Soluble Phosphate Concentrations Research Articles

Green solutions for antibiotic pollution: Assessing the phytoremediation potential of aquatic macrophytes in wastewater treatment plants

We compared the ability of one emergent (Sagittaria montevidensis), two floating (Salvinia minima and Lemna gibba), and one heterophyllous species (Myriophyllum aquaticum) to simultaneously remove sulfamethoxazole, sulfadiazine, ciprofloxacin, enrofloxacin, norfloxacin, levofloxacin, oxytetracycline, tetracycline, doxycycline, azithromycin, amoxicillin, and meropenem from wastewater in a mesocosm-scale constructed wetland over 28 days. Antibiotic concentrations in plants and effluent were analyzed using an LC-MS/MS to assess the removal rates and phytoremediation capacities. M. aquaticum did not effectively mitigate contamination due to poor tolerance and survival in effluent conditions. S. minima and L. gibba demonstrated superior efficiency, reducing the antibiotic concentrations to undetectable levels within 14 days, while S. montevidensis achieved this result by day 28. Floating macrophytes emerge as the preferable choice for remediation of antibiotics compared to emergent and heterophyllous species. Antibiotics were detected in plant tissues at concentrations ranging from 0.32 to 29.32 ng g−1 fresh weight, highlighting macrophytes' ability to uptake and accumulate these contaminants. Conversely, non-planted systems exhibited a maximum removal rate of 65%, underscoring the persistence of these molecules in natural environments, even after the entire experimental period. Additionally, macrophytes improved effluent quality regardless of species by reducing total soluble solids and phosphate concentrations and mitigating ecotoxicological effects. This study underscores the potential of using macrophytes in wastewater treatment plants to enhance overall efficiency and prevent environmental contamination by antibiotics, thereby mitigating the harmful impact on biota and antibiotic resistance. Selecting appropriate plant species is crucial for successful phytoremediation in constructed wetlands, and actual implementation is essential to validate their effectiveness and practical applicability.

Effect of ammonium stress on phosphorus solubilization of a novel marine mangrove microorganism Bacillus aryabhattai NM1-A2 as revealed by integrated omics analysis

BackgroundPhosphorus is one of the essential nutrients for plant growth. Phosphate-solubilizing microorganisms (PSMs) can alleviate available P deficiency and enhance plant growth in an eco-friendly way. Although ammonium toxicity is widespread, there is little understanding about the effect of ammonium stress on phosphorus solubilization (PS) of PSMs.ResultsIn this study, seven PSMs were isolated from mangrove sediments. The soluble phosphate concentration in culture supernatant of Bacillus aryabhattai NM1-A2 reached a maximum of 196.96 mg/L at 250 mM (NH4)2SO4. Whole-genome analysis showed that B. aryabhattai NM1-A2 contained various genes related to ammonium transporter (amt), ammonium assimilation (i.e., gdhA, gltB, and gltD), organic acid synthesis (i.e., ackA, fdhD, and idh), and phosphate transport (i.e., pstB and pstS). Transcriptome data showed that the expression levels of amt, gltB, gltD, ackA and idh were downregulated, while gdhA and fdhD were upregulated. The inhibition of ammonium transporter and glutamine synthetase/glutamate synthase (GS/GOGAT) pathway contributed to reducing energy loss. For ammonium assimilation under ammonium stress, accompanied by protons efflux, the glutamate dehydrogenase pathway was the main approach. More 2-oxoglutarate (2-OG) was induced to provide abundant carbon skeletons. The downregulation of formate dehydrogenase and high glycolytic rate resulted in the accumulation of formic acid and acetic acid, which played key roles in PS under ammonium stress.ConclusionsThe accumulation of 2-OG and the inhibition of GS/GOGAT pathway played a key role in ammonium detoxification. The secretion of protons, formic acid and acetic acid was related to PS. Our work provides new insights into the PS mechanism, which will provide theoretical guidance for the application of PSMs.

Promoting the growth of Sulla flexuosa L. by endophytic root nodule bacteria authors and affiliations.

Legume plants rely upon multipartite interactions between rhizobia and bacterial endophytes within root nodules to facilitate plant growth. This study aimed to isolate and identify indigenous endophytic bacteria from root nodules of Sulla aculeolata L. in Northeast Morocco. Based on their tri-calcium phosphate (TCP) solubilization capacity, five endophytes were chosen for further evaluation of their plant growth traits. All isolates were hydrogen cyanide (HCN) and siderophore producers, while only BCH24 tested positive for ACC deaminase activity. Indole-3-acetic acid (IAA) synthesis ranged from 1.27 mgL- 1 to 2.89 mgL- 1, while soluble phosphate concentrations was between 7.99mg L- 1 and 110.58mg L- 1. Additionally, all the endophytes were able to produce more than two lytic enzymes. Based on the analysis of 16S rRNA gene sequences five isolates were identified as Enterobacter sp (BCH13, BCH2), Pseudomonas sp (BCH16, BCH24), and Serratia sp (BCH10). The strains inhibited the growth of three phytopathogenic fungi, with BCH13 exhibiting the highest rate against Aspergillus ochraceus (45%), followed by BCH24 against Fusarium oxysporum (40%) and Botrytis cinerea (35%), respectively. In vivo inoculation of halotolerant strains Enterobacter hormaechei (BCH13) and Pseudomonas moraviensis (BCH16) under gnotobiotic conditions revealed that co-inoculation with Rhizobium sullae KS6 improved plant development compared to single inoculation, making it a promising eco-friendly bio-inoculant for legume Sulla flexuosa L. production.

Assessment of Potent Phosphate-Solubilizing Bacteria Isolated from the Olive Tree Rhizosphere Grown on Phosphate Sludge and Their Effect on Common Bean Growth

One of the most restricting macronutrients for crop yield worldwide is phosphorus, which is often less than 1% of the total amount contained in soils. To promote its bioavailability, there are microorganisms considered vital that can solubilize and mineralize their pools in soils. In the current study, we assessed the potential of phosphate-solubilizing bacteria (PSB), isolated from the olive tree rhizosphere grown on phosphate sludge, to solubilize phosphate, promote plant growth, and tolerate abiotic stresses. Based on 16S rRNA gene sequencing, twenty-four PSB strains were identified and retained for in vitro analysis. According to the results, all the strains were able to solubilize the Moroccan rock phosphate, with soluble phosphate concentrations ranged from 5.34 µg/mL to 227 µg/mL. Furthermore, the majority of the strains are thermo-tolerant and halotolerant. Nonetheless, only five strains produced indole acetic acid. Regarding biocontrol potentialities, several PSB strains were characterized by producing hydrogen cyanide and hydrolytic enzymes (cellulase, and chitinase), of which three strains identified as Pseudomonas moraviensis, Bacillus cereus, and Bacillus aryabhattai, with a remarkable multi-trait combination were selected for antagonism and co-inoculation tests. The findings revealed that these PSB strains significantly inhibited Fusarium oxysporum (17.65%–62.35%) and Verticillium dahliae (52.35%–66.87%) and promoted common bean growth. The consortium of the three strains showed the best results by significantly increasing both plant height and tap root length and dry biomass compared to individual inoculation. The PSB selected from the olive tree rhizosphere growing on phosphate sludge have the potential to be useful as biofertilizer and biocontrol agents for attaining sustainable food crop production.

Comparative physiological and proteomic response to phosphate deficiency between two wheat genotypes differing in phosphorus utilization efficiency

Genetic variation in phosphorus utilization efficiency (PUE) widely exists among wheat genotypes. However, the underlying mechanisms are still unclear. Two contrasting wheat genotypes, Heng4399 (H4399) and Tanmai98 (TM98), were screened out from 17 bread wheat genotypes based on shoot soluble phosphate (Pi) concentrations. The TM98 had a significantly higher PUE than the H4399, especially under Pi deficiency. The induction of genes in the PHR1-centered Pi signaling pathway was significantly higher in TM98 than in H4399. Collectively, through a label-free quantitative proteomic analysis, 2110 high-confidence proteins were identified in shoots of the two wheat genotypes. Among them, 244 and 133 proteins were differentially accumulated under Pi deficiency in H4399 and TM98, respectively. The abundance of proteins related to nitrogen and phosphorus metabolic processes, small molecule metabolic process, and carboxylic acid metabolic process weas significantly affected by Pi deficiency in the shoots of the two genotypes. The abundance of proteins in energy metabolism, especially photosynthesis, was decreased by Pi deficiency in the shoots of H4399. Inversely, the PUE-efficient genotype TM98 could maintain protein abundance in energy metabolism. Moreover, the proteins involved in pyruvate metabolism, glutathione metabolism, and sulfolipid biosynthesis were significantly accumulated in TM98, which probably contributed to its high PUE. SignificanceImproving the PUE of wheat is urgent and crucial for sustainable agriculture. Genetic variation among wheat genotypes provides materials for exploring the underlying mechanisms for high PUE. This study selected two wheat genotypes with contrasting PUE to reveal the differences in the physiological and proteomic responses to phosphate deficiency. The PUE-efficiency genotype TM98 greatly induced the expression of genes in the PHR1-centered Pi signaling pathway. Subsequently, the TM98 could maintain the abundance of proteins related to energy metabolism and enhance the abundance of proteins involved in pyruvate metabolism, glutathione metabolism, and sulfolipid biosynthesis to increase PUE under Pi deficiency. The differentially expressed genes or proteins between the genotypes with contrasting PUE would provide potential and basis for breeding wheat varieties with improved phosphorus use efficiency.

Molecular Characterization and Mineralizing Potential of Phosphorus Solubilizing Bacteria Colonizing Common Bean (Phaseolus vulgaris L.) Rhizosphere in Western Kenya.

Phosphorus solubilizing bacteria (PSB) are a category of microbes that transform insoluble phosphates in soil into soluble forms that crops can utilize. Phosphorus in natural soils is abundant but poorly soluble. Hence, introducing PSB is a safer way of improving its solubility. The aim of this study was to genetically characterize and determine the mineralization capability of selected PSB colonizing rhizospheres of common beans in Western Kenya. Seven potential phosphorus solubilizing bacteria (PSB) were isolated from various subregions of Western Kenya. 16S ribosomal RNA gene sequencing and National Center for Biotechnology Information (NCBI), Basic Local Alignment Search Tool (BLAST) identified the isolates. The phosphate solubilization potential of the isolates was evaluated under agar and broth medium of National Botanical Research Institute's phosphate (NBRIP) supplemented with tricalcium calcium phosphate (TCP). Identified isolates were as follows: KK3 as Enterobacter mori, B5 (KB5) as Pseudomonas kribbensis, KV1 as Enterobacter asburiae, KB3 as Enterobacter mori, KK1 as Enterobacter cloacae, KBU as Enterobacter tabaci, and KB2 as Enterobacter bugandensis. The strains B5 and KV1 were the most effective phosphorus solubilizers with 4.16 and 3.64 indices, respectively. The microbes converted total soluble phosphate concentration in broth medium which was 1395 and 1471 P μg/mL, respectively. The least performing isolate was KBU with a 2.34 solubility index. Significant (p ≤ 0.05) differences in plant biomass for Rose coco and Mwitemania bean varieties were observed under inoculation with isolates B5 and KV1. PSB isolates found in common bean rhizospheres exhibited molecular variations and isolates B5 and KV1 are the potential in solving the insufficiency of phosphorus for sustainable crop production.

Effect of mixing iron-containing sludge to domestic wastewater on wastewater characteristics under different conditions: types of domestic wastewater, varying pH and mixing ratios

Large volumes of iron-containing sludge (Fe-Sludge) would be generated with the application of iron salts in drinking water treatment plants, which must be disposed appropriately. One of the common disposal solutions for Fe-Sludge is through direct disposal into the municipal sewer system, whereby it would be mixed with domestic wastewater and treated in the wastewater treatment plant. To better understand the properties of Fe-Sludge and the effect of dosing Fe-Sludge to the real domestic wastewater (WW) on the wastewater characteristics, a serial batch tests were conducted on a local wastewater reclamation plant (WRP). It was found that the impact of dosing Fe-Sludge at a Fe/P ratio of 5 did not vary with the types of WW, i.e., filtered or non-filtered by the 5 mm screen. In addition, the soluble organic, phosphate and total soluble iron concentrations mostly decreased with the dosing of Fe-Sludge within the dosage range of 0–5 (Fe/P ratio). In contrast, the suspended solid (SS) and volatile suspended solid (VSS) concentrations increased with the dosage of Fe-Sludge within the dosage range of 0–5 (Fe/P ratio). Furthermore, the pH condition of the domestic wastewater affected the phosphate removal efficiency by Fe-Sludge and influenced the total soluble iron concentration and iron species distribution. These findings will provide fundamental support for the further study of the effect of Fe-Sludge on the biological treatment performance and membrane filtration performance of the membrane bioreactor (MBR) system.

Enhanced phytoremediation of hexavalent chromium contamination in phosphate mining wasteland by a phosphate solubilizing bacterium

Soil chromium (Cr) contamination poses a significant threat to the environment and public health. A phosphate solubilizing bacterial strain Bacillus megaterium PMW-03 was used to enhance the phytoremediation of Cr(VI) contamination by Pteris vittata in phosphate mining wasteland in this study. The results showed that the strain PMW-03 could promote the solubilization of phosphate rock (PR) and the removal of Cr(VI) by Pteris vittata in the phosphate mining wasteland. Compared with the groups not inoculated with PMW-03, the available phosphate content in the rhizosphere soil of the inoculated groups increased by 17.6% and 24.9%, respectively (in the group with Cr(VI) added and the group with Cr(VI) and PR added), and the available Cr(VI) content decreased by 28.2%, 25.2% and 33.4%, respectively. In addition, the strain PMW-03 also promoted the growth of Pteris vittata by secreting indole acetic acid (IAA) and siderophore, promoting Pteris vittata to produce chlorophyll, increasing the concentration of soluble phosphate and reducing the concentration of Cr(VI) in root and shoot. The results of metagenomic analysis showed that changes in biological community structure, enrichment of related functional abundances, and activation of genes (FTH1, FTL, HSP90A, glgP, htpG, glnA, and GLUD1_2) located in microbes contributed to the microbial-phytoremediation of Cr(VI) contamination. These results provide a reference for future research on the microbial-phytoremediation of Cr(VI) contamination in phosphate mining wasteland.

Thermodynamics and Kinetics of pH-dependent Dissolution of Sparingly Soluble Alkaline Earth Hydroxides in Source-Separated Human Urine Collected in Decentralised Sanitation Systems

Alkaline earth hydroxides are widely used in water and wastewater treatment. Within the emerging niche of source-separating sanitation, these chemicals have found a new application—to prevent urease-catalysed degradation of urea present in freshly excreted human urine. However, little is known about the dissolution behaviour of these hydroxides in biological fluids like human urine. Herein, we investigate the solubility of Mg(OH)2 and examine factors that govern its dissolution in different types of urine (real fresh urine, synthetic fresh urine, synthetic dephosphatised fresh urine and real fresh urine concentrated by CO2-free drying). We report experimentally determined as well as thermodynamically simulated data on Mg(OH)2 solubility, dissolution kinetics, and chemical speciation in urine. We find that it takes between 6 and 16 min for Mg(OH)2 to dissolve and the average solubility in real fresh urine at 25°C to be 650 mg L−1. We show that solubility is influenced mainly by concentration of organic compounds, soluble phosphate, and magnesium excreted in fresh urine. When fresh urine is supersaturated with Mg(OH)2, the pH increases to >10.5 and urease-catalysed degradation of urea is inhibited for >14 days. Removing 95% water present in urine increases the solubility of Mg(OH)2 to 16,240 mg L−1 but reduces pH to < 10. Because relative increase in Mg(OH)2 solubility decreases as more water is removed and the solubility is retrograde with respect to temperature, to increase the urine pH to >10 and prevent enzymatic ureolysis, the temperature must be kept < 29°C at 75% water removal and < 22°C at 95% water removal. We find this dissolution behaviour of Mg(OH)2 in concentrated urine solutions to be unlike other alkaline earth hydroxides. These findings have significant implications for the design of new sanitation systems that separately collect and recycle plant-essential nutrients present in human urine.

Effect of the phosphate solubilization and mineralization synergistic mechanism of Ochrobactrum sp. on the remediation of lead.

Phosphate-solubilizing bacteria (PSB) promotes the formation of mineralized precipitation through phosphorous dissolution and mineralization, forming stable lead (Pb(II)) minerals and reducing the migration of Pb(II) in the environment. In this study, a Pb-tolerant strain Ochrobactrum sp. J023 from a contaminated soil around a battery factory in Jiangsu Province, China, was screened for experiments to investigate the phosphate solubilization and mineralization mechanism of this strain. The organic acids and the acid phosphatase produced by the bacteria have a synergistic effect on phosphate dissolution. When the pH of the culture medium decreased to the lowest 4.55, the amount of soluble phosphate and the activity of acid phosphatase reached the maximum 161.29mgL-1 and 61.98UmL-1, and there was a significant correlation between the concentration of soluble phosphate and the activity of acid phosphatase (R = 0.832**, P < 0.05). It was found that acetic acid played the most important role in the secreted organic acids. During the mineralization reaction, the extracellular polymeric substances (EPS) chelates part of the Pb(II) on the surface of the cell wall, preventing the metal Pb from penetrating into the cell, thus providing protection to the strain. Meanwhile, due to the nucleation sites provided by cell surface groups (carboxyl and phosphate groups), a large number of metal ions are absorbed to promote the formation of crystallization. The final mineralized product of Pb(II) by strain J023 was pyroxite (Pb5(PO4)3X, where X = Cl, OH). The mechanism of phosphate dissolution and mineralization proposed by us is that the organic acids and acid phosphatases secreted by phosphate-solubilizing bacteria promote the increase of PO43- concentration in the solution, the complexation of metal cations and cell surface groups will induce the formation of mineralized precipitation under the catalysis of enzyme. Therefore, it is a promising strategy for bioremediation of lead pollution by screening functional strains with strong abilities of phosphate solubility and mineralization.

ISOLATION AND CHARACTERIZATION OF ENDOPHYTIC ACTINOMYCETES ASSOCIATED WITH THYMUS SATUROIDES AND LAVANDULA MULTIFIDA GROWN IN BENI-MELLAL REGION IN MOROCCO

ABSTRACT The present study aims to isolate endophytic actinomycetes (EPM) that are able to tolerate abiotic stresses, solubilize tricalcium phosphate (TCP) and produce indole-3-acetic acid (IAA), amylase and cellulose activities, while exhibiting high antagonistic activity against Fusarium oxysporum. f. sp. albedinis. Endophytic actinomycetes were isolated from roots, stems and leaves of Thymus saturoides and Lavandula multifida plant grown in Beni Mellal region, Morocco. According to the macro- and micro-morphological characteristics, a total of eleven EPM isolates were isolated and purified. Results indicated that the majority of isolates were able to tolerate pH and salt stresses. Moreover, the majority of the isolates were able to solubilize TCP on Pikovskaya (PVK)-agar medium which ranged from 25% to 458%. Additionally, on PVK-liquid medium, soluble phosphate content varied from 163.81 µg/mL recorded for the isolate LRP1 to 730 µg/mL observed for the isolate TSRP2. For IAA production, the amount produced varied from 1.70 µg/mL recorded for the isolate LRP1 to 14.13 µg/mL recorded for both LTP2’ and TSRP2. Endophytic actinomycetes isolated in this work also showed a remarkable capacity to degrade some compounds such as cellulose and starch. In addition, some of them showed a strong inhibitory activity against the fungus F. albedinis with a percentage of inhibition ranged from 69.13% observed for LTP2’ to 86.6% recorded for the isolate LRP2. Results from this study indicate that the two isolates LTP2’ and TSRP2 were the most efficient and that actinomycetes could be used in biocontrol against the fungus F. albedinis.

Earthworm-Collembola interactions affecting water-soluble nutrients, fauna and physiochemistry in a mesocosm manure-straw composting experiment

A mesocosm fermentation experiment was undertaken to investigate interactions between Eisenia fetida and Collembola affecting composting processes. Earthworms, Collembola, respiration, water soluble nutrients and compost characteristics (near infrared spectra – NIRS) were monitored on four occasions over 136 days. Earthworms were the main drivers of early changes in composts, increasing the general abundance of Collembola, although responses varied with species. Earthworms accelerated substrate mineralisation and release of soluble nutrients whilst also changing compost characteristics. Collembola alone had little direct effect on soluble nutrient concentrations or respiration; they did however alter compost characteristics (NIR spectra). Earthworm-Collembola interactions affecting respiration and soluble nutrients were mainly antagonistic in the early stages of composting but synergistic in later stages. In the later stages of composting, the higher abundance of Collembola when combined with earthworms resulted in greater concentrations of soluble nitrate and phosphate. These findings emphasise the importance in vermicomposting practice of different invertebrate groups having access to feedstock at appropriate stages of the process. The high concentrations of soluble nutrients released during vermicomposting indicate the need for control measures to avoid off-site pollution and loss of this resource.

Qualitative and quantitative estimation for phosphate solubilizing ability of Trichoderma isolates: A natural soil health enhancer

India is an agricultural country. Nearly 70% of the populations thrive in rural areas, engaged in agriculture making the backbone of our economy. The Trichoderma genus is widely distributed and provides an alternative to chemical pesticides in crops and plants growth. Trichoderma species are free living and commonly found in soil and root ecosystems. Root colonization by Trichoderma also regularly promotes growth and development of plants. They also perform beneficial and significant role in enhancing crop productivity, fight against pathogens, resistant to abiotic stress and increase of nutrients uptake from soil. The present study was undertaken to investigate quantitative and qualitative estimation of phosphate solubilizer by using nineteen isolates of Trichoderma grown on Pikovskaya’s Agar and NBRIP media. It was found that all isolates were capable of differentially utilizing 5 g/L TCP in NBRIP broth. This was indicated by the soluble phosphate concentrations and increase in acidity of growth medium. Out of 19 isolates, all isolates were capable in phosphate solubilization. However, the P- solubilizing efficiency was found higher in case of the isolate number-59 and 89. While isolate number-102 was the strongest and isolate number-23 was the weakest P-solubilizer. Minimum Phosphate solubilization concentration was observed in 3rd day (0%) that simultaneously increased on 7th day (52.63%) followed by 9th day (100%) and remaining all days 13th, 17th and 21st days also observed 100% efficiency.

Effective Solubilization of Rock Phosphate by a Phosphate-Tolerant Bacterium Serratia sp.

Phosphate-solubilizing bacteria (PSB) can effectively promote the recovery of phosphate-contaminated soil to environmentally safe phosphate levels. The ability and mechanisms of rock phosphate (RP) solubilization were studied using strain LX2 isolated from a phosphate mining wasteland, which was identified as Serratia sp. It was found that strain LX2 could grow at phosphate concentrations of 0–350 mg/L. Optimization of carbon and nitrogen sources was also conducted to increase RP solubilization. and maximum soluble phosphate concentration of 288.69 mg/L with glucose 20 g/L and NH4Cl 0.5 g/L were obtained. The RP solubilization effect under different soluble phosphate concentrations showed that the effective RP solubilization ability by strain LX2 was always accompanied by a decrease in pH. Further, the mechanisms of RP solubilization were studied through Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The presence of strain LX2 caused more corrosive pores on RP surface, which represented the excellent insoluble phosphate solubilization ability. As the soluble phosphate content increased, a gypsum film covered the RP surface, which might prevent further RP solubilization. These results suggested that strain LX2 had great potential in solubilizing RP and could be used as a bioremediation approach of excessive phosphate in phosphate mining wasteland.

Effect of &lt;i&gt;Pomacea canaliculata&lt;/i&gt; grazing on three submerged macrophytes and the related physicochemical factors

外来种福寿螺（Pomacea canaliculata）相较我国本土螺类其牧食量更大且繁殖速度更快，对栖息地水生植物的现存量和实施水生植被恢复的生态治理工程的成功性可能构成威胁，目前对福寿螺影响浅水湖泊沉水植物的重建缺乏足够的研究.本文通过设置不同沉水植物种类组合系统，研究福寿螺对3种常用于浅水富营养化湖泊治理的沉水植物密刺苦草（Vallisneria denseserrulata）、轮叶黑藻（Hydrilla verticillata）、穗花狐尾藻（Myriophyllum spicatum）的牧食偏好以及不同植物配置系统理化因子的响应变化，结果表明福寿螺对沉水植物植株附着偏好为密刺苦草>轮叶黑藻>穗花狐尾藻，而牧食破坏强度为轮叶黑藻>穗花狐尾藻>密刺苦草，轮叶黑藻最容易受到福寿螺牧食影响而快速消亡，穗花狐尾藻叶片也会被全部牧食仅剩下茎，而苦草存活受到的影响较小.福寿螺会导致轮叶黑藻+密刺苦草组合系统中总氮、氨氮、总磷、正磷酸盐浓度显著升高，而密刺苦草+穗花狐尾藻组合中总磷、正磷酸盐浓度显著升高，但是在轮叶黑藻+穗花狐尾藻组合中仅总氮浓度显著升高.研究表明福寿螺能够影响沉水植物间的竞争关系，但是3种沉水植物均不能阻止福寿螺的牧食；福寿螺牧食会显著降低沉水植物生物量，最终会影响草型清水态系统的稳定性.;Compared with native snails in China, Pomacea canaliculata snails exert a higher grazing pressure on plants and have faster growth and reproduction rates, which may negatively affect aquatic plants' standing stock and ecological reestablishment. However, few studies have examined the potential effects of the presence of P. canaliculata on submerged macrophyte reestablishment. In this study, we assessed the preference of P. canaliculata for three submerged plants, namely Vallisneria denseserrulata, Hydrilla verticillata, and Myriophyllum spicatum—which have been largely planted for recovering Chinese eutrophic shallow lakes. The results indicated that the attachment preference of P. canaliculata for submerged macrophytes was in the following order: V. denseserrulata>H. verticillata>M. spicatum. Moreover, P. canaliculata grazing negatively affected plant survival in the following order of magnitude: H. verticillata>M. spicatum>V. denseserrulata. H. verticillata was the most vulnerable to snail grazing and died out rapidly. M. spicatum leaves had been completely consumed by the end of the experiment. V. denseserrulata was the least influenced by P. canaliculata. Compared with the controls, the concentrations of total nitrogen (TN), ammonia nitrogen (NH₃-N), total phosphorus (TP), and soluble reactive phosphate (SRP) were higher with the H. verticillata + V. denseserrulata treatment; TP and SRP concentrations were higher with the V. denseserrulata + M. spicatum treatment; and TN concentrations were higher with the V. denseserrulata + M. spicatum treatment. These results suggest that the grazing preference of P. canaliculata alters the competitive advantage of submerged macrophyte. However, none of the submerged macrophytes prevented P. canaliculata grazing, resulting in decreases in the production of the submerged macrophytes and in the likelihood of clear-water state establishment.

Characteristics of plant growth-promoting rhizobacteria SCPG-7 and its effect on the growth of Capsicum annuum L.

The strain SCPG-7 was isolated from saline soil in a cotton field. It is confirmed that the strain SCPG-7 is Pseudomonas sp. by means of the analysis of its phenotypic features and 16S rRNA sequence. SCPG-7 was capable of dissolving mineral tri-calcium phosphate (Ca3(PO4)2) and tri-magnesium phosphate (Mg3(PO4)2). In contrast, no showing iron phosphate (FePO4) or aluminum phosphate (AlPO4) solubilizing activities were detected by this experimental approach. The ratio of the dissolved P diameter to the colony diameter was 1.86. To study the phosphate dissolving mechanisms of the strain, we analyzed the changes of the pH value, the soluble phosphate content, the concentration of alkaline phosphatase, and the production of organic acid in the insoluble phosphate liquid medium. 2-keto-D-gluconicacid, α-ketoglutaric acid, succinic acid, etc. were characterized by LC-MS/MS in NBRIP medium. The concentration of 2-keto-D-gluconicacid increased to 88.6 mg/L after being cultured for 216 h. The strain decreased the pH value of the medium from 7.4 to 4.7 and the released soluble phosphate up to 516 mg/L, which proved the production of organic acids and alkaline phosphatase to be mechanism for solubilizing P. Under low phosphorus stress, Pseudomonas global regulatory protein PhoB regulates the transcription of the alkaline phosphatase gene. IAA and siderophore were secreted by SCPG-7. After treatment with SCPG-7, the individual plant height and dry weight of pepper increased by 23.3 and 31.2%, respectively, compared to the control group. The results show that the strain SCPG-7 has the potential to convert insoluble inorganic phosphorus to plant-available phosphorus. It can enhance soil phosphorus release through biological pathways, thereby increasing crop yield, and providing germplasm resources for the development of biological fertilizers.

A method to prepare a high-strength building material from press-formed phosphogypsum purified with waste zeolite

The production of by-product phosphogypsum is very problematic. In order to recycle the phosphogypsum into a building material, its harmful acidic impurities (especially the soluble phosphate) should be purified, and the mechanical properties improved. Therefore, in this study, a novel method of processing the phosphogypsum is proposed. It consists in the addition of waste zeolite to adsorb the phosphate impurities, and in the application of press-forming processing to improve the compressive strength of the hardened specimens. The zeolite additive has proven to be an efficacious adsorbent, which reduced the soluble phosphate content by 3.2–7.5 times and surprisingly improved the hydration degree of the phosphogypsum. Moreover, the press-forming of phosphogypsum by applying 15 and 20 MPa pressure produced specimens with a compressive strength over 50 MPa.

Physicochemical properties of skim milk powder dispersions prepared with calcium-chelating sodium tripolyphosphate, trisodium citrate, and sodium hexametaphosphate

Due to health benefits of proteins, the demand for protein beverages has grown rapidly. Translucent protein drinks with neutral pH may have advantages over acidic beverages that may cause dental erosion, and skim milk powder (SMP) is an affordable protein ingredient. Dissociating casein micelles by calcium chelators is a well-known method to reduce SMP dispersion turbidity, but much is to be studied for physicochemical properties as affected by chelator type and concentration. The objective of the present study was to characterize physicochemical properties of dispersions with 5% (wt/vol) SMP after addition of 0 to 30 mM sodium tripolyphosphate, trisodium citrate, or sodium hexametaphosphate. The turbidity was decreased with increasing chelator concentration, with the lowest turbidity observed in the SMP dispersions with sodium hexametaphosphate. The smallest hydrodynamic diameter was observed at an intermediate chelator concentration, resulting from the balance of casein micelle dissociation and aggregation of dissociated caseins induced at an elevated ionic strength. Heating at 90°C for 5 min increased turbidity but lowered hydrodynamic diameter of SMP dispersions, with some exceptions. The morphology of SMP dispersions differed for each chelator and was also affected by chelator concentration and heating. Trisodium citrate was the most effective to demineralize colloidal calcium phosphate in casein micelles, but the amount of dissolved calcium was not directly correlated with the decreased turbidity, indicating different chelating mechanisms by each chelator. Analysis of serum calcium and phosphorus concentrations also suggested that the type and concentration of soluble and insoluble calcium phosphates and their partitioning in the serum and casein micelles were dynamically changed by the studied parameters to affect dispersion turbidity and structures of casein micelles. Findings from the present study may be used to formulate translucent beverages incorporating SMP and other casein micelle ingredients.

Introducing the Self‐Cleaning FiLtrAtion for Water quaLity SenSors (SC‐FLAWLeSS) system

AbstractSensor‐based, semicontinuous observations of water quality parameters have become critical to understanding how changes in land use, management, and rainfall‐runoff processes impact water quality at diurnal to multidecadal scales. While some commercially available water quality sensors function adequately under a range of turbidity conditions, other instruments, including those used to measure nutrient concentrations, cease to function in high turbidity waters (&gt; 100 nephelometric turbidity units [NTU]) commonly found in large rivers, arid‐land rivers, and coastal areas. This is particularly true during storm events, when increases in turbidity are often concurrent with increases in nutrient transport. Here, we present the development and validation of a system that can affordably provide Self‐Cleaning FiLtrAtion for Water quaLity SenSors (SC‐FLAWLeSS), and enables long‐term, semicontinuous data collection in highly turbid waters. The SC‐FLAWLeSS system features a three‐step filtration process where: (1) a coarse screen at the inlet removes particles with diameter &gt; 397 μm, (2) a settling tank precipitates and then removes particles with diameters between 10 and 397 μm, and (3) a self‐cleaning, low‐cost, hollow fiber membrane technology removes particles ≥ 0.2 μm. We tested the SC‐FLAWLeSS system by measuring nitrate sensor data loss during controlled, serial sediment additions in the laboratory and validated it by monitoring soluble phosphate concentrations in the arid Rio Grande river (New Mexico, U.S.A.), at hourly sampling resolution. Our data demonstrate that the system can resolve turbidity‐related interference issues faced by in situ optical and wet chemistry sensors, even at turbidity levels &gt; 10,000 NTU.

Implementing an Extended Kalman Filter for estimating nutrient composition in a sequential batch MBBR pilot plant.

Online monitoring of water quality parameters can provide better control over various operations in wastewater treatment plants. However, a lack of physical online sensors, the high price of the available online water-quality analyzers, and the need for regular maintenance and calibration prevent frequent use of online monitoring. Soft-sensors are viable alternatives, with advantages in terms of price and flexibility in operation. As an example, this work presents the development, tuning, implementation, and validation of an Extended Kalman Filter (EKF) on a grey-box model to estimate the concentration of volatile fatty acids (VFA), soluble phosphates (PO4-P), ammonia nitrogen (NH4-N) and nitrate nitrogen (NO3-N) using simple and inexpensive sensors such as pH and dissolved oxygen (DO). The EKF is implemented in a sequential batch moving bed biofilm reactor (MBBR) pilot scale unit used for biological phosphorus removal from municipal wastewater. The grey-box model, used for soft sensing, was constructed by fitting the kinetic data from the pilot plant to a reduced order version of ASM2d model. The EKF is successfully validated against the standard laboratory measurements, which confirms its ability to estimate various states during the continuous operation of the pilot plant.