MODERN BIOGEOCHEMISTRY: SECOND EDITION Phần 2

BIOGEOCHEMICAL STRUCTURE OF ECOSYSTEMS 33 The general scheme of an algorithm for simulation of biogeochemical cycles of various chemical species is shown in Figure 3. We will consider this scheme in detail. Each system will be described as a com-bination of biogeochemical food webs and relationships between them. System 1. soil-forming rock (I); waters (II); atmosphere (III); soil (IV). This system would not be active without living matter. System 5. soil-forming rock (I); soil, soil waters and air (IV); soil microbes (bacteria, fungi, actinomicetes, algae) (V); atmospheric air (III, 25). The activity of this systemdependsontheactivityoflivingsoilbiota(V).WecanrefertoVernadsky (1932)here:“Thereisnootherrelationwiththeenvironment,i.e.,abioticbodies, exceptthebiogenicmigrationofatoms,inthelivingbodiesofourplanet”.During the consideration of the system organization of the biogenic cycle of a chemical species, the relationship between various links (I, II, V) and the subsequent mechanisms of causal dependence are estimated. Most attention should be paid to the biogeochemistry of soil complex compounds, which include the trace metals. The organic substances exuded to the environment by living organisms are of the most importance. The chemical substances from decomposed dead matter play minor role in biogeochemical migration of chemical species. The vital synthesis and excretion of metabolites, bioligands, is the main process of including chemical species from geological rocks into biogeochemical cycle. When trace elements are input into a cell in ionic form, the formation of metal– organic compounds inside the cell is the first step in the biogeochemical cycles. Ferments, metal–ferment complexes, vitamins, and hormones stimulate the cell biochemical processes. After extraction of metabolites into soil, the formation of soil metal–organic complexes proceeds. These complexes are subjected to further biogeochemical migration. System 7. soil–soil waters, air (IV); atmosphere air (III, 26); roots–rizosphere mi-crobes (VII); microbiological reactions—metabolisms (VII). The root exudates andmicrobesoftherizosphereprovideorganiccompoundsfortheextra-cellular synthesis of metal–organic compounds. Plants can selectively uptake these compounds, thus determining the specificity of biogenic migration. This speci-ficity was formulated during plant evolution in specific biogeochemical soil conditions. System 7, 9, 10. roots–rizosphere (VII); plants (VIII); their biological reactions— metabolism (VIII); soil–soil solution, air (IV); aerosols—atmospheric air (26, 28).Inthissystem,theinfluenceofmetal–organiccomplexesontheplantdevel-opmentandtheirmetabolismisconsidered.Underdeficientorexcessivecontents of some chemical species, the metabolism may be destroyed (see Figure 2). System 6. soil–soil solution, air (IV); atmospheric air (III, 27); soil animals (VI); biological reactions of organisms, metabolism, exudates, including microbial exudates (VI); into soils (VI → IV); into waters (II, 4b); into air as aerosols 34 CHAPTER 2 Figure 3. General model of biogeochemical cycles in the Earth’s ecosystems. The left part is biogeochemical cycling in terrestrial ecosystems, the right part is aquatic ecosystems and the central part is connected with the atmosphere. The fine solid lines show the biogeochemical food webs (the Latin numbers I–XXI) and directed and reverse relationships between these BIOGEOCHEMICAL STRUCTURE OF ECOSYSTEMS 35 (III, 27). This system is very important for biogeochemical mapping but until now it has not been understood quantitatively. System 12, soil cycle. soil-forming geological rocks (I); soil (dynamic microbial pattern) (IV); soil solution, air (IV); atmospheric air (III) (aerosols—3a, 3b, 12a, 25, 26, 27); soil organisms, their reactions, and metabolism (V, VI, VII). We should consider the content of essential trace elements in the atmospheric aerosols, both gaseous and particulate forms. These aerosols originate both from natural processes, like soil and rock deflation, sea salt formation, forest burning, volcanic eruption and from human activities, like biomass combustion, industrial and transport emissions. The processes are complicated because of the existence of metal absorption from air and desorption (re-emission) from plant leaves. The first process was studied in more detail. But the second process has not been understood quantitatively and even qualitatively at present. The experimental data in vitro with plant leaves showed the emission of radioisotopes of zinc, mercury, copper, manganese and some other metals. The rates of re-emission are very small, however the fluxes may be significant due to much greater size of leaf surface areas in comparison with soil surface area. For instance, the leaf area of alfalfa exceeds the soil surface 85 times, and that for tree leaves is greater by n ×10–102 times. Furthermore, the animals and human beings can also absorb trace metals from air as well as exhale them. System10.soil(IV);plants(VIII);theirbiologicalreactions,endemicdiseases(VIII); atmospheric air, aerosols (III, 28). During consideration of System 7–9–10, we have discussed the influence of the lower and upper limits of concentrations on plant metabolisms, including endemic disease. The study of link (VIII) should start with the correct selection of characteristic plant species. The following steps should include the different research levels, from floristic description up to biochemical metabolism. System 13. soil–plant cycle: soil-forming geological rocks (I); soil (IV); soil living matter (community of soil organisms) (V, VI, VII); aerosols, atmosphere air (12a, III); plants (VIII); their biological reactions, endemic diseases (VIII). In thecomplexsystem13,theinnerrelationshipsandbiochemicalandbiogeochem-ical mechanisms are shown for natural and agroecosystems. The system 11 and link IX show the ways for interrelation of system 13 with terrestrial animals. ← Figure 3. (Continued) webs; the thick solid lines show the primary systems of biogenic cycling organization, usually joining two links of a biogeochemical food web, for instance, 7, 11, 18, etc., and secondary more complicated complexes of primary systems, for instance, counters 12, 13, 19, 17, 20, etc.; fine dotted lines show the stage of initial environmental pollution, for instance, soils, 40, waters, 44, air, 43, due to anthropogenic activities; the thick dotted lines show the distribution of technogenic and agricultural raw materials, goods and wastes in biosphere, for instance, in soils, 41, in air, 42, in waters, 45, leading to the formation of technogenic biogeochemical provinces; the different arrows show the social stages of human activity, from human being up to the noosphere (After Kovalsky, 1981; Bashkin, 2002). 36 CHAPTER 2 System 11. terrestrial plant (VIII); wild terrestrial animal (IX); aerosols, atmosphere air (28, 29); biological reactions (VIII, IX). System 7–9–10 considers the biological reactions of terrestrial plants on deficient or excessive content of essential elements. System 11 includes the new link of biogeochemical migration, terrestrial animal (IX). The terrestrial plants play the most important role in this biogeochemical food web, linking plant chemical composition with the physiological functions and adaptation of herbivorous animals. The links between herbivorous and carnivorous animals should be also set in the given systems 11. The inner relations between content of elements in fodder crops and their bioconcentration in herbivorous animals are connected with the formation of digestible species in the intestine–stomach tract, penetration through the tissue membranes (suction) with further deposit and participation in metabolism asmetal–fermentcomplexes.Theaccumulatedamountwillfinelydependonthe processes of subsequent extraction from the organisms through kidney (urea), liver (bile), and intestine walls (excrements). These processes depend on both the limit concentrations of elements in animal organism and cellular and tissue metabolic reactions. The development of pathological alterations and endemic diseases are related to the combination of metabolism reaction and element exchange. We should again refer to Figure 2 for the explanation of how to de-termine the relationships between environmental concentrations and regulatory processes in animal organisms. Between lower and upper limits of concentra-tions, the adaptation is normal, however the resistance of adaptation increases with an approximation to both limit values. Some organisms of population may already show disturbance of metabolism and development of endemic diseases, but the alterations of the whole population will be statistically significant only when the concentrations of chemical species achieve the limits. Under optimal concentrations, there is no requirement in improving the element intake. System 19. soil (IV); terrestrial plants (VIII); terrestrial animal (IX); forage with including the technological pre-treatments (XIV). This system shows the dependence of essential element contents from environmental conditions. System21.compositionandquantityofcropsandforage:foodandcropsofterrestrial origin including technological treatments (XIV); food and crops of aquatic origin including technological treatments (XV). In many countries, the daily intake standards have been set for humans and animals (see Radojevic and Bashkin, 1999). Sub-systems 211. foodstuffs of terrestrial origin (XIV) + foodstuffs of aquatic origin (XV); drinking water (39); balanced essential trace element daily intake for domestic animals (XVI). System 221. foodstuffs of terrestrial origin (XIV) + foodstuffs of aquatic origin (XV); drinking water (39); balanced essential trace element daily intake for humans (XVI). BIOGEOCHEMICAL STRUCTURE OF ECOSYSTEMS 37 System 23. balanced intake of various essential elements (XVI); atmosphere air (33); domestic animals—their productivity and biological reactions, endemic diseases(XVII);human,biologicalreactions(XVIII).Therecommendationsfor balanced essential trace element daily intake for humans are under development in various countries. System 241. feeding of domestic animals, forage (XIV, XV); balanced essential trace element daily intake (XVI); domestic animals (XVII). The additions of require-ment trace elements should be applied for forage in various biogeochemical provinces. System 242. human nutrition, foodstuffs (XIV); balanced essential trace element daily intake for humans (XVI); human health (XVIII). Research should be carried out on the endemic diseases induced by deficient or excessive content in the biogeochemical food webs of different essential elements, like N, Cu, Se, I, F, Mo, Sr, Zn, etc. System 14. geological rocks (1, 2a, 2b); waters (II); bottom sediments (X). The chemical composition and formation of natural waters and bottom sediments depend strongly on the geochemical composition of rocks. System 15. bottom sediments (X); sediment organisms and their biological reactions (XI). The invertebrates of bottom sediment are important in biogeochemical migration of many chemical species in aquatic ecosystems. System 17. bottom sediments (X); sediment organisms and their biological reactions (XI); waters (II); aquatic plants and their biological reactions (XII); atmosphere air (17a, 30, 31). The chemical interactions between aquatic and gaseous phases play an extremely important role in the composition of both water and air. These interactions determine the development of aquatic ecosystems. The example of oxygen content in the water is the most characteristic one. System 18. aquatic plants and their biological reactions, endemic diseases (XII); aquatic animals, including bentos, plankton, bottom sediment invertebrates, fishes,amphibians,mammals,vertebrates,theirbiologicalreactionsandendemic diseases(VIII).Bioconcentrationisthemosttypicalandimportantconsequence of biogeochemical migration of many chemical species in aquatic ecosystems. System 20. aquatic plants—bentos, plankton, coastal aquatic plants (XII); aquatic animalsincludingbottomsedimentinvertebrates,fishes,amphibians,mammals, vertebrates, their biological reactions and endemic diseases (VIII); aerosols, atmospheric air (31, 32)—foodstuffs, forages (XV). Human poisoning through consumptionoffishandotheraquaticfoodstuffswithexcessivebioaccumulation of pollutants is the most typical example of biogeochemical migration and its consequences. System XVIII, XIX; human being (XVIII); human society (XIX). development of agri-culture,industryandtransport(XIX);accumulationofwastesinsoil(40),air(43) ... - tailieumienphi.vn