Soil Chemistry 1 2024 Lecture Notes PDF
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Uploaded by InspiringNumber
University of Montana
2024
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Summary
These notes from a Soil Chemistry 1 lecture in 2024 cover various aspects of soil chemistry, including soil colloids, soil particle sizes, and chemical weathering. The document also references YouTube videos relevant to the topics. This may be important lecture notes for a soil science or geology course.
Full Transcript
Announcements (10/24/24) Exams returned next Tuesday What’s left? Part 3: Soil Chemistry & Acidity (5 Lectures) Part 4: Soil Ecology, Fertility, & Nutrient Cycling (5 Lectures) Today: Soil Colloids & Chemistry Lecture Outline Soil Chemistry: Colloid formation, structure and...
Announcements (10/24/24) Exams returned next Tuesday What’s left? Part 3: Soil Chemistry & Acidity (5 Lectures) Part 4: Soil Ecology, Fertility, & Nutrient Cycling (5 Lectures) Today: Soil Colloids & Chemistry Lecture Outline Soil Chemistry: Colloid formation, structure and properties Isomorphous substitution Non-crystalline colloids Recall Soil Particle Sizes Colloidal Fraction: Defined by very small size Clay and OM (colloidal) particles Critical Characteristics: 1. High surface area 2. Electrostatic (-) charges define properties (e.g., exchange nutrients, water, and other molecules) General properties of soil colloids Very small size (< 2 µm; 0.000002 m) = Very large surface area / unit mass Net electrostatic charge (usually -) https://www.youtube.com/watch ?v=C0d5wfQLEj0 Clay Mineral Formation: Chemical Weathering Primary Secondary Other Mineral Minerals + weathering products 2KAlSi3O8 Al2Si2O5(OH)4 + 2K+ Orthoclase Kaolinite Pota (clay mineral) (nutrient!) How do clays form? 1. Chemical alteration of primary minerals (like feldspar/mica) 2. Decomposition and recrystallization of minerals from breakdown products (many elements present in soil solution) -Some have noted similarities between clay mineral formation and DNA recombination. https://www.youtube.com/watch?v=fvJYpWFgVW0 Silicate Clay Mineral Structure Silicate Clay Crystal (Mycelle) Adsorption of Cations & Anions Mycelle = colloid particle in sheetlike layers Usually negatively charged Cation adsorption (cations are exchangeable) Layer Silicate Clays Derived from weathering of mica and feldspar minerals Layered structure; phyllosilicates Predominantly negatively charged Charge is mainly due to: isomorphous substitution!!!! Soil characteristics (i.e., shrink- swell) depend on crystalline structure. Structural Components of Silicate Clays In clays, 1000s of these building blocks are connected to form planes of Si & Al (or Mg) ions What Causes Charges to Develop? Isomorphous Substitution https://www.youtube.com/watch?v=w_-PvlgcnNQ
