Water & Soil Properties: Conductivity, Tension, Density, Viscosity, Pressure & Formation, Quizzes of Environmental Science

Download Water & Soil Properties: Conductivity, Tension, Density, Viscosity, Pressure & Formation and more Quizzes Environmental Science in PDF only on Docsity! TERM 1 Valence shell electron pair repulsion (VSEPR) DEFINITION 1 Electron pairs will assume angles as far as possible from each other to minimize the destabilizing effect of like-charge repulsion between these electron pairs TERM 2 Water as Solvent DEFINITION 2 Water attracted to polar substances Small size allows it to fit between larger molecules Hydration spheres disrupt the structure of water Dissolve = Wrap apolaror acharged ionwith an envelope of water molecules TERM 3 Conductor DEFINITION 3 Allows e- to freely move TERM 4 Insulator DEFINITION 4 Holds tightly onto e- TERM 5 Does Pure Water Conduct Electricity? DEFINITION 5 Yes (a little), because of self-ionization TERM 6 Other physical properties of water DEFINITION 6 Surface tension Density Viscosity Vapor pressure Heat capacity TERM 7 Surface Tension, DEFINITION 7 Cohesive forces act between water moleculesAt a gas-liquid interface, the cohesionbetween liquid molecules can be greater than theadhesion between the liquid and gasThermodynamic reason: All about minimizing energy (and maximizing entropy) TERM 8 Measuring Surface Tension DEFINITION 8 Wilhelmy Plate method du Noy Ring method TERM 9 Density, DEFINITION 9 Density is the mass of a substance within a given volume TERM 10 Viscosity DEFINITION 10 drag or resistance to flow Can be measured by -Plate and Cone Viscometers -Falling Sphere Viscometer TERM 21 E Horizon DEFINITION 21 horizon of mass lossBleachedDepletedLightenedEluviated TERM 22 Soil Orders DEFINITION 22 Gelisols - soils with permafrost within 2 m of the surface Histosols - organic soils Spodosols - acid forest soils with a subsurface accumulation of metal-humus complexes Andisols - soils formed in volcanic ash Oxisols - intensely weathered soils of tropical and subtropical environments Vertisols - clayey soils with high shrink/swell capacity Aridisols - CaCO3-containing soils of arid environments with subsurface horizon development Ultisols - strongly leached soils with a subsurface zone of clay accumulation and <35% base saturation Mollisols - grassland soils with high base status Alfisols - moderately leached soils with a subsurface zone of clay accumulation and >35% base saturation Inceptisols - soils with weakly developed subsurface horizons Entisols - soils with little or no morphological development TERM 23 The Munsell Color System DEFINITION 23 Hue Basic spectral color, R = Red, YR = Yellow Red, Y = Yellow. Most color books have one hue per page Value The intensity of a given hue. Value and lightness increase from bottom to top of the page Chroma The purity or richness of color. Chroma and pigment richness increase from left to right on the page. Low chroma colors are gray TERM 24 Coloring agents in the soil Red, Orange? Brown? Black? Gray DEFINITION 24 Reds, oranges, and yellows are due to various types of Fe-oxides. Browns and overall black hues are due to organic carbon accumulation. The darker the hue, the more OC. Some black nodules and masses of color may be due to Mn-oxides or charcoal, however. Gray colors are the background color of soil without any oxidized coatings or pigments masking it. Results from reducing and leaching conditions. TERM 25 Factors Leading to Reduction DEFINITION 25 Saturation leads to poor gas exchange and oxygen diffusion from surface Palatable/oxidizable organics must be present Microbial population must be active; warmth, pH, etc., important Water must be stagnant long enough for oxygen depletion TERM 26 (Dry) Bulk Density DEFINITION 26 Dry mass per unit volumepb =mass in volume v/ Volume v ms/Vt Vt = the total volume useds = solid phase, without fluidDimensions: [M] [L-3](Can also have wet bulk density) TERM 27 Solid phase density DEFINITION 27 Upper limit on b is density of pure mineral sps =mass of pure volume/ Volume of pure volume ms/Vs Typical values of specific gravity 2.65 for quartz (commonly assumed for typical minerals 2.54 2.76 for feldspar (most common mineral in earths crust) 2.72 for calcite 5.0 for pyriteNot amenable to a universal value TERM 28 Soils are porous media DEFINITION 28 It varies widely (~30 60%) Particle sizes vary widely (sand, clay) Geological and/or organic materials of varying mineralogy and composition Permeability varies widely Granular, fractured, and/or amorphous Vary spatially & temporally Most complex & widespread biomaterial on the planet So it is hard to generalize! TERM 29 Porosity DEFINITION 29 The total amount of pore space (Vwater + Vair /Vsolid +Vwater + Vair)Or 1-(Vsolid/Vtotal) = 1-(pb/ps) TERM 30 Soil Particles DEFINITION 30 Soil can be divided into threesizeclasses Sand (50 2000 m)Silt (2 50 m)Clay (< 2 m) TERM 31 Particle Size Distribution DEFINITION 31 Uniform particle size distribution(i.e., well-sorted) give slow packing density Increasing the range of particle sizes gives rise to greater bulk density. TERM 32 Sand Particles DEFINITION 32 Relatively large, relatively inert Low natural fertility Little or no cohesion between particles Susceptible to liquefaction Does not form ribbons Gritty feel Rapid drainage and little water-holding capacity TERM 33 Silt Particles DEFINITION 33 Capable of being carried long distances by wind (loess deposits) Settles freely, but cannot be discriminated by eye Neither slippery nor gritty between your fingers (feels like flour) Doesnt make strong ribbons TERM 34 Clay Particles DEFINITION 34 Platey shape (flat and thin) Wont settle in suspension Doesnt feel gritty High surface area High porosity Susceptible to erosion and easily transported in surface waters Often have negative intrinsic charge Dominate hydraulic chemical behavior TERM 35 Three Principle Layer Types DEFINITION 35 Phyllosilicates(1:1) Phyllosilicates(2:1) Phyllosilicates(2:1:1) TERM 46 Measuring soil particle sizes: Sedimentation DEFINITION 46 V=2(ps-pw)r2g / 9u)Particles are smooth spheresParticles fall slowly (laminar flow)All particles have the same densityDilute: particles dont affect each otherFluid is otherwise at rest Terminal velocity is reached instantly TERM 47 Drivers of Aggregate Stability DEFINITION 47 Aggregate stability is controlled by both internal (soil- specific) and external drivers Internal drivers include: Mineralogy (clays, iron oxides) Organic matterSoil solution characteristics External drivers include: Climate (wetting/drying; freeze-thaw;temperature; wind) Biology TERM 48 Soil-specific Drivers of Aggregate Stability Clay mineralogy DEFINITION 48 Most clay particles have high specific surface area and intrinsic charge Encourages attraction between particles (particularly when bridging cations are present) Expansion and contraction of clay particles can drive aggregation and disaggregation TERM 49 Soil-specific Drivers of Aggregate Stability Fe and Al oxides DEFINITION 49 Generally stabilize aggregates: Iron and aluminum in solution act as flocculants Sesquioxides bind clay particles to organic molecules Sesquioxides can precipitate as gels on clay surfaces TERM 50 Soil-specific Drivers of Aggregate Stability Organic Matter DEFINITION 50 Polysaccharides can glue together micro-aggregates Roots and hyphae can produce hydrophobic exudates Provide stability Slow down the wetting rate Reduce slaking TERM 51 Slaking DEFINITION 51 Rapid wetting of aggregate can trap and pressurize air Wetted soil also has lower strength, leading to collapse TERM 52 Soil-specific Drivers of Aggregate Stability Electrolyte characteristics DEFINITION 52 SARGreater SAR = More clay dispersion Less aggregate stability Loss of structure pH Clay dispersion increases as pH increases TERM 53 External Drivers of Aggregate Stability Wetting and drying cycles DEFINITION 53 Typically enhances aggregate formation and stability Drying: the soil comes together and aggregates Wetting: the process not entirely reversed But sometimes also seen to decrease the aggregate number TERM 54 External Drivers of Aggregate Stability Freezing and thawing cycles DEFINITION 54 Generally decreases aggregate stability Freezing: expansion of ice crystals in pores breaks aggregate bonds Thawing: large pores created while freezing collapse, breaking thea ggregates This process can be important in compacted clays TERM 55 External Drivers of Aggregate Stability Temp and Wind DEFINITION 55 Air and soil temperature - Affects water content- Microbial activity Wind velocity Wind often erodes particles less than0.84 mm in diameter TERM 56 External Drivers of Aggregate Stability Time and Biological factors DEFINITION 56 Time (aging) - As time goes more stable aggregates are formed Biological factors - Plant roots- Soil microbes- Soil fauna TERM 57 Soil Strength DEFINITION 57 is defined as the amount of force required to move or rearrange soil particles. is an important physical property affecting plant growth and seedling emergence. TERM 58 4 Stresses commonly encountered DEFINITION 58 Compressive Tensile Shear Torsion(not typical in soil) TERM 59 Shearing strength DEFINITION 59 Ability to withstand shearing forces TERM 60 Behaviors under stress - 4 DEFINITION 60 Elastic materials regain their pre-stress form -Example: rubber Plastic materials remain in stressed form Example: modeling clay Viscous materials deform slowly Example: tar Brittle materials fracture under stress Example: brick TERM 71 Consistency Index (CI) DEFINITION 71 Indication of soil firmness CI= (LLw)/(LLPL) TERM 72 Polarity DEFINITION 72 Polarity allows formation of hydrogen bonds TERM 73 Aggregate Stability DEFINITION 73 The ability of soil aggregates to resist disintegration during disruption TERM 74 What is a milli-equivalent (meq)? DEFINITION 74 equivalent = unit of electrical charge # of moles of a given ion in a solution Calculated as amount of substance multiplied by its valence 1 mmole of Na+= 1 meq TERM 75 What are Exchangeable Ions? DEFINITION 75 Exchangeable ions in soil are those that can be replaced easily by leaching with an electrolyte solution of prescribed composition, concentration and pH value TERM 76 absorption DEFINITION 76 the filling of pores in a solid