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With the popularization of environmental protection knowledge, we believe everyone is familiar with the word "heavy metal". Heavy metal pollution is a kind of environmental pollution. In terms of environmental pollution, the heavy metals mentioned in terms of environmental pollution mainly refer to heavy elements with significant biological toxicity such as mercury, cadmium, lead, chromium, and metalloid arsenic. So what harm do heavy metals have on the human body?
What are the hazards of heavy metals to the human body?
The harm of excessive mercury
Hg is what we commonly call mercury, poisoning will occur if it exceeds the standard, often manifests as neurasthenia, memory loss, emotional instability, irritability, depression, timidity, etc. in the nervous system. It may even lead to shock, cardiovascular system failure, renal failure and severe damage to the gastrointestinal tract, and even death in more severe cases.
The hazards of excessive cadmium
A large amount of cadmium accumulated in the human body will cause damage to the liver and kidneys, and also affect the central nervous system of the human body, and it is extremely difficult to excrete it from the body. Cadmium poisoning can cause intramuscular atrophy, joint deformation, unbearable bone pain, inability to sleep, pathological fractures, and even death.
The dangers of excessive lead
A large amount of lead accumulates in the human body, endangering the brain tissue, nervous system and other organs of the human body, and affecting children's intellectual and physical development.
The hazards of excessive chromium
If the human body takes in trivalent chromium for a long time, it will damage the antioxidant system, and it is easy to get diabetes, high blood pressure, abnormal tumor proliferation and other diseases. And if hexavalent chromium is ingested, it will damage the skin, cause dermatitis, pharyngitis, etc.; damage the digestive system, cause gastritis, gastric ulcer and intestinal ulcer, and in severe cases, it will cause renal failure and even cancer.
The dangers of excessive arsenic
Arsenic exists widely in nature, and its compound arsenic trioxide is a well-known highly toxic arsenic. Many studies at home and abroad have proved that excessive intake of arsenic will increase the risk of mutation, carcinogenesis and teratogenicity.
Generally speaking, excessive heavy metals threaten people's health, so how can we fundamentally eliminate the problem of excessive heavy metals? The answer is soil testing and soil treatment!
Today, we will introduce to you the method of soil heavy metal detection!
Broadly speaking, soil heavy metal detection methods can be divided into chemical methods, physical methods and biological methods.
Chemical methods for the detection of heavy metals in soil
To determine the content of heavy metals in soil by chemical methods, first of all, different acid systems or alkali fusion methods are used to completely destroy the mineral lattice of the soil, so that all the elements to be measured in the sample enter the test solution in an ionic state.
Mercury detection method
After the sample is digested, under acidic conditions, mercury ions and dithizone form an orange-red complex, which is determined colorimetrically.
Cadmium detection method
After the sample is digested, under alkaline conditions, cadmium ions and 6-bromophenylprophiazole azonaphthol form a red complex, which is determined by colorimetry.
Lead detection method
After the sample is digested, under weakly alkaline conditions, lead ions and dithizone form a red complex, which is determined colorimetrically.
Chromium detection method
After the sample is digested, in the presence of divalent manganese, the chromium ion reacts with diphenylcarbohydrazide to form a purple complex. The depth of the color of the complex is directly proportional to the content of hexavalent chromium, and the content of chromium can be obtained by colorimetric determination.
Arsenic detection method
After the sample is digested, potassium iodide-thiourea is added and heated to reduce pentavalent arsenic to trivalent arsenic. Under acidic conditions, potassium borohydride will reduce trivalent arsenic to negative trivalent arsenic, and the arsenic content can be obtained by instrument detection.
Physical methods for the detection of heavy metals in soil
X-ray fluorescence spectroscopy
X-ray fluorescence spectrometry uses ground state atoms to absorb radiation of a specific specific frequency to be excited to a high energy state, and then emit fluorescence at a characteristic wavelength in the form of light radiation during the excitation process. Determine the type and content of elements by measuring the wavelength and intensity of resonance fluorescence.
Laser induced
Laser-induced breakdown spectroscopy is a kind of atomic emission spectroscopy, and its excitation source is a pulsed exciter. The pulser emits a laser with high power density, and a few micrograms of plasma will be ejected from the surface of the material to be tested. The plasma will gradually cool down during the injection process, and emit a spectrum that characterizes the component information of the sample, and use a photodetector and a spectrometer to collect the plasma emission spectrum. By analyzing the plasma spectrum and combining with the quantitative analysis model, the type and content information of the analyzed sample components can be obtained.
Neutron activation analysis
The neutron activation of the instrument is a non-destructive analysis, which can directly measure heavy metals in soil samples, mainly including La, Ge, Sm, Eu, Yb, Ln, Hf, U, Se, Co, etc.
Biological methods for the detection of heavy metals in soil
Biological detection method refers to the technology of evaluating soil pollution from the biological point of view by detecting the response of biological individuals, populations or communities growing or living in the soil to soil heavy metals, mainly including enzyme inhibition method and biosensor method.
3.1 Enzyme inhibition method
Enzyme inhibition method is the indirect qualitative determination of heavy metal content in soil by using the inhibitory effect of heavy metal content on enzyme activity, and a suitable enzyme buffer system is the key to its determination. Among them, the most sensitive enzyme is urease.
3.2 Biosensor method
The biosensor method is a rapid detection technology. The enzyme biosensor is used to measure mercury ions in soil, which avoids the complexity of sample pretreatment in traditional methods.
The above are the several methods I have listed for you to detect heavy metals in soil. When the content of heavy metals in the soil exceeds the standard, we must carry out soil heavy metal treatment in time to prevent these heavy metals from entering the human body along the food chain and endangering everyone's health.
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