Laserfiche WebLink
<br />CONCEPT 18: Small amounts of pollution contaminate larQe amounts of <br />groundwater. <br /> <br />Action: Have students note that only a small amount of dye was added in <br />each of the actions from Concept 17. They should see that the water <br />pumped out via the wells is colored water. Have the students guess: (1) <br />which color of dye will be cleaned up first and (2) how many flasks of <br />water will be required to clean up the dye. Discuss why so many flasks <br />of water are required to remove the dye entirely. <br /> <br />Discussion: The contamination will move throughout the aquifer as long <br />as there is a pressure gradient. The model shows that a lot of water is <br />required to remove the dye (representing contamination). A lot of water <br />will be pumped out because the water is coming from all directions, not <br />just the location of the dye; how much water depends on how strong a dye <br />is used and how far the dye is from the pumping source. Also keep in <br />mind that the dye gets diluted as water is added to the model. <br /> <br />CONCEPT 19: Wells can be contaminated by human activities at or near the land <br />surface. <br /> <br />'Action: Use the orange pump to remove water from the unconfined <br />aquifer. The dyes used in the 4 actions from Concept 17 will "move" <br />toward the well. <br /> <br />Discussion: The well draws water toward it from all directions. Any <br />contamination in the water will also be drawn towards the well and <br />therefore would end up in our drinking water supply. Students should <br />see that all contamination in' the unconfined aquifer does not reach the <br />confined aquifer because of the confining layer. However, improperly <br />sealed wells in confined aquifers can result in an interconnection <br />between the two aquifers which can allow water to flow and contaminants <br />to move into or out of the confined aquifer. <br /> <br />CONCEPT 20: Confined aquifers can be contaminated naturally or throuQh human <br />activities. <br /> <br />Action: Human activity contamination can be demonstrated by injecting <br />dye into the injection well, piezometer, or pumping well. <br /> <br />Discussion: Natural contamination is due to high concentrations of <br />minerals in the aquifer materials (confined and/or unconfined) that are <br />dissolved in the water as the water passes through the aquifer. For <br />,example, sands that were deposited in an ocean environment will contain <br />salts that can later be dissolved by fresh water passing through the <br />sand. <br /> <br />Human activity can contaminate the confined aquifer if chemical.s are <br />injected into any of the wells. Contamination from the unconfined <br />aquifer can move into the confined aquifer if the wells are improperly <br />sealed or if there is a leaky. confining layer. <br /> <br />7 <br />