Heating of this surface is accomplished by three physical processes— radiationconductionand convection —and the temperature at the interface of the atmosphere and surface is a result of this heating. The relative contributions of each process depend on the wind, temperature, and moisture structure in the atmosphere immediately above the surface, the intensity of solar insolation, and the physical characteristics of the surface. The temperature occurring at this interface is of critical importance in determining how suitable a location is for different forms of life. Radiation The temperature of the atmosphere and surface is influenced by electromagnetic radiationand this radiation is traditionally divided into two types:
Note that ammonia is much more than the product with which it is most readily associated: In fact, ammonia is an extremely abundant substance, occurring naturally, for instance, in the atmospheres of Venus and other planets in our solar system.
The importance of ammonia is reflected by the fact that it and water are the only two substances that chemists regularly refer to by their common names, as opposed to a scientific name such as carbon dioxide.
As for ammonium, its extra hydrogen atom makes it a substance that dissolves in water and is attracted to negatively charged surfaces of clays and organic matter in soil.
Therefore, it tends to become stuck in one place rather than to move around, as nitrate does. Plants in acidic soils typically receive their nitrogen from ammonium, but in nonacidic soils, nitrate is typically the more useful form of fertilizer.
The two fertilizers are also combined to form ammonium nitrate, which is powerful both as a fertilizer and as an explosive.
Ammonium nitrate was used both in the first World Trade Center bombing, inand in the even more devastating Oklahoma City bombing two years later. In just a few months, once-productive farmland turned into worthless fields of stubble and dust, good for virtually nothing. By the time it was over, the region had acquired a bitter nickname: Farmers happily reaped abundant yields, year after year, not knowing that they were actually preparing the way for soil erosion on a grand scale.
Farmers in the s had long known about the principle of crop rotation as a means of giving the soil a rest and restoring its nutrients. But to be successful, crop rotation must include fallow years i. Cotton and wheat are examples of crops that deplete nutrient content in the soil, and in fact wheat was the crop of choice in the future dust bowl.
In some places, farmers alternated between wheat cultivation and livestock grazing on the same plot of land. The hooves of the cattle further damaged the soil, already weakened by raising wheat.
The land was ready to become the site of a full-fledged natural disaster, and in the depths of the Great Depression, that disaster came in the form of high winds.
These winds scattered vast quantities of soil from the Great Plains of the Midwest to the Atlantic seaboard, and acreage that once had rippled with wheat turned into desert-like wastelands.
The farmlands of the plains states have long since recovered from the dust bowl, and farming practices have changed considerably. Instead of alternating one year of wheat with a year of grazing livestock, farmers in the dust bowl region apply a three-year cycle of wheat, sorghum, and fallow land.
They also have planted trees to serve as barriers against wind. Years after the dust bowl, the American West could have again become the site of another disaster, had not farmers and agricultural officials learned from the mistakes of an earlier generation.
During the s, American farms enjoyed such a great surplus that farmers increasingly began to sell their crops to the Soviet Union, and farmers were encouraged to cultivate even marginal croplands to increase profits. This alarmed environmental activists, who called attention to the flow of nutrients from croplands into water resources.
As a result of public concerns over these and related issues, Congress in passed the Soil and Water Resource Conservation Act, mandating measures to conserve or protect soil, water, and other resources on private farmlands and other properties.
Leaching and Its Effect on Soil Like erosion, leaching moves substances through soil, only in this case it is a downward movement. Leached water can carry all sorts of dissolved substances, ranging from nutrients to contaminants.
The introduction of manufactured contaminants to the soil, and hence the water table, is of course a serious threat to the environment. On the other hand, where human waste and other, more natural forms of toxin are concerned, nature itself is able to achieve a certain amount of cleanup on its own.
In a septic tank system, used by people who are not connected to a municipal sewage system, anaerobic bacteria process wastes, removing a great deal of their toxic content in the tank itself.
These bacteria usually are not introduced artificially to the tank; they simply congregate in what is a natural environment for them. The waste-water leaves the tank and passes through a drain field, in which the water leaches through layers of gravel and other filters that help remove more of its harmful content.
In the drain field, the waste is subjected to aerobic decay by other forms of bacteria before it either filters through the drain-pipes into the ground or is evaporated.
In addition to purifying water, leaching also passes nutrients to the depths of the A horizon and into the B horizon—something that is not always beneficial.In a study published in the journal Science, a team of scientists, led by researchers from Princeton University in New Jersey, tested the concentration of oxygen in the atmosphere and found that.
When Earth first formed, Earth's atmosphere may have contained more greenhouse gases and CO 2 concentrations may have been higher, with estimated partial pressure as large as 1, kPa (10 bar), because there was no bacterial photosynthesis to reduce the gas to carbon compounds and oxygen.
Earth's atmosphere is about miles ( kilometers) thick, but most of it is within 10 miles (16 km) the surface. Air pressure decreases with altitude. In the 20th century science of the atmosphere proceeded to the study of the composition of air and to the consideration of how concentrations of gases existing as traces in the atmosphere had modified over time and of chemical processes that create and destroy compounds in the air.
surfaces. On Earth, volatiles that constitute the atmosphere are principally represented by the gases nitrogen, which makes up seventy-eight percent, oxygen (twenty percent), water vapor.
Carbon dioxide (CO 2) is an important trace gas in Earth's rutadeltambor.com is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere.
Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by .