Environmental Engineering Reference
In-Depth Information
Atmosphere
(most carbon is in carbon dioxide)
Combustion
of fossil
fuels
volcanic action
Terrestrial
rocks
Land food webs
Producers, consumers,
decomposers, detritivores
Soil water
(dissolved carbon)
Peat,
fossil fuels
applied to the soil. This gas can warm the atmosphere
and deplete ozone in the stratosphere.
Third
, nitrate (NO
3
) in inorganic fertilizers can
leach through the soil and contaminate groundwater.
This contaminated groundwater is harmful to drink,
especially for infants and small children.
Fourth,
we release large quantities of nitrogen
stored in soils and plants as gaseous compounds into
the troposphere through destruction of forests, grass-
lands, and wetlands.
Fifth,
we upset aquatic ecosystems by adding ex-
physicist Robert Socolow calls for countries around the
world to work out some type of nitrogen management
agreement to help prevent this problem from reaching
crisis levels.
The Phosphorus Cycle
Phosphorus cycles fairly slowly through the earth's
water, soil, and living organisms.
Phosphorus circulates through water, the earth's crust,
and living organisms in the
phosphorus cycle,
de-
picted in Figure 3-29 (p. 59). Bacteria play less impor-
tant roles here than in the nitrogen cycle. Very little
phosphorus circulates in the atmosphere because soil
conditions do not allow bacteria to convert chemical
forms of phosphorus to gaseous forms of phosphates.
The phosphorus cycle is slow, and on a short human
time scale much phosphorus flows one way from the
land to the oceans.
Phosphorous typically is found as phosphate salts
containing phosphate ions (PO
4
3
) in terrestrial rock
formations and ocean bottom sediments. As water
runs over phosphorus-containing rocks, it slowly
erodes away inorganic compounds that contain phos-
phate ions.
cess
nitrates
in
agricultural
runoff
and
discharges
from municipal sewage systems.
Sixth,
we remove nitrogen from topsoil when we
harvest nitrogen-rich crops, irrigate crops, and burn or
clear grasslands and forests before planting crops.
Since 1950, human activities have more than dou-
bled the annual release of nitrogen from the terrestrial
portion of the earth into the rest of the environment
(Figure 3-28, p. 58). This excessive input of nitrogen into
the air and water represents a serious local, regional,
and global environmental problem that has attracted
relatively little attention compared to global environ-
mental problems such as global warming and deple-
tion of ozone in the stratosphere. Princeton University
