Bioconcentration refers to the phenomenon that biological organisms or many biological populations at the same trophic level accumulate certain elements or refractory 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 many microorganisms are absorbed directly on the body surface;Higher plants mainly rely on root absorption;Most animals absorb mainly by swallowing.The first two are taken directly from the environment, while the latter needs to be taken through the food chain.Pollutants may also be enriched in organisms.Whether pollutants accumulate along the food chain depends on the following three conditions: pollutants must be relatively stable in the environment, pollutants must be bioabsorbable, and pollutants are not easy to be decomposed in the process of biological metabolism.[1]
Bioconcentration refers to the phenomenon that organisms accumulate certain elements or decomposed compounds from the surrounding environment to make their concentration in the body exceed the concentration in the environment.The research on the mechanism of biological concentration can reveal the toxicity, toxicology and ecological impact of pollutants from the macro and micro levels, so as to deeply understand the distribution, migration and transformation of pollutants in organisms.[2]
Development status
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A substance in a specific biological individual, organ or cell has a higher concentration than that in the surrounding environment.For example: inplant cellOr the accumulation of various salts or metals in bacteria as metabolites;The accumulation of iodine in human thyroid;The accumulation of vanadium by ascidians.The mechanism of biological concentration is mostly due to the fact that once these substances enter the organism, they are difficult to be discharged;In addition, some components mainly related to metabolism can be precipitated from body fluid or cell fluid in the form of solid, and these processes will be accumulated in the body after repeated.As a result of bioconcentration, species or populations in the upper food chain will accumulate into higher concentrations.Therefore, harmful substances will have a significant impact on these organisms, and biological concentration has become an important social issue (such as the impact of raptors onOrganochlorine pesticideAnd human diseases caused by organic mercury poisoning).In the past, we didn't mind the low concentration of harmful substances discharged into the environment, but from the perspective of biological concentration, this is very wrong.[3]
Related concepts
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Biological organism or being in the sameTrophic levelThe phenomenon that many biological populations in the organism accumulate some element or refractory compound from the surrounding environment, making the concentration of the substance in the organism exceed the concentration in the environment;It is also called biological concentration and biological enrichment.For the degree of biological concentrationConcentration coefficientexpress.
BioconcentrationBioaccumulationandBioamplificationThe degree of is expressed by the concentration coefficient of elements from the environment or compounds that are difficult to decompose, but there are three different concepts.
BioconcentrationIt refers to the comparison between the concentration of a substance in the organism and that in the environment;
BioaccumulationIt refers to the concentration comparison of the same biological individual in the body at different metabolic active stages;
BioamplificationIt refers to the comparison of the concentration of certain substances in the organism of different trophic levels in the same food chain.
Concentration mechanism
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The pollutants enter the organism through various ways such as biological respiration, food and skin absorption, and then disperse to various parts of the body according to the blood circulation, and are absorbed and concentrated by various tissues and organs of the organism.Obviously, the concentration of a pollutant by various organs and tissues of the organism depends on the degree of contamination of the substance in the blood, the difference of affinity between biological tissues and blood for the substance, and the metabolism of biological tissues for the substance.[2]
influence factor
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The concentration coefficient is related to the nature of the substance itself, biological and environmental factors.The concentration coefficient of the same organism for different substances will be very different.For example, under the same conditions, the concentration coefficient of tuna for copper is 100, but for magnesium is 0.3;The concentration coefficient of brown algae to molybdenum is 11, but the concentration coefficient to lead is as high as 70000, which is very different.The concentration coefficient of the same substance varies with its structure.For example, BHC is extremely difficult to decompose in the organism,Propyl hexachlorocyclohexaneIt is easy to decompose, and the concentration coefficient of mice to the former is higher than that to the latter.The concentration coefficients of the same organism for the same class of compounds with different molecular weights are also very different, such as Daphnia pulex（Daphnia pulex）Under the same test conditions, the concentration coefficient of azaarenes with different molecular weights (such as isoquinoline, acridine and benzoacridine) varies according to the molecular weight.
The valence state of the substance or element, as well as the solubility in the medium, also have a direct impact on the concentration coefficient.
Different species of organisms have different metabolic functions. Under the same conditions, the concentration coefficient of the same substance will also be different.Institute of Oceanography, Chinese Academy of SciencesAccording to our research report, under the same conditions, the concentration coefficient of black porgy (Sparus macrocephalus) skeleton to 137 caesium is 11.02, while that of stone flounder (Plati chth у s bicoloralus) skeleton to 137 caesium is 8.95.The concentration capacity of different organs of organisms to the same substance is often different.The concentration capacity of organs with more fat is generally higher than that of organs with less fat.
The different development stages and physiological characteristics of organisms also have a direct impact on the concentration capacity.Young leaf pairs of most woody plantssulfur dioxideThe concentration capacity of the leaves was lower than that of mature leaves.
The number of aquatic organisms in the water has a great impact on the concentration coefficient. For example, when the number of cells in the pure culture medium of Scenedesmus platensis increases, the concentration coefficient 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, will affect the existence form, valence, concentration and residence time of substances in the environment. Therefore, under different environmental conditions, the concentration coefficient of the same organism to the same substance may be different.[4]
When organisms that have concentrated a large amount of pollutants leave the polluted environment, the pollutants accumulated in the body will gradually be discharged from the body through metabolism, and the residual amount in the body will gradually decrease.The time required to reduce the residual amount to half of the original storage amount is calledBiological half-life。
Absorption pathway
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The ways for organisms to absorb substances in the environment are as follows: First, various algae, fungi and protozoa are absorbed directly on the body surface;Second, higher plants are mainly absorbed by roots, and leaf surface and stem surface also have certain absorption capacity;Third, most animals mainly swallow.For fish, respiration is also a main way.The first two ways are directly ingested from the environment, and the latter way must be completed through the food chain.When various substances enter the organism, they participate in the metabolic process of the organism.Some of the substances necessary for life are involved in the composition of the organism, and the easily decomposed substances are quickly discharged from the body through metabolism in excess of the necessary substances and the substances not necessary for life;Those that are not easy to decompose, have strong fat solubility, and have high affinity with proteins or enzymes will remain in the organism for a long time.Pesticides such as DDT and Dieldrin are stable and fat soluble. They can be dissolved in fat after ingestion into animals, and are difficult to decompose and excrete.With the increase of intake, the concentration of these substances in the body will gradually increase.
research meaning
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The study of bioconcentration is of great significance for clarifying the migration and transformation laws of substances or elements in the ecosystem, evaluating and predicting the possible hazards of pollutants entering the environment, and monitoring and purifying the environment by using organisms.This study can also be used to determine theenvironmental capacityAnd formulate environmental standards to provide scientific basis.
