Po Concentration Research Articles

Ipoma batatas (sweet potato) leaf and leaf-based biochar as potential adsorbents for procion orange MX-2R removal from aqueous solution

The industrial sector of textile effluent discharge comprised majorly of toxic pollutants of synthetic dyes. Lignocellulosic based biomass is a potential precursor for the preparation of biochar type adsorbent for treating wastewater. The present research examined the leaf of Ipoma batatas in the synthesis and application of biochar in the adsorptive removal of procion orange MX-2R (PO) from aqueous solution. The Ipoma batatas biochar (IBB) was prepared from the treatment of Ipoma batatas leaf (IBL) biomass with CaCl2, further activation using microwave-assisted electromagnetic radiation and pyrolysis approach. The batch adsorption assessments of the process parameters were performed with the range of experimental conditions such as initial PO concentration of 1.0–70.0 mg/L, adsorption contact time up to 240 min, solution pH 1.0–11.0, IBL/IBB dosage 0.05–0.30 g/L and adsorption temperature of 303–333 K. The total surface area of IBB exhibited high value of 1175.47 m2/g compared to that of IBL surface area 439.25 m2/g. The equilibrium model analysis showed the adsorption capacity according to Liu model presents 221.20 mg/g (IBL) and 750.80 mg/g (IBB). This study showed the potential of IBB over IBL towards the adsorptive removal of PO from simulated solution.

Influence of phytoplankton, bacteria and viruses on nutrient supply in tropical waters

Diel investigations of water environments are one means to holistically understand the dynamics and functional roles of phytoplankton, bacteria and viruses in these ecosystems. They have the potential to substantially impact carbon (C), nitrogen (N) and phosphorus (P) biogeochemistry through their respective roles. This study characterizes the phytoplankton, bacteria and virus communities and the elemental composition of various C, N and P nutrients flow over three diel cycles in tropical urban lake. Our results show that ratios of C:N:P fluctuated strongly from the lack of dissolved organic phosphorus (DOP) and PO4. Specifically, green algae peaked during day time and exudate dissolved organic matter (DOM) that strongly modulate dissolved organic carbon (DOC):DOP ratio to diel DOP limitation. Multiple linear regression and Stella modelling emphasize the roles of viruses together with Synechococcus as important nutrient recyclers of NH4 and PO4 in nutrients-limited waters. Respective normalised surface PO4 and combined surface and bottom NH4 concentration selected both viruses and Synechococcus as important drivers. Process model of N and P biogeochemical cycles can achieve 69% and 57% similar to observed concentration of NH4 and PO4, respectively. A short latent period of 9 hr was calculated, in addition to the calibrated high infectivity of viruses to Synechococcus. Taken together, the rapid turn-over between Synechococcus and viruses has biogeochemical significance, where the rapid recycling of essential nutrients allows for shortcuts in the N and P cycle, supporting a wide range of microbes.

Mobility of Nitrates and Phosphates from Animal Manure-Amended Soil to Runoff and Seepage Water from a Sweet Potato Field

Ammonia, nitrate, and phosphate in animal manure used as fertilizer reduce environmental quality by running off agricultural fields into natural water resources. Runoff and seepage water from five soil management practices (chicken manure CM, sewage sludge SS, chitin CH, biochar Bio, and no-amendment NA control plots), were investigated for their potential nutrient catching down the field slope of a sweet potato, Ipomoea balata field. The results revealed that CM-amended soil released the greatest runoff water volume (172.6 L plot −1) compared to the control treatment (98.6 L plot −1), indicating a 75% increase in the runoff water volume. CM also increased the percolated water into the rhizosphere of the growing plants by 55% compared to the control, whereas SS reduced the runoff water volume and increased the leaching water by 36% and 82%, respectively (a desirable attribute of water conservation), compared to the control plots. The concentration of PO4−3 ions in the percolated water from the biochar treatment was significantly greater compared to the other treatments, indicating there was no impact of biochar on binding PO4−3 ions. SS reduced the nitrate concentrations in the runoff and increased the seepage water volume percolated towards the roots of the growing plants; a desired attribute for preventing surface water contamination by nitrates. Observing the precipitation pattern and improving the N application rate are recommended.

Enhanced removal efficiency of nitrogen and phosphorus from swine wastewater using MgO modified pig manure biochar

Pig manure and swine wastewater from livestock and poultry contain high levels of nitrogen and phosphorus, which can seriously threaten ecosystems. In this study, biochar derived from pig manure (PMBC) was modified by various magnesium salts to obtain pig manure biochar modified with MgO (MgO-PMBC), Mg(OH)2 (Mg(OH)2-PMBC) and MgCl2 (MgCl2-PMBC), and their capacities of simultaneous adsorption of NH4+-N and PO43--P were investigated. Results showed that the adsorption quantities for NH4+-N and PO43--P decreased in the order: MgO-PMBC >Mg(OH)2-PMBC > MgCl2-PMBC > PMBC. When the optimal dosage for MgO-PMBC was determined to be 0.6 g/L and the initial solution pH was set to the ideal value of 7, the maximum adsorption quantities for NH4+-N and PO43--P by MgO-PMBC reached 122.01 mg/g and 206.85 mg/g, respectively, which were 49.8 and 85.5 times of those of the PMBC. The specific surface area and total pore volume of MgO-PMBC were 9.4 times and 4.1 times of the PMBC. Removal rate of PO43--P from swine wastewater was 97.57%, and the concentration of PO43--P from treated swine wastewater was lower than 0.5 mg/L, the primary discharge standard of China’s Comprehensive Wastewater Discharge Standard. The enhanced simultaneous adsorption of NH4+-N and PO43--P by modified PMBC (MgO-PMBC) was ascribed to its greater specific surface area and total pore volume, and the reaction of crystallisation of struvite. Our results demonstrated that pig manure biochar modified by MgO can be used to treat swine wastewater effectively.

Simultaneous nitrogen and phosphorus control from alkali and zeolite sludge fermentation process: Mechanism and application

Sludge alkali fermentation (NaOH treatment) can achieve a substantial production of volatile fatty acids (VFAs) while releasing a large amount of ammonia nitrogen (NH4+-N) and phosphorus (PO43--P). To address these issues, a combination of zeolite and NaOH/Ca(OH)2 mixed alkali fermentation was proposed. The results demonstrated that the concentration of PO43--P with mixed alkali treatment was 17.9 mg/L, whereas it was 109.21 mg/L for the NaOH treatment group. At the 8th day, the VFAs production was 1.42 times higher than the control group when using NaOH/Ca(OH)2 mixed alkali treatment. Furthermore, the addition of zeolite strengthened the fermentation by adsorbing NH4+-N. Besides, the sludge after fermentation had good dehydration performance and increased microbial community diversity and richness. Macellibacteroides, Proteiniclasticum, Exiguobacterium, Sporacetigenium and Bacillus were the dominant microorganisms with zeolite treatment. Zeolite combined with mixed alkali induced metabolic changes and the abundances of amino acid and carbohydrate metabolisms were the highest.

Linking soil phosphorus fractions to abiotic factors and the microbial community during subalpine secondary succession: Implications for soil phosphorus availability

Soil phosphorus (P) availability plays a critical role in sustaining ecosystem productivity during vegetation succession. However, our understanding of the factors driving soil P dynamics along this process, particularly in cold regions like the Tibetan Plateau, remains poorly limited. To address this, we sampled soils from four vegetation types along a secondary successional gradient (grassland → shrubland → secondary forests → primary forests) in the subalpine region of the Tibetan Plateau. Our aim was to investigate the drivers of soil P dynamics along the successional gradient. We assessed soil P dynamics by analyzing sequential soil P fractions using a modified Hedley fractionation procedure. Our results revealed significant increases in the concentrations of total inorganic P (Pi) (58.3%), Resin-Pi (93.5%), NaHCO3-Pi (63.1%), and HCl-Pi (81.7%) along the successional gradient. In contrast, we did not observe any significant changes in total P or residual P concentration along the successional gradient. Soil organic P (Po; dominated by c. HCl-Po) initially increased by 16.7% but then exhibited a subsequent decrease by 37.5% during secondary succession. The observed increase in Pi was found to be linked to the accrual in soil organic carbon during vegetation succession. Conversely, the decrease in soil Po concentration was associated with the decline in vegetation richness and fungal richness along the successional gradient. Additionally, we identified the increased relative abundance of Basidiomycota, Mortierella and Russula as potential contributors to the decrease in the soil Po concentration in the late, mid, and late successional stages, respectively. Overall, our study underscores the joint influence abiotic factors and the microbial community on soil P dynamics during vegetation succession. These findings provide valuable insights into the processes influencing soil nutrient availability in cold regions such as the Tibetan Plateau.

CAPABILITY OF SEA CUCUMBER Holothuria scabra TO REMOVE NITROGEN AND PHOSPHOR WASTE FROM SHRIMP PONDS CULTURE

Solid organic waste (PSW) in shrimp ponds contains relatively high levels of nitrogen and phosphorus and can endanger the ecological balance of the waters. This study evaluates the ability of sea cucumber Holothuria scabra to remove nitrogen and phosphorus loads from shrimp pond sediment waste in water and sediment. Sea cucumbers were reared for 40 days with a density of 20 individuals/m2 (average body weight 2.65±0.09 g) and a double-bottom recirculation system. Five levels of PSW accumulation were inserted into the aquarium substrate and were the sole source of nutrition for sea cucumbers without additional feeding: 10%, 20%, 30%, 40%, and 50% (with three replications). The results showed that increasing the PSW content in the aquarium research substrate significantly increased the substrate's TOC, TN, and TP content and increased the concentrations of TOM, DOC, NH3, NO2, and PO4 in the water column. The activity of sea cucumbers in utilizing PSW nutrients in all treatments up to a PSW level of 50% significantly reduced TOC, TN, and TP in sediments. This activity also substantially removes the concentration of TOM, DOC, NH3, NO2, and PO4 in the water. It is estimated that every kilogram of H. scabra can remove up to 12.65-12.73 g of nitrogen/day and 2.57-2.60 g of phosphorus/day contained in the solid organic waste of shrimp ponds. Therefore, this study concluded that H. scabra has great potential to be used as integrated multi-trophic aquaculture (IMTA) species, especially to remove nitrogen and phosphorus loads from shrimp pond sediment waste in waters.

Phosphorus removal by iron–carbon microelectrolysis: A new way to achieve phosphorus recovery

Abstract Iron–carbon microelectrolysis was employed to remove phosphorus in this study. The efficiency, mechanism, influence factors, and feasibility of actual wastewater were investigated. The results showed that iron–carbon microelectrolysis had an excellent phosphorus removal ability. When the initial concentration of PO 4 3 − {\text{PO}}_{4}^{3-} –P was 19.44 mg·L−1, after 120 min reaction time, the remaining PO 4 3 − {\text{PO}}_{4}^{3-} –P in wastewater was 4.65 mg·L−1, and the removal rate was 76.05%. The precipitate formed in the reaction was mainly ferric phosphate (FePO4), which had a high recovery value. There was a linear correlation between initial phosphorus concentrations and phosphorus removal velocity. As to actual wastewater, 88.37 ± 0.44%, 89.78 ± 1.88%, and 94.23 ± 0.16% phosphorus removal rates were achieved in the influent of municipal wastewater treatment plant, effluent of secondary sedimentation tank, and actual high salinity wastewater, respectively, after 120 min reaction time. This study provides a new method for phosphorus removal and recovery from wastewater.

Sugarcane green harvest management influencing soil phosphorus fractions

Few researchers have evaluated phosphorus (P) fractions in soils from humid tropical regions in which sugarcane (Saccharum spp) is harvested without prior burning. Aiming to evaluate if that practice may promote substantial changes in the availability of soil P, we analyzed the differences in total P, organic P (Po), and extractable inorganic P (Pi) fractions in soil samples collected from an Oxisol. A long-term (14 years) randomized block design was employed with six replicates and two treatments: green-harvest (GH) and burned-harvest (BH) in a sugarcane plantation. Soil samples, with six replicates, were collected at depths of 0–0.05 m, 0.05–0.1 m, 0.1–0.2 m, 0.2–0.3 m, and 0.3–0.4 m from the planting row, 0.25 m perpendicular to the row, and in the inter-row. The total Po fraction had the greatest variation between the GH and BH systems. Total Po concentration was lower in the 0–0.05 m soil layer of the GH system than that of the BH system. Total Po had also accumulated in the 0.2–0.3 m layer, which is where P fertilizer was applied at planting. These differences were observed in the planting row and 0.25 m from the planting row, but not in the inter-row. There was also no relationship between Pi fractions and row position or sampling depth in the two harvest systems. Long-term GH management rather than conventional BH sugarcane promoted greater cycling of Po in the soil, while concentrations of Pi fractions did not differ between harvest systems.

Sediment resuspension enhances nutrient exchange in intertidal mudflats

Intertidal coastal sediments are important centers for nutrient transformation, regeneration, and storage. Sediment resuspension, due to wave action or tidal currents, can induce nutrient release to the water column and fuel primary production. Storms and extreme weather events are expected to increase due to climate change in coastal areas, but little is known about their effect on nutrient release from coastal sediments. We have conducted in-situ sediment resuspension experiments, in which erosion was simulated by a stepwise increase in current velocities, while measuring nutrient uptake or release in field flumes positioned on intertidal areas of a tidal bay (Eastern Scheldt) and an estuary (Western Scheldt). In both systems, the water column concentration of ammonium (NH4+) and nitrite (NO2−) increased predictably with greater erosion as estimated from pore water dilution and erosion depth. In contrast, the phosphate (PO43−) dynamics were different between systems, and those of nitrate (NO3−) were small and variable. Notably, sediment resuspension caused a decrease in the overlying water PO43− concentration in the tidal bay, while an increase was observed in the estuarine sediments. Our observations showed that the concentration of PO43− in the water column was more intensely affected by resuspension than that of NH4+ and NO2−. The present study highlights the differential effect of sediment resuspension on nutrient exchange in two contrasting tidal coastal environments.

Removal of phosphate from brewery wastewater by cerium(III) chloride originating from spent polishing agent: Recovery and optimization studies

This paper presents the possibility of using hydrated cerium(III) chloride (CeCl3∙7H2O) recovered from a spent polishing agent containing cerium(IV) dioxide (CeO2) to remove phosphate and other impurities from brewery wastewater (phosphate 43.0 mg/L, total P 19.8 mg/L, pH 7.5, COD(Cr) 827 mg O2/L, TSS 630 mg/L, TOC 130 mg/L, total N 46 mg/L, turbidity 390 NTU, colour 170 mg Pt/L. CCD (Central Composite Design) and RSM (Response Surface Methodology) were applied to optimise the brewery wastewater treatment process. The removal efficiency (mainly of PO43−) was the highest under optimal conditions (pH 7.0–8.5, Ce3+:PO43− molar ratio of 1.5–2.0). Applying recovered CeCl3 under optimal conditions yielded a treated effluent in which the concentration of PO43− decreased by 99.86 %, total P by 99.56 %, COD(Cr) by 81.86 %, TSS by 96.67 %, TOC by 60.38 %, total N by 19.24 %, turbidity by 98.18 %, and colour by 70.59 %. The Ce3+ ion concentration in the treated effluent was 0.058 mg/L. These findings suggest that CeCl3‧7H2O recovered from the spent polishing agent may constitute an optional reagent for phosphate removal from brewery wastewater. The sludge from wastewater treatment can be recycled for Ce and P recovery. The recovered cerium can be reused for wastewater treatment, creating a cyclic cerium cycle in the process, and the recovered phosphorus can be used, for example, for fertilization purposes. The optimised cerium recovery and application is in accordance with the ideas of circular economy.

RESPON TANAMAN KANGKUNG DARAT (Ipomoea reptans Poir) TERHADAP PEMBERIAN BERBAGAI TAKARAN PUPUK KANDANG SAPI PO

The aim of this study was to determine the response of ground kale plants to various doses of PO cow manure and the best number of PO cow manure doses for growth and yield of ground kale plants. The research method used was a non-factorial Randomized Block Design (RBD) with five levels, namely without cow manure PO 0 tons/ha (control), cow manure concentration PO 10 tons/ha, cow manure concentration PO 20 tons/ha, concentration of cow manure PO 30 tons/ha and concentration of cow manure PO 40 tons/ha. Based on the results of the study, it was shown that the application of various doses of PO cow manure had no significant effect on the growth and yield of ground kale and the best number of PO cow manure doses was seen from the average observation parameter, namely at the concentration of PO cow manure of 20 tons/ha. Keywords: land kale, doses, cow manure PO

Spatio-temporal variation of major ion chemistry and nutrient stoichiometry in a tropical monsoonal estuary: insight into biogeochemical processes

Major ions and nutrient chemistry of surface water from the Devi river estuary, eastern India has been studied in order to understand the governing biogeochemical processes. Concentration of Na, K, Ca, Mg, Cl, SO4 and PO4 increases toward higher salinity; however, NO3 and dissolved silica (DSi) decreases from upper to lower estuary. All major ions, except NO3 and DSi, show the highest and lowest concentration in summer and monsoon season, respectively. Increased surface runoff has resulted in the highest concentration of NO3 and DSi in the monsoon period. The Na, Cl, SO4, NO3 and PO4 ions show conservative mixing behavior in the estuary throughout the year. Non-conservative behavior of DSi is attributed to the combined process of mineral weathering and biological removal by diatoms. Enrichment and depletion of Ca and Mg in the estuary is owed to carbonate mineral precipitation and dissolution processes. Decreasing carbonate saturation indices (SI) with reducing pH accompanied by lowering of DO% suggests the influence of organic matter degradation on the carbonate precipitation and/or dissolution potential. Nutrient stoichiometric ratios—NO3:PO4, DSi:PO4 and DSi:NO3—are found to vary spatially and seasonally as a result of differences in geochemical processes prevailing in the fresh- and marine-water environment. A prominent PO4 limitation is observed in the upper estuary during summer and winter. However, this limitation reduces toward the lower estuary owing to precipitation of Fe-sulfide under the influence of higher salinity. In contrast, the influx of PO4-limited freshwater into the estuary controls the nutrient stoichiometric ratios in the monsoon season. The spatial variation of chlorophyll concentration in the estuary is in accordance to the nutrient stoichiometric ratios. Thus, this study emphasizes on the role of unique biogeochemical processes in controlling the spatial and seasonal distribution of major ions and nutrient stoichiometry in a tropical estuarine system.

Extraction and transformation of elements in phosphogypsum by electrokinetics

Phosphogypsum (PG), as a typical industrial solid waste produced in the wet production process of phosphoric acid, is harmful to the environment and difficult to utilize. In order to explore the migration behavior of impurities in PG under electrokinetic treatment and provide a new treatment technology for the purification and harmless treatment, this paper studied the distribution of soluble impurities (PO43−, F−, Sr, Pb, Cr, Cu, and Mn) in PG under different electrokinetic treatment conditions. The results indicated that most of water-soluble impurities demonstrated obvious migration distribution laws at different voltages. Under the influence of electroosmotic flow, F− accumulated continually at the cathode. Positive MF+ was produced in acidic circumstances by combining F− and metal ions and travelled to the cathode under the combined action of electric field force and electroosmotic flow. Under electrokinetic treatment, the concentration of PO43− in the anode chamber increased while that of in the cathode chamber decreased. A large number of anions in PG were attached to the anode by coulomb force, reducing the potential. PO43− was s largely enriched in the anode chamber, which is controlled by the free diffusion effect of ions. Heavy metals exhibited higher leaching efficiency under anodic acid conditions. With the increase of applied voltage, the concentration of heavy metals in the anode chamber gradually increased, which was related to the activity of solution, pH and other factors. The above results indicate that electrokinetic treatment is a novel and efficient PG treatment technology, which has a broad application prospect in impurity removal and PG resource recovery.

Separation and Concentration of Nitrogen and Phosphorus in a Bipolar Membrane Electrodialysis System.

Struvite crystallization is a successful technique for simultaneously recovering PO43- and NH4+ from wastewater. However, recovering PO43- and NH4+ from low-concentration solutions is challenging. In this study, PO43-, NH4+, and NO3- were separated and concentrated from wastewater using bipolar membrane electrodialysis, PO43- and NH4+ can then be recovered as struvite. The separation and concentration of PO43- and NH4+ are clearly impacted by current density, according to experimental findings. The extent of separation and migration rate increased with increasing current density. The chemical oxygen demand of the feedwater has no discernible impact on the separation and recovery of ions. The migration of PO43-, NH4+, and NO3- fits zero-order migration kinetics. The concentrated concentration of NH4+ and PO43- reached 805 mg/L and 339 mg/L, respectively, which demonstrates that BMED is capable of effectively concentrating and separating PO43- and NH4+. Therefore, BMED can be considered as a pretreatment method for recovering PO43- and NH4+ in the form of struvite from wastewater.

A new sampling method with zirconium‐loaded resin for phosphate oxygen isotope analysis in oligotrophic freshwater systems

The phosphate oxygen isotope ratio ( ) is a useful technique to trace the sources and biogeochemical cycles of phosphorus (P) in aquatic ecosystems. However, has not been widely used in oligotrophic freshwater systems due to technical and methodological difficulties in collecting sufficient phosphate (PO4 ) for the analysis, which sometimes requires hundreds of liters of the water sample. In this study, a new approach (PaS-Zir) was developed for the analysis in oligotrophic freshwater systems using zirconium (Zr)-loaded (ZrIRC) resin, which has a high affinity for PO4 . ZrClO2 was added to Amberlite IRC748 to obtain the ZrIRC resin. The adsorption/desorption experiment using KH2 PO4 with a known value of was conducted to determine the adsorption/desorption properties of the resin and the likelihood of isotopic fractionation. By installing mesh bags filled with the resin, the PaS-Zir approach was used in two rivers with low PO4 concentrations (0.2 and 5.3μmol/L). A conventional sampling method was also performed in the study river with a higher PO4 concentration to validate the efficacy of the PaS-Zir method. The adsorption/desorption experiment demonstrated that the ZrIRC resin possessed a sufficient adsorption capacity (153 μmol/resin-mL) and exhibited little isotopic fractionation during the adsorption/desorption processes. Using the PaS-Zir method, we were able to collect sufficient PO4 samples for the analysis from the rivers within at least 4 days of mesh bag installation. The values (14.2‰ ±0.2‰) obtained using the PaS-Zir method were comparable to those obtained using the conventional method (14.0‰ ±0.03‰). We proved that the PaS-Zir method is applicable to oligotrophic freshwater systems and is generally more efficient than the conventional method. In addition, our method is useful for improving the understanding of the P dynamics of oligotrophic ecosystems because of the extremely low concentration of PO4 commonly found in them, which are often prone to P pollution.

Evaluation of the radiological dose due to 210Po in commercial clupeid fish collected in the near-shore environment of the high background natural radiation area (HBNRA) on the southwest coast of India

In this study, we quantified the tissue concentration of 210 Po in a variety of commercial sardine fish species of the family Clupeidae from an area of high background natural radiation area on the southwest coast of India. The smooth belly sardine Amblygaster leiogaster had the lowest 210 Po concentration in its muscle (45.6 ± 7.9 Bq kg −1 fresh), while the goldstripe sardine Sardinella gibbosa had the highest (103.4 ± 10.1 Bq kg −1 fresh). The Annual Committed Effective Dose (ACED) of fried sardine and sardine curry were 134.3–304.3 μSv y −1 and 226.6–513.5 μSv y −1 , respectively. Of the 210 Po loss, 20 % was due to frying and 10 % to preparing sardine curry. The effective dose was found to be globally comparable and well below the world limit. Consumption of sardines containing 210 Po would not pose a health hazard to the residents of Manavalakurchi. • 210 Po quantified in the muscle tissue of sardine fishes. • The study carried out in the high background natural radiation area. • The annual committed effective dose was computed using raw and cooked sardines. • The effective internal dose does not impact much to the residents.

Polyacrylic Acid-Ca(Eu) Nanoclusters as a Luminescence Sensor of Phosphate Ion.

In this study, we synthesized polyacrylic acid (PAA)-Ca (Eu) nanoclusters as a luminescence sensor of phosphate ion by a complex method, and we aimed to achieve the quantitative detection of PO43− based on the sensitivity of the charge transfer band of Eu3+ to anionic ligand. The resulting PAA-Ca(Eu) nanoclusters showed a well-dispersed and a dot-like morphology, with an ultra-small diameter (the average size of 2.17 nm) under high resolution transmission electron microscopy(HRTEM) observation. A dynamic light scattering particle size analyzer (DLS) showed a hydrodynamic size of 2.39 nm. The (PAA)-Ca (Eu) nanoclusters as a luminescence sensor showed a significantly higher sensitivity for PO43− than other anions (CO32−, SiO32−, SO42−, SO32−, Br−, Cl−, F−). The luminescence intensity displayed a linear increase (y = 19.32x + 74.75, R2 > 0.999) in a PO43 concentration range (0–10 mM) with the concentration of PO43− increase, and the limit of detection was 0.023 mM. The results showed good recovery rates and low relative standard deviations. These (PAA)-Ca (Eu) nanoclusters are hopeful to become a luminescence sensor for quantitatively detecting PO43−.

Why do red tides occur frequently in some oligotrophic waters? Analysis of red tide evolution history in Mirs Bay, China and its implications

The process and management of red tide in oligotrophic waters are poorly understood as most studies on red tide were focused on eutrophic areas. In this study, 404 red tide events together with the historical water quality dynamics during 1991–2020 were investigated in an anthropogenically influenced bay in China - Mirs Bay, whose most region is oligotrophic except small inshore areas. Red tides of oligotrophic offshore accounted for 20 % of all. With the effective governmental management on inshore areas, concentration of PO4 and DIN has been decreased to a low level (PO4 <0.01 mg/L while DIN <0.1 mg/L) in the bay since about 2000. However, the reduction of nutrients was still accompanied by the frequent outbreaks of red tides, as well as a shift of dominant algae from diatoms to dinoflagellates, which might be due to the unbalanced nutrient reduction, such as N:P ratio fluctuation and organic nutrient increase. This shift might trigger more red tide events and even some super ones (long-duration or large-scale) in oligotrophic areas. Detailed analysis on red tide events combined with model simulation proved that the outbreak of red tide in Mirs Bay was caused by the joint contribution of nutrients and hydrodynamics. Nutrients of inshore area supported the red tides there, and with the help of physical conditions, red tides inshore could be transferred to offshore areas and then were likely to bloom again or be preyed to support blooms of other organisms. This study acknowledged that the reduction of both N and P either inorganic or organic nutrients was essential to control red tides, even in oligotrophic waters, but a balanced strategy considering the dual reduction of both nitrogen and phosphorus was of pivotal role to restore the health of coastal water systems disturbed by human.

Effects of pH Adjustment on the Release of Carbon Source of Particulate Organic Matter (POM) in Domestic Sewage

The use of anaerobic hydrolytic fermentation to develop more available carbon sources from domestic sewage influent particulate organic matter (POM) has received increasing attention. However, the slow hydrolysis rate of POM limits the application of this technology. This study aimed to improve the carbon source release efficiency of POM by pH adjustment and to reveal the hydrolysis mechanism. Results showed that adjusting the initial pH of POM to 3, 9, and 11 enhanced carbon source release in the anaerobic hydrolysis fermentation process of POM. The pretreatment under pH value of 11 contributed to the highest yield and productivity of carbon source, reaching the soluble chemical oxygen demand (SCOD) of 2782 mg/L at the 4th day. The pH 3 pretreatment was more beneficial for phosphorus resource recovery, which contributed to the highest release concentration of PO43−-P, reaching 48.2 mg/L at the 3rd day, accounting for 90% of TP. Microbial community structure analysis indicated that pH 11 preconditioning promoted the enrichment of proteolytic bacteria (Proteocatella and Proteiniclasticum) and polysaccharide hydrolytic bacteria (Trichococcus and Acinetobacter) and inhibited the growth of acetate-consuming methanogenic archaea, which contributed to the highest carbon release of POM in domestic sewage.