I need help with my ecology homework. 3. What effect does grain size have on sed

Question

I need help with my ecology homework.

3. What effect does grain size have on sediment permeability and flow velocity? 4. What effect does grain size have on sediment porosity? 5. What effect does grain sorting have on porosity and permeability? 6. Water wells are sunk into aquifers, units of rock that store and transmit water, meaning they have good porosity and high permeability. Which of the four sediments would make the best water source for a water well? Why? 7. Ima these four types of sediment. Describe he spill. gine that a tanker truck carrying pesticide rolled over and spills its contents on each of

Explanation / Answer

Porosity and Permeability Both are important properties that are related to fluids in sediment and sedimentary rocks.

3) A high content of fine -grained micrtic material ,as found in mudstone and wack stones,results in a low permiability.The resulting low rate of fluid flow inhibits.sediments with grain -supported fabric and a low content mirite( grain stone to pack stone) have a higher permeability and as a consequence, higher fluid flow.

Porosity: the volume of void space (available to contain fluid or air) in a sediment or sedimentary rock. Permeability: related to how easily a fluid will pass through any granular material.

4) There are some indirect relationships between size and porosity. i) Large grains have higher settling velocities than small grains. When grains settle through a fluid the large grains will impact the substrate with larger momentum, possibly jostling the grains into tighter packing (therefore with lower porosity). ii) A shape effect. Unconsolidated sands tend to decrease in porosity with increasing grain size. Consolidated sands tend to increase in porosity with increasing grain size.. The larger the grain size the larger the pore area.

5)

The size of pore space and interconnectivity of the spaces help determine permeability, so shape and arrangement of grains play a role.  Permeability is a measure of a soil's or rock's ability to transmit a fluid, usually water. Often the term hydraulic conductivity is used when discussing groundwater and aquifer properties. Hydraulic conductivity simply assumes that water is the fluid moving through a soil or rock type.

Water can permeate between granular void or pore spaces, and fractures between rocks. The larger the pore space, the more permeable the material.   However, the more poorly sorted a sample (mixed grain sizes), the lower the permeability because the smaller grains fill the openings created by the larger grains. "The most rapid water and air movement is in sands and strongly aggregated soils, whose aggregates act like sand grains and pack to form many large pores.

6) An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well.because An aquifer is a body of porous and permeable rock, with saturated pore space, that holds economically useful amounts of water. Without permeability the water could not be extracted via springs or wells. Conglomerates, sandstones, and many limestones can form aquifers. In mountain regions like Colorado, fractured granites can also act as aquifers. Here, the water fills the fractures.

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