Chemical reduction of phosphate on the primitive earth.
ABSTRACT If phosphorus played a role in the origin of life, some means of concentrating micromolar levels of phosphate (derived from the calcium phosphate mineral apatite), must first have been available. Here we show that simulated (mini)lightning discharges in model prebiotic atmospheres, including only minimally reducing ones, reduce orthophosphates, including apatite, to produce substantial yields of phosphite. Electrical discharges associated with volcanic eruptions could have provided a particularly suitable environment for this process. Production of relatively soluble and reactive phosphite salts could have supplied a pathway by which the first phosphorus atoms were incorporated into (pre)biological systems.
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ABSTRACT: Matrix bound phosphine (MBP), a kind of chemically reduced phosphorus, has received limited attention in prevailing modeling of the phosphorus biogeochemical cycle. MBP has been found to occur in marine sediments. MBP in the sediments of the Yellow Sea and its coastal areas was measured by gas chromatography from 2004 to 2007. MBP levels in surface sediments were 0.19–38.24 ng kg−1 in the shelf of the Yellow Sea, 0.34–17.15 ng kg−1 in the Jiaozhou Bay, 2.11–71.79 ng kg−1 in the Sanggou Bay and 0.28–319.32 ng kg−1 in the rivers around the Jiaozhou Bay. High levels of MBP occurred in the northern and middle areas of the Yellow Sea. Obvious seasonal variation of MBP was observed in surface sediments of the Sanggou Bay, with the highest MBP level occurring in summer and the lowest in winter. MBP in surface sediments of the inner Jiaozhou Bay was higher than those in the outer region. MBP levels increased with depth in the top 5–10 cm sediments of the Jiaozhou Bay and on the intertidal flats. Environmental factors such as type of sediments, temperature, organic matter and human activity were found to affect the concentrations and distribution of MBP in marine sediments.Continental Shelf Research 01/2010; · 1.89 Impact Factor
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ABSTRACT: The establishment of a sensitive and specific method for the detection of reduced phosphorus (P) is crucial for understanding P cycle. This paper presents the quantitative evidence of phosphite (P, +3) from the freshwater matrix correspondent to the typically eutrophic Lake Taihu in China. By ion chromatography coupled with gradient elution procedure, efficient separation of micromolar levels of phosphite is possible in the presence of millimolar levels of interfering ions, such as chloride, sulfate, and hydrogen carbonate in freshwater lakes. Optimal suppressed ion chromatography conditions include the use of 500 μL injection volumes and an AS11 HC analytical column heated to 30 °C. The method detection limit of 0.002 μM for phosphite was successfully applied for phosphite determination in natural water samples with recoveries ranging from 90.7 ± 3.2% to 108 ± 1.5%. Phosphite in the freshwater matrix was also verified using a two-dimensional capillary ion chromatography and ion chromatography coupled with mass spectrometry. Results confirmed the presence of phosphite in Lake Taihu ranging from 0.01 ± 0.01 to 0.17 ± 0.01 μM, which correlated to 1-10% of the phosphate. Phosphite is an important component of P and may influence biogeochemical P cycle in lakes.Environmental Science & Technology 09/2012; 46(19):10667-74. · 4.80 Impact Factor
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ABSTRACT: The seasonal occurrence and distribution of phosphite (HPO32-, P) in sedimentary interstitial water from Lake Taihu was monitored from 2011 to 2012 to better understand its possible link to P cycle in the eutrophic shallow lake. Phosphite concentrations ranged from < MDL to 14.32 ± 0.19 μg P/Kg with a mean concentration of 1.58 ± 0.33 μg P/Kg, which accounts for 5.51% total soluble P (TSPs) in surficial sediments (0-20 cm). Spatially, the concentrations of sedimentary phosphite in the lake's northern areas were relatively higher than those in the southern areas. Higher phosphite concentrations were always observed in seriously polluted sites. Generally, phosphite in the deeper layers (20-40 cm and 40-60 cm) showed minor fluctuations compared to that in the surficial sediments, which may be associated with the frequent exchange at the sediment-water interface. Phosphite concentrations in surficial or core sediments decreased as: spring > autumn > summer > winter. Higher phosphite levels occurred in the areas with lower redox (Eh), higher P contents, and particularly when metal bonded with P to form Al-Ps and Ca-Ps. Phosphite may be an important media in the P biogeochemical cycle in Lake Taihu and contribute to its internal P transportation.Environmental Science & Technology 05/2013; · 4.80 Impact Factor
CHEMICAL REDUCTION OF PHOSPHATE ON THE PRIMITIVE
D. GLINDEMANN1, R. M. DE GRAAF2and ALAN W. SCHWARTZ2∗
1University of British Columbia, Dept. of Chemistry, 2036 Main Mall, Vancouver, BC, V6T 1Z1,
2Evolutionary Biology Research Group, Faculty of Science, University of Nijmegen, Postbus 9010,
6500 GL Nijmegen, The Netherlands
(Received 24 March, 1999)
Abstract. If phosphorus played a role in the origin of life, some means of concentrating micro-
molar levels of phosphate (derived from the calcium phosphate mineral apatite), must first have been
available. Here we show that simulated (mini)lightning discharges in model prebiotic atmospheres,
including only minimally reducing ones, reduce orthophosphates, including apatite, to produce sub-
stantial yields of phosphite. Electrical discharges associated with volcanic eruptions could have
provided a particularly suitable environment for this process. Production of relatively soluble and
reactive phosphite salts could have supplied a pathway by which the first phosphorus atoms were
incorporated into (pre)biological systems.
The relative insolubility of apatite is a recognized problem in the origin of life. In a
perceptive review of the role of phosphate in the origin of life, Gulick (1955) pro-
posed that reduction of phosphate might have led to the formation of water-soluble
salts of hypophosphorous (H3PO2) and phosphorous (H3PO3) acids (hypophos-
phites and phosphites) on the primitive Earth, and that the first organisms utilized
such ‘low-oxygen compounds’ for their metabolisms. This proposal has not been
widely accepted, since the reduction of orthophosphate is a highly endergonic
process (Miller and Urey, 1959). In a later review of the likely prebiotic sources
of phosphorus, it was postulated that the reduction of phosphate to elemental phos-
phorus, phosphine and phosphorous acid might have occurred as a result of core
formation in the early Earth (Schwartz, 1972). The unique conditions at the time of
core formation, considered together with the known process of high temperature
reduction of phosphate by carbonaceous material, was suggested as a possible
mechanism for the reduction. Because of the possibility that the high temperatures
generated in lightning discharges might, under reducing conditions, similarly be
capable of reducing phosphate, we decided to carry out a test of the hypothesis
using simple apparatus.
∗Author for all correspondence.
Origins of Life and Evolution of the Biosphere 29: 555–561, 1999.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
D. GLINDEMANN ET AL.
Figure 1. Experimental assembly. After applying samples to quartz caps (not shown) covering the
ends of the open tungsten loop and filling the system with gas, the entire assembly was placed into
a 1 kW commercial (domestic) microwave oven. A spark discharge between the ends of the loop
occurred several seconds after applying a microwave field.
2. Materials and Methods
Sodium phosphate (Na2HPO4·12H2O, p.a.) was from Merck. Fluorapatite (Mex-
ico) and montmorillonite #26 were purchased from Ward’s. Dowex AG 50W-X8
was from Bio-Rad. Methane (99.9995%) and nitrogen (99.999%) were from Air
Liquide. Water was double-distilled.
Our experimental arrangement consisted of a 10 cm length of tungsten wire
(1 mm diameter) which was bent into the form of an open loop (Figure 1). Samples
were applied as solutions (in the case of Na2HPO4) or as pastes (mixtures of
fluorapatite with montmorillonite) to the ends of the loop. Fluroapatite and mont-
morillonite samples were ground separately and mixtures were prepared by grind-
ing with addition of a small amount of water. In order to rule out any possibility
that metallic tungsten could play a role in the reduction, we covered the ends
of the loop with capillary sleeves constructed of quartz and sealed at one end.
The phosphate-containing samples were applied to the quartz and did not come
into contact with metal. After application, samples were dried under vacuum over
NaOH and weighed by difference (1–3 mg). The loop was placed on a quartz stand
and transferred into a quartz tube. Water (1 mL) was introduced into the vessel,
frozen by immersion of the tube into liquid N2, and the system was degassed under
vacuum (three freeze-thaw cycles with back-filling with N2). After introducing the
required gas mixture, the reaction assembly was placed into a 1 kW commercial
(domestic) microwave oven, and the microwave source switched on. After several
seconds, a bright discharge was observed. The discharge was ended by switching
off the power after approximately two seconds (range, 1.6 to 2.1 s). We made no
attempt to study the influence of the length of the discharge time on the yield.
At the conclusion of each experiment, the tubes were cooled and the contents
were extracted several times with water (total volume 30 mL). Water extracts were
filtered and evaporated to dryness under vacuum. Residues were dissolved in 3–
4 mL of water, passed through a column (10×0.8 cm) of Dowex 50W-X8 (H+,
50–100 mesh) to convert sodium salts to free acids and evaporated to dryness.
CHEMICAL REDUCTION OF PHOSPHATE ON THE PRIMITIVE EARTH
Figure 2. A typical gas chromatographic analysis of products. The peaks are labelled as fol-
lows: PO3, the di(trimethylsilyl) and tri(trimethylsilyl) derivatives of phosphorous acid; PO4, the
tri(trimethylsilyl) derivative of orthophosphoric acid; X is derived from H2WO3(tentatively identi-
fied as the di(trimethylsilyl) derivative) and is an artifact of the extraction of the tungsten loop. I.S.
is the internal standard (phenanthrene).
D. GLINDEMANN ET AL.
Formation of phosphite by reduction of orthophosphate in CH4+ N2mixturesa
Phosphate source Matrixb
(wgt % phosphate)
(% in N2)
(µmol/mg sample ×102)
aThe yield of phosphite is based on the amount of phosphate deposited on the loop. For
hydroxyapatite and fluorapatite the theoretical formula weights have been used. Yields are
averages of three to seven determinations and ± indicates the average deviation of the mean.
bMixtures were prepared with montmorillonite #26, containing the indicated wgt % of the
phosphate mineral shown.
Analysis by gas chromatography- mass sprectrometry (GC-MS) was as described
previously (De Graaf et al., 1995). In a few cases we also checked for the presence
ofhypophosphite by qualitative thin-layer chromatography (Grassine and Ossicine,
The experimental conditions and results are summarized in Table I. In 10% CH4
in N2(v/v) an average yield of 11% phosphite was obtained using Na2HPO4as the
source of phosphorus. In several of these experiments we could also detect small
yields (up to about 0.5%) of methylphosphonic acid by gas-chromatography (data
not shown) as well as traces of hypophosphite. The yield of phosphite decreased to
4% in 1% methane, and to 0.1% in pure N2.
In order to extend these results to a geochemically more plausible model, we
then examined the reduction of fluorapatite – the most important accessory phos-
phate mineral inigneous rocks (Koritnig, 1978) –bypreparing mixtures offluorapat-
ite (20%) with the clay mineral montmorillonite. In these experiments, a yield of
7% phosphite was obtained in the presence of 10% methane. As with the experi-
ments with Na2HPO4, the yield of phosphite decreased, but was still substantial, as
CH4was decreased from 10% to 1% in N2. These results suggest that gas mixtures
which are only marginally reducing may be effective for this process.
CHEMICAL REDUCTION OF PHOSPHATE ON THE PRIMITIVE EARTH
We suggest the following mechanism of reduction of phosphate. The electrical
discharge produces a hot plasma containing atomic and molecular radicals which
originate from the gases present, as well as by volatilization of the target solid
phase. We have not been able to measure the spark temperature in our simula-
tions exactly, but estimate that the temperature of the sample may have approached
3000 K. By rapid cooling of the plasma, recombination products such as phosphite
are kinetically trapped. Although we have thus far only been able to systematic-
ally examine materials containing relatively high proportions of phosphate, we are
encouraged to think that apatite present in most common igneous minerals, which
typically contain 0.2% P2O5(equivalent to about 0.5% fluorapatite) but can exceed
this value (Koritnig, 1978), might be similarly reduced.
We do not believe that the direct effect of lightning upon minerals has been con-
sidered previously in the prebiotic context. Although lightning is often thought to
have been a potent source of chemical activation on the primitive Earth, it is gener-
ally the atmospheric effects of lightning or corona discharge processes which have
been modelled (Miller, 1953). Several authors have called attention to the possible
prebiotic importance of lightning associated with volcanic activity and the presence
of reduced gases (Podkletnov and Markhinin, 1981; Lavrentiev et al., 1984; Hill,
1992; Basiuk and Navarro-Gonzalez, 1996; Navarro-Gonzalez et al., 1996, 1998).
Although the potential significance of the presence of volcanic ash in proximity
to lightning has therefore been considered, and even modelled (Lavrentiev et al.,
1984; Navarro-Gonzalez et al., 1998), the role envisioned has been that of adsorp-
tion and catalysis ofreactions among the initial products of gas-phase reactions. We
now suggest that the direct interaction of volcanic lightning with ash particles in
a volcanic eruption cloud, in which locally higher concentrations of reduced gases
arecombined withthe presence of highly dispersed phosphate-containing minerals,
represents a possible source of soluble phosphorus-containing compounds on the
primitive Earth. The mineral andesite, which is a reasonable average composition
for volcanic ash in such clouds, contains 0.3% P2O5(Macdonald, 1972).
We find the production of several percent of phosphite under the relatively
crude conditions of our experiments to be surprisingly high. An eruption cloud
could have provided much more favourable circumstances for reduction. An idea
of the amount of ash which might be exposed to lightning in an eruption can be
given by the eruption of Sakurajima, for which the mass loading of the plume was
calculated to be 5×10−3kg m−3, and by the Mount St. Helens eruption, for which
the initial eruption cloud was calculated to have supported a total of 8.5×10−3kg
m−3of fine particles (Gilbert and Lane, 1994). Let us suppose that 10 m3of such a
cloud, containing up to 100 g of dust, were heated by each flash of lightning, so as
to approximate the conditions in our experiments. We calculate, similarly to Hill
(1992) that, on the primitive Earth, the rate of production of phosphite rained out of
the cloud into atypical ‘catchment area’ could have been 1.3×10−9molcm−2yr−1