Unit 8 Water and the Environment

Unit 8 Water and the Environment

Unit 8—Water and the Environment

Chapter 24 Earth’s Water Systems

24 1 watercycle

24.1 The Water Cycle

The amount of water on Earth is about the same as it was during the age of the dinosaurs, 65 to 220 million years ago.

The water cycle is also known as the hydrologic cycle

With about 70 percent of its surface covered with water, Earth is truly a water planet.

Of the total amount of water on Earth, less than 1 percent is available for our consumption.

Most is too salty or frozen as ice at the poles.

Body of water / Percent
Oceans / 97.1%
Polar ice / 2.24%
Groundwater / 0.61%
Lakes / 0.016%
Moisture in the atmosphere / 0.001%
rivers / 0.0001%

Lakes, ponds, streams, and rivers are collectively referred to as fresh surface water

The four main processes of the water cycle are:





Define each of the above.

What is the driving force of the water cycle?______

Although not one of the four main processes of the water cycle, plants and animals contribute water to the atmosphere through a process known as respiration.

Define respiration.

Aquifers contain groundwater. The Ogallala Aquifer is the largest aquifer in the world, found in the Midwest U.S. (Kansas, Texas, Oklahoma, Nebraska)

Define aquifer.

Define groundwater.

Groundwater that is not collected for our use will continue to flow through sediments and eventually enter the ocean, thus continuing the water cycle.

A watershed is an area of land that catches all rain and snow and collects it one place like a river.

24.2 Water Quality

Standards are used to judge water quality.

Water that meets these standards is safe for drinking, cooking, and other household activities.

The variety and amount of ions in your tap water give it a certain taste.

Possible components of tap and/or surface water and their sources are listed below

Possible Component / Source
Acid (hydrogen ion) / Dissolved carbon dioxide from soils
Base (hydroxide ion, OH−1) / Calcium and magnesium salts occurring naturally in the water supply
Chlorine / An additive in water treatment to kill bacteria
Fluoride ion / Added as sodium fluoride in water treatment to prevent tooth decay
Iron ions / Dissolved from iron or steel pipes
Copper ions / Dissolved from copper pipes
Lead ion / Dissolved from lead pipes or solder for pipes, affects central nervous system
Phosphorus / Detergents and surface runoff from fertilizers, leads to algae blooms

Hard water is water that contains a lot of dissolved calcium and magnesium. Many homes use a water softener to remove these and other ions (makes soft water).

Tests that are performed to asses water quality:

Unit 8—Water and the Environment

Chapter 24 Earth’s Water Systems

—Water temperature

—Dissolved oxygen test

—Biological oxygen demand test

—Turbidity test

—Nitrate test

—Phosphate test

—pH test

Unit 8—Water and the Environment

Chapter 24 Earth’s Water Systems

24.3 Acid Rain

Rainwater is normally a bit acidic because natural sources of carbon dioxide exist. CO2 is emitted by plants and mixes with the water in the atmosphere to make carbonic acid, H2CO3.

Any rain, snow, or fog that has a pH lower than 5.6 is called acid rain or acid precipitation.

Acid rain is harmful to natural environments because most life and life processes function in nearly neutral environments.

Acid rain reduces the amount of calcium in the soil.

The main cause of acid rain is the mixing of precipitation with by-products from the combustion of fossil fuels. The four gases primarily responsible for acid rain are SO2, SO3, NO and NO2. In addition to damage to buildings, statues, structures, acid precipitation affects the respiratory system in people and animals. Further affects can be seen in other animal populations.

A catalytic converter is a device that converts nitrogen oxide to nitrogen gas (N2) and oxygen (O2) before these emissions enter the atmosphere.

24.4 Oceans

Oceans are part of the water layer of Earth’s surface, called the hydrosphere.

This layer covers much of its surface.

Earth has five major oceans, Atlantic, Pacific, Indian, Arctic, and Southern

There are six major ions dissolved in sea water, and approximately 70 additional trace elements/ions found in sea water.

Ion Name / Ion Symbol / Percent
chloride ion / Cl−1 / 55
sodium ion / Na+1 / 31
sulfate ion / SO4−2 / 8
magnesium ion / Mg+2 / 4
calcium ion / Ca+2 / 1
potassium ion / K+1 / 1

The term salinity describes the “saltiness” of seawater.

Salinity describes how much salt is dissolved in one kilogram of water.

The salinity of the oceans has remained relatively constant for 600 million years because physical and chemical processes create a balance, as shown in the picture below.

Calcium carbonate buffers the ocean.

More CO2 in the atmosphere could mean a more acidic ocean since more gas will dissolve in the oceans

A food chain is a series of steps through which energy and nutrients are transferred, from organism to organism, in an ecosystem.

—Producers are plants and one-celled organisms that concentrate energy from the sun through photosynthesis.

—Herbivores feed on producers.

—Many carnivores, the next step on a food chain, feed on herbivores.

A food chain can be represented as a pyramid, with producers forming the base, herbivores next, and carnivores at the top.

This arrangement represents how energy is lost in the food chain.

Decomposers recycle materials back to the food chain.

As producers store energy, they also absorb small amounts of toxic pollutants in the water.

Next, herbivores eat large numbers of producers to obtain enough energy.

Top carnivores, who prey on other carnivores, can accumulate dangerous levels of toxic pollutants.