Suspended particulate matter (SPM) is a general term for solid and liquid particulate matter (or aerosol) suspended in the atmosphere.Due to different sources and formation, its shape, density, particle size, optical, electrical, magnetic and other physical properties and chemical composition are very different.The particle size of particles in the atmosphere ranges from 0.001 μ m to more than 1000 μ m. Generally, particles larger than 50 μ m settle to the ground quickly under the action of gravity and remain in the atmosphere for several minutes to several hours;The particles with a diameter of 0.1 μ m not only have a long residence time in the atmosphere, but also have a long migration distance.Sources can be divided into natural sources and man-made sources.Anthropogenic emissionThe source is soot generated from the combustion of fossil fuels;Industrial dust, metal dust and water generated by industrial production and constructionMud dustEtc;Automobile, aircraft exhaust, etc.Natural sources include soil dust, volcanic ash, forest fire ash, sea salt particles, etc.
Chinese name
Suspended particles
Shape
Solid and liquid particulate matter in the atmosphere
Suspended particulate matter (SPM) is a general term for solid and liquid particulate matter (or aerosol) suspended in the atmosphere.Due to different sources and formation, its shape, density, particle size, optical, electrical, magnetic and other physical properties and chemical composition are very different.[1]The particle size of particles in the atmosphere ranges from 0.001 μ m to more than 1000 μ m. Generally, particles larger than 50 μ m settle to the ground quickly under the action of gravity and remain in the atmosphere for several minutes to several hours;The particles with a diameter of 0.1 μ m not only have a long residence time in the atmosphere, but also have a long migration distance.
source
Announce
edit
The particle size of particles in the atmosphere ranges from 0.001 μ m to more than 1000 μ m. Generally, particles larger than 50 μ m are subject to gravity very quicklysettlementTo the ground and stay in the atmosphere for several minutes to several hours;The particles with a diameter of 0.1 μ m not only have a long residence time in the atmosphere, but also have a long migration distance.
The sources of particulates can be divided into natural sources and artificial sources.Anthropogenic emission sources include soot generated by fossil fuel combustion;Industrial dust, metal dust, cement dust, etc. generated by industrial production and construction;Automobile, aircraftexhaustEtc.Natural sources include soil dustash, forest fire ashsea saltGrain, etc.
classification
Announce
edit
In aerodynamics and environmental meteorology, suspended particles are classified by diameter. Those less than 100 microns are called TSP, that is, total suspended particles;Those less than 10 microns are called PM10, which can inhale particulates.It should be pointed out that such particles can enter the respiratory system of the human body and may cause damage to human health.The particles with a diameter of less than 2.5 microns are called PM2.5. From the perspective of image proportion, the diameter of human hair is about 50 microns to 70 microns. PM2.5 is equivalent to 3.6% to 5% of the hair diameter. PM2.5 can be inhaled into the lungs and adhered to the alveoli, causing great harm to the human body.[2]
Particles can also be divided into primary particles and secondary particles.Primary particulates are liquid or solid particulates discharged directly into the atmosphere from the emission source, and have not changed in the atmosphere.Secondary particulates are gaseous pollutants discharged from emission sources and transformed into liquid or solid particulates through chemical reaction or physical process.Such as sulfate, nitrate, chloride, ammonium salt and organic aerosol formed by chemical reaction of sulfur dioxide, nitrogen oxide, hydrogen chloride and chlorine, ammonia, organic gas, etc.
influence
Announce
edit
The impact of respirability (particle size less than 2.5 μ m) and inhalable particles (particle size less than 10 μ m) on human health has attracted more and more attention.When the particle size is less than 10 μ m (calledInhalable particles）You can inhale hundreds of organic compounds such as organic benzenedioxinPAHs, PAHs, and dozens of metals containing highly toxic components such as lead and cadmium will invade the human body, which will easily cause respiratory tract infection, heart disease, bronchitis, asthma, pneumonia, emphysema and other diseases, affecting human health.Therefore, inhalable particles are selected as an indicator in the daily air quality report.[3]
Suspended particles can also causeAtmospheric visibilityLower.Where 0.1 to 1 μ m particle pairvisibilityThe impact of is the largest, especially when the concentration is greater than 100 μ g/m3.
Since particles may be active or can absorb chemically active substances, they are corrosive and can cause direct chemical damage to materials.Such as corroding the metal surface and damaging the surface with paint and coating.
testing
Announce
edit
At present, the most commonly used particle detector in China is the laser dust detector.
Laser dust meter
Laser dust meterinstrumentApplicable to inhalable particles in public places (PM10)Rapid determination of concentration, industrial and mining enterprise production site and other aspects of labor hygiene dust concentration detection, as well as the environmental protection field of inhalable dust concentration monitoring, can also be used to evaluate the purification efficiency of air purifier.More than 1000 setsinstrumentIt has been used all over the country and has been well received by users.
instrumentComply with WS/T206-2001 Determination of Inhalable Particulate Matter (PM10) in the Air of Public Places - Light Scattering Method issued by the Ministry of Health, LD98-1996 Light Scattering Method for Determination of Dust Concentration in the Air issued by the Ministry of Labor, and TB/T2323-92 Conversion Method for Determination of Relative Mass Concentration and Mass Concentration of Dust in Air Instruments in Railway Workplace issued by the Ministry of RailwaysAnd other industrial standards, as well as the Hygienic Code for Centralized Air Conditioning and Ventilation System in Public Places issued and implemented by the Ministry of Health (WJF [2006] No. 58).
Main features:
The mass concentration of particulate matter (mg/m3) can be read directly, and the results can be obtained in one minute, or the sampling time can be set arbitrarily according to the user's needs;
Fast and accurate measurement, high detection sensitivity;
Self calibration system is designed,instrumentStable and reliable performance;
It has the air curtain shielding and clean gas self-cleaning function to ensure that the optical system is not polluted;
Realize software automatic zero setting;
It has the function of two-way communication with the computer, and can process data and print out curves and tables through a PC;
It has multiple functions such as continuous monitoring of particle concentration, regular sampling and alarm of dust concentration exceeding the standard;
Power supply: AC/DC, with rechargeable battery and charger
Size: 192 × 69 × 140 mm
Weight: 1.4Kg
New laser dust meter
The new laser dust meter has a new type of microcomputer laser dust meter with a new type of built-in filter membrane online sampler, which is advanced in the new century. While continuously monitoring the dust concentration, it can collect particles, so as to analyze their components and calculate the mass concentration conversion coefficient K.Direct reading dust mass concentration (mg/m), with PM10, PM5, PM2.5 and TSP cutters for selectioninstrumentPowerful air pump is adopted to make it more suitable for central air conditioners with long sampling pipesexhaustDetection of concentration of inhalable particles in PM10.
instrumentComply with the Hygienic Standard for Industrial Enterprises (GBZ1-2002), the exposure limit for hazardous factors in the workplace (GBZ2-2002), the Ministry of Health WS/T206-2001 Determination of Inhalable Particles (PM10) in the Air of Public Places - Light Scattering Method, and the Ministry of Labor LD98-1996 Light Scattering Method for Determination of Dust Concentration in the AirStandard, TB/T2323-92, Method for Conversion of Relative Mass Concentration and Mass Concentration of Dust in the Air of Railway Workplace, and other industrial standards, as well as the Hygienic Code for Centralized Air Conditioning and Ventilation System in Public Places issued by the Ministry of Health in document WFJF [2003] No. 225.
Main technical indicators
1. Configure 40mm filter membrane online sampler;
2. With replaceable particle cutters PM10, PM5, PM2.5 and TSP for selection;
3. Directly read the dust mass concentration (mg/m3), and the results will be given in 1 minute;
9. Measurement time: the standard time is 1 minute, with 0.1 minute and manual gear (sampling time can be set arbitrarily).
10. It has public place monitoring mode, atmospheric environment monitoring mode and labor hygiene mode.Time weighted average (TWA) and allowable concentration for short-term exposure (STEL) can be calculated.
11. Storage: 99 groups of data can be stored circularly.
12. Timing sampling: the measurement time (1~9999) seconds, shutdown time (0~9999) seconds, warm-up time (0~10) seconds and sampling times (1~9999) can be set.
13. Dust concentration over limit alarm threshold setting: maximum concentration threshold: 65mg/m3;Measurement time: (1~9999) seconds
14. Output interface: (1) PC communication serial interface: RS232;(2) Micro printer output interface;(3) Analog output interface: 0-1V;(4) Digital output interface: level signal.
15. Power supply: Ni MH rechargeable battery pack (1.2V x 4), which can be used continuously for 8 hours;220VAC/12VDC power adapter is attached.
16. With humidity correction function, the data is more accurate
17. Weight: 2.4kg.
Electron microscopic observation
Announce
edit
Scanning electron microscope observation showed that the atmospheric particles in the campus area had various shapes and sizes, most of which were small particles with irregular shape and uneven surface distribution, and the particle size was 0.1~1.0 μ m;There are a few spherical particles with smooth surface and size of 0.1~0.5 μ m;Some are cotton wadding particles with rough surface and size of 0.8~4.5 μ m;Some are long strip shaped particles with the size of 1.7~7.9 microns;Others are polygonal particles with the size of 1.1~2.3 μ m, and fibrous substances are analyzed as filter membranes by X-ray energy spectrometer.The atmospheric particulates in industrial areas are also diverse, most of which are particles with uncertain shape, rough surface and 1.2~3 μ m in size;Some are spherical particles with unsmoothed surface and size of 0.5~5.9 μ m;Some particles are irregular in shape, uneven in surface, and 1.0~2.0 μ m in size;Some particles are square and smooth with a size of 1.1~1.3 microns;Some particles are long and smooth with a size of 2.5~5.8 microns;Some particles are ellipsoidal with rough surface and size of 3.5~6.2 microns;Fibrous and honeycomb materials are filter membranes.The above observations show that these particles with different shapes and sizes are mixtures of various source dusts, some of which are only a few hundred nanometers. Therefore, the morphology of atmospheric particles can be observed and analyzed in a deeper level using scanning electron microscopy.[4]
Development of monitoring abroad
Announce
edit
The monitoring of suspended particulates in the air in major developed countries in the world has experienced a process from wide to strict standards and from large to small monitoring objects.
In 1987, the U.S. Environmental Protection Agency first formulated the PM10 limiting standard.In 1997, the United States added the requirement for the upper limit of PM2.5 concentration in the National Ambient Air Quality Standard.In 2005, the World Health Organization (WHO) formulated the Air Quality Guidelines according to the limit standards for particles that pose a hazard to human health based on scientific research, which set the standard values for the annual and daily average concentrations of PM10 and PM2.5. If they are higher than the standard values, the risk of human death will rise significantly.At the same time, the World Health Organization has also set up three target values for the transition period, providing phased goals for countries and regions at different stages of development.The World Health Organization believes that too strict indicators are difficult for developed countries to achieve in a short period of time. Therefore, it is very necessary to set the target value of echelon transition, which helps countries to assess the progress made in their efforts to reduce particle concentration.By taking continuous and lasting pollution control measures, these transition target values can be gradually achieved.
In 2006, the United States revised the air quality standard and put forward a stricter limit standard for PM2.5 concentration.
The EU monitored suspended particulates early, almost in step with the United States, but introduced laws relatively late.In 2005, the EU's decree on limiting PM10 came into force.In 2010, the EU's monitoring standard for PM2.5 came into effect.At present, the air quality standards of the European Union include the requirements for the daily average and annual average concentration of PM10 and the annual average concentration of PM2.5.Among them, the EU PM10 daily average concentration limit has reached the criteria set by the World Health Organization.
Judging from the specific situation of current implementation in various countries, Australia's standards are the most stringent, and the average annual standard is lower than that of the World Health Organization.
Some emerging economies such as India and Mexico have also accelerated the introduction of monitoring standards for PM2.5 and PM10.In 1994, the air quality standard formulated and implemented by the Ministry of Environment and Forestry of India only included the monitoring requirements for total suspended particulates and PM10, and the newly revised standard in 2009 added the limiting indicators for PM2.5.[2]
