Download 3/7-3/12 Nitrogen and Phosphorus

GEOL 1070 Global Change 2 READING ASSIGNMENT 3/07/01
3/7-3/12 Nitrogen
page 1 of 6
and Phosphorus
Assigned Reading:
1) Xeroxes: Nitrogen and Phosphorous cycle overviews (2 pages text, 2 figures)
Phosphorous in Lake Erie (1 page)
2) Env. Sci.: p. 66-70, 49-50, and 421-422
What to know (from readings and class)
* the major chemical forms of nitrogen
* that nitrogen is an essential element for humans (amino acids), how humans get nitrogen
* the processes in the nitrogen cycle, and which processes are facilitated by microorganisms
* the main reservoir of nitrogen
* the species of nitrogen involved in acid rain
* the main anthropogenic source of nitrogen in acid rain
* the species of nitrogen involved in stratospheric ozone depletion
* the species of nitrogen involved in eutrophication
* the species of nitrogen involved in blue baby syndrome
* the major chemical forms of phosphorus
* the species of phosphorus involved in eutrophication
* two main anthropogenic sources of phosphate
Vocabulary See next page
Vocabulary
page 2 of 6
dinitrogen N2
ammonia NH3
ammonium ion NH4+
nitrite NO2nitrate NO3nitrous oxide N2O
nitric acid HNO3
NOx
nitrogen fixation
industrial fixation
nitrification
denitrification
ammonification
oxidation
acid rain
buffer
liming
essential nutrient
eutrophication
blue baby syndrome (methaemogloninaemia)
phosphate PO43apatite Ca5(PO4)3(F,Cl, OH)
GEOL 1070 Global Change 2 READING, NITROGEN CYCLE OVERVIEW page 3 of 6
Modified slightly from: http://www.britannica.com
nitrogen cycle
circulation of nitrogen in various forms through nature. Nitrogen, a component of
proteins and nucleic acids, is essential to life on Earth. Although 78 percent by volume
of the atmosphere is nitrogen gas, this abundant reservoir exists in a form unusable
by most organisms. Through a series of microbial transformations, however, nitrogen is
made available to plants, which in turn ultimately sustain all animal life. The steps,
which are not altogether sequential, fall into the following classifications: nitrogen
fixation, nitrogen assimilation, ammonification, nitrification, and denitrification.
Nitrogen fixation, in which nitrogen gas is converted into inorganic nitrogen
compounds, is mostly (90 percent) accomplished by certain bacteria and blue-green
algae (see nitrogen fixation). A much smaller amount of free nitrogen is fixed by
abiotic means (e.g., lightning, ultraviolet radiation, electrical equipment) and by
conversion to ammonia through the Haber-Bosch process.
Nitrates and ammonia resulting from nitrogen fixation are assimilated into the specific
tissue compounds of algae and higher plants. Animals then ingest these algae and
plants, converting them into their own body compounds.
The remains of all living things--and their waste products--are decomposed by
microorganisms in the process of ammonification, which yields ammonia. (Under
anaerobic, or oxygen-free, conditions foul-smelling putrefactive products may appear,
but they too are converted to ammonia in time.) Ammonia can leave the soil or be
converted into other nitrogen compounds, depending in part on soil conditions.
Nitrification, a process carried out by nitrifying bacteria, transforms soil ammonia into
nitrates, which plants can incorporate into their own tissues.
Nitrates also are metabolized by denitrifying bacteria , which are especially active in
water-logged, anaerobic soils. The action of these bacteria tends to deplete soil
nitrates, forming free atmospheric nitrogen.
GEOL 1070 Global Change 2 READING, NITROGEN CYCLE DIAGRAM page 4 of 6
Source:
Environmental Chemistry, 2nd Edition, O'Neill, P., 1993
GEOL 1070 Global Change 2 READING, PHOSPHORUS CYCLE OVERVIEW
Modified slightly from: http://www.britannica.com
page 5 of 6
phosphorus cycle
circulation of phosphorus in various forms through nature. Of all the elements recycled in the
biosphere, phosphorus is the scarcest and therefore the one most limiting in any given
ecological system. It is indispensable to life, being intimately involved in energy transfer and
in the passage of genetic information in the deoxyribonucleic acid (DNA) of all cells.
Much of the phosphorus on Earth is tied up in rock and sedimentary deposits, from
which it is released by weathering, leaching, and mining. Some of it passes through
freshwater and terrestrial ecosystems via plants, grazers, predators, and parasites, to be
returned to those ecosystems by death and decay. Much of it, however, is deposited in the
sea, in shallow sediments, where it circulates readily, or in ocean deeps, whence it wells up
only occasionally. Phosphorus is brought back to the land through fish harvests and through
collection of guano deposited by seabirds. Although there are seasonal pulses of availability,
there appears to be a steady loss of phosphorus to the ocean deeps.
Because of its high reactivity, phosphorus exists in combined form with other
elements. Microorganisms produce acids that form soluble phosphate from insoluble
phosphorus compounds. The phosphates are utilized by algae and terrestrial green plants,
which in turn pass into the bodies of animal consumers. Upon death and decay of organisms,
phosphates are released for recycling.
Because of the steady diversion of phosphorus into the oceans, the element must be
added (in fertilizers) to soils to maintain fertility and agricultural productivity.
PHOSPHORUS CYCLE DIAGRAM
Source: Environmental Chemistry, 2nd Edition, O'Neill, P., 1993
page 6 of 6
Single page Xerox on restoration of Lake Erie ecosystems
(Handed out in class, See Dr. Lubinski for copy)