In the ground-water study illustrated in Figures 17.25 and 17.26, a chemical tracer was injected at 640 parts per million. After 461 days, the highest concentration measured was only 39 parts per million. How did the chemical tracer get so diluted?
What will be an ideal response?
The chemical tracer was diluted by spreading out over a large area. Each time the water containing the tracer encountered a sand grain, it had to flow around the grain. The flow of water over many curving paths caused the chemical tracer to spread out over a larger and larger area, diluting its concentration.
You might also like to view...
Which of the following best describes Geographic Information Systems?
A) deriving accurate measurements from photographs B) a constellation of satellites for accurately determining location anywhere near Earth's surface C) acquiring information about objects without having physical contact with them D) a modern map-making tool for determining the appropriate map projection to use E) computer-based tool for management and analysis of geographic information
Most commercial loggers prefer "clear-cut" harvesting because it
A. Is the most efficient, cheapest harvest method using large, fast machinery instead of costly labor B. Is the most environmentally sustainable type of harvest C. Does not waste any trees D. Is the most efficient way to get valuable small timber without disturbing the larger early successional trees E. Is the most effective way to refresh soil with sun and rain
Human demands and pressures have surpassed Earth's ability to regenerate resources. Indicate whether the statement is true or false
Traditional suburban development does not
A. Consist of only house lots and streets B. Facilitate social interactions among neighbors C. Consume agricultural land and wildlife habitat D. Typically consist of identical parcels of land without open space E. All of these are characteristics of traditional suburban development