Geology Reference
In-Depth Information
Fig. 1. Fractionation of phosphorus in the seven tufa samples (as ppm P dry wt.). Euclad., Eucladium verticillatum;
Palust., Palustriella commutata; Riv., Rivularia haematites; Schiz., Schizothrix species.
Acid fractions
is assumed that most of this P was associated with
organic matter.
These were all small and ranged between 1.5 - 15%
of the total, being lowest in the fossil material.
The fraction was subdivided into a strong (5 N
HCl) and weak (0.5 N HCl) acid extraction and
most of the P was removed by the strong acid.
These extractions will remove some P associated
with detrital minerals and some acid - hydrolysable
organic P from the organic matter. Since the
highest fractions appear in the modern material it
Alkali fraction
This was a large fraction, particularly in the modern
bryophyte tufas. The procedure removed most of the
remaining organically-bound P, and it is clear that
this is a significant fraction even in the fossil
material.
Table 2. Percentage fractionation of phosphorus in the tufas
Fraction
1 Riv.
modern
2 Riv.
fossil
3 Schiz.
modern
4 Palust.
modern
5 Palust.
26 yr
6 Euclad.
modern
7 Euclad.
fossil
Water-soluble
7.9
1.4
7.6
1.8
2.3
1.7
3.0
EDTA
17.3
64.4
12.1
39.3
32.9
8.4
48.0
EDTA-dithionite
26.8
22.1
21.2
21.4
13.6
10.0
16.5
H
2
SO
4
0.5 N
0.8
0.5
1.5
0.6
0.1
0.3
0.1
HCl 5 N
14.2
1.0
12.1
9.5
2.3
2.5
3.0
Alkali
31.5
9.6
39.4
23.8
47.7
71.2
28.5
Na
2
CO
3
1.6
1.0
6.1
3.6
1.1
5.9
0.8
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