CN105510548A - Water quality real-time monitoring system instrument calibration method for complex water environment - Google Patents

Abstract

The invention discloses a water quality real-time monitoring system instrument calibration method for a complex water environment. A sensor probe for sensing specific water quality parameters is placed into a water body to be monitored; an electric signal is read by utilizing a computer and is taken as a horizontal ordinate; accurate concentration parameters of the water quality to be measured are obtained by other methods; the measurement results are taken as a longitudinal ordinate; a regression curve is established; multi-point calibration is directly performed by taking the water to be measured as a standard solution. According to the calibration method, the real-time characteristics of the water quality can be described accurately on the basis of the conventional instrument calibration technology, and by combing the characteristics of complexity of the water environment and adopting the data monitored in real time; a field test is performed by the device involved in the calibration method in underground water; results show that the measurement results are relatively accurate on that day and the subsequent measurement results are far from the actual concentration when the instrument is calibrated by utilizing the conventional method, while the real-time measurement results are relatively identical with laboratory analysis results within one week of continuous monitoring when the instrument is calibrated by utilizing the method.

Description

A method for calibrating instruments of a water quality real-time monitoring system for complex water environments

technical field

The invention belongs to the technical field of environmental protection monitoring, and in particular relates to an instrument calibration method for a real-time water quality monitoring system suitable for complex water environments.

Background technique

With the increasingly prominent ecological and environmental problems, both the international community and China have paid more and more attention to the protection of the water environment. Water quality monitoring and evaluation have become an important basis for government departments to make environmental protection decisions. Due to the influence of my country's vast territory, complex topography and other factors, large-scale and long-term monitoring of the region is time-consuming and labor-intensive, or even impossible to achieve by relying on traditional manual monitoring. Real-time automatic monitoring has become a common trend at home and abroad. The research and development of groundwater real-time monitoring system is more advanced than that of our country, and these instruments play an important role in the monitoring of water environment in our country. However, in the application process, it is found that various real-time monitoring instruments can accurately measure water quality during the test process, but cannot obtain satisfactory results in complex water environments. This is mainly due to the interference of various factors in some complex water environments , including a series of external environmental factors and changes in other interfering ions in the water body, this determines that the concentration of pollutants cannot be accurately measured in these complex water environments after laboratory calibration, which has become a constraint for the application and development of real-time water quality monitoring technology An important bottleneck. Based on the above reasons, the establishment of a real-time water quality monitoring system instrument calibration method suitable for complex water environment characteristics has become a major demand at present.

Contents of the invention

Therefore, the problem to be solved by the present invention is how to combine the existing technology while taking into account the complexity of the water environment, and then propose a scientific and easy-to-operate instrument calibration method suitable for complex water environment conditions.

The purpose of the present invention is achieved with the following technical solutions:

A water quality real-time monitoring system instrument calibration method for complex water environments, by placing the sensor probe that senses a specific water quality parameter in the water body to be measured, using a computer to read the electrical signal in real time, as the abscissa, and using other methods to obtain Accurate concentration of the water quality parameters to be measured, use the measurement results as the ordinate, establish a regression curve, and use the water to be tested as a standard solution for direct multi-point calibration.

During the calibration process, it is necessary to immerse the sensor probe in the water body to be measured, and read the data every 4-6 minutes until the electrical signal is stable. The stable electrical signal is used as the abscissa, and the water body to be measured where the sensor probe is immersed is used for The exact concentration obtained by other methods is used as the ordinate; the measurement time for determining one electrical signal should not exceed 30 minutes, and when the electrical signal is still not stable within 30 minutes, restart the timing.

Stable electrical signal means: within 30 minutes, the variation range of the electrical signal does not exceed 5%, or after the electrical signal has two peaks and two valleys, when the next electrical signal differs from the average value of the above peaks and valleys by no more than 5%, considered to be a stable value.

The calibration curve requires two or more corresponding electrical signals and concentrations.

The method is predicted and verified every 25-35 days. When the measurement error exceeds the tolerance, it needs to be re-calibrated.

Compared with the prior art, the above-mentioned technical solution of the present invention has the following characteristics: 1. This method relies on the existing instrument calibration technology, and at the same time combines the complex characteristics of the water environment; 2. The device uses real-time monitoring data, which can accurately describe the real-time Features; 3, the applicant carried out the field test of the device described in the present invention in groundwater, and the results showed that, using conventional methods to calibrate, the measurement results can only guarantee that the day is more accurate, and then the measurement results deviate far from the actual concentration, while using this method Methods During the continuous monitoring period of one week, the real-time determination is in good agreement with the laboratory analysis results. Based on the above three points, this method has broad application prospects.

Description of drawings

Fig. 1 is a schematic diagram of calibration work of the present invention;

Fig. 2 is the calibration curve that adopts this method and laboratory to obtain;

Fig. 3 is the measurement result obtained by using this method and the calibration curve obtained in the laboratory within 7 consecutive days.

detailed description

A water quality real-time monitoring system instrument calibration method for complex water environments, by placing sensor probes that sense specific water quality parameters in the complex water body to be measured on site, using a computer to read electrical signals in real time, as abscissas, and Use other methods such as chemistry and electrochemistry to obtain accurate concentrations of water quality parameters to be measured, use the measurement results as the ordinate, establish a regression curve, and use the water to be tested as a standard solution for direct multi-point calibration.

During the calibration process, it is necessary to immerse the sensor probe in the water body to be measured, and read the data every 4-6 minutes until the electrical signal is stable. The stable electrical signal is used as the abscissa, and the water body to be measured where the sensor probe is immersed is used for The exact concentration obtained by other methods is used as the ordinate, and a point on the calibration curve can be determined at this time; the measurement time for determining an electrical signal should not exceed 30 minutes, and when the electrical signal is still not stable within 30 minutes, the water quality at this time If there may have been a change, restart the timing; the stability of the electrical signal means that the electrical signal does not change more than 5% within 30 minutes, or after the electrical signal has two peaks and two valleys, the next electrical signal will be the same as the above peaks and valleys. When the average value differs by no more than 5%, it is considered as a stable value.

After determining a point on the above standard curve, repeat the above steps to determine the on-site measurement concentration corresponding to another electrical signal, and determine the second point of the calibration curve. When accurate quantification is required, 5 to 9 points can be used to determine the calibration curve , usually 2~3 points are enough.

The prediction verification of the method should be carried out regularly, generally 25-35 days, when the measurement error exceeds the tolerance, it needs to be re-calibrated. This method is not only suitable for the calibration of instrument parameters when monitoring general surface water and groundwater, but also has stronger applicability for groundwater with complex environmental characteristics, large errors in measurement results obtained by general laboratory calibration methods, and inapplicability.

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, immerse the probe of the sensor 1 into the water body 2 to be tested, then connect the USB interface of the sensor 1 to the computer 3, open the calibration program software that comes with the instrument, and then use the computer 3 to measure once every 2 minutes At the same time, take sample 4 from the water body to be tested, and use other chemical, electrochemical and other methods to measure its concentration on site. When the electrical signal is stable, fill in the actual measured concentration of sample 4 to the corresponding concentration in the calibration software, and confirm Add 1 line, follow the above method, enter another concentration in the program, and confirm, so that by determining 2 to 9 points, draw a standard curve, and then automatically monitor the water quality, and verify the results after a period of time during the monitoring process Whether it still conforms to the standard curve, if not, perform calibration again.

The following uses this method and the laboratory calibration method to compare the results of detecting chloride ions.

First of all, use chemical reagents to configure standard solutions in the laboratory, and calibrate the instrument in the laboratory, monitor the concentration of pollutants ⁱⁿ a monitoring well in a certain area for one week, and record the data. or electrochemical methods to measure the concentration of pollutants in the water body, immerse the sensor probe into the above-mentioned monitoring well water, calibrate after the electrical signal is stable, and monitor the concentration of the pollutant Cl ⁱⁿ the water body for a week, and record the data, laboratory calibration curve and The standard curve determined by this method is shown in Figure 2, and the monitoring results of the two methods for one week are shown in Figure 3. It can be seen that the Cl ^- concentration measured by the laboratory calibration method on the 7th day seriously deviates from the Cl ^- in groundwater. However, the results of this method are still more in line with reality.

The above experiments carried out by the applicant show that this method can accurately measure the concentration of pollutants in complex water environments for at least one week, but it still needs to be verified or corrected regularly in combination with the measured values during long-term monitoring, so as to ensure that the disturbance factors in the water environment are not affected by sudden changes. The monitoring results deviate from reality.

Claims (5)

1. A water quality real-time monitoring system instrument calibration method for complex water environment, it is characterized in that: by the sensor probe of induction specific water quality parameter being placed in the water body to be measured, utilize computer to read electric signal in real time, as abscissa , and obtain the accurate concentration of the water quality parameters to be measured by other methods, and use the measurement results as the ordinate to establish a regression curve, and use the water to be tested as a standard solution for direct multi-point calibration. 2. The instrument calibration method for the real-time monitoring system of water quality in complex water environment as claimed in claim 1, characterized in that: in the calibration process, the sensor probe needs to be immersed in the water body to be measured, and read at intervals of 4-6min. Take the data once until the electrical signal is stable, take the stable electrical signal as the abscissa, take the water body to be measured where the sensor probe is immersed and use other methods to obtain its accurate concentration, and use it as the ordinate; the measurement time of one electrical signal should not exceed 30 Minutes, when the electrical signal is still not stable within 30 minutes, restart the timer. 3. The instrument calibration method for a real-time water quality monitoring system for complex water environments as claimed in claim 2, characterized in that the electrical signal stability refers to: within 30 minutes, the amplitude of the electrical signal does not exceed 5%, or the electrical signal has two peaks After two valleys and two valleys, when the difference between the next electrical signal and the average value of the above peaks and valleys does not exceed 5%, it is considered to be a stable value. 4. The instrument calibration method for a real-time water quality monitoring system for complex water environments as claimed in claim 1, wherein the calibration curve requires two or more corresponding electrical signals and concentrations. 5. The instrument calibration method for the real-time monitoring system of water quality in complex water environment as claimed in claim 1, characterized in that: the method is predicted and verified every 25-35 days, and when the measurement error exceeds the tolerance, it needs to be re-performed calibration.