EESB05H3 Lecture Notes - Lecture 4: Hygroscopy, Soil Texture, Potential Gradient
Document Summary
Changes in precipitation worldwide effects many environmental aspects (food, agriculture, freshwater etc. ) Cohesion (with other water molecules) and adhesion (with surface of soil particle) Cohesion with other molecules around in (can only go a certain number of directions since at surface) Surface has greater attraction for other water molecules (cohesion) than air above. Examples: why light animals can balance on surface. At any water surface (at molecular level) = net downward force of water. What creates meniscus (combination of cohesion/adhesion forces) = why water can rise up against force of gravity (pressure differential) Degree to which water can move up in soil depends on how large soil pores are. Both rate of water rising and total height water will rise = function of soil pore size. Micropores in clay are small enough to hold water against force of gravity: smaller pores = higher rise. Macropores in sane can not hold water against force of gravity: larger pores = lower rise.
