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Closed System Thermodynamics

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Closed System Thermodynamics Closed System Thermodynamics •1st Law of Thermodynamics – Irreversible processes result in spontaneous conversion of internal energy to heat and work – At equilibrium a state of minimum internal energy is attained –Enthalpy Closed System Thermodynamics •2nd Law of Thermodynamics – All isolated systems will spontaneously approach a state of equilibrium – Entropy Open System Thermodynamics • Natural setting – only closed system is the entire universe • Most natural bodies/systems are open – allowing energy/material to flow into and out of them • Natural systems – highly ordered and energy rich – goes against idea of increasing entropy and decreasing enthalpy Equilibrium versus Steady State • Closed systems – move towards equilibrium – time invariant state with entropy maximization • Open systems – move towards steady- state and entropy minimization Energy Source Energy Flow Energy Sink Dissipative Processes E ppt Soil System • Respiration • Humus Decomposition Enpp • Mineral Weathering • Leaching • Erosion Ordering Processes • Humus Accumulation • Structure Formation • Horizonation •Illuviation–Eluviation • 2º Mineral Formation Pedogenic Trajectory • Rasmussen et al. (2005) Testing hypothesis that if soils are open systems, one should be able to quantify soil forming environment and soil development based on energy flux into the soil system Energy Source Energy Flow Energy Sink Dissipative Processes E ppt Soil System • Respiration • Humus Decomposition Enpp • Mineral Weathering • Leaching • Erosion Ordering Processes • Humus Accumulation • Structure Formation • Horizonation •Illuviation–Eluviation • 2º Mineral Formation • How to quantify energy flux? – Effective precipitation – Biologic production • Water balance • Timing of precipitation 300000 250000 ) 1 - 200000 r y 2 - m 150000 J k ( n i 100000 E 50000 0 25 700 20 600 15 ) 500 o C 10 ( 400 AT 300 5 A M M AP 200 0 (c 100 m) Jenny 1941 Idealized Model Quantitative data from White and Blum 1995 0.14 0.12 ) -1 0.10 yr -2 0.08 0.06 0.04 Si Flux (mol m (mol Flux Si 0.02 0.00 0 5000 10000 15000 20000 25000 30000 -2 -1 Ein (kJ m yr ) Calculated energy flux versus quantitative Si flux data from White and Blum 35000 30000 ) -1 25000 yr -2 20000 (kJ m15000 in E 10000 f 5000 g h a b d 0 c e Arid Moll Ent And Alf Incept Spod Ult 100 80 60 40 20 Energy Type Distribution (%) 0 Arid Moll And Ent Alf Incept Spod Ult Pedogenic Trajectory Table 3. Average slope for soil orders† High slope and landscape Soil Order Slope %‡ stability Andisol 26 (2.1) a Inceptisol 26 (1.2) a Impacts on pedogenic Spodosol 26 (3.4) ab trajectory and degree of Entisol 15 (1.1) bc soil development Mollisol 12 (0.5) cd Alfisol 10 (0.7) de Ultisol 10 (0.5) e Aridisol 9 (1.9) cde †Average of map unit slope from STATSGO ‡Values in parentheses are standard errors of the mean. Pairwise comparison done with Tamhane post-hoc test (95% confidence interval). Slopes followed by the same lowercase letter are not significantly different. Ein (kJ m-2 yr-1) High : 162,260 Low : 0 Figure 1. EIN for the continental U.S. Calculated using the PRISM dataset (30 yr average MAP and MAT, 1971-2000).
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