HUMAN ACTIVITIES AND EARTHS WATER

What factors influence how long it takes for water to migrate from a deep aquifer to the surface  

M FIGURE 18.17 Groundwater is water located In aquifers below the soii. An 

As water runs off the land on its way to the oceans, it dissolves a variety of cations (mainly Na, K, Mg, Ca, and Fe ), anions (mainly CD, S04 , and FIC03 ), and gases (principally O2, N2, and CO2). As we use water, it becomes laden with additional dissolved material, including the wastes of human society. As our population and output of environmental pollutants increase, we find that we must spend ever-increasing amounts of money and resources to guarantee a supply of freshwater. 

Approximately 20% of the world s freshwater is under the soil, in the form of groundwater. Groundwater resides in aquifers, which are layers of porous rock that hold water. The water in aquifers can be very pure and accessible for human consumption if near the surface (A FIGURE 18.17). Dense rock that does not allow water to readily penetrate can hold groundwater for years or even millennia. 

All life on Earth depends on the availability of suitable water. Some organisms can thrive under temperature, pH, and ionic conditions where other organisms would die. Many human activities rely on waste disposal via Earth s waters, even today, and this practice can be detrimental to aquatic organisms. 

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