[Detection Instrument] Environmental Chemical Pollution Accident Emergency Monitoring Technology and Instrumentation Equipment

Abstract : This paper introduces the main technologies and equipments for on-site emergency monitoring of environmental chemical pollution accidents, and analyzes their respective advantages and disadvantages; according to the characteristics of environmental pollution accidents in China. The principle of selection of monitoring items and methods that should be given priority has been proposed.

Keywords: emergency monitoring; technology and instrumentation; method selection

1 Preface

From the perspective of urban public security protection, the main types of accidents are: 1) Chemical emergency accidents, that is, a large number of poisonous and harmful gases suddenly leak out and spread, causing large-scale pollution and endangering the population; 2) Nuclear leakage accidents, mainly Refers to a large number of radioactive materials leaked from nuclear power plants, nuclear fuel mines, and post-processing plants. The amount of environmental radiation is excessively excessive; 3) Major fires and explosions involving evacuation and transfer of population; 4) Abrupt water pollution, explosive transmission of viruses or germs spread.

In 1995 , Sarin gas attacks occurred on the Tokyo subway in Japan, killing 10 people and poisoning 5,510 .

In 1992 , a natural gas explosion occurred in the post-Darazena area of ​​Mexico, killing 210 people and injuring 1,500 people.

In 1986 , the Rhine River in Europe caused water pollution accidents due to the discharge of more than 30 kinds of organic matter in chemical plants , causing a large number of aquatic life deaths and affecting the lives of millions of people.

In 1986 , explosions and radioactive leaks took place in the former Soviet Union’s Chernobyl nuclear power plant, killing 250 people and injuring more than 300 people.

December 3, 1984, Union Carbide in Bhopal, India occurred 55t methyl isocyanate leak occurred, killing more than 2,500 people dead and 50,000 people blind. 13 hurt. With 50,000 people and 200,000 people migrating , the world is shocked.

In 1979 , the explosion of chlorine and toluene transport occurred in Mississauga , Canada . Evacuate 250,000 people.

In 1975 . A factory in Seveso , Italy , reacted uncontrollably, causing dioxin and other pollution incidents. 193 people were poisoned.

From 1971 to 1972 , methylmercury contamination seed accidents occurred in Iraq, killing 459 people and injuring 6071 people.

In 1995 , a chlorine leak occurred in Fushun City in China, causing more than 200 people to become poisoned.

In 1995 , an ammonia, phenol, and oil leaking water pollution accident occurred in Panzhihua City in China, causing many people to become poisoned.

In 1987 and 1995 , a phosgene pollution accident occurred in the Jingjiang area of ​​China and poisoned more than 50 people.

In 1993 , explosions and fire accidents occurred in the dangerous goods warehouse in Qingshuihe, Shenzhen, China. They involved various chemicals and caused 15 deaths. Loss of more than 200 million yuan.

2 Sources of Chemical Disasters in China

The four conditions that may constitute the source of hazards for chemical accidents are: high toxicity, high dosage, easy diffusion, and dense population around them. Human-induced factors that turn this potential threat into an actual disaster include: improper site selection, unreasonable layout; flaws in design; poor equipment quality, or excessive overtime due to non-contained standards ( or failure to implement the standards ) . , overload operation; poor corporate management or misconduct; violation of command or illegal operation; safety protection settings and personal protection and other ineffective.

The hidden dangers of China's environmental pollution accidents include: many hidden dangers of industrial pollution, especially the problems of chemical industry enterprises and petrochemical industrial enterprises; the improper disposal of industrial wastes, the hidden dangers of some mines in the barrage, and the poor management of toxic chemicals. , Chemical spills in transport are frequent; oil spills from marine vessels and the loss of some radioactive sources.

The hazards of toxic chemicals that should be given special attention are as follows:

(1) Phosgene, a scientific name known as carbon trichloride ((3OC12) , is a military agent. It has been used in recent years as an important raw material for various products such as artificial leather, dyes, pesticides, and medicine.

(2) Methyl isocyanate (â„–), an intermediate is phosgene, larger than toxic phosgene. It is an important raw material for pesticides and rocket fuels. Of phosgene and methyl isocyanate company 32 (1985).

(3) Chlorine (C1) , used as a military poison. It is now the main raw material for plastics, synthetic fibers, pesticides and other products. It is also widely used in the disinfection of textiles, paper and tap water. Except Tibet, all of our provinces, municipalities and autonomous regions have chlorine production enterprises, a total of 180 companies caustic soda (1985).

(4) Other toxic gases or toxic liquids with high volatility mainly include formaldehyde, allyl chloride, vinyl chloride, carbon disulfide, monomethylamine, dimethylamine, sulfur dioxide, 05) , ammonia, hydrocyanic acid, benzene, HF , and sulfur Hydrogen, hydrogen chloride, toluene, styrene, dimethyl sulfate, acrylonitrile, methyl bromide, toluene diisocyanate, ethylene oxide, cycloethylamine, aniline and more than 30 kinds of toxic chemicals.

Features 3 emergency monitoring, the role and requirements

Because pollution accidents may cause various degrees of damage to various environmental elements ( such as air, ground/groundwater, soil, etc. ) , they determine the difficulty of monitoring tasks. Moreover, due to the fact that the monitoring objects in the environment samples, especially accidents, have instantaneously changed characteristics, this difficulty is further increased.

(1) Characterize the characteristics of the accident: such as release amount, form and concentration of pollutants, rate of diffusion into the environment, contaminated areas, presence or absence of superposition, degradation rate, and characteristics of pollutants ( including toxicity, volatility, and residues) Sex ) etc. According to the field test results, it can provide many useful first information sources for further laboratory analysis, such as correct sampling locations, sampling ranges, sampling methods, and analysis methods. Emergency ( on-site ) rapid monitoring and emergency response expert systems during accident prevention, accidents, and post-accident environmental remediation can provide high-quality data quickly, and can be modified to mitigate the damage and damage caused by environmental pollution accidents. And take effective response to deal with measures to provide scientific decision-making support.

(2) Special requirements for emergency monitoring:

1 The grasp of time scale ( analysis and research on the rapid and recovery phases in accidents ) ;

2 Grasping the scope of the space ( different source intensity, different weather conditions, such as: unsteady wind field, quasi-static wind hazard area ) .

3 method selection: must provide the most general monitoring technology to achieve faster use of a variety of instruments and equipment in order to quickly and effectively conduct a more comprehensive on-site emergency monitoring; analysis method is best to have a fast screening (screening) function, and have a Good sensitivity, accuracy, and reproducibility; the selectivity of the analysis method and the ability to resist interference are better; the operating procedures of the analysis method should be simple, without professional knowledge and talent, or even without training.

4 On-site emergency monitoring technology and equipment

4 . 1 sensory detection method

This is the simplest monitoring method. That is, human organs ( also called human biosensors ) such as a nose, an eye, a mouth, and a skin sense the presence of a substance to be detected. For example, cyanide has almond flavor, sulfur dioxide has a special pungent taste, organophosphorus pesticides containing thiol have bad odor, nitro compounds emit yellow smoke when burning, black smoke from the chimney is caused by incomplete combustion; some chemicals Substances such as HC1 can stimulate eye tears, acidic substances have a sour taste, alkaline substances have a bitter taste, and acids and bases can also stimulate the skin. But this method can directly injure the monitoring staff, and because many chemicals are colorless and odorless, such as ∞ is a colorless and odorless gas. There are many chemical substances in the same form and color and cannot be distinguished. So this can only be an expedient measure. Sensory testing alone is definitely not enough. And for highly toxic substances can not be detected using sensory methods.

4 . 2 animal detection method

The use of animal sense of smell or sensitivity to detect toxic and hazardous chemicals, such as the dog's sense of smell is particularly sensitive, the use of dogs to detect drugs abroad is common. The U.S. military had trained dogs to detect chemical poisons so that six chemical poisons could be detected in their sense of smell. When dogs smelled traces of chemical poisons, they reflected different snoring noises. The minimum concentration detected was 0 . 5 ~ lmg / L. There are also some birds that are particularly sensitive to toxic and harmful gases, such as raising a golden bird or a chick in the production plant of a pesticide factory. When a trace of chemical substances leaks, the animal will immediately feel uneasy and even struggle to die.

4 . 3 plant detection

Detecting the damage of plant epidermis is also a simple monitoring method, which has gradually been paid attention by people. Some plants are very sensitive to certain atmospheric pollution. For example, people can smell sulfur dioxide odors ranging from 1 to 19 ppm . They feel obvious stimulation such as causing coughing, tearing, etc. Their concentrations are 10-20 ppm ; and some sensitive plants are at 0 . 3 to 0 . At 5 ppm , there is a visible spot on the blade. After HF contaminated the leaves, the lesions showed a band-like shape, distributing the tips and edges of the leaves, and gradually developed inwards. Photochemical smog leaves the back of the leaves silvery or bronze, and a necrotic zone across the entire leaf appears on the front of the leaf. Using the “symptoms” that plants hold can provide circumstantial evidence for the monitoring and management of environmental pollution.

4 . 4 chemical production method

U.S. chemical inspection workers had once imagined using an agent to quickly react with odorless toxic chemicals to produce odorous, non-toxic volatile compounds that would then be detected with the senses. For example, it has been studied that dehydration forms a hydrocarbyl isocyanide by reacting N -alkyl carboxamides with various electrophiles such as arylsulfonyl chlorides. Such compounds have a pungent odor and rotten, very unpleasant but non-toxic to mammals and high odor detection sensitivity, minimum detectable concentration of up to 10 ~ ~ 10L. The main disadvantages are that some chemical reactions are complex and the reaction speed is slow; some reactions are carried out in organic solvents and some are dehydration reactions.

4 . 5 test paper method

The filter paper is soaked in chemical reagents and then air-dried, cut into strips, squares, etc., and packed in a sealed plastic bag or container. When used, the air to be measured passes through the filter paper soaked with the reagents, and the harmful substances and reagents are on the paper. A chemical reaction occurs to produce a color change; or the air to be measured passes through a non-soaked filter paper, so that harmful substances are adsorbed or retained on the filter paper, and then reagents are dropped on the test paper to generate a color change; and according to the generated color depth Standard colorimetric plates are compared for quantification. The former is mostly suitable for gases or vaporous hazardous substances that can rapidly react with reagents; the latter is suitable for the determination of aerosols, allowing a certain reaction time. Such as: chlorine biphenyl indicator method.

Or when in use, take a piece of test paper, immersed in the test solution, and take it out after a certain time, compared with a standard color plate. It has been reported by the United States E. Merck 's pH test paper measured the rain acidity and the results were exactly the same as those measured with a pH meter. Another example is the determination of arsenic used for mercury bromide test paper, is a common filter paper soaked in mercuric bromide solution after drying, sealed in a glass bottle, can be stable for more than 3 years. In use, the sample solution is placed in a test arsenic bottle, and the generator is added to react with arsenide to generate arsine. Arsenic immediately reacts with the gas and reacts with the mercury bromide test paper. The test paper is yellow-brown and the arsenic spot is positive. , detection sensitivity up to 0 . 2L . The colorimetric method of the test paper is characterized by simple and rapid operation and wide measurement range. However, the measurement error is large. Some chemical reagents have poor stability on the paper, and the measurement range and intervals are relatively coarse. It is suitable for the determination of high-concentration pollutants. It is a semi-quantitative method.

4 . 6 detectable powder or detective chalk method

The advantage of detection powder is that it is easy to use, economical, and can be used in a large area. The disadvantage is that the specificity is not strong, the sensitivity is poor, and it cannot be used for the detection of harmful substances in the atmosphere. The detective powder is mainly dyestuffs. If quartz powder is used as a carrier, dyes such as German Khan, yellow, permanent red B and Sudan red are added and mixed, and when the mustard gas leaks, it is blue-red. Detection Chalk is a detection device that mixes reagents and fillers and presses them into chalk. It can be coated directly on the surface of the material or powdered and sprinkled on the surface of the material for testing. For example, chloramine T and barium sulphate as the main reagents can be used to detect cyanogen chloride. The scratches change from white to red and then to blue. Sensitivity up to 5ppm . Detective chalk can be stored for three years at room temperature. The detection of chalk due to its small surface area reduces the chance of interacting with foreign substances. It is usually better than the test strip, and it is also easy to carry. The disadvantage is that the reaction is not specific and the sensitivity is poor.

4 . 7 detection method

Most of them are soaked in filter paper or made into tablets and sealed in transparent thin plastic sheets. When inspected, place it in the sample and observe the color change. Similar to the test strip, but with different packaging forms, stability has improved.

Another detective film for measuring organophosphorus compounds is a plastic clip with one end having a circular shape, and a piece of paper or glass fiber sheet containing a certain amount of acetylcholinesterase and a buffer agent is placed in the middle and sealed by vacuum drying. Open plastic sheet is detected, one end side of the sample was done, one end of a blank round, dropwise contaminated water samples in one end side of the sheet or the enzyme exposing 0 in the polluted air. 5 to 2 minutes . When making a water sample, add a clean water to the blank end, and then add a few drops of indicator and matrix solution, such as bromothymol blue (BTB) and acetylcholine chloride solution, on both ends. After a few minutes, if the end of the sample is indicated The agent is still blue, or the blue color does not fade, and the indicator blue at one end of the blank fades quickly, indicating the presence of phosphorus-containing organic compounds. This method is very sensitive and can be used for semi-quantitative analysis.

4 . 8 detection tube method

Including detection tube method, direct detection tube method ( rapid measurement tube method ) and adsorption detection tube method.

(1) Color reaction type ( water ) test tube method: This method is to make the reagents into fine or powdery and seal in the capillary glass tube, and then assemble it in a polyethylene soft plastic test tube. A plug with a micro hole is plugged. When in use, the test tube is pinched with fingers, the air in the tube is discharged, the water is inserted into the water sample, and the water sample is automatically inhaled by releasing the finger. The capillary reagent tube in the test tube is then crushed, and the color is developed within a few minutes. The swatches are compared to determine the concentration of the contaminants. Such as: Cr ( VI ) test tube.

(2) filled (gas) detector tube: internal filling a cuvette Chemicals display indication powder, is generally used in an inner diameter of 2 ~ 6rrma, a length of E-120 ~ 180rnrn of thin glass. The indicator powder is a porous solid fine particle adsorbed with a chemical agent, and each chemical agent usually has a special effect only on one compound or a group of compounds. When the air to be measured passes through the detection tube, the toxic gas to be detected contained in the air reacts quickly with the indicator powder in the tube and displays the color. The wall is marked with a scale ( usually rng / m3) , and the concentration of the contaminant can be read out quantitatively or semi-quantitatively based on the scale position shown in the discoloration ring ( column ) . Such as: rapid detection of benzene vapor tube.

(3) (air or water) direct detection tube method (speed test tube): This method is the detection reagent placed in a thin glass, and the like at both ends with cotton wool or blocked, then both ends of the fusion seal . Before use, the test tube is cut at both ends, immersed in a certain volume of the tested water sample, and the water sample is sucked by capillary action. The sample can also be connected to the contaminated water sample or air sample to observe the change of color or to compare the depth of color. And length to determine the type and content of contaminants. If there is a chloride detection tube, a mixture of silver chromate and silica gel is used to make tea brown reagent, and the detection tube is made according to the above method. When the chloride in the water comes into contact with the silver chromate silica gel reagent, the tea brown reagent turns white ( white-colored AgC1) . The length of the reagent discoloration in the test tube is proportional to the amount of chloride in the water. Therefore, the contents of the scale can be drawn on the outer wall of the test tube or the specification, which can be used as the chloride quantification. Another example is the sulfate detection tube made of tetrahydroxyanthraquinone and silica gel. When there is sulfate in the water sample, the pink reagent is discolored and the length of discoloration is proportional to the sulfate content in the water. A sulfate quantitative scale can be drawn. There is also a test tube for detecting automobile exhaust gas that can detect the 0O and hydrocarbon content in the vehicle exhaust . The content scale is printed on the pipe wall, which is easy to use and intuitive to observe.

(4) ( Gas or water ) adsorption detection tube method: The method is to set the front end of a thin glass tube adsorbent, and the rear end is placed in a glass ampoule bottle of reagents, separated by glass wool and other inert substances. Both ends are blocked with absorbent cotton or glass wool, and the two ends are sealed. Before use, the ends of the test tube are cut open, and the polluted water sample or the air sample is pumped into the adsorbent by the helium cylinder, and then the reagent ampoule bottle is broken, so that the contaminant on the adsorbent and the reagent are reacted, and the adsorbent is observed. The color change is compared with a standard swatch to determine the contaminant concentration. If there is a detection tube that can measure HCN in the air, the reagent-treated silica gel is used as an adsorbent and assembled into a detection tube with alkali and ninhydrin solutions respectively contained in a small ampoule bottle. If the HCN adsorbent is blue-violet, the sensitivity can reach 0 . 05mg / L.

At present, there are many kinds of harmful gases or gas detection tubes and water pollution detection tubes that are rapidly measured on site. For example: The Drager test tube is a powerful tool for qualitative and quantitative gas detection with its proven simplicity, rapidity, and accuracy. With appropriate accessories, the Drager tube can also be used for air, gas, water, liquid, and soil, respectively. And on-site rapid detection of sewage and other samples. The Drager gas detection tube is made of glass and is filled with an inert carrier material. The carrier has been treated with chemical reagents. A color reaction occurs when the gas or vapor to be measured is present. These reagents are very stable and generally have a service life of two years. In addition, some of these gas detection tubes can be used for short-term measurements ( giving an instantaneous actual concentration ) , and some can be measured for more than several hours ( giving a time-weighted average concentration ) . The measurement range is extremely wide, from a few thousandths of ppm up to several % of volume; it can be read directly or used for laboratory sampling. At present, there are more than 200 types of detection tubes , which can measure 350 to 500 kinds of harmful gases .

According to its function, measurement method, and application range, it can be divided into many types. Such as: Short - Term Tubes , Long - Term Tubes , Sampling Tubes ( Active Sampling Tubes , Passive Diffusion Samplers, etc. ) , Direct Reading Alarm Detection tube (Badges with direct Indication), when the direct reading diffusion tube length (Dif - fusion - tubes with direct Indication) and the like.

In addition, Henan Hebi Gas Detection Tube Factory can produce series of long-term gas detection tubes. Measurement items include: (30 , o32 , S()2 , C12 , NH3 , HiS , HC1 , PH3 , NOx , benzene, toluene, xylene, vinyl chloride, styrene and formaldehyde, etc. ) Rapid test tubes manufactured by Japan J1I Corporation There are more than 160 kinds of gas detection tubes produced by Gas Tec Inc. , USA . The measurement items include inorganic and organic pollutants. There are 180 gas detection tubes, which can be used for emergency monitoring of the working environment and pollution accidents.

4 . 9 Chemical Colorimetry ( Chemical Test Component Method )

This method is one of the commonly used methods in simple monitoring and analysis. The colorimetric method utilizes the principle of chemical reaction chromogenic analysis. The advantages of the colorimetric method are that it is easy to operate and the reaction is rapid. The reaction results can produce color or color change, which can be easily visualized or measured quantitatively using a portable spectrophotometer. Due to the simple equipment and low monitoring cost, it is easy to promote and use. However, the selectivity of the colorimetric method is poor and the sensitivity is limited.

When the chemical reagent test kit is used for on-si

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