Method for automatically monitoring nitrogen and phosphorus loss of agricultural non-point source in watershed scale

Abstract

The invention discloses a drainage basin scale agricultural non-point source nitrogen and phosphorus loss automatic monitoring method. The method comprises the following steps: firstly, performing hydrological analysis to extract small drainage basins in a research area; screening out a nitrogen and phosphorus standard-exceeding section of which the surface water quality is mainly influenced by agricultural production activities, and selecting a small watershed of which the section water quality exceeds the standard and the agricultural non-point source influence is large as a key catchment area in combination with land utilization data; then constructing a water quality environment intelligent monitoring system, and arranging on-line monitoring station houses on water quality sections of entrances and exits of the key catchment areas according to an entrance and exit total quantity control method to synchronously monitor water quality conditions and water regimen conditions; and finally, the water quality and water regimen data are sent to the Internet of Things wireless monitoring micro base station through the Internet of Things wireless monitoring node, and the Internet of Things wireless monitoring micro base station transmits the water quality and water regimen data to the Internet of Things cloud platform through GPRS. The problems of distortion and overestimation of calculation results caused by traditional agricultural non-point source monitoring are solved, and the agricultural non-point source pollution monitoring precision is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural non-point source pollution monitoring, and particularly relates to an automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale. Background Art

[0002] According to years of positioning monitoring data, the average nitrogen fertilizer utilization rates of the main food and cash crops in China, such as rice, corn, and vegetables, are 18%-36% respectively, and the average phosphorus fertilizer utilization rates are 10%-15% respectively. The high chemical fertilizer application intensity and low fertilizer utilization rate have exacerbated the risk of agricultural non-point source pollution and restricted the green and high-quality development of agriculture in China. Therefore, it is necessary to strengthen the monitoring and prevention and control of agricultural non-point source pollution.

[0003] Agricultural non-point source pollution refers to the diffusion of pollutants (such as nitrogen, phosphorus, pesticides, sediments) into water bodies and soil through rainfall, runoff, seepage, etc. during agricultural production activities. It is difficult to trace the specific emission sources and has the characteristics of dispersion, intermittency, and complexity. Therefore, carrying out agricultural non-point source pollution monitoring is of great significance for environmental management, precision agriculture, and ecological security. At present, the development progress of agricultural non-point source pollution monitoring work varies at home and abroad. In European and American countries, the United States mainly uses the SWAT (Soil and Water Assessment Tool) model + automatic monitoring network to establish a long-term pollution load database; the European Union has implemented the "Water Framework Directive" (WFD), requiring member states to monitor agricultural non-point source pollution and formulate management plans. Japan mainly combines remote sensing and ground sensors to focus on monitoring nitrogen and phosphorus loss in paddy field drainage. In China, agricultural non-point source pollution monitoring work is mainly carried out in the way of pilot monitoring + model simulation. Non-point source pollution monitoring stations have been set up in key basins such as Taihu Lake and Chaohu Lake, and models such as AnnAGNPS and CREAMS are used to simulate and predict pollution loads.

[0004] The existing agricultural non-point source pollution monitoring technologies are divided into two types: traditional methods and modern technologies. Traditional methods include manual sampling + laboratory analysis technology (the principle is to regularly collect water samples / soil samples and conduct laboratory tests), and runoff field observation method (the principle is to set up runoff plots to collect rainfall runoff samples). Modern technologies include the combination of sensors and on-line monitoring (water quality sensors + soil moisture sensors + Internet of Things (IoT)), the combination of remote sensing and GIS (satellite remote sensing + unmanned aerial vehicle aerial survey), and model simulation method (mechanism models such as SWAT and AnnAGNPS + data-driven models such as machine learning).

[0005] However, although existing monitoring technologies have promoted the development of agricultural non-point source pollution monitoring and prevention to a certain extent, there are still many technical problems that need to be solved urgently. The existing nitrogen and phosphorus monitoring methods are mainly based on the "point" monitoring data of small-scale fields. According to the loss coefficients of the first national pollution census, the "areal" loss and emission amounts of nitrogen and phosphorus in farmland on a large-scale whole basin are estimated by superimposing the total area of regional farmland. The processes of nitrogen and phosphorus emission, retention, fixation, and reduction between different fields and in channels are not considered, resulting in huge differences between the total loss amount of fields and the total emissions at the basin outlet, and serious distortion and overestimation of calculation results. On the other hand, compared with industrial and mining point source pollution, agricultural non-point source pollution of chemical fertilizers has the characteristics of fragmented and scattered fields, heterogeneous soil texture with diverse nutrients, spatial variability of large basin scale and complex terrain, unpredictable high-frequency and high-intensity variable rainfall climate, human disturbance of scattered farmers' crop cultivation and fertilization, and non-linear calculation of nitrogen and phosphorus runoff and infiltration superposition and ablation between fields. These factors greatly increase the technical difficulty of monitoring large agricultural non-point source nitrogen and phosphorus data, early warning risk assessment, and low-cost prevention and control work. Summary of the Invention

[0006] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the existing technology, and provide an automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale, solve problems such as distorted and overestimated calculation results caused by traditional agricultural non-point source monitoring, effectively improve the monitoring accuracy of agricultural non-point source pollution, and provide technical support for comprehensively constructing an agricultural non-point source pollution monitoring system.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions: An automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale, comprising the following steps: Using digital elevation model data to conduct hydrological analysis on the study area, and extracting small basins within the study area; Based on the historical surface water environment data and agricultural non-point source statistics of the study area, screening out nitrogen and phosphorus exceeding-standard sections where the surface water quality is mainly affected by agricultural production activities, and at the same time, combining land use data to select small basins with exceeding-standard section water quality and large agricultural non-point source influence as key catchment areas; Constructing a water quality environment intelligent monitoring system, including an on-line monitoring station house, an Internet of Things wireless monitoring node, an Internet of Things wireless monitoring micro base station, and an Internet of Things cloud platform; According to the total amount control method for import and export, arranging on-line monitoring station houses at the water quality sections at the entrances and exits of key catchment areas to carry out synchronous monitoring of water quality conditions and water regime conditions; the water regime conditions include water level, flow velocity, flow rate, and volume; the water quality conditions include pH, total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus, particulate phosphorus, dissolved phosphorus, and COD; The water quality and water condition data of the online monitoring station are sent to the IoT wireless monitoring micro base station through the IoT wireless monitoring node, and the IoT wireless monitoring micro base station then transmits the water quality and water condition data to the IoT cloud platform via GPRS.

[0008] As a preferred technical solution, the extraction of small watersheds within the study area is specifically as follows: Collect digital elevation model data of the study area based on professional geospatial information software; The digital elevation model data were projected and transformed into the 2000 National Geodetic Coordinate System of the 114° projection zone, and hydrological analysis was carried out to extract small watersheds within the county boundaries of the study area.

[0009] As a preferred technical solution, the online monitoring station includes a water quality automatic sampling unit, a quality control unit, a detection and analysis unit, a flow monitoring unit, an auxiliary unit, a data acquisition and transmission control unit, and a base station control unit; The automatic water quality sampling unit collects raw water samples in a timed, quantitative or triggered manner according to a preset program or remote instruction, and provides the samples to the detection and analysis unit; The quality control unit is connected and interacted with the detection and analysis unit to automatically calibrate the detection and analysis unit and simultaneously feed back the quality control results to the data acquisition and transmission control unit; The detection and analysis unit is used to receive the original water sample collected by the water quality automatic sampling unit, use sensors or chemical analysis methods to analyze the water quality in real time, and output the water quality to the data acquisition and transmission control unit; The flow monitoring unit is used to measure the flow velocity and flow of water and to collect the data into the data acquisition and transmission control unit; The auxiliary unit provides infrastructure support for power, temperature and humidity control, lightning protection, and security monitoring for other units, and communicates with the base station control unit for alarms; The data collection and transmission control unit is used to receive data from all units, aggregate the data of each unit, perform preliminary data processing, and then transmit it to the Internet of Things cloud platform via a wired / wireless network. At the same time, it is managed by the base station control unit and communicates bidirectionally with the Internet of Things cloud platform; The base station control unit is used to coordinate and control the operation of each unit, and is deeply integrated with the data acquisition and transmission control unit to issue instructions or receive feedback.

[0010] As a preferred technical solution, the automatic water quality sampling unit includes a sampling pump, a sampling pipeline, a sample dispenser, a container, a refrigeration device, a cleaning system and a spare bottle rack; the sampling pump is used to extract the original water sample and transport the original water sample through the sampling pipeline, the sample dispenser is used to distribute the original water sample to different containers, the refrigeration device is used to store the original water sample, the cleaning system is used to flush the pipeline and container, and the spare bottle rack is used to store the reference water sample; The quality control unit includes a standard solution storage tank, a liquid adding device, a blank sample generator, and quality control software; the standard solution storage tank is used to store standard solutions with known concentrations, the liquid adding device is used to quantitatively add standard solutions to the detection and analysis unit, the blank sample generator is used to prepare ultrapure water for blank tests of the detection and analysis unit, and the quality control software is used to automatically execute the calibration process and generate quality control reports; The detection and analysis unit includes a sensor group, a pretreatment module, and a reagent warehouse; the sensor group includes a pH electrode, a dissolved oxygen sensor, a turbidity meter, a conductivity meter, an online COD analyzer, an ammonia nitrogen analyzer, and a total phosphorus / total nitrogen analyzer; the pretreatment module includes an automatic cleaning filter and a digestion device; the reagent warehouse is used to store chemical reagents used in detection and analysis; The flow rate monitoring unit includes a flow meter, a water level sensor, and a weir / flume; the flow meter includes an ultrasonic flow meter, an electromagnetic flow meter, and a Doppler flow velocity meter; the water level sensor is used to assist in calculating the flow rate; the weir / flume is used for open channel flow monitoring and standardizing the water flow cross-section; The auxiliary unit includes a power supply subsystem, a temperature control system, safety equipment, and network equipment; the power supply module includes a UPS and a solar panel; the temperature control system includes an air conditioner and a heater; the safety equipment includes a lightning protection module, a smoke sensor, and a camera; the network equipment includes a 4G / 5G router and an optical fiber modem; The data acquisition and transmission control unit includes a data collector, a communication module, a storage device, and a protocol converter; the data collector is used to collect data of each unit in real time; the communication module supports 4G / 5G, satellite, and wired Ethernet transmission; the storage device is used to store local data; the protocol converter is used to unify the standard protocol; The base station control unit includes a main control computer / embedded controller, a human-machine interface, and an alarm module.

[0011] As a preferred technical solution, when arranging the online monitoring station house, install the online monitoring station house and deploy the water quality automatic sampling unit at the place where the key catchment area just enters the basin and has not been affected by the agricultural non-point source pollution in this area; install the online monitoring station house and deploy the water quality automatic sampling unit at the downstream of the sewage discharge outlet in the key catchment area and as close as possible to the water system outlet.

[0012] As a preferred technical solution, also install the online monitoring station house at the branch / confluence of the key catchment area or upstream / downstream of the urban and rural residential areas, and deploy the water quality automatic sampling unit.

[0013] As a preferred technical solution, the deployment of the water quality automatic sampling unit is specifically as follows: Obtain the water surface width of the water quality section at the installation location of the online monitoring station house; Determine the number of sampling vertical lines on the water quality section based on the water surface width. The formula is: Mp = ⌈W÷W0⌉, where Mp is the number of sampling vertical lines, W is the water surface width, and W0 is the set unit water surface width. Determine the layout position and number of water quality automatic sampling units according to the depth of the sampling vertical lines.

[0014] As a preferred technical solution, the on-line monitoring station house is arranged on a platform cast with reinforced concrete. Fences are arranged around the platform; double doors are opened on the front of the on-line monitoring station house for the fences.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: An automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale proposed by the present invention first selects key water-collecting areas, and then according to the total amount control method at the inlet and outlet, arranges on-line monitoring station houses at the water quality sections at the inlets and outlets of the key water-collecting areas, conducts synchronous monitoring of water quality conditions and water regime conditions, and transmits them to the Internet of Things cloud platform. The present invention can realize rapid and accurate monitoring of water quality and water regime indicators such as total nitrogen and total phosphorus of agricultural non-point sources in a large-scale range, can effectively reduce the cost and error of large-scale agricultural non-point source monitoring, further improve the agricultural non-point source pollution monitoring ability, and thus provide technical support for improving the monitoring accuracy of agricultural non-point source pollution and comprehensively constructing the national agricultural non-point source pollution monitoring system. In addition, the water quality environment intelligent monitoring system constructed by the present invention can realize on-line, continuous, automatic and accurate monitoring of basin water quality, water regime and meteorological indicators, realize real-time on-line collection and transmission of massive monitoring data at the basin scale, ensure the reliability and traceability of monitoring data, and realize remote control of the on-site monitoring terminal by the cloud platform. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings.

[0017] Figure 1 It is the overall flow chart of an automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale in the embodiment of the present invention.

[0018] Figure 2 It is the schematic diagram of the digital elevation model in the embodiment of the present invention.

[0019] Figure 3 It is the schematic diagram of the result of extracting small watersheds in the research area in the embodiment of the present invention.

[0020] Figure 4 This is the land use data map of the research area in the embodiment of the present invention.

[0021] Figure 5(a) is a schematic diagram of the key catchment area of Daping Village in the embodiment of the present invention, Figure 5(b) is a schematic diagram of the key catchment area of Luohu Village in the embodiment of the present invention, Figure 5(c) is a schematic diagram of the key catchment area of Jiantou Village in the embodiment of the present invention, and Figure 5(d) is a schematic diagram of the key catchment area of Chizhujing Reservoir in the embodiment of the present invention.

[0022] Figure 6 This is the structural schematic diagram of the water quality environment intelligent monitoring system in the embodiment of the present invention.

[0023] Figure 7 This is the internal layout diagram of the on-line monitoring station house in the embodiment of the present invention.

[0024] Figure 8 This is the layout diagram of the on-line monitoring station house in the embodiment of the present invention. Detailed implementation manners

[0025] In order to enable those skilled in the art of the present technology to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0026] Referring to "embodiments" in the present application means that specific features, structures or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments.

[0027] As Figure 1 shown, an automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the watershed scale in this embodiment takes the catchment area of Xinfengjiang Reservoir in Heyuan City, Guangdong Province as an example for easy elaboration, and details the steps of this method, including: S1. Use digital elevation model data to perform hydrological analysis on the research area and extract small watersheds within the research area.

[0028] Furthermore, first determine the small watersheds within the catchment area of Xinfengjiang Reservoir, specifically: S1.1. Collect digital elevation model (DEM) data of the catchment area of Xinfengjiang Reservoir based on professional geospatial information software, and the result is as Figure 2as shown S1.2. Project and convert the digital elevation model data to the CGCS2000 coordinate system (2000 National Geodetic Coordinate System) of the 114° projection zone, and conduct hydrological analysis to extract the small watersheds in the catchment area of the Xinfengjiang Reservoir. The extraction results are as Figure 3 shown

[0029] S2. Based on the historical surface water environment data and agricultural non-point source statistics of the study area, screen out the sections where the surface water quality exceeds the standards for nitrogen and phosphorus mainly affected by agricultural production activities. At the same time, combined with the land use data, select the small watersheds where the section water quality exceeds the standards and the agricultural non-point source has a great impact as the key catchment areas.

[0030] In the embodiment of the present invention, the small watersheds are extracted by conducting hydrological analysis on the catchment area of the Xinfengjiang Reservoir in Heyuan City. Combining the historical surface water environment data and agricultural non-point source statistics of the catchment area of the Xinfengjiang Reservoir in Heyuan City, screen out the sections where the surface water quality exceeds the standards for nitrogen and phosphorus mainly affected by agricultural production (planting, breeding and rural life) activities. At the same time, combined with the land use data ( Figure 4 ), select the small watersheds of Daping Village in Shuntian Town, Luohu Village in Luohu Town, Jiantou Village in Jiantou Town and Chizhujing Reservoir as 4 key catchment areas for monitoring. The location distribution is as shown in Figure 5(a), Figure 5(b), Figure 5(c) and Figure 5(d).

[0031] S3. Construct a water quality environment intelligent monitoring system, including an online monitoring station house, Internet of Things wireless monitoring nodes, Internet of Things wireless monitoring micro base stations and an Internet of Things cloud platform.

[0032] At present, the monitoring tools for dissolved water environment indicators generally mainly rely on sensors, and it is difficult to achieve rapid and accurate monitoring of nitrogen and phosphorus pollution sources in the water quality of the watershed. Therefore, the present invention has carried out research and development of field automatic online monitoring equipment, optimized and integrated single monitoring equipment and sensors, and formed an online monitoring station house with key indicators such as water quality, water regime and meteorology, which can realize online, continuous, automatic and accurate monitoring of water quality, water regime and meteorological indicators in the watershed. At the same time, considering problems such as the large number and wide distribution of non-point source monitoring points at the watershed scale, and the small number of existing Internet of Things nodes for agriculture and industry and small transmission ranges on the market, it is difficult to meet the needs of this research. Therefore, the present invention integrates the developed online monitoring station house and existing environmental Internet of Things base stations and terminal node devices, combines Lora wireless access technology, self-developed transmission protocols, cloud server clusters, etc., realizes real-time online collection and transmission of a large amount of monitoring data at the watershed scale, and finally constructs a set of water quality environment intelligent monitoring system for field automatic online monitoring integration at the watershed scale. The structure is as Figure 6 shown

[0033] Furthermore, the online monitoring station is designed based on new technical specifications for water pollution sources such as HJ / T 353-2019 and HJ / T 354-2019, including an automatic water quality sampling unit, a quality control unit, a detection and analysis unit, a flow monitoring unit, an auxiliary unit, a data acquisition and transmission control unit, and a base station control unit. The station is based on intelligent online monitoring equipment to achieve automatic online monitoring with low maintenance and low operating costs. At the same time, it is equipped with a complete quality assurance and control system to ensure the reliability and traceability of monitoring data, and realize remote control of the on-site monitoring end by the central platform. Among them, the water quality automatic sampling unit collects original water samples in a timely, quantitative or triggered manner according to a preset program or remote instruction, and provides the original water samples for the detection and analysis unit; the quality control unit interacts with the detection and analysis unit to detect the status of the detection and analysis unit, complete the automatic calibration of the detection and analysis unit (such as standard solution verification, blank test, sensor drift correction), and at the same time feeds back the quality control results to the data acquisition and transmission control unit to ensure the accuracy, reliability and compliance of the monitoring data (in compliance with environmental protection standards); the detection and analysis unit is used to receive the original water samples collected by the water quality automatic sampling unit, use sensors or chemical analysis methods (such as spectroscopy, electrode method) to analyze the water quality in real time, and output the water quality to the data acquisition and transmission control unit to support the watershed non-point source pollution assessment and early warning work; the flow monitoring unit is used to measure the water body flow rate and flow, and import the data into the data acquisition and transmission control unit for pollutant flux calculation and total nitrogen and phosphorus emission assessment Provide basic data; the auxiliary unit is used to provide infrastructure support such as power, temperature and humidity control, lightning protection, and security monitoring for other units, and communicate with the base station control unit for alarms to ensure the stable operation of the equipment in the field online monitoring station; the data acquisition and transmission control unit is used to receive data from all units, summarize the data of each unit, perform preliminary processing (such as unit conversion, validity verification), and transmit it to the Internet of Things cloud platform via wired / wireless network. At the same time, the unit is managed by the base station control unit and can communicate with the Internet of Things platform in both directions (such as remote configuration parameters), thereby realizing remote monitoring and data sharing (interconnection with the environmental protection department platform); the base station control unit is used to coordinate the operation of each unit (such as directly controlling the trigger sampling of the water quality automatic sampling unit, the start-up of the quality control process of the quality control unit, etc.), and is deeply integrated with the data acquisition and transmission control unit to issue instructions or receive feedback. It is the "brain" of the online monitoring station to ensure the automation and intelligence of the system.

[0034] Furthermore, the automatic water quality sampling unit includes a sampling pump (such as a submersible pump, peristaltic pump), a sampling pipeline (such as a corrosion-resistant pipeline made of PTFE), a sample distributor, containers, a refrigeration device, a cleaning system, and a spare bottle rack. Among them, the sampling pump is used to extract the original water sample and transport it through the sampling pipeline. The sample distributor is used to distribute the original water sample into different containers. The refrigeration device is used to store the original water sample to prevent the water sample from deteriorating. The cleaning system is used to flush the pipeline and containers to avoid cross-contamination. The spare bottle rack is used to store reference water samples (such as blank samples, parallel samples, etc.).

[0035] The quality control unit includes a standard solution storage tank, a liquid addition device (such as a precision injection pump or peristaltic pump), a blank sample generator, and quality control software. Among them, the standard solution storage tank is used to store standard solutions with known concentrations (such as COD, ammonia nitrogen standard solutions). The liquid addition device is used to quantitatively add standard solutions to the detection and analysis unit. The blank sample generator is used to prepare ultrapure water for blank tests in the detection and analysis unit. The quality control software is used to automatically execute the calibration process and generate a quality control report.

[0036] The detection and analysis unit includes a sensor group, a pretreatment module, and a reagent warehouse. Among them, the sensor group includes a pH electrode, dissolved oxygen, turbidity meter, conductivity meter, on-line COD analyzer, ammonia nitrogen analyzer, and total phosphorus / total nitrogen analyzer, etc., which are used to detect and analyze the water quality situation. The pretreatment module includes an automatic cleaning filter (a filtering device for removing suspended solids) and a digestion device (for high-temperature and high-pressure digestion of samples such as COD and total phosphorus). The reagent warehouse is used to store chemical reagents (such as oxidants, color reagents, etc.) used in detection and analysis.

[0037] The flow monitoring unit includes a flow meter, a water level sensor, and a weir / flume. Among them, the flow meter includes an ultrasonic flow meter (suitable for non-contact measurement in open channels), an electromagnetic flow meter (used for full pipe flow of conductive liquids), and a Doppler flow velocity meter (suitable for irregular river channels). The water level sensor is used to assist in calculating the flow rate. The weir / flume is used for open channel flow monitoring and standardizing the water flow cross-section.

[0038] The auxiliary unit includes a power supply subsystem, a temperature control system, safety equipment, and network equipment. Among them, the power supply module includes a UPS and a solar panel, which continuously supply power to the on-line monitoring station house. In this embodiment, the power supply module uses a set of 8V-3W monocrystalline silicon solar panels. Since most instruments have glassware inside, to avoid freezing or high-temperature damage, a temperature control system needs to be installed inside the station house to ensure that the working environment temperature of the instruments is maintained within the range of 5-45°C, including air conditioners and heaters. The safety equipment includes a lightning protection module, a smoke sensor, and a camera. The network equipment includes a 4G / 5G router and a fiber optic modem.

[0039] The data acquisition and transmission control unit includes a data collector (such as a PLC or an industrial control computer), a communication module, a storage device (such as a local SD card or a hard disk), and a protocol converter. Among them, the data collector is used to collect data of each unit in real time; the communication module supports 4G / 5G, satellite, and wired Ethernet transmissions; the storage device is used to store local data; and the protocol converter is used to unify standard protocols (such as environmental protection standard protocols like Modbus and HJ / T212).

[0040] The base station control unit includes a main control computer / embedded controller (used to run control software, such as the Linux / WinCE system), a human-machine interface (HMI) (such as a touch screen or an industrial control panel, which supports parameter setting and status viewing), and an alarm module (such as an audible and visual alarm and a text message push, used for early warning of abnormal situations). The actual distribution diagram of each instrument is as Figure 7 shown.

[0041] S4. Since the non-point source pollution in the basin has a dispersed origin, diverse components, spatio-temporal heterogeneity, and the occurrence location is difficult to identify and determine, according to the total amount control method at the inlet and outlet, online monitoring stations are arranged at the water quality sections at the entrances and exits of key catchment areas to conduct synchronous monitoring of water quality and water regime conditions; the water regime conditions include water level, flow velocity, flow rate, volume, etc.; the water quality conditions include pH, total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus, particulate phosphorus, dissolved phosphorus, and COD, etc.

[0042] Furthermore, when arranging the online monitoring stations according to the total amount control method at the inlet and outlet, an online monitoring station and a water quality automatic sampling unit are installed at the location where the key catchment area just enters the basin and has not been affected by the agricultural non-point source pollution in this area, to reflect the water quality conditions when the water system enters the small basin. An online monitoring station and a water quality automatic sampling unit are installed at a position downstream of the sewage discharge outlet in the key catchment area and as close as possible to the water system outlet, to reflect the overall outlet water quality of the small basin.

[0043] In addition, in order to understand the changes in water quality upstream and downstream of the basin / catchment area as much as possible, if necessary, it is also possible to consider reasonably installing online monitoring stations and arranging water quality automatic sampling units at the runoff diversion or confluence points between the inlet and outlet points of the key catchment area, and upstream and downstream of urban residential areas.

[0044] Furthermore, the specific method for arranging the water quality automatic sampling unit is as follows: Obtain the water surface width of the water quality section at the installation location of the online monitoring station; Determine the sampling vertical lines on the water quality section based on the water surface width. The formula is: Mp = ⌈W÷W0⌉, where Mp is the number of sampling vertical lines, W is the water surface width, and W0 is the set unit water surface width; Determine the layout position and number of water quality automatic sampling units according to the depth of the sampling vertical line. The formula is: Mq = ⌈H÷H0⌉, where Mq is the number of water quality units, H is the depth of the sampling vertical line, and H0 is the set unit depth.

[0045] In this embodiment, the basic principle for the layout of sampling points at the water body monitoring section in the catchment area of Xinfengjiang Reservoir in Heyuan City is as follows: Obtain the water surface width of the water quality section at the installation location of the online monitoring station house, and set the set unit width W0 to 50 m. Therefore, when the water surface width is less than 50 m, set a mid-channel vertical line; when the water surface width is 50 - 100 m, set a vertical line at each obvious water flow location near the left and right shores; when the water surface width is 100 - 1000 m, set three vertical lines on the left, middle, and right; when the water surface width is greater than 1500 m, set at least 5 equally spaced vertical lines. When the depth of the sampling vertical line ≤ 5 m, set a sampling point at 0.3 - 0.5 m below the water surface to layout the water quality automatic sampling unit; when the depth of the sampling vertical line is 5 - 10 m, set a water quality automatic sampling unit at 0.3 - 0.5 m below the water surface and 0.5 m above the river bottom respectively; when the depth of the sampling vertical line is 10 - 50 m, set three sampling points, set a water quality automatic sampling unit at 0.3 - 0.5 m below the water surface and 0.5 m above the river bottom respectively, and set a water quality automatic sampling unit at 1 / 2 water depth; when the depth of the sampling vertical line is greater than 50 m, increase the number of sampling points. Based on the above layout principle, a total of 9 section points are laid out in 4 key catchment areas in the catchment area of Xinfengjiang Reservoir in Heyuan City to carry out synchronous monitoring of water quality and water regime changes. Among them, 2, 2, 3, and 2 automatic monitoring points are set in the small watershed of Daping Village, Shuntian Town, the small watershed of Luohu Village, Luohu Town, the small watershed of Jiantou Village, Jiantou Town, and the small watershed of Chizhujing Reservoir respectively. The results are shown by the automatic sampling site marks in (a), (b), (c), and (d) in Figure 5.

[0046] S5. Send the water quality and water regime data of the online monitoring station house to the IoT wireless monitoring micro base station through the IoT wireless monitoring node, and the IoT wireless monitoring micro base station then transmits the water quality and water regime data to the IoT cloud platform through GPRS.

[0047] The IoT cloud platform processes the received data through multi-dimensional information and multi-level processing to realize the online analysis and summary of nitrogen and phosphorus loss data for online monitoring at the basin scale; on the one hand, the IoT cloud platform provides a web service, uses a Web visualization interface to view the operation status of the system, and timely feedbacks the data results; on the other hand, it uses the interfaces provided by the platform to connect its own applications and realizes the control of the system and the recording and analysis of data through the mobile terminal.

[0048] Further, as Figure 8As shown in the figure, in order to fix the on-line monitoring station house and maintain its working stability, the present application arranges it on a platform cast with reinforced concrete; fences are arranged around the platform; the fences are provided with double doors on the front of the on-line monitoring station house to facilitate the entry and exit of instrument maintenance personnel. In this embodiment, the platform is 4.3 m long, 3.5 m wide and 0.3 m high, with a floor area of 15.05 m 2 ; the fence is 1.9 m high, and the enclosed area is 3.9 m long and 3.1 m wide.

[0049] It should be noted that for the foregoing method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously.

[0050] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0051] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. An automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale, characterized in that The steps include: Use digital elevation model data to conduct hydrological analysis of the study area and extract small watersheds within the study area; Based on the historical surface water environmental data and agricultural non-point source statistics of the study area, we screened out sections where nitrogen and phosphorus levels exceeded standards and were primarily affected by agricultural production activities. At the same time, combined with land use data, we selected small watersheds where water quality exceeded standards and was significantly affected by agricultural non-point source pollution as key catchment areas. Build an intelligent water quality and environmental monitoring system, including an online monitoring station, IoT wireless monitoring nodes, IoT wireless monitoring micro base stations, and an IoT cloud platform; Based on the total import and export volume control method, online monitoring stations will be set up at the water quality sections at the entrances and exits of key catchment areas to carry out simultaneous monitoring of water quality and water conditions; the water conditions include water level, flow rate, flow rate and volume; the water quality conditions include pH, total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus, particulate phosphorus, dissolved phosphorus and COD; The water quality and water condition data of the online monitoring station are sent to the IoT wireless monitoring micro base station through the IoT wireless monitoring node, and the IoT wireless monitoring micro base station then transmits the water quality and water condition data to the IoT cloud platform via GPRS.

2. The automatic monitoring method for nitrogen and phosphorus losses from agricultural non-point sources at the watershed scale according to claim 1, wherein The extraction of small watersheds within the study area is specifically: Collect digital elevation model data of the study area based on professional geospatial information software; The digital elevation model data were projected and transformed into the 2000 National Geodetic Coordinate System of the 114° projection zone, and hydrological analysis was carried out to extract small watersheds within the county boundaries of the study area.

3. The automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale according to claim 1, characterized in that The online monitoring station includes a water quality automatic sampling unit, a quality control unit, a detection and analysis unit, a flow monitoring unit, an auxiliary unit, a data acquisition and transmission control unit, and a base station control unit; The automatic water quality sampling unit collects raw water samples in a timed, quantitative or triggered manner according to a preset program or remote instruction, and provides the samples to the detection and analysis unit; The quality control unit is connected and interacted with the detection and analysis unit to automatically calibrate the detection and analysis unit and simultaneously feed back the quality control results to the data acquisition and transmission control unit; The detection and analysis unit is used to receive the original water sample collected by the water quality automatic sampling unit, use sensors or chemical analysis methods to analyze the water quality in real time, and output the water quality to the data acquisition and transmission control unit; The flow monitoring unit is used to measure the flow velocity and flow of water and to collect the data into the data acquisition and transmission control unit; The auxiliary unit provides infrastructure support for power, temperature and humidity control, lightning protection, and security monitoring for other units, and communicates with the base station control unit for alarms; The data collection and transmission control unit is used to receive data from all units, aggregate the data of each unit, perform preliminary data processing, and then transmit it to the Internet of Things cloud platform via a wired / wireless network. At the same time, it is managed by the base station control unit and communicates bidirectionally with the Internet of Things cloud platform; The base station control unit is used to coordinate and control the operation of each unit, and is deeply integrated with the data acquisition and transmission control unit to issue instructions or receive feedback.

4. The automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the watershed scale according to claim 3, characterized in that The automatic water quality sampling unit includes a sampling pump, a sampling pipeline, a sample distributor, containers, a refrigeration device, a cleaning system, and a spare bottle rack; the sampling pump is used to extract the original water sample and transport the original water sample through the sampling pipeline, the sample distributor is used to distribute the original water sample into different containers, the refrigeration device is used to store the original water sample, the cleaning system is used to flush the pipeline and containers, and the spare bottle rack is used to store reference water samples; The quality control unit includes a standard solution storage tank, a liquid adding device, a blank sample generator, and quality control software; the standard solution storage tank is used to store standard solutions with known concentrations, the liquid adding device is used to quantitatively add standard solutions or blank samples to the detection and analysis unit, the blank sample generator is used to prepare ultrapure water for blank tests of the detection and analysis unit, and the quality control software is used to automatically execute the calibration process and generate a quality control report; The detection and analysis unit includes a sensor group, a pretreatment module, and a reagent warehouse; the sensor group includes a pH electrode, a dissolved oxygen sensor, a turbidity meter, a conductivity meter, an on-line COD analyzer, an ammonia nitrogen analyzer, and a total phosphorus / total nitrogen analyzer; the pretreatment module includes an automatic cleaning filter and a digestion device; the reagent warehouse is used to store chemical reagents used during detection and analysis; The flow rate monitoring unit includes a flow meter, a water level sensor, and a weir / flume; the flow meter includes an ultrasonic flow meter, an electromagnetic flow meter, and a Doppler current meter; the water level sensor is used to assist in calculating the flow rate; the weir / flume is used for open channel flow monitoring and standardizing the water flow cross-section; The auxiliary unit includes a power supply subsystem, a temperature control system, safety equipment, and network equipment; the power supply module includes a UPS and a solar panel; the temperature control system includes an air conditioner and a heater; the safety equipment includes a lightning protection module, a smoke sensor, and a camera; the network equipment includes a 4G / 5G router and a fiber optic modem; The data acquisition and transmission control unit includes a data collector, a communication module, a storage device, and a protocol converter; the data collector is used to collect data from each unit in real time; the communication module supports 4G / 5G, satellite, and wired Ethernet transmission; the storage device is used to store local data; the protocol converter is used to unify the standard protocol; The base station control unit includes a main control computer / embedded controller, a human-machine interface, and an alarm module.

5. The automatic monitoring method for nitrogen and phosphorus losses from agricultural non-point sources at the watershed scale according to claim 3, wherein When arranging the on-line monitoring station house, install the on-line monitoring station house and deploy the automatic water quality sampling unit at the place where the key catchment area just enters the river basin and has not been affected by the agricultural non-point source pollution in this area; install the on-line monitoring station house and deploy the automatic water quality sampling unit at the downstream of the sewage discharge outlet in the key catchment area and as close as possible to the water system outlet.

6. The automatic monitoring method for agricultural non-point source nitrogen and phosphorus losses at the watershed scale according to claim 5, wherein Also install the on-line monitoring station house at the sub / confluence or upstream / downstream areas of urban and rural settlements in the key catchment area, and deploy the automatic water quality sampling unit.

7. The automatic monitoring method for agricultural non-point source nitrogen and phosphorus losses at the basin scale according to claim 5 or 6, characterized in that The deployment of the automatic water quality sampling unit is specifically as follows: Obtain the water surface width of the water quality section at the installation location of the on-line monitoring station house; Determine the number of sampling vertical lines on the water quality cross-section based on the water surface width. The formula is: Mp = ⌈W÷W0⌉, where Mp is the number of sampling vertical lines, W is the water surface width, and W0 is the set unit water surface width; Determine the layout position and number of water quality automatic sampling units according to the depth of the sampling vertical lines.

8. The automatic monitoring method for agricultural non-point source nitrogen and phosphorus loss at the basin scale according to claim 1, characterized in that The on-line monitoring station house is arranged on a platform cast with reinforced concrete; Fences are arranged around the platform; double doors are opened on the front of the on-line monitoring station house in the fence.

Images