Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Environmental Chemistry → Soil Chemistry ↓


Nutrient cycling


Introduction

Nutrient cycling is a fundamental concept in soil chemistry and environmental chemistry. It involves the transformation, movement, and recycling of essential chemical elements such as carbon, nitrogen, phosphorus, and others within an ecosystem. These cycles are vital for maintaining ecosystem productivity and stability. In this comprehensive lesson, we will explore the various nutrient cycles, their chemical reactions, and their roles in the environment.

Importance of nutrient cycling

Nutrient cycling is important to an ecosystem for several reasons:

  • This ensures the availability of essential nutrients for plant growth.
  • It promotes soil fertility and agricultural productivity.
  • It helps maintain energy flow and biological productivity in the ecosystem.
  • This minimises the loss of nutrients from the ecosystem.

In the absence of effective nutrient cycling, the ecosystem will collapse due to lack of essential elements.

Carbon cycle

The carbon cycle involves the movement of carbon elements in various forms through the atmosphere, hydrosphere, lithosphere, and biosphere. The primary processes in the carbon cycle include photosynthesis, respiration, decomposition, and combustion.

Major Processes:

  • Photosynthesis: Plants convert atmospheric carbon dioxide into glucose (C_6H_{12}O_6) through photosynthesis.
  • Respiration: Animals and plants convert glucose back into carbon dioxide (CO_2), releasing stored energy.
  • Decomposition: Decomposers break down organic matter and release carbon dioxide.
  • Combustion: The burning of fossil fuels and organic matter releases carbon dioxide back into the atmosphere.
    Photosynthesis: 6 CO_2 + 6 H_2O + light energy -> C_6H_{12}O_6 + 6 O_2
    Respiration: C_6H_{12}O_6 + 6 O_2 -> 6 CO_2 + 6 H_2O + energy
Atmosphere CO 2 ↔ photosynthesis Respiration ↔ CO 2

Nitrogen cycle

Nitrogen is essential for the synthesis of proteins and nucleic acids in living organisms. The nitrogen cycle describes the series of processes by which nitrogen is converted between its different chemical forms in the environment.

Major Processes:

  • Nitrogen fixation: Conversion of atmospheric nitrogen (N_2) to ammonia (NH_3) by bacteria.
  • Nitrification: Conversion of ammonia to nitrite (NO_2^−) and then to nitrate (NO_3^−) by nitrifying bacteria.
  • Assimilation: Absorption of nitrates by plants to form proteins and other compounds.
  • Ammonification: Decomposition of organic nitrogen into ammonium (NH_4^+).
  • Denitrification: Reduction of nitrates back to nitrogen gas (N_2) by denitrification bacteria.
    Nitrogen fixation: N_2 + 3 H_2 -> 2 NH_3
    Nitrification: NH_3 -> NO_2^- -> NO_3^-
    Denitrification: NO_3^- -> N_2
N2 in the atmosphere Nitrogen fixation NH 3 / NH 4 + No. 2 - / No. 3 - Denitrification

Phosphorus cycle

Unlike the carbon and nitrogen cycles, the phosphorus cycle operates on a local rather than a global scale, as phosphorus does not have a gaseous phase and is instead cycled within ecosystems through the lithosphere, hydrosphere, and biosphere.

Major Processes:

  • Weathering: The release of phosphate ions from rocks through weathering and leaching.
  • Absorption by plants: Assimilation of phosphate ions by plants for various biological functions.
  • Decomposition: Organic matter breaks down, releasing inorganic phosphate back into the soil.
  • Runoff: Transport of phosphorus compounds from soil to aquatic systems.
    Weathering: ${text{Ca}_3(text{PO}_4)_2 + text{H}_2text{O} -> text{HPO}_4^{2-} + text{Ca}^{2+}}
    Decomposition: ${(text{PO}_4)_{text{organic}} -> text{PO}_4^{3-}}
Plants Absorb Phosphorus Rock Weathering Drainage

Sulfur cycle

The sulfur cycle describes the movement of sulfur through the environment. Sulfur is an essential element for proteins and vitamins in living organisms.

Major Processes:

  • Mineralization: Conversion of organic sulfur compounds into inorganic forms such as hydrogen sulfide (H_2S).
  • Oxidation: Conversion of sulfide and elemental sulfur to sulfate (SO_4^{2-}).
  • Assimilation: Absorption of sulphate by plants.
  • Reduction: Reduction of sulphate back to sulphur compounds under anaerobic conditions.
    Mineralization: (text{R-SH}) -> text{H}_2text{S}
    Oxidation: text{H}_2text{S} + text{O}_2 -> text{SO}_4^{2-}
    Reduction: text{SO}_4^{2-} -> text{H}_2text{S}
Sulfur cycle H 2 S SO 4 2-

Conclusion

Nutrient cycling is an integral part of maintaining ecological balance, agricultural productivity, and environmental health. Each cycle of carbon, nitrogen, phosphorus, and sulfur involves unique pathways and chemical transformations that ensure the continual supply and recycling of essential nutrients. Understanding these cycles is critical for fields such as ecology, agriculture, and environmental management. As we continue to explore and preserve our ecosystems, a thorough understanding of nutrient cycling remains paramount.


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Nutrient cycling

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