Geology Reference
In-Depth Information
photosensitiser: a substance that absorbs light and subsequently initiates
a photochemical reaction or photophysical alteration in the chemical of
interest.
photosynthetically active radiation (PAR): electromagnetic energy in the
400-700 nm wavelength range that can be absorbed by chlorophyll or
other light-harvesting pigments in plants and is used for photosynthesis.
physico-chemical speciation: the various physical and chemical forms in
which an element may exist in a specified system.
phytoplankton: microscopic plants living in the oceanic water column.
phytoremediation: the use of living plants to reduce the risk posed by
contaminated soil, sludges, sediments, and groundwater by removing,
degrading, immobilizing, or containing contaminants in situ.
planetary albedo: the reflectivity of the world with respect to incident
sunlight: calm seawater (
B
2%), vegetated regions (10-25%), deserts
(
B
35%), and snow covered surfaces (
B
90%).
podsolization: the leaching of soluble complexes of aluminum and fer-
rous iron from the A horizon and the subsequent deposition of these
metals, together with organic matter, in the B horizon.
potential density, r
h
: the density defined on the basis of potential
temperature instead of in situ temperature.
potential temperature: the temperature that a water parcel would have if
raised adiabatically to the ocean surface.
pycnocline: a region in the water column that exhibits a sharp change in
density.
pyrolytic hydrocarbon: an organic compound originating from combus-
tion sources.
quantum yield: number of molecules of reactant consumed per photon of
light absorbed.
radiolaria: single-celled planktonic organisms that build a skeleton of silica.
Redfield ratio: the constant relative amount of nutrients taken up by
phytoplankton during photosynthesis, being 106C:16N:1P.
refractometer: instrument for measuring the indices of refraction of various
substances.
remineralisation: bacterial degradation of particulate organic nitrogen
(POC) into dissolved organic nitrogen (DON).
residence time: the average lifetime of the component in a specified system,
which is, in effect, a reciprocal rate constant.
respiration: biochemical and cellular processes within an organism by which
carbon is combined with absorbed oxygen to produce carbon dioxide.
Revelle factor (R): a resistance to the dissolution of CaCO
3(s)
by carbonic
acid indicating that the ocean is relatively well buffered against changes in
SCO
2
in response to variations in atmospheric pCO
2
.
