Phosphate Enrichment Research Articles

Method for phosphate oxygen isotopes analysis in water based on in situ enrichment, elution, and purification

The phosphate oxygen isotope (δ18OP) ratio has been proven to be an effective tool to trace the sources and biogeochemical cycles of phosphorus (P) in aquatic ecosystems. However, the enrichment of phosphate (PO4) and the removal of impurities are quite complex and easy to cause PO4 loss in current δ18OP analytical methods. Moreover, the δ18OP value obtained by the commonly-used instantaneous sampling method is more of the instantaneous information of P, which is accidental or uncertain for accurate identification of the P source. In this study, a new method of in situ enrichment, elution, and purification of PO4 (ISEEP) was developed for δ18OP analysis in waters. This method utilized a PO4 binding phase (Zr-Oxide gel) to selectively in situ adsorb PO4 in water and exhibited an adsorption capacity per unit area of up to 789.3 μg P/cm2. The PO4 on the gel was eluted easily with a 1 M NaOH solution. More than 99.7% of the common anions, cations, and dissolved organic matter (DOM), as well as more than 90% of the trace elements were removed synchronously after adsorption and elution of PO4. The recovery rate of PO4 in the whole procedure was as high as 92.8%. The XRD and SEM examinations showed that the ISEEP can obtain high-purity Ag3PO4 solid for the δ18OP measurement. The reliability of the ISEEP method is confirmed by the measured δ18OP value and standard deviation of parallel samples from different types of natural waters obtained by both the ISEEP and the current popular McLaughlin (2004) method. It provides a good prospect of this new method for tracing the P sources and their biogeochemical cycling in aquatic ecosystems.

Impact of aerobic availability of readily biodegradable COD on morphological stability of aerobic granular sludge

Operational disturbances in aerobic granular sludge (AGS) systems can result in aerobic availability of readily biodegradable COD (rbCOD). Different from activated sludge, morphological consequences on the short and long term are not well described in literature. This study investigated the effect of incomplete anaerobic uptake of acetate on the morphological and process stability of AGS using a lab-scale reactor. A fraction of the total acetate load was dosed aerobically, which was increased stepwise while monitoring granular morphology. A good granular morphology and an SVI of 40 ml/g were obtained during initial enrichment and maintained for ≤20% aerobic acetate load dosed at 4 mg COD/g VSS/h. Biological phosphorus removal efficiency was initially unaffected, but the aerobic acetate dosage rate did decrease the aerobic phosphate uptake rate. This led to loss of phosphorus removal for >20% aerobic acetate load dosed at 8 mg COD/g VSS/h over the course of 12 days. Subsequently, significant outgrowth formed on the granular surfaces and developed over time into finger-like structures. Under these high aerobic acetate loads the SVI increased to 80 ml/g and resulted in significant biomass washout due to deteriorating settling properties of the sludge. The sludge settleability and biological phosphorus removal recovered 10 days after aerobic feeding of acetate was stopped. Aerobic presence of rbCOD can be tolerated if mostly anaerobic acetate uptake is maintained, thereby ensuring stable granular morphology and good settleability. The high enrichment of phosphate accumulating organisms in the granular sludge through bottom-feeding and selective wasting of flocs makes aerobic granular sludge resilient to morphological deterioration in aerobic presence of rbCOD.

Diammonium Phosphate and Sucrose Enrichment on Fermentation for Anti-bacteria Activity by Lactic Acid Bacteria

Diammonium Phosphate and Sucrose Enrichment on Fermentation for Anti-bacteria Activity by Lactic Acid Bacteria

A hidden sedimentary phosphate pool inside benthic foraminifera from the Peruvian upwelling region might nucleate phosphogenesis

Phosphorus is essential for all living organisms, being a component of DNA and RNA and the energy carrier ATP. Phosphogenesis is a main sink of reactive phosphorus in the oceans. The present study reports the presence of intracellular dissolved inorganic phosphate (DIP) in benthic foraminifera from the Peruvian oxygen minimum zone (OMZ). The mean intracellular DIP concentration was 28 ± 3 mM; two to three orders-of-magnitude higher than in the ambient pore waters. The biological implications of the high intracellular phosphate enrichment may be related to the synthesis of polyphosphates or phospholipids for cell-membranes. The comparative genomics analysis of multiple species of foraminifera from different environments reveals that foraminifers encode the genes required for both phospholipid and polyphosphate metabolism. Rapid phosphogenesis and phosphorite formation associated with foraminiferal tests is hypothesized due to the pre-concentration of intracellular phosphate in these organisms. The results indicate that foraminifera may play a key and previously overlooked role in the global phosphorus cycle.

Apatite-glaucony association in the Ediacaran Doushantuo Formation, South China and implications for marine redox conditions

Major phosphogenic events took place in the late Paleoproterozoic and the Ediacaran, both of which followed an episode of atmospheric oxygenation. These apparent coincidences have led to suggestions that the Precambrian phosphorus cycle was partly regulated by oceanic redox conditions, although direct evidence is lacking. In this paper, we report the discovery of glaucony in drill cores from the phosphorite-rich Ediacaran Doushantuo Formation at Weng'an, South China, which provides new insights into redox conditions and geochemical cycles during the deposition and early diagenesis of the lower Doushantuo Formation. The presence of flaser and lenticular bedding in the sandstones suggests deposition in a tidally-influenced shallow water environment. Apatite is present as millimeter-scale flasers in sandstones, but more commonly as intraclastic grains. Glaucony typically occurs as interstitial aggregates cementing and replacing detrital minerals and phosphatic grains, with an upsection decrease in abundance. The Doushantuo glauconies have consistently high K2O (7.5–9.6 wt%). In particular, phosphorite-hosted glaucony has generally higher total iron (TFe2O3) than sandstone-hosted glaucony, consistent with Al3+–Fe3+ substitution in the octahedral site, as supported by Raman peaks slightly shifted towards lower wavenumbers for higher Fe content. A decrease in detrital input probably resulted in limited Al availability during early diagenesis, which in turn led to the waning of glaucony upsection. The phosphate grains do not show any negative Ce anomalies, consistent with precipitation of authigenic apatite in suboxic environments with insignificant preferential remobilisation of Ce during deposition and early diagenesis. REE + Y features show variable diagenetic REE enrichment in phosphorites, but identical concave-down patterns. The wide occurrence of glaucony cement further documents the presence of a generally suboxic early diagenetic environment on the seafloor, which was in active exchange with bottom seawater. Slight fluctuations of redox states in the porewater and bottom water would have promoted the cycling of Fe, enrichment of phosphate and REE, and extensive glaucony authigenesis. Therefore, the glaucony-bearing phosphorites in the Doushantuo Formation are a direct result of Fe-redox driven diagenesis. Apatite-glaucony association likely forms in suboxic environments and is considered as a useful mineralogical proxy for paleoredox conditions on the Precambrian ocean floors.

Symbiont transmission and reproductive mode influence responses of three Hawaiian coral larvae to elevated temperature and nutrients

Elevated temperatures and nutrients are degrading coral reef ecosystems, but the understanding of how early life stages of reef corals respond to these stressors remains limited. Here, we test the impact of temperature (mean ~ 27 °C vs. ~ 29 °C) and nitrate and phosphate enrichment (ambient, + 5 µM nitrate, + 1 µM phosphate and combined + 5 µM nitrate with 1 µM phosphate) on coral larvae using three Hawaiian coral species with different modes of symbiont transmission and reproduction: Lobactis scutaria (horizontal, gonochoric broadcast spawner), Pocillopora acuta (vertical, hermaphroditic brooder) and Montipora capitata (vertical, hermaphroditic broadcast spawner). Temperature and nutrient effects were species specific and appear antagonistic for L. scutaria and M. capitata, but not for P. acuta. Larvae survivorship in all species was lowest under nitrate enrichment at 27 °C. M. capitata and L. scutaria survivorship increased at 29 °C. However, positive effects of warming on survivorship were lost under high nitrate, but phosphate attenuated nitrate effects when N/P ratios were balanced. P. acuta larvae exhibited high survivorship (> 91%) in all treatments and showed little change in larval size, but lower respiration rates at 29 °C. Elevated nutrients (+N+P) led to the greatest loss in larvae size for aposymbiotic L. scutaria, while positive growth in symbiotic M. capitata larvae was reduced under warming and highest in +N+P treatments. Overall, we report a greater sensitivity of broadcast spawners to warming and nutrient changes compared to a brooding coral species. These results suggest variability in biological responses to warming and nutrient enrichment is influenced by life-history traits, including the presence of symbionts (vertical transmission), in addition to nutrient type and nutrient stoichiometry.

Evaluation of Present Lake Environment from Geochemistry of Bottom Sediment of Hartbeespoort Dam, North-West Province, South Africa

Present Lake Environment of Hartbeespoort Dam was evaluated from Geochemistry of bottom Sediment. Ten (10) bottom sediment samples were collected across the entire Lake. The geochemical composition of the sediment samples was determined using X-ray fluorescence (XRF); trace and major elements determined includes As, Pb, Zn, Cu, Ni, Cr, Fe 2 O 3 , TiO 2 , MnO, CaO and P 2 O 5 . The trace elements concentrations of the sediment were grouped into three zones base on their spatial distribution. The Western zone of the lake shows a remarkable enrichment in Nickel (Ni) and Chromium (Cr) and could be associated with geogenic source. However high enrichment of phosphate (P 2 O 5 ) observed in the same zone could be attributed to anthropogenic source, due to agricultural activities on the catchment of Magalies River. Moderate enrichment of As, Zn, Cu, Cr and Pb was recorded in the central zone and could be ascribed to entrapment by fine-grained organic and Fe-rich clay deposit in the central part of the lake; this was showcased by the strong positive correlation between the trace elements and Fe 2 O 3 . As, Zn, Pb and Cu were highly enriched in the South – Eastern zone and anthropogenic source could be responsible for the enrichment due to the influence of the Crocodile River. The average concentration of As, Pb, Zn, Cu, Ni and Cr in the sediment were evaluated by comparison with the upper continental crust (UCC), Shale standard (Turekian and Wedepohl, 1961) and Sediment quality guidelines (SQG); the result indicates that As, Pb, Zn, Cu and Cr in the study area were above the lowest effect level (LEL) but below the severe affect level (SEL) which shows that the impact on biota is moderate. However, Nickel (Ni) was above the severe effect level and could therefore have severe effect on the aquatic environment. Keywords: aquatic environment, Bottom Sediment, Heavy Metals, Hartbeespoort Dam, X-ray fluorescence DOI : 10.7176/JEES/9-11-10 Publication date: November 30 th 2019

Phosphatic alteration of lead-rich glazes during two centuries of burial: Bartlam, Bonnin & Morris, and Chelsea porcelain

Discolored lead-rich glazes on phosphatic porcelain sherds from the sites of the Bartlam (Cain Hoy, SC), Bonnin & Morris (Philadelphia, PA), and Chelsea (London, UK) factory sites record the effects of alteration after two centuries of burial. The alteration presents as a dark brown to black scale on the American samples, and as pale brown crazing of the Chelsea glaze. Backscattered electron images of this material show the development of Liesegang rings and a sharp corrosion boundary where in contact with (relatively) unaltered glaze material. Compared with their unaltered counterparts, the altered glazes are variably but in some instances massively (≥ 90%) depleted in SiO2 and alkalis, and enriched in P2O5, CaO, PbO, and various trace elements, notably V. Some of the Bonnin & Morris samples have had bone ash components—especially CaO—leached from the now-porous phosphatic paste, so their CaO/P2O5 (molecular proportions) ratios (~ 2) are much lower than those of the relatively unaltered Bonnin & Morris samples (3.1–3.5). The ceramic body is not, however, the source of phosphate (and calcium) enriched in the altered glazes because phosphate enrichment characterizes glaze alteration even when there is no evidence of bone ash dissolution. Anthropogenic sources are likely for this and other components enriched in the altered glazes. Glaze alteration is interpreted in terms of leaching (de-alkalization) and silica-network dissolution in the presence of subsurface alkaline aqueous fluids (pH ≥ 9). Unaltered glazes on both creamware and phosphatic porcelain sherds from Cain Hoy have overlapping trace element concentrations, supporting the hypothesis that John Bartlam manufactured porcelain there, despite the apparent absence of biscuit wasters at this site.

Effects of Aerobic Carbon Sources on Biofilm with Simultaneous Phosphate Removal and Enrichment

In a cyclic alternating O/A operation mode, phosphorus accumulating organisms (PAOs) can undertake phosphate removal and enrichment as the main process in wastewater treatment plants. The effects of the concentration of carbon sources during the aerobic stage on phosphate removal and enrichment performance of PAO biofilms, and the microbial population structure in the biofilms, were investigated. The results showed that the aerobic COD concentration decreased from 200 mg·L-1 to 0 mg·L-1, the phosphorus uptake rate improved by 1.29 times, the phosphorus concentration in effluent stabilized below 0.5 mg·L-1, the phosphorus release rate increased by 3.56 times, and the phosphate concentration in the circulating solution increased from 27.125 mg·L-1 to 55.91 mg·L-1. With respect to the change in microbial communities, the identification showed that the abundance of Proteobacteria increased by approximately two times, and the enrichment effects of Rhodocyclaceae and Anaerolineaceae increased by 2.28 and 5 times, respectively. Reducing the concentration of the carbon source in the aerobic section was beneficial to the screening and enrichment of PAOs, strengthening the removal of phosphate in the aerobic section and the release of phosphate in the anaerobic section. This resulted in an enriched phosphate solution. These observations provide a theoretical basis for future urban sewage treatment plants seeking to reduce their carbon demand.

The transformation of α-(Al, Fe)OOH in natural fire: Effect of Al substitution amount on fixation of phosphate

The transformation of Al-substituted goethite in oxidative and reductive atmosphere, which models natural fire, was investigated in detail. Various characterization results indicated that Al-substituted goethite transformed into hematite in an oxidative atmosphere and magnetite followed by zero-valent iron in a reductive atmosphere. Interestingly, the substitution of Al for Fe not only changed the crystal morphology affecting crystal surface reactivity, but also restrained the transformation of goethite into hematite, magnetite and zero-valent iron. In addition, the Al in the goethite was embedded into the crystal structure of thermally formed hematite and magnetite, considerably influencing their surface reactivity. The macroscopic adsorption results indicated that the substitution of Al for Fe increased the adsorption capacity of goethite and the corresponding derivatives except zero-valent iron. For the same Al amount, the adsorption capacity followed an order of goethite > hematite > magnetite, implying a loss of phosphate in goethite-rich soil after experiencing natural fire. However, with increasing in temperature in the reductive atmosphere, Al-magnetite transformed into a mixture of Al-magnetite and zero-valent iron which displayed excellent phosphate adsorption capacities increasing to 1.21–5.96 mg/g. The phosphate adsorption behaviors to thermally formed products were fitted well by surface complexation modeling with five complexation sites, which were more obvious for goethite than for hematite and magnetite. These findings presented in this study represent significant progress toward an understanding of the migration, enrichment and transformation of phosphate in Al-substituted goethite-rich soil in cases experiencing natural fire.

A novel platform based on gold nanoparticles chemically impregnated polyurethane foam sorbent coupled ion chromatography for selective separation and trace determination of phosphate ions in water

The sorption characteristics of phosphate ions from aqueous molybdate solution of pH ≤ 2 onto malachite green (MG) impregnated thiophenol (TP) functionalized Au nanoparticles based polyurethane foam (PUF) solid platform (MG-AuNPs-treated PUF) was studied. Phosphate uptakes followed Langmuir and Freundlich models. Based on the retention profile, a dual mechanism involving a “weak base anion exchanger i.e. solvent extraction” and a “surface adsorption” of phosphate retention as complex ion associate {[MG]+.[H2PMo12O40]−}PUF is anticipated. Complete retention of phosphate at various concentrations (0.01–100.0 μg mL−1) onto the sorbent packed column at 3–5 mL min−1 flow rate was achieved. A highly sensitive strategy for enriching, quantitative recovery and trace determination of phosphate in water using the sorbent packed column was developed. Under the optimized parameters, a linear concentration range of 0.07–25 μg L−1 and limits of detection (LOD) and quantification (LOQ) of 0.02 and 0.07 μg L−1 phosphate were achieved, respectively. The proposed and reference methods for analysis of phosphate in water samples were subjected to statistical treatment (student's t and F tests) at 95% confidence with no significant difference indicating the precision and accuracy of the proposed assay. The settled sorbent in flow mode was robust sufficient to be reused for five times without significant decrease in its performance. The intraday repeatability and interday stability of the established sorbent packed column towards phosphate (10.0 μg L−1) determination was studied. An estimated coefficient of variation less than ±5% was achieved revealing the suitably of the modified PUFs in column mode. The established column enabled multiple enrichment of phosphate from water and expanded the range of phosphate level which can be determined in water.

Enrichment and Biopelletization of Phosphate Solubilizing Diazotrophic Bacterial Isolates Using Earthworm as a Tool

Aims: The beneficial role of earthworm Eudrilus eugeniae in enhancing the populations of two phosphate solubilizing diazotrophic isolates viz., Bacillus sp. (DT) and Azotobacter chroococcum (DT), isolated from the rhizosphere of finger millet [Eleusine coracana (L) Gaertn] was studied.
 Place and Duration of Study: The experiments were conducted at the campus of M/s. Chaitra Biofertilizers and Chemicals (P) Ltd, Mysore, between January – June 2018.
 Methodology: To the glass jars containing three week old partially decomposed green leafy material and cow dung, 0.5 gram of lignite based phosphate solubilizing diazotrophic isolates were added. To this eight medium sized earthworms were allowed and moisture is maintained at 50-60%. The population of isolates in the gut of earthworm and vermicasts were estimated on 2nd, 20th, 40th and 60th day by dilution plate method using Pikovskaya’s and Jensen’s agar medium
 Results: The population of Bacillus sp. (DT) and A. chroococcum (DT) increased by 22.14, 42.14 and 97.62 percent in the fore gut, mid gut and hind gut regions respectively while A. chroococcum (DT) by 24.05, 41.19 and 110.95 percent as compared to their initial population in the feeding material. Both the isolates increased enormously in the vermicasts up to 40th day and thereafter declined as recorded in 60 days old vermicasts. Bacillus sp. (DT) increased by 196.91 and 247.16 percent in 20 and 40 day old vermicasts and decreased by 54.72 percent on 60th day while A. chroococcum (DT) recorded an increase of 217.34 and 270.77 percent and thereafter declined by 41.18 percent in 60 days old casts.
 Conclusion: The earthworm can be used as a tool for secondary level multiplication and biopelletization of the isolates to produce enriched vermicompost for use in finger millet cultivation. It also indicated that the vermicasts should be applied soon after it is harvested.

Application of geochemical techniques for prospecting unconventional phosphate sources: A case study of the lake sediments in Eppawala area Sri Lanka

Jaya-Ganga is a water canal constructed bisecting the phosphate deposit in Eppawala, Sri Lanka. It nourishes three lakes around the vicinity of Eppawala Phosphate Deposit (EPD). In this study, the lake sediment samples were analyzed for major oxides and phosphate solubility for prospecting unconventional phosphate sources. Analyses of the geochemical content of the surface sediments in both upstream and downstream lakes revealed higher contents of P2O5, TiO2, Al2O3, Fe2O3 and MnO and, low levels of SiO2, MgO, Na2O, K2O and CaO compared with the norms of Upper Continental Crust (UCC) values. Log plots of (Na2O/K2O) vs log (SiO2/Al2O3) and (Fe2O3/K2O) vs (SiO2/Al2O3) showed chemical immaturity and mineralogical instability of the sampled sediments. The average Chemical Index of Alteration (CIA) values of 93 for upstream and 92 for downstream portrayed extreme chemical weathering conditions in the sediment source area, facilitating the breakdown of the EPD under prolonged exposure. Besides the transportation of detrital sediments, the above could convert residual phosphate into a more soluble form enabling transportation through Jaya-Ganga and re-deposition in downstream sediments. Thus, positive anomalies of P2O5 and high phosphate solubility on surface and core sediments in the downstream lake indicated the contribution of the EPD. The results of the study reflect the potential of secondary phosphate enrichment in downstream sediments and its applicability as a low-grade phosphate fertilizer. Continuous nourishment of phosphate-bearing materials, into lake sediments, increase the quantity of the phosphate content in downstream sediments and the minable quality of the lake sediments as an economically viable phosphate source.

Phosphate Enrichment Hampers Development of Juvenile Acropora digitifera Coral by Inhibiting Skeleton Formation.

Coral reef degradation due to various local stresses, such as nutrient enrichment and terrestrial run-off into coastal waters, is an increasing global concern. Inorganic phosphates have been considered to possibly inhibit skeleton formation in corals. Despite many studies available on the effects of nutrients on corals, a clear consensus on how nutrients exert deteriorative effects on corals has not been established satisfactorily. In this study, we examined the effects of phosphates and nitrates on in vitro aragonite CaCO3 formation by using biogenic polyamines and in vivo aragonite formation in the skeleton of juvenile Acropora digitifera corals. We showed that the phosphates at similar concentrations clearly inhibited both in vitro and in vivo CaCO3 formation. In contrast, nitrates inhibited neither in vitro aragonite CaCO3 formation nor in vivo aragonite formation in juvenile coral skeleton. Furthermore, our findings showed that inhibition of coral skeleton formation was due to absorption of phosphate on the skeleton, which inorganically inhibited normal development of juvenile coral skeleton.

Nutrient release to oceans from buoyancy-driven upwelling at Greenland tidewater glaciers

The discharge of nutrient-rich meltwater from the Greenland Ice Sheet has emerged as a potentially important contributor to regional marine primary production and nutrient cycling. While significant, this direct nutrient input by the ice sheet may be secondary to the upwelling of deep-ocean-sourced nutrients driven by the release of meltwater at depth in glacial fjords. Here, we present a comprehensive suite of micro- and macronutrient observations collected in Sermilik Fjord at the margin of Helheim, one of Greenland’s largest glaciers, and quantitatively decompose glacial and ocean contributions to fjord dissolved nutrient inventories. We show that the substantial enrichment in nitrate, phosphate and silicate observed in the upper 250 m of the glacial fjord is the result of upwelling of warm subtropical waters present at depth throughout the fjord. These nutrient-enriched fjord waters are subsequently exported subsurface to the continental shelf. The upwelled nutrient transport within Sermilik rivals exports by the largest Arctic rivers and the ice sheet as a whole, suggesting that glacier-induced pumping of deep nutrients may constitute a major source of macronutrients to the surrounding coastal ocean. The importance of this mechanism is likely to grow given projected increases in surface melt of the ice sheet. Glacial meltwater from the Greenland Ice Sheet causes buoyancy-driven upwelling of nutrient-rich, subtropical waters from depth to the continental shelf. This nutrient transport may exceed the direct ice sheet inputs, according to geochemical analyses of transect samples from Sermilik Fjord.

Nutrient‐enriched soils and native N‐fixing plants in New Zealand

AbstractApproximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha−1), lime (6000 kg CaCO3 ha−1), and superphosphate (470 kg ha−1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha−1 y−1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.

The Effect of Bioinduced Increased pH on the Enrichment of Calcium Phosphate in Granules during Anaerobic Treatment of Black Water.

Simultaneous recovery of calcium phosphate granules (CaP granules) and methane in anaerobic treatment of source separated black water (BW) has been previously demonstrated. The exact mechanism behind the accumulation of calcium phosphate (Cax(PO4)y) in CaP granules during black water treatment was investigated in this study by examination of the interface between the outer anaerobic biofilm and the core of CaP granules. A key factor in this process is the pH profile in CaP granules, which increases from the edge (7.4) to the center (7.9). The pH increase enhances supersaturation for Cax(PO4)y phases, creating internal conditions preferable for Cax(PO4)y precipitation. The pH profile can be explained by measured bioconversion of acetate and H2, HCO3– and H+ into CH4 in the outer biofilm and eventual stripping of CO2 and CH4 (biogas) from the granule. Phosphorus content and Cax(PO4)y crystal mass quantity in the granules positively correlated with the granule size, in the reactor without Ca2+ addition, indicating that the phosphorus rich core matures with the granule growth. Adding Ca2+ increased the overall phosphorus content in granules >0.4 mm diameter, but not in fine particles (<0.4 mm). Additionally, H+ released from aqueous phosphate species during Cax(PO4)y crystallization were buffered by internal hydrogenotrophic methanogenesis and stripping of biogas from the granule. These insights into the formation and growth of CaP granules are important for process optimization, enabling simultaneous Cax(PO4)y and CH4 recovery in a single reactor. Moreover, the biological induction of Cax(PO4)y crystallization resulting from biological increase of pH is relevant for stimulation and control of (bio)crystallization and (bio)mineralization in real environmental conditions.

Low cerium among the dissolved rare earth elements in the central North Pacific Ocean

Seawater samples were collected at the Vertex IV site at 28°N, 155°W in the central North Pacific Ocean. The very old deep waters show low concentrations of dissolved Ce, and the lowest values worldwide of dissolved Ce relative to the other REE, as defined by either the Ce/Nd ratio or the Ce anomaly Ce/Ce∗. The very old deep waters in the central North Pacific show the highest concentrations of dissolved strictly trivalent REE, i.e. except for Ce. Within the thermocline region there exist very close linear relations of the REE series with the nutrients PO4 and NO3, but curvature versus nutrient SiO4. This and the general about twofold enrichment of deep Pacific versus deep Atlantic of REE and PO4, NO3, would support the notion that ocean biogeochemical cycling of the REE is coupled with the ocean cycling of organic matter. Multiple regressions of Nd, representing the LREE, and Er, representing the HREE, versus both phosphate and silicate are significant. Nevertheless there is room for the hypothesis of invoking additional net deep water scavenging of mostly the LREE (i.e. Nd) but also the HREE (i.e. Er). There is a trend of increasing REE abundance with increasing atomic number, when the dissolved seawater data at Vertex IV site are normalized versus PAAS reference. This trend is consistent with stabilization in seawater due to stronger inorganic complexation with carbonate ion with increasing atomic number from La to Lu. There are indications for a positive Gd anomaly at Vertex IV site and also in other datasets of dissolved REE in other oceans. Interoceanic comparison between the North Pacific and the Northwest Atlantic shows for the deep Pacific an up to 2.5-fold relative enrichment for the strictly trivalent REE, that is parallel with enrichment of phosphate and nitrate, suggesting REE-cycling along with the ocean cycle of organic matter. The Pacific/Atlantic concentration ratio does not increase with increasing atomic number along the REE series. The deep Pacific shows an up to 3-fold relative Ce depletion versus the deep Atlantic. The deep North Pacific is enriched with Eu relative to the deep Northeast Atlantic, likely due to more emissions of Eu-enriched hydrothermal fluids in the Pacific basin.

GROWTH OF Phormidium bigranulatum-DOMINATED MAT IN RELATION TO NATURE OF THE SUBSTRATUM, TIME, pH AND NUTRIENT AVAILABILITY

The growth of a non-axenic Phormidium bigranulatum-dominated mat was tested under a range of chemical parameters and types of substrate. Total biomass yield (in term of mg chlorophyll a) of mats grown on muslin cloth (0.64 mg) and cotton mesh (0.62 mg) were significantly higher than those on other substrates, such as, nylon net (0.50 mg), sands of river Sone (0.43 mg) and river Ganga (0.30 mg), rice husk (0.38 mg) and saw dust (0.21 mg). The Phormidium mat would be easy to handle in bioremdation process as it grew well enmeshed in nylon net. The mat biomass increased with increasing phosphate enrichment of the medium up to 0.25 mM, whereas higher concentrations were inhibitory. At low levels of phosphate (<0.10 mM) in the medium, green algae, especially Oocystis lacustris (13%), Scenedesmus obliquus (10%), and Chlorella vulgaris (9%), became abundant in the mat community. Whereas ammonium chloride, ammonium nitrate, urea and glutamic acid (1 to 10 mM) failed to support the growth of the test mat, nitrate best supported the growth of the mat at concentrations above 10 mM. Low concentrations of nitrate (1 and 5 mM) could not sustain the growth of the mat for 30 days experimental period. The optimum sulfate concentration for mat growth was 0.10 mM. Air bubbles were seen entrapped in the mat due probably to the dense matrix of exopolymers which seem to have hindered the escape of oxygen and other gases. Conditions favoring high rate of photosynthesis, such as, optimal nutrient supply, led to the entrapment of a large number of air bubbles in the mat. Since the test mat requires high phosphate and nitrate concentrations for growth, it is a good candidate for removing nutrients from wastewaters.

Rise and fall of dissolved phosphate in South African rivers

&#x0D; &#x0D; &#x0D; Eutrophication of water resources following nutrient loading is a global threat to water quality, and has been found to be one of the major threats to water quality in South Africa. Eutrophication is large-scale autotroph growth following nutrient enrichment and has several consequences, including loss of biodiversity, oxygen depletion, taste/odour generation and algal toxin production. Phosphate enrichment is often (but not always) the cause of freshwater eutrophication, and limitation of phosphate is commonly used as a means of controlling eutrophication. This study reports on a survey of trends in nutrient levels in South African freshwater resources. The research reported on here shows a significant decrease in dissolved phosphate levels in recent years, following a long period during which phosphate levels had been increasing with time. While changes in inorganic nitrogen were found, these changes did not match those in phosphate levels. Several potential causes of these changes were assessed, and it is concluded that no one cause can explain the changes observed. While the decrease in freshwater phosphate levels bodes well for water quality management, internal phosphorus cycling and other mechanisms are likely to mask the short-term impact of phosphate decreases.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; Significance: &#x0D; &#x0D; &#x0D; &#x0D; Eutrophication, caused by nutrient loading, is a threat to water quality.&#x0D; Phosphate levels in South African fresh water have risen steadily with time, but recently have shown a sharp decrease, which cannot easily be attributed to one phosphate source.&#x0D; The decrease has promise for eutrophication management but changes may not occur in the short term.&#x0D; &#x0D; &#x0D; &#x0D;