way connector, and each of the exhaust pipes and the injection tube is provided with an electromagnetic valve, and the water sample collection device is provided with a control device, which uses the control device to time the actions of the peristaltic pump and the electromagnetic valve, so that multiple water samples can be collected in one day.

[0022] In order to make the technical solutions of the lake water DGT testing device and testing method described in the present invention more clear, the present invention is further described in detail below in conjunction with specific drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] like Figure 1 The figure shows the overall structure schematic diagram of the lake water DGT testing device of the present invention;

[0024] like Figure 2 The figure shows the overall structure schematic diagram of the water sample sampling unit of the lake water DGT testing device of the present invention;

[0025] like Figure 3 Shown is an exploded view of the water sample sampling unit of the present invention;

[0026] like Figure 4 Shown is an exploded view of the integrated sampler of the present invention;

[0027] like Figure 5 The figure shows a schematic diagram of the connection relationship between the multi-way connector, the one-way electric valve and the peristaltic pump of the integrated sampler of the present invention;

[0028] like Figure 6 The figure shows the overall structure schematic diagram of the DGT detection device of the present invention;

[0029] like Figure 7 The figure shows a partially disassembled structural diagram of the DGT detection device of the present invention;

[0030] like Figure 8 Shown is an exploded view of the water quality multi-parameter probe detection device of the present invention;

[0031] like Fig. 9 The figure shows a schematic diagram of the installation of the water sampling unit on the sampler auxiliary frame after the sealing cylinder is removed according to the present invention;

[0032] Wherein, the accompanying drawings are marked as:

[0033] 1-Floating ball; 2-Water sample sampling unit; 4-Sampler auxiliary frame; 5-Counterweight chassis;

[0034] 21-Integrated sampler; 22-DGT detection device; 23-Water quality multi-parameter probe detection device;

[0035] 221-round DGT; 222-guide column; 223-DGT fixing ring; 224-electrode fixing base; 225-BPK6 plunger; 227-placement hole;

[0036] 231-electrode wire; 232-water quality multi-parameter electrode; 233-electrode fixing cover; 234-base; 235-water sample inlet; 236-top hanging ring; 237-exhaust port; 238-sealing joint; 239-third O-ring; 2310-fixing rod; 2311-electrode fixing sleeve;

[0037] 212-fixed plate; 213-exhaust main pipe; 214-first O-ring; 215-data storage device; 216-water pipe of peristaltic pump; 217-start switch; 218-power supply fixed side plate; 219-switch mounting base; 2110-PLC controller; 2111-power supply; 2112-power supply fixed block; 2113-first multi-way connector; 2114-water pump fixed base; 2115-peristaltic pump; 2116-connection seat; 2117-solenoid valve and connector Fixed ring; 2118- one-way solenoid valve; 2119- sampling bottle fixed ring; 2120- sampling bottle assembly fixed block; 2121- circuit board mounting sleeve; 2122- solenoid valve module fixed ring; 2123- sampling bottle fixed base; 2124- sampling bottle; 2125- rotating screw; 2126- sealing cylinder; 2127- second O-ring; 2128- sealing bottom cover; 2129- bottom lifting ring; 2130- second multi-way connector; 2131- power supply fixed seat; 2132- mounting ring at the top of the sealing bottom cover;

[0038] 41 - Hole on the placement ring of the sampler auxiliary rack. DETAILED DESCRIPTION

[0039] This embodiment provides a lake water DGT testing device, the entire device is made of opaque PVC plastic, foam plastic, integrated block, wire, ordinary plastic and stainless steel, etc. Figure 1As shown, the top of the device is a float 1 with a diameter of 30 cm. The float 1 is made of foam plastic and has a certain buoyancy, which allows the device to suspend in the water body and can be used for positioning. Below the float 1, three water sampling units 2 are arranged in sequence from top to bottom in the vertical direction, which are used to detect the water quality of surface water, middle layer and lower layer water in turn and implement DGT testing. A counterweight chassis 5 is arranged at the bottom of the lowest water sampling unit 2, and every two adjacent water sampling units 2 and the water sampling device and the float 1 at the top are connected by cables. In this embodiment, the height of each water sampling unit 2 is 51.9 cm and the maximum external diameter is 23 cm; the diameter of the counterweight chassis 5 is 15 cm, the thickness is 8 cm, and the weight is 3 kg. It is hoisted under the third layer of water sampling units 2. When in use, the counterweight chassis 5 is placed on the surface sediment, and the depth of the three layers of water sampling units 2 in the water is determined by the depth of the lake and the cables connecting the three devices.

[0040] like Figure 2 and Figure 3 As shown, each of the water sampling units 2 is provided with a DGT detection device 22, a water quality multi-parameter probe detection device 23 and a water sample collection device; wherein the water sample collection device comprises: a plurality of sampling bottles 2124, each of which is provided with an inlet tube and an exhaust pipe; a one-way solenoid valve 2118 is provided on each of the inlet tube and the exhaust pipe; a peristaltic pump 2115, the water sample outlets of the peristaltic pump 2115 are respectively connected to the inlet tubes of the plurality of sampling bottles 2124 through a first multi-way connector 2113; at the same time, the exhaust pipes of the plurality of sampling bottles 2124 are connected to an exhaust main pipe 213 through a second multi-way connector 2130; a control device is connected to the peristaltic pump 2115 and the one-way solenoid valve 2118 on each of the inlet tube and the exhaust pipe. In this embodiment, four sampling bottles 2124 are provided, and the first multi-way connector 2113 and the second multi-way connector 2130 are both five-way connectors, wherein one connector of the first multi-way connector 2113 is connected to the water sample outlet of the peristaltic pump 2115, and the other four connectors are respectively connected to the inlet tubes of the four sampling bottles 2124; one of the second multi-way connectors 2130 is connected to the exhaust main pipe 213, and the other four connectors are respectively connected to the exhaust pipes of the four sampling bottles 2124. The connection relationship between the multi-way connector, the one-way solenoid valve and the peristaltic pump is as shown in FIG. Figure 5 shown.

[0041] The water sample collection device in this embodiment is provided with an integrated sampler 21, such as Figure 4 As shown, the integrated sampler 21 comprises:

[0042] A fixed plate 212, on the bottom surface of which a power supply 2111, a control device and a data storage device 215 are fixedly mounted, wherein the control device is a PLC controller 2110, a mounting hole is provided at the center of the fixed plate 212, a disc-shaped power supply fixing seat 2131 is provided in the mounting hole of the fixed plate 212, and the power supply fixing seat is detachably mounted on the fixed plate 212, specifically, fixed to the fixed plate 212 by screws, and a first O-ring 214 is provided at the junction of the power supply fixing seat 2131 and the mounting hole of the fixed plate 212. The power supply 2111 is fixedly mounted on the power supply fixing seat 2131 via a power supply fixing side panel 218, and the power supply fixing side panel 218 is located on both sides of the power supply 2111. A power supply fixing block 2112 is also provided between each of the power supply fixing side panel 218 and the power supply 2111. The circuit board of the PLC controller 2110 is placed in a vertical direction and is fixed to the outer wall of the power supply fixing side panel 218 via the circuit board mounting sleeve 2121. The power supply 2111 is also provided with a starting switch 217, and the switch is fixedly mounted on the fixing plate 212 via a switch mounting base 219. The power supply 2111 is connected to the control device 2110 and the data storage device 215.

[0043] The water pump fixing base 2114 is located below the fixing plate 212 and is fixedly connected to the fixing plate 212. Specifically, the water pump fixing base 2114 is fixedly connected to the power supply fixing side plate 218 by bolts. The peristaltic pump 2115 is installed on the upper surface of the water pump fixing base 2114, and the peristaltic pump 2115 is connected to the power supply 2111.

[0044] A solenoid valve and a joint fixing ring 2117 are fixedly installed below the water pump fixing base 2114, and the solenoid valve and the joint fixing ring 2117 are fixedly connected to the water pump fixing base 2114 via a columnar connecting piece located at the center; the solenoid valve and the joint fixing ring 2117 are located below the water pump fixing base 2114, and are fixedly connected to the water pump fixing base 2114, a connecting seat 2116 is installed on the solenoid valve and the joint fixing ring 2117, and the first multi-way connector 2113, the second multi-way connector 2130 and the one-way solenoid valve 2118 on the injection tube and the exhaust pipe are fixedly installed on the connecting seat 2116, wherein the multiple solenoid valves 2118 are fixedly connected via a solenoid valve module fixing ring 2122, and the one-way solenoid valve 2118 is connected to the power supply 2111.

[0045] The sampling bottle fixing ring 2119 is located below the solenoid valve and connector fixing ring 2117. The sampling bottle fixing ring 2119 and the solenoid valve and connector fixing ring 2117 are also fixedly connected via a columnar connector located at the center. A sampling bottle assembly fixing block 2120 is formed at the bottom end of the columnar connector. A disc-shaped sampling bottle fixing base 2123 is provided at the center position of the sampling bottle fixing ring 2119. The sampling bottle fixing base 2123 is fixedly connected to the sampling bottle assembly fixing block 2120 via bolts. Four sampling bottles 2124 are installed below the sampling bottle fixing base 2123.

[0046] A DGT detection device 22 is also provided above the integrated sampler 21. Figure 6 and Figure 7 As shown, the DGT detection device 22 includes a DGT fixing ring 223. In this embodiment, 8 placement holes 227 are arranged on the DGT fixing ring 223. The 8 placement holes 227 are arranged in a row and are evenly arranged along the circumferential direction of the DGT fixing ring 223, and 8 circular DGTs 221 can be installed. As an optional embodiment, the DGT placement holes 227 of the DGT detection device 22 can also be made into a double-layer installation mode, so that the number of circular DGT tests can be increased to 16. In this embodiment, the outer diameter of the DGT fixing ring 223 is 23 cm and the height is 6.5 cm. The placement hole 227 is a circular groove, and two BPK6 plungers 225 are installed above the inside of the groove to fix the circular DGT 221 in the groove. When the DGT is removed, the plunger 225 can be automatically loosened.

[0047] The water quality multi-parameter probe detection device 23 is as follows Figure 8As shown, it includes: four water quality multi-parameter electrodes 232, which can be used to measure Eh, pH, temperature and conductivity respectively. The four water quality multi-parameter electrodes 232 are respectively vertically installed between the base 234 and the electrode fixing base 224 located below the DGT fixing ring 223. The base 234 is fixedly installed above the DGT detection device 22 through a fixing rod 2310. In this embodiment, the lower end of the fixing rod 2310 is set through the DGT fixing ring 223, and the lower end of the fixing rod 2310 is fixed to the electrode fixing base 224 by bolts. The terminal wire 231 of the water quality multi-parameter electrode 232 is connected to the sealing joint 238, and then connected to the cavity below the base 234, and connected to the power supply 2111 and the data storage 215, wherein the data storage 215 is fixedly installed on the fixing plate 212 of the integrated sampler 21, and is set close to the power supply fixing side plate 218. The probe of the water quality multi-parameter electrode 232 passes through the electrode fixing sleeve 2311 between the two fixing rods 2310, and then passes through the DGT fixing ring 223 and the electrode fixing base 224 located below the DGT fixing ring 223, and finally extends to 2 cm below the DGT detection device 22; wherein the top end of the electrode fixing sleeve 2311 is in contact with the base 234, and the bottom end is in contact with the DGT fixing ring 223. In this embodiment, the detection electrode is fixedly mounted on the base 234 through the electrode fixing cover plate 233, and a mounting hole is provided on the base 234. Two fixing bolts are provided on the lower surface of the electrode fixing cover plate 233. The electrode fixing cover plate 233 covers the top end of the electrode, and the fixing bolts can be inserted into the mounting holes on the base 234, thereby fixing the top end of the electrode.

[0048] The water sample sampling unit 2 of this embodiment is also provided with a sealing cylinder 2126, and the integrated sampler 21 is detachably installed in the sealing cylinder 2126. A detachable sealing bottom cover 2128 is provided at the bottom of the sealing cylinder 2126, and a mounting ring 2132 is provided at the top of the sealing bottom cover 2128. The mounting ring 2132 is suitable for being inserted into the bottom opening of the sealing cylinder 2126 and fixed to the sealing cylinder 2126 by screws. A base is provided at the lower end of the mounting ring 2132, and a step is formed at the connection between the base and the mounting ring 2132. When the mounting ring is inserted into the bottom opening of the sealing cylinder 2126, the step contacts the bottom end of the sealing cylinder 2126. In order to achieve a better sealing effect, a second O-ring 2127 is provided between the step and the bottom edge of the sealing cylinder 2126. A bottom hanging ring 2129 is provided on the bottom surface of the sealed bottom cover 2128 for connecting with the water sample sampling unit 2 or the counterweight chassis 5 located below.

[0049] The diameter of the sealing cylinder 2126 in this embodiment is 19.7 cm and the height is 48.5 cm. The sealing cylinder 2126 in this embodiment is a cylindrical cylinder, and a cylindrical fixing seat is arranged on the bottom surface of the base 234. The top of the sealing cylinder 2126 is open, and the top opening of the sealing cylinder 2126 can be set on the cylindrical fixing seat and fixedly installed on the fixing seat by rotating the screw 2125; when the sealing cylinder 2126 is installed on the fixing seat, the top edge of the sealing cylinder 2126 conflicts with the bottom surface of the base 234, and a third O-ring 239 is arranged between the top of the sealing cylinder 2126 and the base 234. A top hanging ring 236 is arranged at the top of the base 234 for connecting with the floating ball 1 or the water sampling unit 2 above.

[0050] After the water quality multi-parameter probe detection device 23 and the sealing cylinder 2126 are fixedly installed, the DGT fixing ring 223 is sleeved on the outer wall of the sealing cylinder 2126 and is located at the upper part of the sealing cylinder 2126.

[0051] In this embodiment, the exhaust main pipe 213 and the water suction pipe 216 of the peristaltic pump 2115 are both installed through the DGT detection device 22 and the water quality multi-parameter probe detection device 23, and finally reach the base 234 of the water quality multi-parameter probe detection device 23. The exhaust port 237 of the exhaust main pipe 213 and the water sample inlet 235 of the water suction pipe 216 are both arranged on the upper surface of the base.

[0052] The lake water DGT testing device is also provided with a sampler auxiliary frame 4, such as Fig. 9 As shown, a placement ring is provided at the top of the sampler auxiliary frame, a plurality of holes 41 are provided on the placement ring, and a plurality of guide posts 222 are provided on the bottom surface of the electrode fixing base 224. The plurality of guide posts 222 are provided corresponding to the plurality of holes on the placement ring and are suitable for being installed in the holes on the placement ring. After the experiment, the sealing cylinder can be disassembled, and the other parts of the integrated sampler 21, which are still in a fixed connection state, except for the sealing cylinder, the DGT detection device 22 and the water quality multi-parameter probe detection device 23 are placed on the sampler auxiliary frame, so as to facilitate the disassembly of the device.

[0053] The lake water body experimental method described in this embodiment comprises the following steps:

[0054] (1) Selection of study area: A total of five sampling points were selected in the Dianchi Lake in Yunnan Province. The water depth in the above area was 4–10 m.

[0055] (2) Preparation of DGT experimental materials: All DGT equipment used in this experiment was purchased from Nanjing Weishen Environmental Protection Technology Co., Ltd. The circular DGT equipment includes: ZrO, A520E and CMI-7000 Cation fixed gels, which are used for the test of phosphorus, NO3-N and NH4-N in water respectively; diffusion gel is 0.50 mm agarose diffusion gel; filter membrane is polyethersulfone microporous filter membrane with a pore size of 0.13 mm; circular DGT shell, the sampling area of ​​the circular DGT shell is 3.14 cm 2 ; For films with a diameter of 2.5 cm. The above DGT materials were assembled to form three circular DGTs for measuring phosphorus, NO3−N and NH4-N. They were sorted and placed in plastic bags, and then 2 mL of 0.001 M NaCl solution was dropped into them and stored in a refrigerator at 4 °C. Before the field test, they were installed on the DGT placement device and the test device was immediately put into place.

[0056] (3) Deployment of DGT testing device in lake water: A portable ultrasonic depth meter was used to measure the depth of lake water. The water depths at the five sampling points were 4.2, 4.8, 5.7, 7.8 and 5.2 m. The surface water depth was 10 cm below the water layer; the middle water was at 2.1, 2.4, 2.85, 3.9 and 2.6 m; and the depth of the water overlying the bottom mud was 4.0, 4.6, 5.5, 7.6 and 5.0 m. A cable was used to connect the top buoy 1, three vertically distributed water sampling units 2 and the weighted chassis 5. The weighted chassis 5, three water sampling units 2 and the top buoy 1 were placed into the water in sequence; when each water sampling unit 2 was placed, the start switch 217 was pressed to start the sampling related devices in the multi-parameter electrode and the integrated sampler 21.

[0057] (4) Retrieval of the DGT test device for lake water: After 24 hours, take out the three water body DGT test devices according to the position of the top float 1; when taking them out, immediately turn off the start switch 217, and at the same time take out the circular DGT from the groove of the DGT placement hole 227, rinse it with deionized water, and then put it into a plastic bag, add a few drops of 0.001 M NaCl solution, and store it; at the same time, take out the electrode, sampling bottle and data storage 215, and disassemble the components of the water body DGT test device; bring the above circular DGT and sampling bottle back to the laboratory, and immediately measure or store them in a refrigerator at 4°C. Bring the data storage 215 back to the laboratory, and use computer software to export and analyze the data. At the same time, repair the device parts. According to the processing effect of the computer software, the physical and chemical properties of the three layers of water at the five sample points, namely Eh, pH, temperature and conductivity data, are obtained.

[0058] (5) Subsequent processing and analysis of DGT: Open the window of the circular DGT, take out the filter membrane, diffusion gel and fixed gel. Then, ZrO fixed gel (for phosphorus determination) was used with 1.0 mol L −1 NaOH was used for elution for 24 h, and then 1.0 mol L -1 The phosphorus concentration of the neutralized gel wash solution was then determined by molybdenum blue spectrophotometry (ascorbic acid reduction) (Murphy and Riley, 1962). A520E (determination of NO3−N) and CMI-7000 Cation fixed gel (determination of NH4-N) were measured using 2 molL -1 NaCl was used for elution; UV spectrophotometry (dual wavelength) (HJ-T 346-2007) and Nessler's reagent colorimetry (HJ 535-2009) were used to measure the NO3-N and NH4-N concentrations of the two eluents, respectively. According to the above method, the DGT concentrations of phosphorus, NO3-N and NH4-N in three water layers at five sample points were obtained.

[0059] (6) Subsequent treatment and analysis of water samples: The water samples collected from the sampling bottles were tested for nitrogen and phosphorus speciation. The molybdenum blue spectrophotometry (ascorbic acid reduction) (Murphy and Riley, 1962) was used to determine: TP (total phosphorus), DTP (soluble total phosphorus) and SRP (soluble reactive phosphorus); UV spectrophotometry (dual wavelength) (HJ-T 346-2007) and Nessler's reagent colorimetry (HJ 535-2009) were used to determine: NO3-N (nitrate nitrogen), NH4-N (ammonium nitrogen) and TN (total nitrogen). According to the above methods, the concentrations of TP, DTP, SRP, NO3-N, NH4-N and TN of the water samples at the five sampling points were determined.

[0060] (7) Follow-up research: Based on the DGT concentrations of nitrogen and phosphorus in the three water depths of the five sampling points, the concentrations of various nitrogen and phosphorus forms tested by conventional analytical methods, and the physical and chemical properties of the water body, combined with the hydrological and geographical background of Dianchi Lake, the degree of nitrogen and phosphorus eutrophication and the eutrophication formation mechanism of the water body profiles of the five sampling points were studied.

[0061] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the claims.

Claims

1. A lake water DGT testing device, characterized in that: include: Float; A plurality of water sampling units are arranged in sequence below the float in the vertical direction, and each two adjacent water sampling units and the water sampling unit at the top and the float are connected by ropes; each water sampling unit is provided with a DGT detection device, a water quality multi-parameter probe detection device and a water sample collection device; The water sample collection device comprises: A plurality of sampling bottles, each of which is provided with a sampling tube and an exhaust tube; each of which is provided with a one-way solenoid valve; A peristaltic pump, wherein the water sample outlets of the peristaltic pump are respectively connected to the sample inlet tubes of the plurality of sampling bottles through a first multi-way connector; meanwhile, the exhaust pipes of the plurality of sampling bottles are connected to an exhaust main pipe through a second multi-way connector; A control device connected to the peristaltic pump and the one-way solenoid valve on each of the inlet pipe and the exhaust pipe; The water sample collection device is provided with an integrated sampler, and the integrated sampler comprises: A fixed plate, on the bottom surface of which a power supply and a control device are fixedly mounted; A water pump fixed base, located below the fixed base and fixedly connected to the fixed plate, and the peristaltic pump is installed on the water pump fixed base; The solenoid valve and joint fixing ring is located below the water pump fixing base and is fixedly connected to the water pump fixing base. A connecting seat is installed on the solenoid valve and joint fixing ring, and the first multi-way joint, the second multi-way joint and the one-way solenoid valve are fixedly installed on the connecting seat; A sampling bottle fixing ring is located below the solenoid valve fixing ring and is fixedly connected to the solenoid valve fixing ring. A sampling bottle is installed below the sampling bottle fixing ring. The power supply is connected to the peristaltic pump, the one-way solenoid valve and the control device through wires respectively. The DGT detection device comprises a plurality of DGT probes, wherein the DGT probes are circular DGTs; the DGT detection device is provided with a DGT fixing ring, and a plurality of placement holes are evenly arranged along the circumferential direction of the DGT fixing ring, and the plurality of DGT probes are respectively installed in the plurality of placement holes; The water quality multi-parameter probe detection device is provided with detection electrodes for measuring Eh, pH, temperature and conductivity indicators; the water quality multi-parameter probe detection device includes a base, a mounting hole is provided on the base, the detection electrode is installed in the mounting hole, and the detection electrode is fixedly installed on the mounting hole of the base through an electrode fixing cover plate; a fixing rod is fixedly installed below the base, and the base of the water quality multi-parameter probe detection device is fixedly installed above the DGT detection device through the fixing rod; the bottom probe of the detection electrode passes through the DGT fixing ring of the DGT testing device and extends to the bottom of the DGT fixing ring.

2. The lake water DGT testing device according to claim 1, characterized in that: The integrated sampler is also provided with a data storage device, and the data storage device is fixedly mounted on the fixing plate and connected to the detection electrode.

3. The lake water DGT testing device according to claim 2, characterized in that: There are four sampling bottles, and both the first multi-way connector and the second multi-way connector are five-way connectors; there are three water sample sampling units.

4. The lake water DGT testing device according to claim 3, characterized in that: A sealing cylinder is also provided, in which the integrated sampler is detachably mounted, and the DGT fixing ring of the DGT detection device is sleeved on the outer wall of the sealing cylinder and is located at the upper part of the sealing cylinder.

5. The lake water DGT testing device according to claim 4, characterized in that: The exhaust main pipe and the water suction pipe of the peristaltic pump both pass through the DGT detection device and the water quality multi-parameter probe detection device, and finally reach the base of the water quality multi-parameter probe detection device. The exhaust port of the exhaust main pipe and the water sample inlet of the water suction pipe are both arranged on the upper surface of the base.

6. The lake water DGT testing device according to claim 5, characterized in that: A sampler auxiliary frame is also provided, and the water sample sampling unit is suitable for being installed on the sampler auxiliary frame in a detachable manner.

7. A testing method based on the lake water DGT testing device according to any one of claims 1 to 6, characterized in that: include: (1) Placing the lake water DGT testing device in the lake water; (2) Using the DGT detection device of the water sampling unit located at different depths, perform DGT detection on the water body at the depth, and use the water quality multi-parameter probe detection device to detect water quality indicators; open the one-way solenoid valves on the inlet tube and exhaust pipe of the sampling bottle of the water sampling device, and use the control device to control the peristaltic pump, the one-way solenoid valves on the inlet tube and the exhaust pipe to pump water into a sampling bottle at fixed intervals for sampling; (3) Take the lake water DGT test device out of the lake water body, take out the circular DGT and the water sample in the sampling bottle, and process and analyze them.

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