What Is Bioconcentration?

Bioconcentration refers to the phenomenon in which a biological organism or many biological populations on the same trophic level accumulate certain elements or difficult-to-decompose compounds from the surrounding environment so that the concentration of the substance in the biological organism exceeds the concentration of the substance in the environment. There are three ways for organisms to absorb substances in the environment: algae, protozoa, and various microorganisms are mainly absorbed directly from the body surface; higher plants are mainly absorbed by the root system; most animals are mainly absorbed by swallowing. The first two are taken directly from the environment, and the latter need to be taken through the food chain. Contaminants may also accumulate in living organisms. Whether pollutants accumulate along the food chain depends on the following three conditions: that the pollutants must be relatively stable in the environment, and the pollutants must be able to be absorbed by the organism, and the pollutants cannot be easily broken down in the process of biological metabolism. ^[1]

Bioconcentration refers to the phenomenon in which organisms accumulate certain elements or decomposed compounds from the surrounding environment so that their concentration in the body exceeds the concentration in the environment. The research on the mechanism of biological enrichment can reveal the toxicity, toxicology and ecological impact of pollutants from macro and micro, so as to understand the distribution, migration and transformation of pollutants in organisms. ^[2]

The phenomenon that a certain substance in a particular biological individual, organ or cell has a higher concentration than in its surrounding environment. For example: the accumulation of various crystals of salts or metals in plant cells or bacteria as metabolites; the accumulation of iodine in the human thyroid; the accumulation of vanadium in true ascidians. The mechanism of bioconcentration is mostly because these substances are difficult to excrete once they enter the body; in addition, certain metabolically related components can be precipitated from body fluids or cellular fluids in solid form, and these processes will be accumulated in the body repeatedly. stand up. As a result of bioconcentration, the biological species or population in the upper food chain will accumulate to a higher concentration. Therefore, harmful substances will have a significant impact on these organisms, and bioconcentration has become an important social issue (such as the accumulation of organochlorine pesticides by raptors, and human diseases caused by organic mercury poisoning). In the past, we did not mind the low concentration of harmful substances discharged into the environment, but from the perspective of bioconcentration, this is very wrong. ^[3]

Biological organisms or in the same

Contaminants enter the body through various means such as biological breathing, food and skin absorption, and then are dispersed to various parts of the body according to blood circulation, and are absorbed and concentrated by various tissues and organs of the organism. Obviously, the degree of concentration of a certain pollutant by various organs and tissues of the organism depends on the degree of pollution of the substance in the blood, the difference in affinity between the biological tissue and blood for the substance, and the metabolism of the substance by the biological tissue. ^[2]

The concentration factor is related to the nature of the substance itself and biological and environmental factors. Concentration coefficients of the same organism for different substances can vary widely. For example, under the same conditions, the concentration factor of copper for tuna is 100, but the concentration factor for magnesium is 0.3; the concentration factor of brown algae for molybdenum is 11, and the concentration factor for lead is as high as 70,000. The same substance has a different structure and a different concentration factor. For example, B-6 is extremely difficult to decompose in living organisms, and C-6 is relatively easy to decompose. The concentration factor of the former is higher than that of the latter. For the same kind of compounds with different molecular weights, the concentration coefficients are also very different.For example, under the same test conditions, Daphnia pulex , for azaaromatic hydrocarbons of different molecular weights (such as isoquinoline, acridine and Benzoacridine), its concentration coefficient varies depending on the molecular weight.

The valence of a substance or element and its solubility in the medium also have a direct impact on the concentration factor.

Different biological species have different metabolic functions. Under the same conditions, the concentration factors for the same substance will also be different. A research report by the Institute of Oceanology, Chinese Academy of Sciences pointed out that under the same conditions, the concentration coefficient of 137 cesium by the black snapper ( Sparus macroce-phalus ) bone is 11.02, while the concentration coefficient of 137 cesium by the platy-chths bicoloralus bone Is 8.95. Different organisms' organs often have different ability to concentrate the same substance. Organs with more fat are generally more concentrated than organs with less fat.

The different developmental stages of the organism and its physiological characteristics also have a direct impact on the ability to concentrate. The young leaves of most woody plants are less capable of concentrating sulfur dioxide than mature leaves.

The amount of aquatic organisms in a water body has a great influence on the concentration factor. For example, when the number of cells in a purely cultured Scenedesmus medium increases, the concentration factor decreases.

Various environmental factors, such as light, temperature, humidity, pH value, wind direction, wind speed, water flow direction, water flow speed, soil composition and structure, etc., the form, valence, concentration, and retention of substances in the environment Time, etc. will have an effect, so under different environmental conditions, the concentration factor of the same organism for the same substance may also be different. ^[4]

There are several ways for organisms to absorb substances in the environment: one is various algae, fungi and various protozoa, which are mainly absorbed directly on the body surface; the other is higher plants, which are mainly absorbed by the root system, The surface of the stem also has a certain absorptive capacity; third, most animals rely mainly on swallowing. For fish, breathing is also a major route. The first two pathways are taken directly from the environment, and the latter pathway must be completed through the food chain. Various substances enter the organism, that is, they participate in the metabolic process of the organism. Among them, the substances necessary for life are partly involved in the composition of the organism. Among the excess essential substances and non-life-required substances, the easily decomposed and metabolized are quickly discharged out of the body; they are not easily decomposed, have strong fat solubility, and interact with proteins or enzymes. Those with higher affinity will remain in the body for a long time. Pesticides such as DDT and Dieldrin have stable properties and strong fat solubility. They are soluble in fats after being ingested into animals, and are difficult to decompose and excrete. As the intake increases, the concentration of these substances in the body gradually increases.

The research on bioconcentration is of great significance to clarify the laws of migration and transformation of substances or elements in the ecosystem, to evaluate and predict the harm that pollutants may cause after entering the environment, and to use biology to monitor and purify the environment. Such research can also provide scientific basis for determining the environmental capacity of pollutants and formulating environmental standards.