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◉ Introduction to PAHs
Polycyclic aromatic hydrocarbons refer to aromatic hydrocarbons containing two or more benzene rings, referred to as PAHs. There are two main ways to combine them, one is non-fused ring type, which includes biphenyl, bipolyphenyl and polyphenyl aliphatic hydrocarbons; the other is fused ring type, that is, two carbon atoms are shared by two benzene rings .
◉ Sources of PAHs
The sources of PAHs are divided into natural sources and anthropogenic sources.
Natural sources mainly come from the biosynthetic process of terrestrial, aquatic plants and microorganisms. In addition, natural fires in forests and grasslands and volcanic eruptions also exist in polycyclic aromatic hydrocarbons from fossil fuels, lignin and sediment; usually the PAH background of soil The value is 100~1000μg/kg. The background value of PAH in freshwater lakes is 0.01~0.025μg/L, the background value of PAH in groundwater is 0.001~0.01μg/L, and the background value of PAH in the atmosphere is 0.1~0.5ng/m3.
Anthropogenic sources are mainly formed by the incomplete combustion of various fossil fuels (such as coal, oil and natural gas, etc.), wood, paper and other hydrocarbon-containing compounds or by pyrolysis under reducing conditions. Simple hydrocarbons and aromatic hydrocarbons are formed at high temperatures. A large number of PAHs can be formed during the pyrolysis process, and it is particularly worth reminding that more than 150 kinds of PAHs have been detected so far in the smoke exhaled from smokers.
◉ Classification of PAHs
According to the different connection modes of benzene rings, polycyclic aromatic hydrocarbons are divided into biphenyls and bipolyphenyls, polyphenyl aliphatic hydrocarbons and fused-ring aromatic hydrocarbons.
(1) Biphenyls and biphenyls
A compound formed by connecting sigma bonds between benzene rings is called biphenyl. Biphenyl derivatives and biphenyl compounds are named after biphenyl. The structure and properties are similar to those of monocyclic aromatic hydrocarbons.
(2) Polyphenyl aliphatic hydrocarbons
Polyphenyl aliphatic hydrocarbons are compounds formed by substituting several benzene rings for hydrogen atoms in aliphatic hydrocarbons. Such compounds are named with phenyl as substituent and aliphatic hydrocarbon as parent. The structure and properties are similar to those of monocyclic aromatic hydrocarbons.
(3) Condensed aromatic hydrocarbons
Condensed aromatic hydrocarbons refer to the fusion of two or more benzene rings sharing two adjacent carbon atoms.
Naphthalene is the most abundant compound in coal tar, containing about 10% in high temperature coal tar. The molecular formula of naphthalene is C10H8, which is formed by the fusion of two benzene rings sharing two adjacent carbon atoms. Naphthalene is a white flaky crystal with a melting point of 80°C and a boiling point of 218°C. It is insoluble in water and easily soluble in hot organic solvents such as alcohol and ether. Volatile, easy to sublime, with special smell.
Anthracene is present in coal tar at about 0.25%. The molecular formula of anthracene is C14H10, which is formed by the fusion of three benzene rings. Philippine also exists in coal tar, and anthracene is an isomer of each other.
(4) Other condensed aromatic hydrocarbons
Aromatic hydrocarbons mainly come from coal tar, in which fused ring aromatic hydrocarbons can be separated, such as indene, fluorene, acenaphthene are aromatic hydrocarbons fused with alicyclic and aromatic rings, tetrabenzene, pyrene, etc. are higher fused ring aromatic hydrocarbons. In addition, the derivatives of anthracene and phenanthrene are condensed aromatic hydrocarbons with significant carcinogenic effects, referred to as carcinogenic hydrocarbons.
◉ Migration and Transformation
PAHs released into the atmosphere due to incomplete combustion of fuel are usually combined with various types of solid particulate matter and aerosols. Therefore, the distribution, residence time, migration, transformation and deposition of PAHs in the atmosphere are restricted by various conditions (such as particle size, atmospheric physical and meteorological conditions, etc.), and particles with a diameter of less than 1 μm can stay in the lower atmosphere. For several days to several weeks, particles with a diameter of 1-10 μm can only stay for a few days at most. PAHs in the atmosphere enter soil and water bodies and sediments through dry and wet deposition, and enter the biosphere.
◉ Toxicity and Hazard
Due to their toxicity, genotoxicity, mutagenicity and carcinogenicity, PAHs can cause various harms to the human body, such as damage to the respiratory system, circulatory system, nervous system, and damage to the liver and kidneys. It is identified as a major organic pollutant that affects human health.
◉ presence of PAHs
Usually found in petrochemical products, rubber, plastics, lubricants, anti-rust oils, incomplete combustion organic compounds, etc. In addition to power tools, PAHs exist in many electrical products. The common ones are: when plastic particles are extruded, there is adhesion between the mold and the mold. At this time, a mold release agent should be added, and the mold release agent may contain PAHs.
PAHs may be present in materials: charcoal, crude oil, creosote, tar (natural), drugs, dyes, plastics, rubber, pesticides (artificial), lubricants, release agents, capacitor electrolytes, mineral oil, asphalt (artificial), insecticides, fungicides, mosquito coils, smoking, gasoline anticoagulant (artificial).
Materials that may contain polycyclic aromatic hydrocarbons: plastic handles/plastic packaging boxes/rubber handles/odorous plastics, rubber products.
◉ The Current Testing Range of PAHs:
Consumer products such as electronics and motors;
Rubber products, plastic products, automotive plastics, rubber parts;
Food packaging materials, toys, container materials, etc.;
other materials, etc.;
◉ Regulatory Requirements
EU countries: 76/769/EEC / Germany German: GS certification, LFGB / USA US: EPA, China: GB, GB/T, GHZ.
◉ Compliance Services
As a professional third-party testing technology service provider, Jiayu Testing boasts qualifications such as CMA, CNAS, CPSC, and CCC. Additionally, we have obtained laboratory accreditation from multiple authoritative certification bodies both domestically and internationally. Our laboratory is constructed and managed in strict accordance with standards, equipped with advanced instruments and equipment, and staffed by a skilled and professional technical team. We possess extensive industry service experience and robust testing technical capabilities, are proficient in various regulatory standards, and assist enterprises in actively responding to regulatory requirements. We help enterprises achieve hazardous substance risk control and effectively enhance product compliance. Welcome to contact us. Jiayu Testing's consultation hotline is: 400-9269-886!
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