MODELLING AND CONTROL OF ENVIRONMENTAL SYSTEMS A.A

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1 Università di Padova SECOND CYCLE DEGREE PROGRAMME (MSC LEVEL) IN ENVIRONMENTAL ENGINEERING MODELLING AND CONTROL OF ENVIRONMENTAL SYSTEMS A.A

2 Reductionism the whole is equal to the sum of the parts Classical scientific models are based on simplifications that are necessary to reduce the computational demand but often this makes the model unrealistic! Heisenberg principle: ΔP ΔX h

3 Holism the whole is greater than the sum of the parts Ø Systemic approach Ø Chaotic systems The estimates in the long term are practically impossible We can never know the world with an arbitrary accuracy We must accept this condition of the new science

4 Holism Most system in nature are inherently IRREDUCIBLE i.e. it is not always possible to interpret observations of system operation through basic principles è We need to resort to empirical model

5 Interpretation of reality through modelling Answer SIMULATION Answer THEORY & COROLLARIES REALITY MODEL THEORY Question Question Simulation with restricted validity Theorizing with general validity

6 Interpretation of reality through modelling Experimental observations do not produce new laws, but a new model of a part of reality The practice of modeling of Environmental Systems is possible thanks to recent developments in: Ecology Computing (PCs)

7 The new scientific paradigm ANALYSIS SYNTHESIS Not enough to understand the enormous complexity of ecological systems New analytical results are used for the formulation of the synthesis Necessary to investigate the emergent properties of systems The synthesis (model) indicates what new analyses are required

8 In conclusion. The world equation DOES NOT EXIST!!! Nature is too complex: Non linear Chaotic/Catastrophic Sensitivity to initial conditions (Butterfly Effect) In the laboratory everything is much easier

9 The ecosystem as an object of research Ecosystem: specific level of organization Requires the selection of appropriate spatial and temporal scales Morowitz (1968): Ecosystems sustain life consistently to the actual conditions Its a property of the entire system rather than of the individual species or populations that constitute it

10 The ecosystem as an object of research EP Odum (1953): An ecosystem is the set of physicalchemical-biological activities in a confined spatio-temporal unit An ecosystem is a unit or functional biotic system: Sustains life Includes all biotic and non biotic components The scales are not defined a priori, instead depend on the objective of the study à Complexity and Self-organization

11 Structure of Ecosystems ECOSYSTEM External Environment Abiotic components Biotic components External Environment Climate Communities energy (solar radiation) Geomorphology Populations Organisms energy (thermal radiation) matter Hydrology Bacteria matter Chemical Physical processes Biochemical processes Internal nutrients cycling

12 The ecosystem as an object of research 1. Empirical studies: trying to assemble pieces of knowledge into an organic description 2. Comparative studies: some functional and structural units of different ecosystems 3. Experimental Studies: Manipulation of the entire system in an attempt to grasp the relevant properties 4. Modeling or computer simulations All these approaches are needed in order to obtain an adequate holistic description

13 The ecosystem as an object of research Order/Disorder (information) Complexity Randomness/Chaos Organization Complexity Auto-organization order disorder

14 Thermodynamics and ecosystems Open systems è Far from thermodynamic equilibrium è Dissipate energy è Accumulate order (information) è Transform energy (quantity à quality) Growth è Accumulation of biomass è Increased flows Development è Structural change

15 Energy flows at the level of Biosphere Closed system, in steady equilibrium è Flow of energy from the sun è Stability is maintained by dissipative processes (degradation) of solar energy The earth s termal machine (climate) è Hadley cells è T average = 287 K 30

16 Energy flows at the level of Biosphere C s =1360 w/m2 (solar constant ) è 9% ultraviolet è 41% visible è 50% IR è The surface receives directly 26% indirectly 25% è UV almost totally absorbed ( km) by O 2, O 3 and N 2 è IR almost totally absorbed (10 km) by CO 2 and NO 2

17 Incident Solar radiation (%) reflected by dust, gas clouds, albedo TROPOSPHERE Ozone ATMOSPHERE Absorbed in atmosphere Absorbed by the earth directly and indirectly (tides, currents, etc.) Clouds Steam Irradiated by the atmosphere Irradiated by the earth Atmospheric circulation (heat of evaporation and convection) LITOSPHERE

18 Efficiency of enrgetic transfers 1, Kcal/year directly incident on the surface Terrestrial vegetation and phytoplankton use 2, Kcal/year produce 5, Kcal/year of biomass è Efficiency = 0,2 % light è Primary production è herbivores è carnivores 0,2% 3% 1 40%

19 Energy associated with biomass Production (Photosynthesis) è Primary production, sinthesis of organic molecules Consumption (Fermentation, Respiration) è ATP, the fuel for cellular porocesses plants algae 19,2 kj/g 21,3 kj/g invertebrates 23,0 kj/g vertebrates 26,3 kj/g carbohydrates 16,7 kj/g proteins 20,9 kj/g lipids 37,6 kj/g

20 History of the biosphere Ages in the evolution of life è prebiotic (from 4,5 to 3,5 bil. years ago) è microcosm (from 3,5 to 1,5 bil. years ago) è macrocosm (from 1,2 bil. years ago up to today) The bacteria have changed the atmosphere, adjusting the levels of è humidity è hydrogen è CO 2 è oxygen (21%) è ozone

21 NIGHT EVOLUTION IN ONE DAY 3 10^6 y h m sec 4600 Birth of the Earth Bacteria Water Photosynthesis Eukaryotes (symbiosis) Aerobic respiration Invertebrates First vertebrates First plants on land Origin of reptiles, anphibians, fishes, seeding plants Insects Superior reptiles Conifers, mammals and birds, dynosaurs Angiosperms, Dynosaurs extinction Origin of modern mammals Hominids ,5 Glacial eras - Homo sapiens ,01 History DAY