As people's understanding of environmental protection continues to deepen, people are no longer content to only know the concentration of PM2.5, but hope to have a deep understanding of the various types of toxic substances contained in PM2.5. Heavy metal pollutants (including heavy metals such as As) are well-known toxic pollutants. The harm of heavy metals is obvious to all. Therefore, strengthening the monitoring of heavy metals in PM2.5 is the only way.

1. Introduction of Atmospheric Heavy Metal Online Analyzer EHM-X200

EHM-X200 Atmospheric Heavy Metal On-Line Analyzer is the world's first dual-function automatic online analytical instrument. It innovatively combines patented technology - X-ray fluorescence (XRF) non-destructive testing technology, beta ray absorption detection technology and air particulate matter auto-enrichment technology. It can not only monitor the airborne particle mass concentration, but also simultaneously carry out the elemental composition in the particulates. Quantitative analysis. The instrument has a detection limit of pg/m3 magnitude and is widely used in air quality monitoring, pollution traceability and source analysis, and environmental assessment.

Fig.1 Picture of Atelier EHM-X200 Atmospheric Heavy Metal On-line Analyzer (from left to right, instrument host, station cabinet instrument and on-board instrument)

1.1 Measurement principle

The instrument sucks air into the particulate cutter at a constant flow rate. Taking PM2.5 as an example, particulate contaminants with a dynamic diameter of 2.5um or less enter the instrument's enrichment system. After a period of enrichment, the enrichment system is automatically switched to a beta ray analysis system, and the mass concentration of the particulate matter is analyzed using the relationship between the attenuation of the beta ray and the mass concentration of the particulate matter. The reel system then precisely moves the air-particle-enriched filter paper to the X-ray fluorescence analysis system, and uses the energy and intensity of the X-ray fluorescence to qualitatively and quantitatively analyze the elemental components in the particles.

Fig. 2 Schematic diagram of atmospheric heavy metal monitoring of Tianrui Instrument EHM-X200

The principle of X-ray fluorescence spectroscopy (XRF) is shown in Fig. 3. It can directly detect ppm-level elements in solid or liquid samples. Using the method of enrichment and detection, the detection limit of XRF technology for heavy metal components in airborne particles was better than 0.001 μg/m3. The conventional laboratory detection technology, due to the need to dissolve microgram quantities of samples into dozens of grams of liquid during the pre-treatment digestion process, the concentration is diluted by a factor of one million, so that most instruments (such as ICP-AES, or atoms Absorption spectrometers cannot detect samples of airborne particles with an element content below 10 μg/m3.

Fig. 3 Schematic diagram of X-ray fluorescence spectroscopy

1.2 Performance Features

(1) An integrated collaborative measurement of airborne particulate concentrations and atmospheric heavy metal concentrations provides more accurate data for pollution traceability and source resolution;
(2) TSP, PM10, PM2.5 three cutters are available for users to choose from, and are used in different environmental evaluation occasions;
(3) The content of more than 30 kinds of heavy metals such as lead, cadmium, and arsenic were accurately measured, and the minimum detection limit was in the order of pg/m3;
(4) Dozens of XRF core technology invention patents from light pipes, detectors, digital multi-channel analyzers (DCMA) to complete machines;
(5) The reliability and accuracy of the instrument have been fully verified.

1.3 Technical parameters

The following lists some of the important technical parameters of the atmospheric heavy metal online analyzer (Table 1).

Table 1 Technical parameters of Tianrui Instrument EHM-X200 Atmospheric Heavy Metal Monitor

2. What can be brought to us by on-line monitoring of atmospheric heavy metals?

2.1 Timely knowledge of the concentration of harmful metals in atmospheric particles to ensure the public’s right to know

Just as we recognized the concept that PM10 is only PM10 and TSP and not PM2.5 a decade ago, we now only pay attention to the concentration of PM2.5 and ignore the specific toxic hazards in PM2.5. What is the substance and how much is it? "Chai Jing's investigation of fog and haze: under the dome" repeatedly emphasized the necessity of controlling the concentration of heavy metals in PM2.5. "After PM2.5 particles enter the human body, macrophages are difficult to digest heavy metals in atmospheric particles, making macrophages The cell ruptured and died, reducing people's immunity." Through on-line analysis of heavy metals in the atmosphere, we can quickly and effectively understand the types and concentrations of heavy metals and non-heavy metals contained in local PM2.5. Just as the concentration of PM2.5 is obtained in real time, the public can know the atmosphere of the place of residence in time. The concentration of heavy metals, reasonable arrangements for their own working life, and take timely measures to protect themselves from pollution damage.

2.2 Facilitate the research department to analyze the diurnal variation trend of atmospheric heavy metals

Conventional atmospheric heavy metal monitoring methods only measure the daily average concentration of heavy metal elements, but atmospheric heavy metals have great changes with meteorological parameters and temperature at different time periods per day, and the daily average concentration cannot reflect these changes. The real-time online monitoring of atmospheric heavy metals can determine the hourly value of heavy metal concentration, which is conducive to the analysis and analysis of the daily variations of atmospheric heavy and non-heavy metal elements.

Fig. 4 Hourly changes of heavy metal pollutants monitored by Tianrui Instrument EHM-X200 Atmospheric Heavy Metal Monitor

2.3 Provide pollution source analysis data for regulatory authorities to help decision-making

Through model processing such as principal component analysis and correlation analysis, we can tell policy makers where the pollution comes from and the ratio of contribution, and provide supporting results for source analysis. Tianrui Instrument EHM-X200 Atmospheric Heavy Metal Monitor was used to analyze the data measured by atmospheric heavy metal on-line analyzer in a long period of time in a certain city in the North.

Table 1 Composition Analysis of Monitoring Data of EHM-X200 Atmospheric Heavy Metal Monitor

In order to further study the relationship between PM2.5 and atmospheric heavy metals, and provide direction for the control of PM2.5, we conducted a correlation analysis between the three components that have been classified and atmospheric PM2.5 concentrations. The results are shown in Fig. 5. It was found that the main source of PM2.5 pollution in the area was component 2 (metallurgical industry exhaust gas).

Figure 5 Correlation of PM2.5 with the monitoring data of the EHM-X200 Atmospheric Heavy Metal Monitor. The depth of the color in the legend indicates the size of the correlation value. The correlation between component 2 and PM2.5 is the strongest, which indicates that the main source of pollution affecting the PM2.5 concentration in this area is metallurgical industry exhaust gas.

The direction of the contaminants of each component can be determined by the relationship between the wind direction and the three components in PM2.5 (Figure 6).

Fig.6 The relationship between each component and the wind direction obtained from the principal component analysis of the elements in the PM2.5 monitoring data of the EHM-X200 heavy metal monitor. Figure A shows the relationship between concentration and wind direction of component 1 (industrial and domestic fuel combustion). It can be seen from the figure that component 1 mainly originates from the southwest direction (dark area) of the monitoring point; Figure B is component 2 (Concentration of the metallurgical industry exhaust gas) and the relationship between the direction of the wind, can be seen from the figure, component 2 comes from the monitoring point itself (dark area); Figure C is the component 3 (dust) concentration and wind direction relationship diagram, It can be seen from the figure that component 3 mainly originates from the east and north (dark areas) of the monitoring sites. The shades of light from dark to dark represent the extent of pollution from small to large.

2.4 Real-time Monitoring of Atmospheric Heavy Metal Concentration to Improve Monitoring Staff Work Efficiency

The existing conventional atmospheric heavy metal monitoring method is still the original manual sampling + laboratory analysis method, and the workload is large and the efficiency is low. Since conventional laboratory analysis techniques require the pretreatment of samples for heavy metal concentration detection, it takes approximately 2 hours from sample weighing to sample digestion. The XRF technology does not require sample pretreatment, and the detection of heavy metal concentration in each sample can be completed within 10 minutes. At the same time, it can also realize unattended, 24-hour real-time monitoring of 30 heavy metal elements in the atmosphere, saving a lot of labor costs, and the relative In terms of laboratory measurement methods, consumables have low prices, low maintenance, and no secondary pollution.

In summary, the EHM-X200 Atmospheric Heavy Metal Monitor by Jiangsu Tianrui Instrument can not only accurately monitor the concentration of atmospheric particulates, but also monitor the concentration of heavy metal elements in atmospheric particulates, providing scientific evidence for the monitoring and control of heavy metal elements in atmospheric particulates. in accordance with.

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