Chapter 4 "Surface Waters and Underground Seas" Summary

The majority of the earth's surface is covered with water, but most of it is seawater, which is not usable for drinking, irrigation, or industry. There is widespread, critical shortage of fresh water across the globe. Much of the world's water is polluted by waste from many sources. Chemical insecticides and herbicides are a relatively new source of water pollution, and they bring unique challenges because they are difficult to detect and remove from water. They combine with other pollutants and substances in water to form new, unidentifiable substances that in some cases are known only as "gunk." Some water pollutants come from chemicals used on land, traveling down watersheds or in underground aquifers to the bodies of water, while others are applied directly to the bodies of water to control...