Phosphate Fractions Research Articles

Biologically induced precipitation in urine-collecting systems

Precipitation in urine-separating toilets (NoMix toilets), waterless urinals, and conventional urinals causes severe maintenance problems. Additionally, the partial fixation of nutrients in precipitates may affect the later use and treatment of source-separated urine. The goal of this study was to characterise the mineral composition of the precipitates and to identify the main causes for precipitation. X-ray diffraction analysis showed that the main crystalline compounds are struvite, hydroxyapatite, and calcite. We measured concentrations in the solutions of the traps and of the urine collection tank for estimating saturation indices, extent of urea degradation, urine dilution, and elimination of solutes. Our results indicate that bacterial urea degradation triggers precipitation. The composition of the precipitates depends on the urine dilution with flushing water: in low diluted urine, struvite is the main compound, while calcite dominates in systems with high urine dilution. HAP occurs over a wide range of dilution factors. A high fraction of phosphate is incorporated into the precipitates. Dilution with tap water increases this fraction by providing the limiting calcium and magnesium ions. Currently, constructing exchangeable traps seems to be the best solution to deal with problematic precipitation.

Individual and competitive adsorption of phosphate and arsenate on goethite in artificial seawater

Phosphate and arsenate adsorption on goethite was studied in single batch experiments at 25 °C upon the addition of Ca 2+, Mg 2+ and SO 4 2− to a 0.7 M NaCl solution at their respective seawater concentrations. Phosphate adsorption increases slightly in the presence of Mg 2+ and Ca 2+ and decreases at low pH upon the addition of SO 4 2−. The enhanced adsorption may result from the formation of ternary surface complexes. In contrast, arsenate adsorption is not affected by the addition of Mg 2+ or Ca 2+ to the 0.7 M NaCl solution. Similarly, phosphate adsorption in seawater is enhanced at neutral pH relative to 0.7 M NaCl, whereas arsenate adsorption is identical in both solutions except for a decrease at low pH in seawater. An equilibrium model derived by combining interaction parameters obtained from the single adsorbate subsystems predicts the phosphate and arsenate adsorption behaviours in the PO 4–SO 4–goethite and AsO 4–Ca–goethite systems very well but fails to accurately reproduce the adsorption data in the PO 4–Ca–goethite, PO 4–Mg–goethite, PO 4–seawater–goethite, AsO 4–Mg–goethite and AsO 4–seawater–goethite systems. The inclusion of ternary surface complexes in the latter systems improves model fits significantly at high pH. Experimental investigations of phosphate and arsenate competitive adsorption in seawater were also carried out. The fraction of phosphate adsorbed in the competitive experiments in seawater is identical to the results obtained in the 0.7 M NaCl solution, whereas arsenate adsorption is greater in seawater at pH>7. The difference in the extent of arsenate adsorption in both solutions is proportional to the initial amount of phosphate in solution. In competitive experiments in seawater, phosphate adsorption is underpredicted at pH<6.5, whereas arsenate adsorption is reproduced well using the constant capacitance model (CCM) with the inclusion of ternary surface complexes.

Sediment phosphate fractionation and interstitial water phosphate concentration in two coastal lagoons (Albuferas de Adra, SE Spain)

The concentrations of o-phosphate and dissolved inorganic carbon were monitored in the interstitial water of the sediment in two highly eutrophic coastal lagoons, Laguna Honda and Laguna Nueva (SE, Spain) from July 2000 to August 2001. Additionally, the organic matter concentration and the P-fractions in the sediment were analysed. Despite their proximity, these two lagoons showed many significant differences (P<0.05). The P-concentration in the interstitial water of the top sediment was higher in the Laguna Honda (up to 1 mg l−1), especially during summer, when both sites registered their highest values. By contrast, the concentration of organic matter and organic P-fractions were higher in the sediment of the Laguna Nueva. The concentration of the organic matter in the vertical profile of the sediment decreased with depth in the Laguna Nueva (from 17% at 0 cm to 7% at 15 cm, annual mean value) while it increased in the sediment of Laguna Honda (from 9% at 0 cm to 12% at 15 cm, annual mean value). The P-concentration in the interstitial water and the organic matter in the top sediment of Laguna Honda followed a seasonal pattern and, were both correlated with the temperature of the bottom water (r=0.706, P<0.05 and r= -0.929, P<0.01, respectively). The inorg-P fractions comprised 63% of the Tot-phosphate in the sediment of Laguna Honda, whereas org-P fractions (68%) dominated in the sediment of Laguna Nueva. The concentrations of Tot-P in the sestonic material collected at three different depths of the water column averaged 2.2 mg g−1d.w. in Laguna Honda and 2.5 mg g−1d.w. in Laguna Nueva. The average atomic C:P ratio of the sestonic material was significantly higher in Laguna Honda than in Laguna Nueva, but the top sediment in Laguna Nueva had a C:P ratio significantly higher than that of the sestonic material (average: 416 and 162, respectively).The different biodegradability of the organic matter in the top sediment probably explained the differences found in sediment composition between these two lagoons. We suggest that the P-reclying from the sediment to the interstitial water was faster in Laguna Honda due to the higher biodegradability of the organic matter. By contrast, the lower biodegradability of the organic matter in the top sediment of Laguna Nueva was probably due to a higher contribution of vascular plants which could explain the organic matter accumulation detected in this lagoon.

Substructure of bovine casein micelles by small-angle X-ray and neutron scattering

The casein micelles of cow’s milk are polydisperse, more-or-less spherical, protein particles of up to several hundred nanometer in size, containing about 7% by dry weight of calcium phosphate. Small-angle neutron scattering with contrast variation and small-angle X-ray scattering were used in critical tests of models of casein micelle substructure. An inflexion in the neutron scattering curve near Q � /0.35 nm � 1 was observed in heavy water which became a more pronounced subsidiary maximum at the match point of the protein. In water-rich buffers, where the contrast between protein and calcium phosphate is small, the inflexion was less apparent. The position of the inflexion and its variation in shape and relative importance with contrast matching are explained poorly, if at all, by the submicelle models of casein micelle substructure. However, the observations are explained by a model in which a relatively uniform protein matrix contains a disordered array of calcium phosphate ion clusters. A notable achievement of the model is the prediction of the position of the subsidiary maximum from independent measurements of the intrinsic viscosity of micelles, their mass fraction of calcium phosphate and the mass of the core of a calcium phosphate nanocluster. # 2002 Elsevier Science B.V. All rights reserved.

Role of calcium ions in rapid effects of L-thyroxine on phosphoinositide metabolism in rat liver cells.

The role of calcium ions in the L-thyroxine-induced initiation of hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdInsP2) and also the course of releasing individual fractions of inositol phosphates and diacylglycerides (DAG) were studied in liver cells during early stages of the hormone effect. L-Thyroxine stimulated a rapid hydrolysis in hepatocytes of PtdInsP2 labeled with [14C]linoleic acid and [3H]inositol mediated by phosphoinositide-specific phospholipase C. This was associated with accumulation of [14C]DAG, total inositol phosphates, [3H]inositol 1,4,5-trisphosphate (Ins1,4,5P3) and [3H]inositol 1,4-bisphosphate (Ins1,4P2). Elimination of calcium ions from the incubation medium of hepatocytes did not abolish the effect of thyroxine on the accumulation of [14C]DAG and total [3H]inositol phosphates. Preincubation of liver cells with TMB-8 increased the stimulatory effect of L-thyroxine on the accumulation of [14C]DAG. During the incubation of hepatocytes in the presence of the hormone the content of 14C-labeled fatty acids did not change. The L-thyroxine-induced accumulation of [3H]Ins1,4,5P3 and [3H]Ins1,4P2 did not depend on the presence of calcium ions in the incubation medium of the cells.

Uranium oxidation state and related variations in geochemistry of phosphorites from the Negev (southern Israel)

Study of the U(IV) fraction in Mishash phosphorites of the Negev reveals an apparently paradoxical trend. The U(IV) fraction is very low (less than 10%) in the pristine, organic-rich laminated phosphorites while this proportion considerably increases (up to 60%) in the recycled (mechanically reworked) granular phosphorites which deposited under more oxidizing conditions. This U(IV) trend seems to differ from that reported in other phosphate sequences elsewhere, and is also quite unexpected in view of the sediment patterns and the specific formational conditions of the two phosphorite facies. In addition, a lower %U(IV) in the analyzed granular phosphorites is coupled with a lower rare earth elements (REE)/P 2O 5 and Y/P 2O 5 ratio, a higher Cd and Zn concentration, less negative Ce (Ce/Ce*) and Eu (Eu/Eu*) anomalies, a lower HREE (Dy-Er) enrichment, and a lower F/P 2O 5 and higher CO 2/F ratio in francolites. This U(IV) trend in the two Negev phosphorite facies may be explained by varying time-spans of apatite growth, changes in sediment burial rates, and principally, different residence times of the phosphate fraction in the suboxic apatite-forming diagenetic zone near the sediment–water interface. The associated varying concentrations of REEs, Y, Cd and Zn in phosphorites and of F and CO 2 in francolites in the two granular phosphorite facies are apparently collectively regulated by the same sedimentary dynamics during phosphate deposition. It is presumed that the U(IV) trend observed in the Negev phosphorites could be detected in other phosphate sequences as well if pristine phosphorites are carefully identified and selectively analyzed.

An oxalate-binding protein with crystal growth promoter activity from human kidney stone matrix.

To fractionate renal-stone matrix proteins, identify the presence of oxalate-binding protein and assess its effect in a calcium oxalate (CaOx) crystal growth system. Proteins were isolated from the matrix of kidney stones containing CaOx as the major constituent, using EDTA as a demineralizing agent. The solubilized proteins were subjected to cellulose-column chromatography by eluting with increasing sodium chloride concentrations in Tris-HCl buffer. Three protein fraction peaks were eluted, i.e. fraction I in buffer, fraction II in 0.05 mol/L NaCl in buffer and fraction III in 0.3 mol/L NaCl in buffer. The protein fractions were tested for their effects on CaOx crystal growth. All three fractions had maximum CaOx binding activity at pH 7.4 but fraction II also had activity at pH 4.5. Fraction I promoted in vitro CaOx crystal growth, while fractions II and III were inhibitory. When fraction I was further separated on a Sephadex G-200 column, two protein fractions (Ia and Ib) were obtained. Fraction Ia protein had high and fraction Ib low CaOx-binding activity. Fraction Ia had a molecular weight of 48 kDa on gel electrophoresis and Western blotting. The 48 kDa protein did not cross-react with crystal matrix protein antibody, band-3 protein antibody, or albumin. The protein promoted CaOx crystal growth, with an optimum temperature of 37 degrees C and pH 6.5. The inhibitory effect of citrate on crystal growth was significantly lower in the presence of the 48 kDa protein. The protein promoted nucleation and aggregation of CaOx crystals in the in vitro crystallization system at pH 6.5, whereas fraction Ib (29 kDa) inhibited both nucleation and aggregation. Using the 48 kDa antibody, the yield of the protein from the stone matrix was 32% by EDTA extraction and only 3% with other methods. The protein was also detected in the nucleus and mitochondria, and in other matrix fractions of calcium phosphate and uric acid stones. The 48 kDa protein isolated from stone matrix is a potent promoter of CaOx crystal growth with high oxalate-binding activity; it is enriched in the nucleus and mitochondria.

Synthesis of [14C]‐ and [35S]‐labelled PI‐88 for pharmacokinetic and tissue distribution studies

AbstractPI‐88, uniformly labelled with [14C] was prepared by incorporating D‐[14C]glucose into the fermentation of Pichia (Hansenula) holstii NRRL Y‐2448 under controlled conditions to produce [14C]‐labelled extracellular phosphomannan. Subsequent acid catalyzed hydrolysis gave the [14C]‐labelled oligosaccharide phosphate fraction which was sulfonated with excess sulfur trioxide pyridine complex to give [14C]PI‐88. [35S]‐labelled PI‐88 was similarly prepared by the sulfonation of unlabelled oligosaccharide phosphate fraction with [35S] sulfur trioxide pyridine complex. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Phosphorus mobilization in hybrid rice rhizosphere compared to high yielding varieties under integrated nutrient management

Soil phosphomonoesterase enzyme activities and phosphate fractions from rhizosphere soils were studied at maximum tillering and panicle initiation stages for three hybrid and two inbred high yielding varieties of rice in a pot culture net-house experiment receiving green manure (Sesbania) and farmyard manure. The P mobilization pattern under integrated nutrient management was also studied. Pusa RH21, a hybrid rice cultivar, showed higher soil alkaline phosphomonoesterase activities, higher plant biomass yield and more P uptake than other cultivars. Under different fertilizer treatments, higher plant biomass and soil phosphomonoesterase (both acid and alkaline) activities at panicle initiation stage of the crop were observed in the green-manure-applied pots. Among the enzymatic activities that were compared, alkaline phosphomonoesterase activity at panicle initiation stage was found to be most significantly correlated to plant biomass yield and P uptake. Selection for this property may be used in rice hybridization programmes to develop better P-efficient cultivars.

Generality of Solvation Effects on the Hydrolysis Rates of Phosphate Monoesters and Their Possible Relevance to Enzymatic Catalysis

Previous work by Kirby and co-workers revealed a significant acceleration of the rate of hydrolysis of p-nitrophenyl phosphate by added dipolar solvents such as DMSO. Activation parameters and kinetic isotope effects have been measured to ascertain the origin of this effect. The generality of this phenomenon was examined with a series of esters with more basic leaving groups. Computational analyses of the effects of desolvation of dianionic phosphate monoesters were carried out, and the possible effect of the transfer from water to the active site of alkaline phosphatase was modeled. The results are consistent with a desolvation-induced weakening of the P-O ester bond in the ground state. Other aryl phosphate esters show similar rate accelerations at high fractions of DMSO, but phenyl and methyl phosphates do not, and their hydrolysis reactions are actually slowed by these conditions.

Effect of traditional, microwave and industrial cooking on inositol phosphate content in beans, chickpeas and lentils

An high-performance liquid chromatography method for determining inositol phosphate fractions was adapted to legumes. The validity of the method was assessed by estimating the following analytical parameters: linearity (linear response between 125 and 5000 μ g inositol hexaphosphate (IP6)/ml); instrumental precision and method precision (relative standard deviation, %) were 1.9% (IP6) for instrumental, and 2.5% (IP6) and 8.2% (IP5) for method precision. An accuracy was estimated by percentage recovery (72 ± 3%). The application of this method to raw, conventional, microwave-cooked and ready-to-eat beans, chickpeas and lentils gave IP 6 contents ranging from 0.63 g/100 g dry matter in ready-to-eat lentils to 1.87 g/100 g dry matter in raw beans. The IP6 content was reduced by all the cooking procedures, while the relative percentage of inositol pentaphosphate increased in all the legumes studied, and reached the maximum of 31% (expressed in relation to dry matter) in ready-to-eat beans.

Determination of the composition of the oligosaccharide phosphate fraction of Pichia ( Hansenula) holstii NRRL Y-2448 phosphomannan by capillary electrophoresis and HPLC

The promising new anticancer agent, PI-88, is prepared by the sulfonation of the oligosaccharide phosphate fraction of the extracellular phosphomannan produced by the yeast Pichia ( Hansenula) holstii NRRL Y-2448. The composition of the oligosaccharide phosphate fraction was determined by capillary electrophoresis (CE) with indirect UV detection using 6 mM potassium sorbate at pH 10.3 as the background electrolyte. Further confirmation of the composition was obtained by HPLC analysis of a sample dephosphorylated by treatment with alkaline phosphatase. The structure of the hexasaccharide component has been determined by isolation and NMR spectroscopic analysis of its dephosphorylated derivative. Additionally, the structure of a second, previously undetected tetrasaccharide component (a hexosamine) has been determined by isolation and NMR spectroscopic analysis of the acetate of its dephosphorylated derivative. It is demonstrated that CE is an ideal method for the quality control of the oligosaccharide phosphate fraction for use in the production of PI-88.

On the reconstruction of upwelling history: Namibia upwelling in context

Eastern boundary upwelling is an important aspect of the modern ocean, despite the relatively small area involved. Consequences of increased upwelling during the Neogene, as a result of intensifying trade winds, include increased heat transport by the ocean, increased mixing, increased fractionation of phosphate from silicate, and opportunities for evolution of new species. Coastal upwelling has been studied since the first decade of the 20th century. The processes involved are complex, and differ depending on geographic setting. Off Namibia, upwelling history has been studied by a number of drilling expeditions; the last of these was ODP Leg 175, which occupied seven sites on the continental slope between Walvis Ridge and Cape Town, during September and October of 1997. Productivity proxies all along southwestern Africa suggest the presence of increased upwelling and organic matter supply to the sea floor during glacial periods. At the same time, there is a decrease in the supply of diatoms and other siliceous plankton remains. This is the Walvis Opal Paradox, established through the contrasting results of studies by Diester-Haass (1985) and Oberhänsli (1991). We propose that the Walvis Opal Paradox is fundamental to the understanding of glacial–interglacial productivity fluctuations on a global scale. Furthermore, a central feature of the history of late Neogene upwelling off Namibia is the Matuyama Opal Maximum, centered between Gauss and Olduvai magnetic chrons [Wefer et al., Proc. ODP 175 (1998)]. It is due to the fact that diatom supply first increases (during the Gauss) when the planet cools and then decreases again during additional cooling, on entering the Quaternary. On a 400 000-year scale, peak productions are coincident with (or slightly lag) maximum seasonal contrast potential in the high-latitude insolation curve. We suggest that this is further evidence that the nutrient content of thermocline waters was diminished during glacial periods. The reasons why this should be so remain to be discovered.

Diagenetic trends of fluorine concentration in Negev phosphorites, Israel: implications for carbonate fluorapatite composition during phosphogenesis

An electron probe and chemical study of bulk phosphorite samples and separated constituents from various Negev deposits was carried out together with XRD, FTIR spectroscopy and textural analysis. The results allow a better understanding of the distribution of fluorine in these Upper Cretaceous phosphorite sequences and shed light on variations in the composition of the carbonate fluorapatite (CFA) phase during phosphogenesis. Two facies are recognized: (1) a pristine, microbially generated phosphorite facies; (2) a recycled, peloidal and biodetrital facies. Fluorine distribution in the Negev phosphorites is facies controlled: F/P2O5 is much lower in the pristine facies (0·090–0·107) than in the recycled facies (0·107–0·120). In addition, F/P2O5 varies considerably between the various constituents of the phosphate fraction; F‐poor francolites (F/P2O5 as low as 0·080) co‐exist with F‐rich francolites (F/P2O5 as high as 0·135) in the same phosphorite bulk sample. A lower F/P2O5 in francolite is associated with higher Cd and Zn concentrations in the phosphorite, an increase in Fe‐rich smectites in the clay fraction and the presence of structural OH in the francolite. The lower F/P2O5 ratios in the pristine facies are attributed to high organic deposition rates during the formation of these matted sediments, leading to rapid burial of the in situ‐forming CFA. This is possibly coupled with diffusion of F from sea water into bottom sediments being hampered by microbial mat coatings. These conditions resulted in O2‐depleted porefluids, inducing the precipitation of Cd‐rich Zn sulphides and the formation of Fe‐rich smectites. F‐enrichment probably takes place when the earlier formed F‐poor ‘primary’ CFA is relocated close to the sea floor and bathed with interstitial sea water solutions of higher F concentrations. Oxidation and removal of the sulphide‐bound Cd and Zn apparently occurred together with enrichment in F of the francolite. Combining chemical data with XRD and FTIR results suggests a multistage growth for the Negev phosphate constituents in shifting formational sites and porefluids of varying F concentrations. This multiphase growth is reflected in the patchy distribution of F in the Negev constituents and might explain the inverse correlation between mean CO2/F and F/P2O5 ratios of the analysed phosphorites in the two facies. It also suggests that CFA (or an amorphous precursor) initially formed with some OH groups in the apatite structure, which were subsequently substituted by F ions in recycled francolite through re‐equilibration with porefluids of higher F concentrations.

Phosphorus Availability in an Artificially Flooded Southeastern Floodplain Forest Soil

Studies of how flooding affects P availability in natural floodplains are rare. We examined the effects of artificial flooding on P availability in a Georgia floodplain forest. We hypothesized that P availability would increase with flooding, because of the flooding‐induced solubilization of phosphate minerals. Field mesocosms (n = 4 per treatment) were flooded with river water according to one of four treatments over ∼6 mo: (i) continuously flooded; (ii) flooded for 3 mo and then drained; (iii) flooded for 2 mo, drained for 1 mo, and repeated; and (iv) nonflooded control. Two additional sets of 3‐mo flooded–drained mesocosms (n = 4 per set) received added P or N (1 and 10 mg L−1, respectively) with flooding. Soils were collected monthly from both inside and outside of the mesocosms and analyzed by Hedley fractionation; anion‐exchange resins (AER) were used to estimate P availability in situ. As indexed by daily supply to AER, P availability was significantly greater in flooded versus control soils, and decreased significantly following drainage, in all treatments at some time during the study. Total P supply to AER was significantly greater in flooded versus control mesocosms regardless of treatment. No significant changes were observed in Fe/Al phosphate fractions. Microbial P was significantly lower in flooded versus control mesocosms during the first 3 mo of flooding and decreased significantly over time in two treatments. In this natural floodplain, biological processes are a more probable explanation for flooding‐induced increases in P availability than solubilization of mineral phosphates.

Fractionation and bioavailability of phosphates in lacustrine sediments: a review

Fractionation and bioavailability of phosphates in lacustrine sediments: a review

Large-scale preparation of the oligosaccharide phosphate fraction of Pichia holstii NRRL Y-2448 phosphomannan for use in the manufacture of PI-88

Mild acid-catalysed hydrolysis of the extracellular phosphomannan of the yeast Pichia holstii NRRL Y-2448 produces a high-molecular-weight phosphomannan core, a low-molecular-weight oligosaccharide phosphate fraction, and a neutral oligosaccharide fraction. A method was developed for the large-scale preparation of the oligosaccharide phosphate fraction, consisting predominantly of the pentasaccharide phosphate, 6- O-PO 3H 2-α- d-Man-(1→3)-α- d-Man-(1→3)-α- d-Man-(1→3)-α- d-Man-(1→2)- d-Man, for use in the manufacture of the promising new anti-cancer agent, PI-88. Further insights were also gained into the structure of the phosphomannan by HPLC analysis of the time course of the hydrolysis reaction.

Interações silício-fósforo em solos cultivados com eucalipto em casa de vegetação

Este trabalho teve o objetivo de avaliar as interações Si-P em dois solos, por meio do estado nutricional de P em mudas de Eucalyptus grandis sob efeito de aplicação de Si. Foram conduzidos dois experimentos em casa de vegetação, utilizando como substratos as camadas superficiais (0-20 cm de profundidade) de um Latossolo Vermelho-Escuro fase cerrado e de um Cambissolo fase campo cerrado da zona fisiográfica Campos das Vertentes, MG . Cada solo foi submetido a três incubações seqüenciais: CaCO3 + MgCO3 para manter o pH em torno de 6, fertilização básica, incluindo o P em dose única, para manter 0,2 mg L-1 de P em solução e seis doses de Si (CaSiO3) definidas com base na dose de P. Foram avaliados a produção de matéria seca da parte aérea (MSPA), conteúdo de P e Si na MSPA e frações fosfatadas e fosfatase ácida em folhas apicais aos 60, 90 e 120 dias após o transplantio das mudas para os vasos. Ajustaram-se superfícies de resposta para essas variáveis em razão das doses de Si e das épocas. Mudas cultivadas no Cambissolo tiveram ganho de 15,25% no conteúdo de P na MSPA. Frações fosfatadas e atividade da fosfatase ácida em plantas não mostraram sensibilidade para avaliar a interação Si-P nos dois solos.

The occurrence and behaviour of phosphate fractions in Izmir Bay, Aegean Sea

The area around Izmir Bay (Turkey) is heavily urbanized and receives, therefore, high concentrations of phosphate originating from industrial and municipal inputs. During the surveys between April 1993 and July 1994, the total phosphate concentrations were highest in the Inner Bay (6.45 μM and 5.59 μM in the surface and bottom water, respectively) where very dense anthropogenic pollution occurs. The total phosphate value gradually decreased towards the Outer Bay where 0.70 μM and 1.18 μM were found in the surface and bottom water, respectively. The distribution of dissolved inorganic, dissolved organic and particulate phosphate along the bay reflected some peculiar spatial and temporal patterns. A high percentage of dissolved organic phosphate was observed in the Outer Bay while the particulate phosphate peaked in the Middle Bay where an upwelling mechanism was observed. In the bay, the biological production was strongly correlated with the variations in the dissolved inorganic, organic and particulate phosphate. The high phosphate concentration in particles caused the particulate phosphate formed in the Inner Bay to be transported to the outer parts of the bay because of the short water residence time. On the other hand, Principal Component Analysis showed that about 35% of the variation in all variables measured were related to the total phosphate, total dissolved phosphate, dissolved inorganic phosphate and particulate phosphate together with ammonium and reactive-Fe while about 14% of the variation was related to the dissolved organic phosphate and the number of phytoplankton cells, chl-a, pH and O2.

Crescimento inicial, níveis críticos de fósforo e frações fosfatadas em espécies florestais

Foi conduzido um experimento em casa de vegetação, com o objetivo de avaliar o crescimento de plântulas, os níveis críticos de P e algumas frações fosfatadas, em três espécies florestais submetidas a quatro doses de P. Mudas de aroeirinha (Schinus terenbinthifolius Raddi), paineira (Chorisia speciosa St. Hill.) e jambolão (Syzygium jambolanum Lam.) foram cultivadas em um Latossolo Variação Una, onde foram aplicados 0, 150, 300 e 600 mg dm-3 de P. Aos 180 dias após a germinação, as plantas foram colhidas e submetidas às análises químicas. Sob todas as doses de P, a paineira produziu maior biomassa da parte aérea e das raízes em comparação à aroeirinha e jambolão, além de apresentar maiores teores de P orgânico (Po) e maior participação relativa do P orgânico (Po) em relação ao P total solúvel em ácido em todos os níveis de fertilização fosfatada. O melhor crescimento da paineira foi atribuído a uma maior eficiência nos ajustes metabólicos desta espécie em relação à nutrição fosfatada, o que indica que esta espécie pode ser plantada em solos com diferentes níveis de P.