Showing papers on "Phosphorus published in 2023"

Insights into the conversion of dissolved organic phosphorus favors algal bloom, arsenate biotransformation and microcystins release of Microcystis aeruginosa.

Abstract: Little information is available on influences of the conversion of dissolved organic phosphorus (DOP) to inorganic phosphorus (IP) on algal growth and subsequent behaviors of arsenate (As(V)) in Microcystis aeruginosa (M. aeruginosa). In this study, the influences factors on the conversion of three typical DOP types including adenosine-5-triphosphate disodium salt (ATP), β-glycerophosphate sodium (βP) and D-glucose-6-phosphate disodium salt (GP) were investigated under different extracellular polymeric secretions (EPS) ratios from M. aeruginosa, and As(V) levels. Thus, algal growth, As(V) biotransformation and microcystins (MCs) release of M. aeruginosa were explored in the different converted DOP conditions compared with IP. Results showed that the three DOP to IP without EPS addition became in favor of algal growth during their conversion. Compared with IP, M. aeruginosa growth was thus facilitated in the three converted DOP conditions, subsequently resulting in potential algal bloom particularly at arsenic (As) contaminated water environment. Additionally, DOP after conversion could inhibit As accumulation in M. aeruginosa, thus intracellular As accumulation was lower in the converted DOP conditions than that in IP condition. As(V) biotransformation and MCs release in M. aeruginosa was impacted by different converted DOP with their different types. Specifically, DMA concentrations in media and As(III) ratios in algal cells were promoted in converted βP condition, indicating that the observed dissolved organic compositions from βP conversion could enhance As(V) reduction in M. aeruginosa and then accelerate DMA release. The obtained findings can provide better understanding of cyanobacteria blooms and As biotransformation in different DOP as the main phosphorus source.

Patterns and driving mechanism of soil organic carbon, nitrogen, and phosphorus stoichiometry across northern China’s desert-grassland transition zone

Abstract: • SOC, TN, and TP stoichiometry differed primarily in soil and vegetation types. • Main driver factors of SOC, TN, and TP stoichiometry were MAP and SC. • Climate, vegetation, and soil jointly impacted SOC, TN, and TP stoichiometry. • Precipitation was vital in regulating SOC, TN, and TP stoichiometry. • Temperature and soil pH directly and negatively affected SOC, TN, C:P, and N:P. Desert-grassland transition zone is a critical ecological barrier frontier against sandstorms and desertification in northern China. Soil nutrient stoichiometry is closely related to plant community biomass, biodiversity, ecosystem functions and stability. However, how the relationship between climate, vegetation, and soil property drives the spatial pattern of soil nutrient stoichiometry remains unclear. We investigated soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and their ratios (C:N, C:P and N:P) from 82 sites located in a desert-grassland transition zone in Inner Mongolia. SOC, TN, and TP contents, and soil C:P and N:P ratios were higher in typical grassland than that in shrub desert, higher in aridisols than in desert soil and desert eolian sand soil. The C:N ratio showed no significant difference between different vegetation types. SOC and TN contents showed an apparent decrease with soil depth in aridisols, of which the surface was well-covered by herbaceous plants. Soil TP content, C:N, C:P, and N:P ratios are different primarily among soil types, but not along soil depth, which may be mainly attributed to SOC, TN, and TP changed synergistically and weak soil leaching in desert areas. Redundancy analysis showed that precipitation, and silt and clay content were the most critical factors influencing SOC, TN, and TP stoichiometry. Structural equation modeling revealed that precipitation could impact soil nutrient stoichiometry by affecting the vegetation and soil physicochemical properties. Temperature and soil pH had impact on the mineralization and decomposition of organic matters, and significant direct and negative effect on SOC, TN, C:P, and N:P (except MAT) ratio. Our results highlighted the importance of current climate change on soil organic C, TN, and TP contents and C:N:P stoichiometry, and future climate change and its eco-impact in the desert-grassland transition zone.

In-Situ Protonated-Phosphorus Interstitial Doping Induces Long-Lived Shallow Charge Trapping in Porous C3-xN4 Photocatalyst for Highly Efficient H2 Generation

Abstract: Efficient photocatalytic solar-to-H2 conversion is pivotal to zero-carbon energy supply. Graphitic carbon nitride (g-C3N4) is a promising visible-light photocatalyst but suffers from intrinsic electron-hole recombination and deep-charge trapping, limiting its...

Characteristics and distribution of phosphorus in surface sediments of a shallow lake.

Abstract: Phosphorus (P) in sediments plays an important role in shallow lake ecosystems and has a major effect on the lake environment. The mobility and bioavailability of P primarily depend on the contents of different P forms, which in turn depend on the sedimentary environment. Here, sediment samples from Baiyangdian (BYD) lake were collected and measured by the Standards, Measurements, and Testing procedure and Phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) to characterize different P forms and their relationships with sediment physicochemical properties. The P content in the sediments varied in different areas and had characteristics indicative of exogenous river input. Inorganic P (334-916 mg/kg) was the dominant form of P. The 31P NMR results demonstrated that orthophosphate monoesters (16-110 mg/kg), which may be a source of P when redox conditions change, was the dominant form of organic P (20-305 mg/kg). The distribution of P forms in each region varied greatly because of the effects of anthropogenic activities, and the regions affected by exogenous river input had a higher content of P and a higher risk of P release. Principal component analysis indicated that P bound to Fe, Al, and Mn oxides and hydroxides (NaOH-P) and organic P were mainly derived from industrial and agricultural pollution, respectively. Redundancy analysis indicated that increases in pH lead to the release of NaOH-P. Organic matter plays an important role in the organic P biogeochemical cycle, as it acts as a sink and source of organic P.

Effect of silicon and phosphorus fertilization on growth, productivity and profitability of aerobic rice (Oryza sativa)

Abstract: A field experiment was conducted at ICAR- Indian Agricultural Research Institute, New Delhi during rainy (kharif) seasons of 2015 and 2016 to study the effect of silicon and phosphorus levels on yield, yield attributes and economics of aerobic rice (Oryza sativa L.). Four levels each of phosphorus (0, 30, 60 and 90 kg P2O5/ha) and silicon (0, 40, 80 and 120 kg Si/ha) were tested in a factorial randomized block design (FRBD) and replicated three times. Growth and yield attributes were significantly higher when phosphorus and silicon were included in the nutrient management of aerobic rice cultivation. Growth, yield, yield attributes and economics were significantly affected by the combined application of silicon and phosphorus. The highest aerobic rice grain yield (5.66 and 5.62 t/ha), net returns (Rupees 92.4×103 /ha and 90.1×103 /ha) and yield attributes were recorded with 90 kg P2O5 /ha during both the years of experimentation. However, it was at par with 60 kg P2O5 /ha during both the years of experimentation. In case of silicon application, highest grain yield (5.53 and 5.65 t/ha), net returns (Rupees 90.7×103 /ha and 92.4×103 /ha) and yield attributes were recorded with 120 kg Si/ha, however, it was at par with 80 kg Si/ha during both the years of experimentation. Therefore, the application of phosphorus and silicon should be adopted for achieving higher productivity and profitability of aerobic rice.

Effect of Phosphorus Modulation in Iron Single-Atom Catalysts for Peroxidase Mimicking.

Abstract: Fe-N-C single-atom catalysts (SACs) exhibit excellent peroxidase (POD)-like catalytic activity, owing to their well-defined isolated iron active sites on the carbon substrate, which effectively mimic the Fe-Nx active site's structure of natural peroxidase. To further meet the requirements of diverse biosensing applications, SACs POD-like activity still needs to be continuously enhanced. Herein, we introduce phosphorus heteroatoms to boost the POD-like activity of Fe-N-C SAC. A one-dimensional carbon nanowire (FeNCP/NW) catalyst with enriched Fe-N4 active sites is designed and synthesized, and phosphorus (P) atoms are doped in the carbon matrix to affect the Fe center through the long-range interaction. The experimental results show that the phosphorus-doping process can boost the POD-like activity more than the non-P-doped one with excellent selectivity and stability. The mechanism analysis results show that the introduction of P into SAC can first significantly enhance POD-like activity, and then decrease with increasing amount of P. As a proof of concept, the FeNCP/NW is employed in an enzyme cascade platform for highly-sensitive colorimetric detection of the neurotransmitter acetylcholine. This article is protected by copyright. All rights reserved.

What drives the change of nitrogen and phosphorus loads in the Yellow River Basin during 2006-2017?

Abstract: The Yellow River Basin (YRB) plays a very important role in China's economic and social development and ecological security. In particular, the ecosystem of the YRB is sensitive to climate change. However, the change of nutrient fluxes in this region during the past years and its main driving forces remain unclear. In this study, a hydrologic model R System for Spatially Referenced Regressions on Watershed Attributes (RSPARROW) was employed to simulate the spatio-temporal variations in the fluxes of total nitrogen (TN) and total phosphorus (TP) during the period of 2006-2017. The results suggested that the TN and TP loads increased by 138% and 38% during 2006-2014, respectively, and decreased by 66% and 71% from 2015 to 2017, respectively. During the period of 2006-2017, the annual mean fluxes of TN and TP in the YRB were in the range of 3.9 to 591.6 kg/km2/year and 1.7 to 12.0 kg/km2/year, respectively. TN flux was low in the upstream area of the Yellow River, and presented a high level in the middle and lower reaches. However, the flux of TP in Gansu and Ningxia section was slightly higher than that in the lower reaches of the Yellow River. Precipitation and point source are the key drivers for the inter-annual changes of TN loads in most regions of the YRB. While the inter-annual variations of TP loads in the whole basin are mainly driven by the point source. This study demonstrates the important impacts of climate change on nutrient loads in the YRB. Moreover, management measures should be taken to reduce pollution sources and thus provide solid basis for control of nitrogen and phosphorus in the YRB.

Life Cycle Assessment (LCA) of the integrated technology for the phosphorus recovery from sewage sludge ash (SSA) and fertilizers production

Abstract: The paper presents an application of Life Cycle Assessment (LCA) method for the environmental evaluation of the technologies for the fertilizers production. LCA has been used because it enables the most comprehensive identifi cation, documentation and quantifi cation of the potential impacts on the environment and the evaluation and comparison of all signifi cant environmental aspects. The main objective of the study was to assess and compare two technologies for the production of phosphorus (P) fertilizers coming from primary and secondary sources. In order to calculate the potential environmental impact the IMPACT 2002+ method was used. The fi rst part of the LCA included an inventory of all the materials used and emissions released by the system under investigation. In the following step, the inventory data were analyzed and aggregated in order to calculate one index representing the total environmental burden. In the scenario 1, fertilizers were produced with use of an integrated technology for the phosphorus recovery from sewage sludge ash (SSA) and P fertilizer production. Samples of SSA collected from two Polish mono-incineration plants were evaluated (Scenario 1a and Scenario 1b). In the scenario 2, P-based fertilizer (reference fertilizer – triple superphosphate) was produced from primary sources – phosphate rock. The results of the LCA showed that both processes contribute to a potential environmental impact. The overall results showed that the production process of P-based fertilizer aff ects the environment primarily through the use of the P raw materials. The specifi c results showed that the highest impact on the environment was obtained for the Scenario 2 (1.94899 Pt). Scenario 1a and 1b showed the environmental benefi ts associated with the avoiding of SSA storage and its emissions, reaching -1.3475 Pt and -3.82062 Pt, respectively. Comparing results of LCA of P-based fertilizer production from diff erent waste streams, it was indicated that the better environmental performance was achieved in the scenario 1b, in which SSA had the higher content of P (52.5%) in the precipitate. In this case the lower amount of the energy and materials, including phosphoric acid, was needed for the production of fertilizer, calculated as 1 Mg P2O5. The results of the LCA may play a strategic role for the decision-makers in the aspect of searching and selection of the production and recovery technologies. By the environmental evaluation of diff erent alternatives of P-based fertilizers it is possible to recognize and implement the most sustainable solutions. Life Cycle Assessment (LCA) of the integrated technology for the phosphorus recovery from sewage sludge ash... 43 be implemented on the local, regional, and global levels (Smol 2019). In Europe, the production of P is carried out in Finland and Russia, and it could cover only up to 12% of European demand for P resources. Almost all demand for phosphate rock (88%) and all demand for phosphorus (100%) is satisfi ed by import, mainly from Morocco, Algeria, Russia, Syria, Kazakhstan and China (COM No. 490, 2017). In order to increase the security of this RM on the European level, in 2013, the European Commission (EC) published the specially dedicated document ‘Consultative Communication on the Sustainable Use of Phosphorus’ (COM No. 517, 2013). The EC underlined that the current situation, where P resources are wasted and lost at every step of its life cycle, causes concerns about future supplies and soil and water pollution, both in the European Union (EU) and worldwide. Therefore, the EC initiated a debate on the state of play and the actions that should be considered in order to increase the P recovery from waste streams. Next year (2014) the phosphate rock, which is an important source of phosphates, was indicated as a Critical Raw Material (CRM) for the European economy (COM No. 297, 2014) due to the risks of its shortage of supply in the EU and its impact of a shortage on the economy is greater than other RMs (COM No. 490, 2017). In the 2017, the list of CRMs was extended and currently next to phosphate rock, phosphorus is also indicated as the CRM. In the presented Communication, the EC indicated ‘End-of-life recycling input rate’ which measures the ratio of recycling from old scrap to EU demand of a given RM (the sum of primary and secondary material supply inputs to the EU). This indicator for the phosphate rock is equal to 17%, and for phosphorus to 0% (COM No. 490, 2017). As there is a high potential for recovery of those materials from waste, the values of presented indicators should be higher in the EU. Therefore, further actions should be taken by the Member states in this area. It must be also pointed out that this concept is in the line with the circular economy (CE) (COM No. 398, 2014, COM No. 614, 2015) which is an essential way to deliver the resource effi ciency agenda, which has been established under the Europe 2020 Strategy for smart, sustainable and inclusive growth (COM No. 2020, 2010). In 2015, the EC presented the CE Action Plan (Circular Economy Package) (COM No. 614, 2015) which includes measures that should help stimulate Europe’s transformation towards the CE model. In the CE Action Plan, the EC provided a concrete and ambitious programme of action, considering the whole cycle: from extraction of primary RMs, their production and consumption to waste management. The CE action plan includes also the issues related to the market for secondary RMs, including the fertilizes resources such as phosphorus, and a revised legislative proposal on waste. The fi rst executive act of the proposed CE Package is the proposal for a regulation of the rules on the making available on the market of CE marked fertilising products, including the fertilizers produced from P-rich waste streams (COM No. 157, 2016). This makes the production of fertilizers from waste extremely important for the EU and it can be expected that technologies in this fi eld will develop in the following years. Phosphorus could be recovered from serval waste streams (Cieślik and Konieczk 2017). One of the most promising P secondary source is domestic waste – in particular sewage sludge (SS) and sewage sludge ash (SSA) (Kalmykova and Fedje 2013, Smol et al. 2016) containing large amounts of P, which, if recycled in line with the CE model, may potentially cover up to 30% of EU’s demand of phosphate fertilizers (COM No. 517, 2013). Currently, there is largely unexploited investment potential remaining in relation to this in the European countries. Anyway, there is a positive trend in this direction. As a consequence of the above EC’s recommendations, in the last years the signifi cant increase in research works on technologies for P recovery from waste streams and fertilizers production is observed and more and more of those technologies are available on the market. For now, the full scale P – recovery technologies from digestate and from liquor are in operation in Germany, Belgium, United Kingdom, Denmark, Netherlands, France, Italy and Spain. In Poland, there is one installation under construction for struvite production at the sewage treatment plant in Cielcza, supervised by the Jarocin Waterworks Company (P-REX project, 2018). All technologies and solutions are focused on use of waste as an alternative source of raw materials (Ciesielczuk et al., 2018) in fertilizer industry should be evaluated from economic (Generowicz et al. 2011, Kowalski et al. 2012, Jóźwiakowski et al. 2015, Makara et al. 2016), environmental (Feng and Reisner 2011, Koneczna and Kulczycka 2011; Moghim and Garna 2019) and social points of view. The impact of the above technologies on the environment can be evaluated using environmental assessment methods (Kowalski et al., 2007, Gaska et al., 2017). One of those methods is the Life Cycle Assessment (LCA), which enables the most comprehensive identifi cation, documentation and quantifi cation of the potential impacts on the environment and the evaluation and comparison of all signifi cant environmental aspects (Heimersson et al. 2016, Kulczycka et al. 2015). The current paper presents an application of LCA method for the environmental evaluation of the integrated technology for the P recovery from SSA and fertilizers production. The technology has been developed in the framework of the Polish project “PolFerAsh – Polish Fertilizers form Ash” which has been conducted in the Cracow University of Technology and Mineral and Energy Economy Research Institute of the Polish Academy of Sciences in Poland, and has received the founding from the National Centre for Research and Development. Materials and Methods Environmental evaluation of the two scenarios of P-based fertilizers production was conducted with use of the Life Cycle Assessment method. It is a widely used technique helpful in the quantifi cation of environmental impacts of products and technologies in the fertilizer sector (Amann et al. 2018, Chojnacka et al. 2019). The conducted LCA is in the line with the ISO 14044 guidelines (ISO, 2006a) and the ISO 14040 principles (ISO, 2006b). The following steps are part of the presented LCA: goal and scope defi nition, Life Cycle Inventory (LCI), Life Cycle Impact Assessment (LCIA) and interpretation of the results. The impact assessment is implemented using the LCA software SimaPro 8 (8.5). In order to calculate the potential environmental impact the IMPACT 2002+ method was used. The methodology of all steps of research is presented in the following sections. 44 M. Smol, J. Kulczycka, Ł. Lelek, K. Gorazda, Z. Wzorek Goal and scope defi nition The aim of the LCA was to assess and compare the processes of P-based fertilizers production from primary and secondary sources. The specific potential environmental impacts were evaluated for the following scenarios:  Scenario 1: P-based fertilizer from secondary sources – waste-based fertilizer production scenario,  Scen

Flame Retardant Combinations with Expandable Graphite/Phosphorus/CuO/Castor Oil in Flexible Polyurethane Foams

Abstract: A series of flexible polyurethane foams (FPUFs) were prepared with single and different combinations of flame retardants and additives. Expandable graphite (EG), phosphorous polyol (OP), copper (II) oxide (CuO), and/or castor oil (CAS) were added to FPUF during the foam preparation in a one-step process. The purpose of the study is to evaluate the synergistic effects of the flame retardants, additives, and the presence of bio-based content on the mechanical properties, flame retardancy, and smoke behavior of FPUFs. The combination of 10 wt % EG and 5 wt % OP in FPUF significantly improves the char yield. In the cone calorimeter experiment, the char yield is nearly three times higher than that with 10 wt % EG alone. The smoke behavior is additionally evaluated in a smoke density chamber (SDC). Comparing the samples with a single flame retardant, 10 wt % EG in FPUF considerably reduces the amount of smoke released and the emission of toxic gases. Replacing the amount of 10 wt % polyether polyol in FPUF with CAS maintains the physical and mechanical properties and fire behavior and enhances the bio-based content. The presence of 0.1 wt % CuO in FPUF effectively reduces the emission of hydrogen cyanide. As a result, this study proposes a multicomponent flame retardant strategy for FPUF to enhance the biomass content and address the weaknesses in flame retardancy, smoke, and toxic gas emissions. A starting point is disclosed for future product development.

Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses

Abstract: Phosphorus (P) is an essential and often limiting element that could play a crucial role in terrestrial ecosystem responses to climate warming. However, it has yet remained unclear how different P cycling processes are affected by warming. Here we investigate the response of soil P pools and P cycling processes in a mountain forest after 14 years of soil warming (+4 °C). Long-term warming decreased soil total P pools, likely due to higher outputs of P from soils by increasing net plant P uptake and downward transportation of colloidal and particulate P. Warming increased the sorption strength to more recalcitrant soil P fractions (absorbed to iron oxyhydroxides and clays), thereby further reducing bioavailable P in soil solution. As a response, soil microbes enhanced the production of acid phosphatase, though this was not sufficient to avoid decreases of soil bioavailable P and microbial biomass P (and biotic phosphate immobilization). This study therefore highlights how long-term soil warming triggers changes in biotic and abiotic soil P pools and processes, which can potentially aggravate the P constraints of the trees and soil microbes and thereby negatively affect the C sequestration potential of these forests.

Recycling phosphorus from waste in China: Recycling methods and their environmental and resource consequences

Abstract: Recycling phosphorus (P) from waste is an effective way to alleviate resource and environmental pollution due to excessive phosphate consumption. In order to better understand the feedback of P cycle to waste recycling methods, a P waste feedback model was built and was then used to predict P waste generation, recycling, loss and phosphate consumption in China under several P management scenarios. Three recycling methods, ‘waste as fertilizer’, ‘waste as feed’ and ‘waste as industrial material’, were analyzed for each scenario. The results show that people choosing a more balanced diet will largely increase P loss and phosphate consumption. The integration of all P sustainable measures can offset these increase and P loss and phosphate consumption will be 50% and 62% lower than 2015, respectively. ‘Waste as fertilizer’ decreases per capita phosphate consumption from 10 kg P y−1 to 2.6 kg P y−1, and ‘waste as feed’ decreases per capita P loss from 6.2 kg P y−1 to 2.2 kg P y−1. ‘Waste as material’ method is less effective among the three methods. Integrated measure with ‘waste as fertilizer’ method minimizes the pressure of P reserve depletion, but the economically recoverable reserve would still be depleted around 2053.

The High Phosphorus Incorporation Promotes the Soil Enzymatic Activity, Nutritional Status, and Biomass of the Crop

Abstract: Phosphorus (P) application in the soil improves soil fertility and thus contributes to reproductive organ development, resulting in a higher cotton yield. However, the effect of increasing phosphorus rate on soil nutrient status, phosphorus-related enzyme activities, and its effects on crop productivity needs excellent attention. A consecutive two-year (2017-2018) field experiment containing three phosphorus levels [0 (P1), 100 (P2), and 200 (P3) kg P 2 O 5 ha -1 ] was accomplished by maintaining three replications. During both cropping years, soil samples were gathered from the topsoil (0-20 cm) and subsurface (20-40 cm) during the harvesting stage of the cotton crop. Soil collected at topsoil showed a significant increase in available and total phosphorus contents and urease and acid, alkaline, and neutral phosphatase enzyme activities compared with the sub-soil. The soil nutrients, viz. ammonium, nitrate, total nitrogen, available potassium, and total potassium, were significantly higher in P3 at the topsoil compared to other treatments. Soil enzymes viz. urease and acid, alkaline, and neutral phosphatase activities in the P3 were improved compared to the P1 and P2 applications. On average, the activities of these enzymes were maximum in 2017 at both soil depths. Moreover, the maximum biomass accumulation was observed in vegetative (root, stem, and leaves) and reproductive (bur, lint, and seed) organs with P3 incorporation in the soil. Similarly, an increase in the phosphorus application rate significantly enhanced the plant biomass and seed cotton yield during the 2017 and 2018 cropping seasons. Conclusively, the findings of this study showed that the P3 (200 kg P 2 O 5 ha −1 ) rate enhanced cotton productivity by improving the soil physicochemical properties, which alternately enhanced

Effective removal of phosphorus from high phosphorus steel slag using carbonized rice husk.

Abstract: High phosphorus steel slag and carbonized rice husk are two common wastes characterized by high generation and low secondary use values. Through the reduction of high phosphorus steel slag by biomass, both wastes were fully utilized, thus reducing the negative impact on the environment. In this study, variables such as temperature, time, and amount of reactants were changed to determine the optimal conditions for the reaction of steel slag with carbonized rice husk at high temperatures. The actual amount of reducing agent consumed during the reduction was significantly greater than that predicted by theoretical calculations. Adding three carbon equivalent of carbonized rice husk and maintaining at 1500°C for 30 min could remove 79.25% of P2O5 in the slag. By modeling the material cycle in which high phosphorus steel slag was treated with biomass, the product could be used for crop growth. Meanwhile, the reduced iron and residual steel slag can be used to make steel again, thereby leading to a sharp reduction in fossil fuel usage and greenhouse gas emissions in this process.

Changes in rhizosphere phosphorus fractions and phosphate-mineralizing microbial populations in acid soil as influenced by organic acid exudation

Abstract: Interactions were explored between organic acids, phosphate-mineralizing microorganisms, and phosphorus fractions in rhizosphere soil. Bulk soil, rhizosphere soil, and root samples were randomly collected from a mature lemon tree plantation. Composition of acid (phoC) and alkaline (phoD) phosphatase gene harboring bacterial populations in rhizosphere soil were different. Whereas only soil properties affected the phoC-harboring bacterial population, soil properties and organic acids shaped the phoD-harboring bacterial population. Organic acids, especially oxalic acid, rather than phosphatase significantly directly and indirectly affected phosphorus fractions. When oxalic acid concentration increased, abundances of phoD-harboring Pseudomonas and Bacillus also increased. Those genera then released alkaline phosphatase, which reduced the contents of calcium-bound organophosphorus, insoluble organophosphorus, and residual phosphorus. By contrast, when oxalic acid concentration decreased, abundance of phoC-harboring Xanthomonas increased. The genus released acid phosphatase, which reduced calcium-bound organophosphorus content. In addition, alkaline phosphatase released by phoD-harboring bacteria was more important than acid phosphatase in acid soil. In conclusion, oxalic acids have essential roles in directly and indirectly changing phosphorus fractions in lemon tree rhizosphere soil.

Foliar nutrient resorption stoichiometry and microbial phosphatase catalytic efficiency together alleviate the relative phosphorus limitation in forest ecosystems.

Abstract: Understanding how plants adapt to spatially heterogeneous phosphorus (P) supply is important to elucidate the effect of environmental changes on ecosystem productivity. Plant P supply is concurrently controlled by plant internal conservation and external acquisition. However, it's unclear how climate, soil, and microbes influence the contributions and interactions of the internal and external pathways for plant P supply. Here, we measured P and nitrogen (N) resorption efficiency (NRE and PRE), litter and soil acid phosphatase (AP) catalytic parameters (Vmax(s) and Km ), and soil physicochemical properties at 4 sites spanning from cold temperate to tropical forests. We found that the relative P limitation to plants was generally higher in tropical forests than temperate forests, but varied greatly among species and within sites. In P-impoverished habitats, plants resorbed more P than N during litterfall to maintain their N:P stoichiometric balance. In addition, once ecosystems shifted from N-limited to P-limited, litter and soil specific AP catalytic efficiency (Vmax(s) /Km ) increased rapidly, thereby enhancing organic P mineralization. Our findings suggested that ecosystems develop a coupled aboveground-belowground strategy to maintain P supply and N:P stoichiometric balance under P-limitation. We also highlighted that N cycle moderates P cycles and together shape plant P acquisition in forest ecosystems.

Microcystin Shows Thresholds and Hierarchical Structure With Physicochemical Properties at Lake Fayetteville, Arkansas, May Through September 2020

Abstract: Highlights Despite little to no dissolved nutrient supply in surface water, harmful algal blooms are sustained throughout the 2020 growing season. Sediment phosphorus release was high in a lake that has annual harmful algal blooms, and it is an important piece of the watershed management puzzle. Thresholds and hierarchical structure with individual physicochemical properties and pigment fluorescence at this lake explain a large portion of microcystin variability. Abstract. Harmful algal blooms (HABs) in freshwaters are a global concern, and research has focused on the nutrient drivers of cyanobacterial growth and toxin production. We explored the importance of nutrients on sustained cyanobacterial HABs producing measurable microcystin at Lake Fayetteville, Arkansas, USA. The specific objectives were to (1) quantify sediment phosphorus (P) flux and estimate potential equilibrium P concentrations (EPC0) in July 2020, (2) assess water quality conditions in the lake from March through September 2020, and (3) evaluate physicochemical thresholds (or change points, CPs) and hierarchical structure with total microcystin concentrations. The sediments were a potential P source under both oxic and anoxic conditions, and the SRP concentrations in the lake water were continuously less than the EPC0 estimated for bottom sediment (~0.03 mg L-1); sediments are likely a potential P source for cyanobacterial HABs at Lake Fayetteville. The physicochemical changes at Lake Fayetteville over the 2020 growing season were typical of small, hypereutrophic reservoirs, with low biomass in winter when nutrient supply was greatest and the greatest cyanobacterial growth and microcystin toxin as nutrient supply diminished into the growing season. Microcystin concentrations were elevated above 1 µg L-1 from mid-June through mid-August 2020, and most physicochemical parameters in this study showed thresholds or change points with microcystin. Hierarchical structure existed with total microcystin concentrations, showing the potential importance of cyanobacterial biomass, N supply, and total P on elevated microcystin. Nutrients and algal pigment raw fluorescence explained 83% of the variation in total microcystin concentrations at Lake Fayetteville during the 2020 growing season. Nutrients (both N and P) from external and internal sources are likely important drivers of these blooms and toxicity at Lake Fayetteville. Keywords: Harmful Algal Blooms, Nutrient Drivers, Sediment Phosphorus Release, Water Quality.

Microbial nitrogen and phosphorus co‐limitation across permafrost region

Abstract: The status of plant and microbial nutrient limitation have profound impacts on ecosystem carbon cycle in permafrost areas, which store large amounts of carbon and experience pronounced climatic warming. Despite the long‐term standing paradigm assumes that cold ecosystems primarily have nitrogen deficiency, large‐scale empirical tests of microbial nutrient limitation are lacking. Here we assessed the potential microbial nutrient limitation across the Tibetan alpine permafrost region, using the combination of enzymatic and elemental stoichiometry, genes abundance and fertilization method. In contrast with the traditional view, the four independent approaches congruently detected widespread microbial nitrogen and phosphorus co‐limitation in both the surface soil and deep permafrost deposits, with stronger limitation in the topsoil. Further analysis revealed that soil resources stoichiometry and microbial community composition were the two best predictors of the magnitude of microbial nutrient limitation. High ratio of available soil carbon to nutrient and low fungal/bacterial ratio corresponded to strong microbial nutrient limitation. These findings suggest that warming‐induced enhancement in soil nutrient availability could stimulate microbial activity, and probably amplify soil carbon losses from permafrost areas.