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1.
Tabtimsai C Keawwangchai S Nunthaboot N Ruangpornvisuti V Wanno B 《Journal of molecular modeling》2012,18(8):3941-3949
The adsorptions of hydrogen molecule of the Fe?-?doped pristine and Stone?-?Wales defected armchair (5,5) single?-?walled carbon nanotubes (SWCNTs) compared with the pristine SWCNT were investigated by using the density functional theory at the B3LYP/LanL2DZ level. The doping of Fe atom into SWCNTs occurring via an exothermic process was found. The adsorptions of hydrogen molecule on the Fe?-?doped structures of either perfect or SW defected SWCNTs are stronger than on their corresponding undoped structures. The structural and electronic properties of the pristine and SW defected SWCNTs, their Fe?-?doped structures and their hydrogen molecule adsorptions are reported. 相似文献
2.
Tabtimsai C Keawwangchai S Wanno B Ruangpornvisuti V 《Journal of molecular modeling》2012,18(1):351-358
The adsorption of NO2, NH3, H2O, CO2 and H2 gases on the undoped, Zn–, Pd– and Os–doped armchair (5,5) single–walled carbon nanotubes (SWCNTs) were studied using density
functional method. The adsorptions of these five gases on the Zn–, Pd– and Os–doped SWCNTs are obviously stronger than on
the undoped SWCNT and their adsorption abilities are in the same order: NO2 > NH3 > H2O > CO2 > H2. Adsorption energies for all the studied gases on the undoped, Zn–, Pd– and Os–doped SWCNTs computed at the B3LYP/LanL2DZ
level are reported. 相似文献
3.
DFT studies of COOH tip-functionalized zigzag and armchair single wall carbon nanotubes 总被引:1,自引:0,他引:1
Structure and energy calculations of pristine and COOH-modified model single wall carbon nanotubes (SWCNTs) of different length
were performed at B3LYP/6-31G* level of theory. From 1 to 9 COOH groups were added at the end of the nanotube. The differences
in structure and energetics of partially and fully functionalized SWCNTs at one end of the nanotube are observed. Up to nine
COOH groups could be added at one end of (9,0) zigzag SWCNT in case of full functionalization. However, for (5,5) armchair
SWCNT, the full functionalization was impossible due to steric crowding and rim deformation. The dependence of substituent
attachment energy on the number of substituents at the carbon nanotube rim was observed. 相似文献
4.
Zabiollah Bolboli Nojini Amir Abbas Rafati Seyed Majid Hashemianzadeh Sepideh Samiee 《Journal of molecular modeling》2011,17(4):785-794
The adsorption of helium and neon mixtures on single-walled carbon nanotubes (SWCNTs) was investigated at various temperatures
(subcritical and supercritical) and pressures using canonical Monte Carlo (CMC) simulation. Adsorption isotherms were obtained
at different temperatures (4, 40, 77 and 130 K) and pressures ranging from 1 to 16 MPa. Separation factors and isosteric enthalpies
of adsorption were also calculated. Moreover, the adsorption isotherms were obtained at constant specific temperatures (4
and 40 K) and pressures (0.2 and 1.0 MPa) as a function of the amount adsorbed. All of the adsorption isotherms for an equimolar
mixture of helium and neon have a Langmuir shape, indicating that no capillary condensation occurs. Both the helium and the
neon adsorption isotherms exhibit similar behavior, and slightly more of the helium and neon mixture is adsorbed on the inner
surfaces of the SWCNTs than on their outer surfaces. More neon is adsorbed than helium within the specified pressure range.
The data obtained show that the isosteric enthalpies for the adsorption of neon are higher than those for helium under the
same conditions, which means that adsorption of neon preferentially occurs by (15, 15) SWCNTs. Furthermore, the isosteric
enthalpies of adsorption of both gases decrease with increasing temperature. 相似文献
5.
An enantio-selective d-Phe imprinted P(AA-co-AN) membrane was prepared using the wet-phase inversion method. The membrane not only selectively adsorbed
phenylalanine but also rejected it with a rejection selectivity of 0.82–0.64 and 0.91–0.63 during the filtration of 100 and
10 ppm (g m−3) racemate solutions, respectively. The fluxes of d-Phe and l-Phe during filtration of 10 ppm racemate solution were 0.0077–0.0229 and 0.0064–0.0208 mg m−2 s−1, respectively, and the fluxes of d-Phe and l-Phe during filtration of 100 ppm racemate solution were 0.1287–0.2522 and 0.1174–0.2458 mg m−2 s−1, respectively. The adsorption selectivity was higher at low concentration. The adsorption selectivities varied from 1.11
to 1.65 and from 1.64 to 2.78 during filtration of 100 and 10 ppm racemate solutions, respectively. In respect to desorption,
the fractional difference between d-Phe and l-Phe in the recovered solution from 10 ppm was higher than that from 100 ppm. 相似文献
6.
Effects of Anions on the Capacity and Affinity of Copper Adsorption in Two Variable Charge Soils 总被引:2,自引:0,他引:2
Effects of nitrate,(NO3−) chloride (Cl−), sulfate (SO42-, and acetate (Ac−) on Cu2+ adsorption and affinity of the adsorbed Cu2+ were evaluated in two Fe and Al enriched variable charge soils from Southern China. The maximum adsorption of Cu2+ (M, a parameter from the Langmuir isotherm model) in the presence of different anions decreased in the order
Cl− > Ac− > NO3− > SO42- for both soils. The clayey loamy soil (mixed siliceous thermic Typic Dystrochrept, TTD), developed on the Arenaceous rock,
adsorbed less Cu2+ than the clayey soil (kaolinitic thermic Plinthudults, KTP), derived from the Quaternary red earths, regardless of anion
type present in the medium. The affinity of adsorbed Cu2+ to both soils could be characterized by the Kd (distribution coefficient) values and successive extraction of the adsorbed Cu2+ with 1-mol NH4Ac L−1. The log10Kd value was smaller for the TTD soil than for the KTP soil and decreased in the order of Cl− > NO3− > SO42- > Ac−
at low initial Cu2+ concentrations (≤40 mg Cu2+L−1), whereas at 80 mg Cu2+L−1, the log10Kd value was similar for NO3−, SO42-, and Ac−, but was slightly higher for Cl−. Complete extraction of Cu2+ adsorbed in the presence of Ac− was achieved. Influence of NO3− and SO42- on the affinity of adsorbed Cu2+ was similar, but the effects of Cl− depended on the initial Cu2+ concentrations. The extracted percentage of the adsorbed Cu2+ in the presence of NO3− or SO42- increased with increasing Cu2+ adsorption saturation. The presence of Cl−, NO3−, or SO42- markedly decreased the equilibrium solution pH for both soils with increasing initial Cu2+ concentrations, and the delta pH values at the highest Cu2+ level were 0.5, 0.63, and 0.55 U for the TTD soil and 0.79, 0.84, and 0.93 U for the KTP soil, respectively for the three
anions. The presence of Ac− had a minimal influence on the equilibrium solution pH because of the buffering nature of the NaAc/HAc medium which buffered
the released protons. The effects of anions on Cu2+ adsorption and affinity of the adsorbed Cu2+ were dependent on anion types and were apparently related to the altered surface properties caused by anion adsorption and/or
the formation of anion– Cu2+ complexes. 相似文献
7.
François Coutte Didier Lecouturier Saliha Ait Yahia Valérie Leclère Max Béchet Philippe Jacques Pascal Dhulster 《Applied microbiology and biotechnology》2010,87(2):499-507
Surfactin and fengycin are lipopeptide biosurfactants produced by Bacillus subtilis. This work describes for the first time the use of bubbleless bioreactors for the production of these lipopeptides by B. subtilis ATCC 21332 with aeration by a hollow fiber membrane air–liquid contactor to prevent foam formation. Three different configurations
were tested: external aeration module made from either polyethersulfone (reactor BB1) or polypropylene (reactor BB2) and a
submerged module in polypropylene (reactor BB3). Bacterial growth, glucose consumption, lipopeptide production, and oxygen
uptake rate were monitored during the culture in the bioreactors. For all the tested membranes, the bioreactors were of satisfactory
bacterial growth and lipopeptide production. In the three configurations, surfactin production related to the culture volume
was in the same range: 242, 230, and 188 mg l−1 for BB1, BB2, and BB3, respectively. Interestingly, high differences were observed for fengycin production: 47 mg l−1 for BB1, 207 mg l−1 for BB2, and 393 mg l−1 for BB3. A significant proportion of surfactin was adsorbed on the membranes and reduced the volumetric oxygen mass transfer
coefficient. The degree of adsorption depended on both the material and the structure of the membrane and was higher with
the submerged polypropylene membrane. 相似文献
8.
To provide beneficial guide for the application of the magnetic field in the bio-treatment of the Cr(VI)-contained wastewater,
sludge samples from the control bio-system A (absent of magnetic field) and the contrast bio-system B (present of magnetic
field) were used to adsorb the synthetic wastewater with 100 mg l−1 Cr(VI). Influences of two adsorption modes, single adsorption and once continuous adsorption, on the Cr(VI) adsorption capacities
of both sludge samples were compared. And the influence of regeneration on the Cr(VI) adsorption capacities were also studied.
The results of adsorption experiments showed that the Cr(VI) adsorption capacities of the first single adsorption for sludge
sample A and B were pretty nearly, which were 9.79 and 9.93 mg, respectively. And after 5 single adsorption periods, the total
Cr(VI) adsorption capacity and efficiency of the sample B were 25.88 and 55.66 mg Cr(VI) g−1VSS, while those of the control were 14.95 and 33.98 mg Cr(VI) g−1VSS, respectively. For the sludge sample A and B after a single adsorption, both functions of regeneration were remarkable.
But after 13 cycles of the single adsorption-regeneration, the Cr(VI) adsorption capacity and efficiency of the sample B were
110.15 and 189.91 mg Cr(VI) g−1VSS, while those of the control were 70.89 and 140.38 mg Cr(VI) g−1VSS, respectively. Though the Cr(VI) adsorption capacity of a once continuous adsorption period was more than that of a single
adsorption period obviously, the Cr(VI) removal rates of the sludge sample A and B in the third period of once continuous
adsorption-regeneration were only 8.12 and 33.51%, respectively. It was concluded that the weak magnetic field did improve
the Cr(VI) bio-removal efficiency and the sludge stability, the batch treatment was an ideal operation mode for the bio-treatment
of the Cr(VI)-contained wastewater, as compared with the continuous operation mode, but regeneration and enough sludge content
were two necessary conditions to ensure the efficiency of batch treatment. 相似文献
9.
The report is on an electrochemical biosensor with remarkably improved sensitivity toward nitrite. In this strategy, positively
charged gold nanoparticle (PCNA) is used in combination with multiwall carbon nanotubes (MWCNT) by electrostatic adsorption
for fabricating PCNA/MWCNT films. Then hemoglobin (Hb) biocatalyst will easily be attached to the surface of the combination
films aforementioned. After that, the Hb/PCNA films are immobilized onto the Hb/PCNA/MWCNT films through layer-by-layer assembly
technique. The (Hb/PCNA)2/MWNT/GC electrode thus prepared exhibits enhanced electrocatalytic behavior to the reduction of nitrite at −0.10 V versus
SCE in 0.05 M H2SO4 solution. On condition of the low detecting potential and low pH, interference caused by direct electrochemical oxidation or oxidizable
substances can be prevented. Therefore, the modified electrode shows fast response time, very high sensitivity, good selectivity
and stability. The current response of the sensor increases linearly with nitrite concentration from a range of 3.6 × 10−6 to 3.0 × 10−3 M with a detection limit(S /N = 3) of 9.6 × 10−7 M. 相似文献
10.
Transport and turnover of dissolved organic carbon (DOC) is important in the C cycle of organic soils. The concentration of
DOC in soil water is buffered by adsorption to the soil matrix, and has been hypothesized to depend on the pool size of adsorbed
DOC. We have studied the effect of frequent artificial excessive leaching events on concentration and flux of DOC in shallow,
organic rich mountain soils. Assuming a constant Kd value for DOC adsorption to the soil matrix, we used these data to assess the change in the pool of adsorbed (or potential)
DOC in the soil. The study involved manipulation of precipitation amount and frequency in summer and autumn in small, heathland
catchments at Storgama, southern Norway. The shallow soils (16–34 cm deep on average) limit the possibility for changes in
water flow paths during events. The mini-catchments range in size from 75 to 98 m2. Our data show that after leaching of about 1.2 g DOC m−2 the DOC concentration in runoff declines by approximately 50%. From this we conclude that the pool size of adsorbed potential
DOC in the shallow soils at any time is of the order 2–3 g m−2. Frequent episodes suggest that the replenishment rate, which depends on the decomposition rate of soil organic matter, is
fast and the potential DOC pool could be fully restored probably within days during summer, but with some more time required
in autumn, due to lower temperatures. Both pool size of potential DOC and replenishment rate are seasonally dependent. The
pool of potential DOC, and thus the DOC concentration in discharge, is at their maximum in the growing season. However, under
non-leaching conditions, the concentration of DOC in soil water and thus the pool size of potential DOC seems to level off,
possibly due to conversion of DOC to less reversibly bound forms, or to further decomposition to CO2. 相似文献
11.
Durmaz-Sam S Sayar NA Topal-Sarikaya A Sayar AA 《Bioprocess and biosystems engineering》2011,34(8):997-1005
The potential of the dried yeast, wild-type Schizosaccharomyces pombe, to remove Ni(II) ion was investigated in batch mode under varying experimental conditions including pH, temperature, initial
metal ion concentration and biosorbent dose. Optimum pH for biosorption was determined as 5.0. The highest equilibrium uptake
of Ni(II) on S. pombe, q
e, was obtained at 25 °C as 33.8 mg g−1. It decreased with increasing temperature within a range of 25–50 °C denoting an exothermic behaviour. Increasing initial
Ni(II) concentration up to 400 mg L−1 also elevated equilibrium uptake. No more adsorption took place beyond 400 mg L−1. Equilibrium data fitted better to Langmuir model rather than Freundlich model. Sips, Redlich–Peterson, and Kahn isotherm
equations modelled the investigated system with a performance not better than Langmuir. Kinetic model evaluations showed that
Ni(II) biosorption process followed the pseudo-second order rate model while rate constants decreased with increasing temperature.
Gibbs free energy changes (ΔG°) of the system at 25, 30, 35 and 50 °C were found as −1.47E + 4, −1.49E + 4, −1.51E + 4, and −1.58E + 4 J mol−1, respectively. Enthalpy change (ΔH°) was determined as −2.57E + 3 J mol−1 which also supports the observed exothermic behaviour of the biosorption process. Entropy change (ΔS°) had a positive value (40.75 J mol−1 K−1) indicating an increase in randomness during biosorption process. Consequently, S. pombe was found to be a potential low-cost agent for Ni(II) in slightly acidic aqueous medium. In parallel, it has been assumed
to act as a separating agent for Ni(II) recovery from its aqueous solution. 相似文献
12.
Analysis of ethanol in fermentation samples by a robust nanocomposite-based microbial biosensor 总被引:1,自引:0,他引:1
A robust microbial biosensor was constructed from a bionanocomposite prepared by a direct mixing of bacterial cells of Gluconobacter oxydans and carbon nanotubes with ferricyanide employed as a mediator for enhanced sensitivity of ethanol oxidation. A successful
integration of the device into flow injection analysis mode of operation provided a high sensitivity of detection of (74 ± 2.7)
μA mM−1 cm−2, a low detection limit of 5 μM and a linear range from 10 μM up to 1 mM. A short response time of the biosensor allowed a
sample throughput of 67 h−1 at 0.3 ml min−1. The biosensor exhibited high operational stability with a decrease in the biosensor response of 1.7% during 43 h of continuous
operation. The device was used to analyse ethanol in fermentation samples with a good agreement with a HPLC method. 相似文献
13.
Louise Aastrup Zimmer Gert Asmund Poul Johansen John Mortensen Benni Winding Hansen 《Polar Biology》2011,34(3):431-439
Long-term impact of former mining activities on the marine sub-Arctic ecosystem in the Ivittuut area, Arsuk Fjord, South Greenland,
was studied by transplantation experiments with the blue mussel Mytilus edulis. Measurements of metal concentration in mussels were conducted using atomic absorption spectrometry (flame AAS) and graphite
furnace atomic absorption spectrometry (graphite furnace AAS). Uptake and release of Pb were documented to be slow processes.
For mussels transplanted from the pristine Kugnait Bay to the polluted mining site at Ivittuut, a continuous accumulation
throughout the experiments was found. Linear uptake rates of 5.86, 6.94 and 11.62 μg Pb month−1 for small, medium and large mussels were found for a 6-week experiment, whereas exponential uptake rates of 0.26, 0.20 and
0.28 month−1 were found for a 9-month experiment. It is estimated that the transplanted mussels will reach the same level as the resident
population 12–16 months following transplantation. Mussels transplanted from the polluted mining site at Ivittuut to the pristine
Kugnait Bay depurated only 7–21% of their original Pb content, and the release was within the first 10 days following transplantation,
after which the Pb content remained constant. 相似文献
14.
Adsorption and decolorization kinetics of methyl orange (MO) by anaerobic sludge in anaerobic sequencing batch reactors were
investigated. The anaerobic sludge was found to have a saturated adsorption capacity of 36 ± 1 mg g MLSS−1 to MO. UV/visible spectrophotometer and high-performance liquid chromatography analytical results indicated that the MO adsorption
and decolorization occurred simultaneously in this system. This process at various substrate concentrations could be well
simulated using a modified two-stage model with apparent pseudo first-order kinetics. Furthermore, a noncompetitive inhibition
kinetic model was also developed to describe the MO decolorization process at high NaCl concentrations, and an inhibition
constant of 3.67 g NaCl l−1 was estimated. This study offers an insight into the adsorption and decolorization processes of azo dyes by anaerobic sludge
and provides a better understanding of the anaerobic dye decolorization mechanisms. 相似文献
15.
Proper determination of the temperature dependence of intrinsic tryptophan fluorescence intensity in native and denatured
states is an essential prerequisite for extracting the free energy of protein unfolding from the thermal denaturation profile.
The most common method employed in determining the temperature dependence of these conformations is through the determination
of slopes of pre- and post-transition baselines. However, simulations of protein unfolding profiles suggest that this method
does not work for marginally stable proteins. We show herein that the temperature dependence of the fluorescence intensity
of N-acetyl tryptophanamide (NATA) in organic solvents and water may be used to represent the temperature dependence of the fluorescence
intensity of tryptophan in native and denatured conformations of a protein, respectively. The wavelength of the emission maximum,
λ
max, of N-acetyl tryptophanamide (NATA) in a particular solvent or tryptophan in proteins is related to the temperature dependence
(m) of its fluorescence intensity by the equation: m (K−1) = (−0.000299 ± 2.2 × 10−5 K−1 nm−1) × λ
max (nm) + (0.0919 ± 0.0025 K−1). 相似文献
16.
This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast
of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km−2 year−1, with an overall area-weighted average of 1,870 kg N km−2 year−1. In 2002, the range of inputs was 490–10,875 kg N km−2 year−1, averaging 2,158 kg N km−2 year−1. Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km−2 year−1 (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km−2 year−1 (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken
at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km−2 year−1 (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated
with variations in streamflow (export = 0.94 × streamflow − 5.65, R
2 = 0.66), with N inputs explaining an additional 16% of the variance (export = 1.06 × streamflow + 0.06 × input − 227.78,
R
2 = 0.82). The percentage of N input that is exported averaged 12%. Percent export was also related to streamflow (%export = 0.05 × streamflow − 2.61,
R
2 = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes
that control watershed N export are not yet completely understood. 相似文献
17.
Tatjana Vujović Đurđina Ružić Radosav Cerović Gordana Šurlan Momirović 《Plant Growth Regulation》2010,61(3):265-275
Adventitious shoot regeneration from leaves of blackberry cultivar Čačanska Bestrna was examined using 30 different combinations
of treatment. Young, fully expanded leaves taken from in vitro proliferating shoots were cultured on Murashige and Skoog (MS)
medium containing either N
6-benzylaminopurine (BAP) (2.0 mg l−1) or thidiazuron (TDZ) (1.0 and 2.0 mg l−1) alone, or either of them combined with indol-3-butyric acid (IBA), α-naphthalene acetic acid (NAA) and 2,4-dichlorophenoxyacetic
acid (2,4-D) at different concentrations (0.1, 1.0 and 2.0 mg l−1). Indirect shoot formation was observed in 12 different treatments, though the efficacy varied greatly among types and concentrations
of plant growth regulators. TDZ at 1.0 mg l−1, applied either alone or combined with IBA, was significantly more effective than BAP in inducing shoot regeneration. The
highest regeneration rate (41.66%) was obtained on medium containing TDZ alone. Cytological, flow cytometry and isozyme analyses
were used for screening of genetic stability/instability in regenerants. Cytological study, based on chromosome counts in
root tip meristems, and flow cytometry analysis indicated that adventitious shoots of Čačanska Bestrna are tetraploid with
2n = 4x = 28 as well as those derived from axillary buds. However, a study conducted on the peroxidase patterns of the different
blackberry regenerating lines showed differences between some lines and control plants (in vivo plants and micropropagated
plants). These differences were visible with 3,3′,5,5′-tetramethylbenzidine (TMBZ) as hydrogenous donor for peroxidase detection. 相似文献
18.
O-Pentynyl dextran (PyD), an amphiphilic polysaccharide derivative with a degree of substitution (DS) of 0.43 was compared
with ion exchange resins Lewatit VP OC 1600, Amberlite XAD 761 and Duolite A568 for immobilization of Lipase from Rhizopus arrhizus by adsorption method. The immobilized enzymes were employed for esterification of octanoic acid with geraniol in n-hexane as model reaction. PyD showed higher lipase adsorption and with 249 μmol min−1 g−1 significant higher esterification activity than the other supports (67–83 μmol min−1 g−1). Biocatalysts from all types of supports except PyD became completely inactive within 8 weeks storing at −10 °C while lipase
immobilized on PyD retained its full esterification activity for at least 14 weeks. In repeated use, yield decreased rapidly
after two cycles for all supports except for PyD. For this biopolymeric support, constantly 90% yield was achieved even after
eight cycles, when the biocatalyst was washed with n-hexane and water and then freeze-dried. To achieve this yield, prolonged reaction times were required, partly on the account
of an increasing delay period, probably to adapt active conformation, until the reaction starts. 相似文献
19.
The bioelectrochemistry of the blue copper protein, pseudoazurin, at glassy carbon and platinum electrodes that were modified
with single-wall carbon nanotubes (SWNTs) was investigated by multiple scan rate cyclic voltammetry. The protein showed reversible
electrochemical behavior at both bare glassy carbon electrodes (GCEs) and SWNT-modified GCEs (SWNT|GCEs); however, direct
electrochemistry was not observed at any of the platinum electrodes. The effect of the carbon nanotubes at the GCE was to
amplify the current response 1000-fold (nA at bare GCE to μA at SWNT|GCE), increase the apparent diffusion coefficient D
app of the solution-borne protein by three orders of magnitude, from 1.35 × 10−11 at bare GCE to 7.06 × 10−8 cm2 s-1 at SWNT|GCE, and increase the heterogeneous electron transfer rate constant k
s threefold, from 1.7 × 10−2 cm s−1 at bare GCE to 5.3 × 10−2 cm s−1 at SWNT|GCE. Pseudoazurin was also found to spontaneously adsorb onto the nanotube-modified GCE surface. Well-resolved voltammograms
indicating quasi-reversible faradaic responses were obtained for the adsorbed protein in phosphate buffer, with I
pc
and I
pa
values now greater than corresponding values for solution-borne pseudoazurin at SWNT|GCEs and with significantly reduced
ΔE
p
values. The largest electron transfer rate constant of 1.7 × 10−1 cm s−1 was achieved with adsorbed pseudoazurin at the SWNT|GCE surface in deaerated buffer solution consistent with its presumed
role in anaerobic respiration of some bacteria. 相似文献
20.
Characterization of phosphorus fractions in the sediments of a tropical intertidal mangrove ecosystem 总被引:2,自引:0,他引:2
Solid phases of phosphorus fractions in the surface and core sediments were studied to understand the biogeochemical cycling
and bioavailability of phosphorus in the Pichavaram intertidal mangrove sediments of India. Total P in surface and core sediments
ranged between 451–552 and 459–736 μg g−1 respectively and Fe bound P was the dominant fraction. Low levels of Fe bound P in the mangrove zone than the two estuarine
zones may be because of high salinity inhibition of phosphate adsorption onto the Fe-oxides/hydroxides. Post-depositional
reorganization of P was observed in surface sediments, converting organic P and Fe bound P into the authigenic P. High levels
of organic P in the mangrove zone is primarily due to intensive cycling and degradation of organic matter and adsorption of
phosphate on the organic molecules. The burial rates and regeneration efficiency of P in the intertidal mangrove ecosystem
ranged from 5.41 to 7.27 μmol P cm−2 year−1 and 0.122 to 0.233 μmol P cm−2 year−1, respectively. High burial efficiency (≈99%) of P proves the earlier observation of limiting nature of P for the biological
productivity. Further, bioavailable P (exchangeable P + Fe bound P + organic P) constituted a considerable proportion of sedimentary
P pool of which an average accounted for 55 and 50% in surface and core sediments respectively. The results indicate that
significant amount of P is locked in sediments in the form of authigenic P and detrital P which makes P as a limiting nutrient
for the biological productivity. 相似文献