Determination of Phosphate Flux from Laboratory Sample
Lake sediment has long been recognized as
The series of biochemical reactions in which
an important source of nutrients such as
glucose is broken down to pyruvate with the
phosphorus. To gain a better understanding
release of usable energy in the form of ATP.
of phosphorus flux at the sediment-water
One molecule of glucose undergoes two
interface, it is crucial to investigate the
phosphorylation reactions and is then split to
sediment porewater. There is also growing
form two triose-phosphate molecules. Each
concern and interest in identifying whether
of these is converted to pyruvate. The net
organic-rich sediment is an important source
energy yield is two ATP molecules per
of greenhouse gases such as CO(2) and
glucose molecule. In aerobic respiration
CH(4). In the present study, we took
pyruvate then enters the Krebs cycle.
sediment samples from West Lake, a
Alternatively, when oxygen is in short supply
shallow hypereutrophic lake in Hangzhou,
or absent, the pyruvate is converted to
Zhejiang Province, China and incubated
various products by anaerobic respiration.
subsamples under anaerobic conditions at
Other simple sugars, e.g. fructose and
25 degrees C for 182 d using a specially
galactose, and glycerol (from fats) enter the
designed microcosm that permits repeated
glycolysis pathway at intermediate stages.
extraction of sediment porewater and
sampling of headspace gases. Anaerobic
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phosphate fluxes and mineralization of
http://www.answers.com/topic/glycolysis#ix
sediment organic carbon were measured.
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Average diffusive flux of soluble phosphorus
was 0.81 mg P m(-2) d(-1) during the initial
18 d of incubation. Decomposition of sediment organic C followed zero-order reaction
kinetics and methane accounted for about 50% of the mineralization products. The results
suggest that organic-rich sediments can be important sources of P and methane under
anaerobic conditions. Laboratory studies simulating field conditions and field studies are
necessary to determine the contribution of sediment as a source of P and greenhouse gases.
Laboratory Data
Start and finish phosphate flux water samples as well as necessary standards were
spectrometrically analyzed in the laboratory to determine phosphate flux. These values can be
seen bellow in table 1.
Table 1: Phosphate absorbance data collected in laboratory for standard solutions
as well as flux start and finish water samples
Solution
Absorbance at 690nm
Absorbance at 890nm
Blank
0.000
0.001
1μm
0.025
0.027
2μm
0.041
0.045
3μm
0.097
0.110
4μm
0.146
0.152
5μm
0.190
0.207
Time Start
0.049
0.038
Time final
0.034
0.034
Determination of Phosphate Flux from Laboratory Sample
Standard Curve
The standard solution absorbances were used to determine a standard curve for phosphate
absorbance against concentration in order determine the concentration of the start and finish
phosphate flux water samples. This graph can be seen below (figure 1).
0.200
0.180
Absorbance (690nm)
0.160
0.140
0.120
0.100
0.080
y = 0.0435x - 0.0307
R2 = 0.9789
0.060
0.040
0.020
0.000
0
1
2
3
4
5
6
Phosphate Concentration (µM)
Figure 1: Standard curve for phosphate absorbance vers. concentration.
Calculation of sediment-water column phosphate flux
The calculation of sediment-water phosphate flux is calculated using the following equation:
F
(Ct  C 0 )  V 10000

T
A
So the phosphate flux for this sediment and water sample is –62.82 μmol m-2 h-1, i.e. sediment
absorbed 62.82 μmol of phosphate per square meter of sediment per hour of incubation.
Definition of phosphate
A salt or ester of phosphoric acid,
containing PO43− or a related anion
or a group such as OPO(OH)2.
|
|
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An effervescent soft drink containing
phosphoric acid, soda water, and
flavoring.
Determination of Phosphate Flux from Laboratory Sample
References
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Determination of Phosphate Flux from Laboratory Sample