Phosphorus Enrichment Research Articles

Resource recycling of nitrogen and phosphorus from waste adsorbents: Implications for soil improvement and plant growth

The enrichment of nitrogen and phosphorus in sewage poses a significant risk of resource loss if not effectively recovered and utilized. This study investigates the sustainable management and conservation of these vital nutrients through the recycling of saturated Mg-loaded adsorbents as soil additives for mint (Mentha spicata) cultivation. The effects of recycled waste adsorbents were compared with new adsorbents, commercial compound fertilizers, and struvite, using a control check (CK) to assess their impact on soil nutrient content and plant growth parameters. Results showed that waste adsorbents significantly enhanced soil nutrient content compared to CK. Although nutrient levels in the first 30 days were lower than with commercial fertilizers, a reversal was noted between 30 and 60 days, indicating a slower nutrient release rate. Furthermore, the germination rate and leaf width of mint increased by 13.34 % and 25.38 %, respectively. Significant improvements in plant height, fresh weight, and dry weight demonstrated positive effects on growth. This study confirms the feasibility of recycling waste Mg-loaded adsorbents for the sustainable reutilization of nitrogen and phosphorus resources from wastewater, contributing to enhanced soil health and sustainable agricultural practices.

Effect of P Reduction on phoD-Harboring Bacteria Community in Solar Greenhouse Soil

Phosphorus (P) enrichment frequently occurs in the soil used in greenhouse vegetable production (GVP). Minimizing the application of P fertilizer represents a crucial approach to mitigating the accumulation of P in the soil and enhancing its utilization efficiency. However, the changes in bacterial communities and the turnover mechanism of soil P fractions related to soil P cycling after P fertilizer reduction are still unclear. To unravel these complexities, we devised three experimental treatments: conventional nitrogen (N), P, and potassium (K) fertilizer (N1P1K1); conventional N and K fertilizer without P (N1P0K1); and no fertilizer (N0P0K0). These experiments were conducted to elucidate the effects of P reduction on cucumber plant growth, soil P fractions, and the phoD-harboring bacterial community in the P-rich greenhouse soil. The results showed that there were no significant differences between the N1P1K1 and N1P0K1 treatments in terms of plant growth, yield, and P uptake, and the values for the N0P0K0 treatment were significantly lower than those for the N1P1K1 treatment. In a state of P depletion (N0P0K0, N1P0K1), the main P sources were Resin-Pi, NaHCO3-Pi, NaHCO3-Po, and NaOH-Pi. The contents of NaOH-Po and CHCl-Po in the N1P0K1 treatment increased significantly. Without P fertilizer, alkaline phosphatase (ALP) activity, phoD gene abundance, and bacterial community diversity were significantly increased. The abundance of Ensifer in the N0P0K0 and N1P0K1 treatments was 8 and 10.58 times that in the N1P1K1 treatment, respectively. Additionally, total phosphorus (TP) and available nitrogen (AN) were key factors affecting changes in the phoD bacterial community, while Shinella, Ensifer and Bradyrhizobium were the main factors driving the change in soil P fractions, and NaHCO3-Pi and NaOH-Pi were key factors affecting crop yield. Therefore, reducing the application of P fertilizer will increases the diversity of phoD-gene-harboring bacterial communities and promote organic P mineralization, thus maintaining the optimal crop yield.

Mobility, Bioavailability, and Enrichment of Soil-Bound Phosphorus in Flood-Prone Paddy Fields: A Case Study of Kunnukara, South India.

Bioavailability, enrichment, and risk of phosphorus (P) and its fraction composition were monitored in the paddy soils of Kunnukara during the pre-cultivation and post-harvest periods in the years 2020 and 2021. Iron-bound P (≥ 105.56 ± 0.05mg/kg) was found highest among the P fractions. The bioavailability of P was recorded at peak value during the post-harvest period, contributed by organic P, Iron bound P, and loosely bound P. Principal component analysis inferred that loosely bound P was pH-dependent and significantly influenced by cation exchange, particle density, soil aggregate stability, and total organic carbon (TOC) in the post-harvest soil, whereas TOC, aluminium-bound P, and calcium-bound P in the pre-cultivation soils. Additionally, physico-chemical parameters like electrical conductivity, bulk density, specific gravity, TOC, and soil aggregate stability have a significant impact on the composition of P fractions in the soil. Bioavailable phosphorus (BAP) ranged from 642.78 ± 0.49 to 594.20 ± 1.23mg/kg during the post-harvest period. Moreover, the contribution of BAP to total P ranged from 99.45 to 99.54%, indicating the fact that soil is sufficient in BAP. Pollution indices revealed that the paddy soils are at risk of eutrophication. Phosphorus Pollution Index (PPI) > 1 exhibited moderate pollution (1.06 to 1.07) at the topsoil (0-15cm) and PPI < 1, mild pollution (0.92 to 0.99) at 15-30cm depths. The organic nitrogen index ≥ 0.133 indicates severe soil pollution in the study site. An extended fertilizer application in the field contributes to nutrient enrichment and warrants the risk of contamination in nearby riverine systems (River Periyar and River Chalakkudy).

Simultaneous treatment and enrichment of total phosphorus from livestock sewage using hydrate technology

The presence of phosphorus in livestock sewage is a key factor that causes eutrophication and the degradation of ecological water quality. Cyclopentane (CP) hydrate-based water treatment technique was utilized for the efficient total removal of phosphorus in effluents. This study assesses the treatment effectiveness and enrichment potential of hydrate technology when applied to real-world samples, specifically livestock wastewater. The treatment process was applied under atmospheric pressure and optimized appropriate conditions comprising the CP-to-sample volume ratio of 1:4, reaction duration of 3 h, and temperature of 2 °C because of the high subcooling and ability to enhance the number of hydrate crystals formed along with water. In addition, various methods, such as vacuum filtration, cold centrifugation, and washing, were employed for the effective and comprehensive removal of phosphorus from water samples with the efficiency exhibited from approximately 30 % to 80 %. The structure and composition of the CPHs formed in wastewater were analyzed via Raman spectroscopy and the phosphorus content was determined according to ISO 6878:2004. After a single-stage hydrate process without pretreatment and posttreatment, the water recovered from the extracted hydrates showed that the phosphorus removal efficiency in livestock sewage was approximately 85 % with a remarkable water recovery above 25 %. The study findings provide insights into the development of hydrate-based treatment technology for the removal of phosphorus and explore opportunities for resource enrichment and recovery from sewage.

Sedimentary geochemistry in P-limited freshwater drained marshes (Charente-Maritime, France): Original drivers for phosphorus mobilization

Phosphorus bioavailability is a major issue in aquatic environments, where it generally limits primary production. In this work, the analysis of the pore water and the solid phase of the sediment was carried out over a 9-month monitoring period between February 2020 and April 2021 in two drained marshes (Marans and Genouillé, France) distinct by their uses and management tools. Soluble reactive phosphorus (SRP) enrichment in the sediment was intimately controlled by iron oxide dissolution. The latter seemed highly controlled by seasonal nitrate inputs (winter and early spring) that favoured denitrification as a major benthic mineralization process promoting iron curtain development and stability. Following benthic mitigation of nitrate other anaerobic metabolisms developed such as iron dissolutive reduction promoting P recycling and planktic bioavailability. Surprisingly, sulphur cycle seemed to affect P dynamics, especially in the absence of nitrate. The absence of NO3− triggered high sulphate reduction rates in the two first centimeters depth, reaching −8.9 E−03 ± 0.5 E−03 and -5.0 E−03 ± 0.2 E−03 nmol cm−3 s−1 in August and July at Marans and Genouillé respectively. These values placed this process at higher rates than the denitrification (maximum in May at Marans with −5.0 E−03 ± 1.1 E−03 nmol cm−3 s−1) and reduced iron production (maximum in July at Genouillé with 0.5 E−03 ± 0.1 E−03 nmol cm−3 s−1). The rapidity with which process changes occur (monthly scale) testified to the dynamism of these systems. The similarity in geochemical patterns regarding NO3− pressure at both sites underlines the importance of diffuse pollution in coastal systems for nitrogen mitigation and phosphorus trapping. The results obtained in this study could lead to the development of a generalized diagenetic operating model for temperate systems with high agricultural pressure. This would enable to target management efforts to both optimize the purification function and limit eutrophication risks in these systems.

Climate change modulates the impact of nitrogen and enhances phosphorus-driven top-down control by zooplankton on harmful algae

Eutrophication and climate change are the main drivers of the increase in Microcystis biomass. These environmental factors also regulate the dynamics between planktonic predators and their prey. Here, we present the results of a controlled laboratory study investigating the top-down control efficiency of Paramecium on Microcystis under different nutrient (nitrogen and phosphorus) levels and climate conditions (current climate: 25 °C, 400 ppm; predicted future climate: 30 °C, 750 ppm). The results showed that Paramecium completely eliminated Microcystis populations under all combinations of nutrient levels and climate conditions. Furthermore, the ability of Paramecium to control Microcystis was modulated by nutrient enrichment and climate change. Specifically, key performance parameters—including the Microcystis population decline index, time for Microcystis elimination, ingestion rate and specific growth rate of Paramecium, and time to reach maximum Paramecium abundance—were inhibited by increasing nitrogen levels but improved by increasing phosphorus levels. This indicates that nitrogen enrichment weakened the ability of Paramecium to control Microcystis, whereas phosphorus enrichment enhanced it. Further analysis revealed that, regardless of nutrient availability, these parameters were optimized under the high-temperature-CO2 scenario, suggesting that climate change has consistently enhanced the top-down control of Microcystis by Paramecium. Notably, an in-depth examination of the overall change patterns of performance parameters and principal component analysis (PCA) revealed that climate change altered the response patterns of these parameters (or their comprehensive scores) to increased nitrogen and enhanced their response magnitude to increased phosphorus. Essentially, climate change compensated for the negative effects of increased nitrogen levels on the performance of Paramecium in controlling Microcystis and amplified the positive effects of increased phosphorus levels. These findings reveal that protozoan predators might enhance their top-down control of harmful algae under the interaction of eutrophication and climate change. This study, using Paramecium and Microcystis as models, provides valuable insights for managing freshwater ecosystems and applying protozoa to mitigate harmful algal blooms.

Enhanced phosphorus removal from anoxic water using oxygen-carrying iron-rich biochar: Combined roles of adsorption and keystone taxa

Anthropogenic enrichment of phosphorus (P) in water environment can cause eutrophication, harmful algal blooms, and water quality deterioration. Adsorbents are often used for the removal and recovery of P from water, however, P is highly susceptible to re-release in anoxic benthic environments. As a response, this study prepared oxygen-carrying iron-rich biochar (O-Fe-BC) as an effective oxygen micro-nanobubble carrier (Q = 8.7024 cm³/g STP at 1.5 MPa) and P adsorbent (qm = 16.7097 mg P/g, q0.1 = 3.1974 mg P/g). Over the 90-day experimental period with O-Fe-BC, dissolved oxygen (DO) levels in the overlying water could maintain at ∼4 mg/L (peaking at ∼9.5 mg/L), and total phosphorus (TP) and soluble reactive phosphorus (SRP) levels decreased by over 96 %. The higher inorganic phosphorus content in the surface sediment-biochar mixture, along with the lower labile P and Fe concentration in the sediment pore water in the O-Fe-BC group compared to other groups, suggested the enhanced P immobilization. Further mechanism exploration revealed the combined roles of adsorption and microbial response, in which O-Fe-BC achieved efficient phosphate adsorption primarily through inner-sphere complexation via ligand exchange and keystone taxa (particularly Candidatus Electronema) played a crucial role in driving water chemistry divergence. Specially, these cable bacteria could provide large pools of Fe oxides in the surface sediment, binding with P to prevent its release, as supported by significant correlations between Ca. Electronema abundance and oxidation–reduction potential (ORP), TP, SRP, and sediment Fe-P variations. Additionally, a pot experiment with mung bean seedlings showed that the recovered O-Fe-BC significantly promoted the seed germination and growth, indicating its potential as a novel material for removing and recovering P from eutrophic waters. Taken together, our work provided a promising strategy for sustainable anoxia and P pollution mitigation, and also highlighted the indispensable roles of inner-sphere adsorption in P recovery and microbial keystone taxa in P cycling regulation.

Formation mechanism of high biofilm phosphorus storage capacity and its effect on phosphorus uptake-release and carbon source consumption

Phosphorus recovery from wastewater is an effective method to alleviate the shortage of phosphorus resources. The biofilm phosphorus recovery process can realize simultaneous removal and enrichment of phosphorus in wastewater. In this study, a sequencing batch biofilm reactor was constructed to study the rapid phosphorus release and slow phosphorus release stages in the phosphorus recovery cycle. The relationship between high biofilm phosphorus storage capacity (Pbiofilm), phosphorus recovery solution concentration, phosphorus uptake-release behavior and carbon source consumption were explored. The increase in phosphorus recovery solution concentration promotes the elevation of Pbiofilm, which, conversely promotes phosphorus release in the next recovery cycle. In addition, the distinct phosphorus uptake-release characteristics of extracellular polymeric substances and cells were illustrated. This study provides a theoretical foundation to elevate the phosphorus recovery efficiency and reduce carbon source consumption in biofilm phosphorus recovery process.

Nitrogen and phosphorus additions alter soil N transformations in a Metasequoia glyptostroboides plantation.

Nitrogen (N) and phosphorus (P) enrichment due to anthropogenic activities can significantly affect soil N transformations in forest ecosystems. However, the effects of N and P additions on nitrification and denitrification processes in Metasequoia glyptostroboides plantations, and economically important forest type in China, remain poorly understood. This study investigated the responses of soil nitrification and denitrification rates, as well as the abundances of nitrifiers and denitrifiers, to different levels of N and P additions in a 6-year nutrient addition experiment in a M. glyptostroboides plantation. Stepwise multiple regression analysis was used to identify the main predictors of nitrification and denitrification rates. The results showed that moderate N addition (N2 treatment, 2.4 mol·m-2) stimulated nitrification rates and abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB), while excessive N and P additions inhibited denitrification rates and reduced the abundance of nirS-type denitrifiers. AOB abundance was the main predictor of nitrification rates under N additions, whereas microbial biomass carbon and nirS gene abundance were the key factors controlling denitrification rates. Under P additions, tree growth parameters (diameter at breast height and crown base height) and AOB abundance were the primary predictors of nitrification and denitrification rates. Our study reveals complex interactions among nutrient inputs, plant growth, soil properties, and microbial communities in regulating soil N transformations in plantation forests. This study also offers valuable insights for formulating effective nutrient management strategies to enhance the growth and health of M. glyptostroboides plantations under scenarios of increasing elevated nutrient deposition.

Evaluation of nutrients and heavy metals of surface soil in the upper watershed of Xiashan Reservoir in Shandong Province, China.

Reservoir is easy to be polluted by nutrients and heavy metals in the surrounding soil. There is a close relationship between heavy metals and nutrients in soil. Nutrient salts will affect the activity of heavy metals, and heavy metal pollution will affect plant growth and nutrient salt absorption, thus affecting ecosystem health. This study was performed to evaluate nutrients (TN, TP) and heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in the upper watershed of Xiashan Reservoir by the enrichment factor, the geoaccumulation index, the enrichment factor and leaching experiments. The results showed that the average enrichment of TN and TP reached the level of moderate pollution. The nutrient enrichment of different sampling sites increased gradually from south to north, which may be affected by the topography of the study area. The comprehensive trophic level exceeds the criteria for a state of severe eutrophication of water bodies, which may lead to the enrichment of nitrogen and phosphorus in the water body through processes such as runoff. Evaluation of the geoaccumulation index and potential ecological risk index revealed that the soil was primarily contaminated by Cd and Hg, which are in the level of considerable potential ecological risk and high potential ecological risk. So most attention should be paid to Cd and Hg pollution. Pollution control of heavy metals in soil is a priority because they are more difficult to leach than nutrients. This study provided an insight into the nitrogen and phosphorus control and heavy metal pollution management in the upper watershed of Xiashan Reservoir.

Plant traits regulated metal(loid)s in dominant herbs in an antimony mining area of the karst zone, China.

Understanding how plant functional traits respond to mining activities and impact metal(loid)saccumulation in dominant species is crucial for exploring the driving mechanisms behind plant community succession and predicting the ecological restoration potential of these plants. In this study, we investigated four dominant herbaceous species (Artemisia argyi, Miscanthus sinensis, Ficus tikoua, and Ageratina adenophora) growing on antimony (Sb) mining sites (MS) with high Sb and arsenic (As) levels, as well as non-mining sites (NMS). The aim was to analyze the variations in functional traits and their contribution to Sb and As concentrations in plants. Our results indicate that mining activities enhanced soil nitrogen (N) limitation and phosphorus (P) enrichment, while significantly reducing the plant height of three species, except for F. tikoua. The four species absorbed more calcium (Ca) to ensure higher tolerance to Sb and As levels, which is related to the activation of Ca signaling pathways and defense mechanisms. Furthermore, plant Sb and As concentrations were dependent on soil metal(loid) levels and plant element stoichiometry. Overall, these findings highlight the regulatory role of plant element traits in metal(loid) concentrations, warranting widespread attention and further study in the future.

Concurrent nitrogen and phosphorus enrichment increases ecosystem carbon use efficiency in an alpine grassland

Ecosystem carbon use efficiency (CUEe) is a crucial indicator for assessing the capacity of ecosystems to sequester atmospheric carbon (C). However, it remains unclear how nitrogen (N) and phosphorus (P) influence CUEe and how climatic factors regulate CUEe. Here, a four-year manipulative experiment was conducted in a semi-arid alpine grassland ecosystem to explore the response of CUEe to N and P additions with fluctuating interannual precipitation. Our study revealed that the N and P combination synergistically improved CUEe; the single additions of N or P did not affect CUEe. The variation in CUEe was correlated to a larger in net ecosystem CO2 exchange (NEE) relative to gross ecosystem productivity (GEP). Similarly, the combination of N and P significantly increased aboveground biomass, whereas addition alone did not. Under the combined addition of N and P, a significant decrease in species diversity led to decreases in CUEe. Moreover, precipitation indirectly increased CUEe by increasing NEE. Our findings underscore the co-limitation of N and P resources for CUEe in the alpine grassland ecosystem and identify community structure and climate factors as key drivers of CUEe variations following nutrient enrichment.

Nitrogen fixation rate and phosphorus enrichment effects on diazotrophic cyanobacteria in the Gulf of Riga

In eutrophied marine systems such as the Baltic Sea, diazotrophic cyanobacteria have the potential to add additional bioavailable nitrogen (N) to the system through fixation of atmospheric dinitrogen (N2). However, their growth is regarded to be limited by phosphorus availability (P). This study investigates the response of two cyanobacteria species, Aphanizomenon flosaquae and Nodularia spumigena, collected from the Gulf of Riga under different environmental conditions to a short-period dissolved inorganic phosphorus (DIP) enrichment. The samples were collected during the summer cyanobacterial bloom of 2022 in the central region of the Gulf of Riga. Contrary to expectations, neither species demonstrated a significant increase in biomass. The study also established that N2-fixation rates did not correlate directly with the total diazotrophic cyanobacteria biomass, but showed a significant correlation with heterocyst presence in both species addressed during this study. The findings suggest the influence of additional factors beyond DIP availability on the N2-fixing cyanobacteria growth in the Gulf of Riga.

Selective extraction of lithium from montebrasite and clean treatment of tailings

To realize the efficient utilization of montebrasite, we conducted a systematic study of sulfuric acid roasting and water leaching processes. In this study, we propose a roasting process at a lower temperature than that proposed in previous studies, which can achieve the selective extraction of lithium from montebrasite and effective enrichment of aluminum and phosphorus. The thermodynamic simulation results of the reaction between montebrasite and sulfuric acid showed that the method was feasible in theory. Under the optimal conditions determined by theoretical analysis and experimental results, Li extraction reached 97.5 %, whereas Al and P extraction only reached 1.9 % and 0.1 %, respectively. The results of XRD characterization and analysis of roasting slag and leaching residue demonstrated that montebrasite was decomposed into Li2SO4, Al2(SO4)3, and H3PO4 by sulfuric acid. The temperature increase facilitated the conversion of these intermediates into Li2SO4 and AlPO4, confirming the absence of SO3 generation within the studied temperature range. Selective extraction of Li achieved water leaching through water leaching, resulting in a leaching residue with over 95 % AlPO4 content. The leaching liquor underwent purification and precipitation, resulting in the attainment of Li2CO3 with a purity level of 99.8 %. This process enables selective extraction of Li from montebrasite while efficiently enriching Al and P components. It represents an efficient and environmentally friendly approach for lithium extraction.

Divergent impacts of fertilization regimes on below-ground prokaryotic and eukaryotic communities in the Tibetan Plateau

Chemical nutrient amendment by human activities can lead to environmental impacts contributing to global biodiversity loss. However, the comprehensive understanding of how below- and above-ground biodiversity shifts under fertilization regimes in natural ecosystems remains elusive. Here, we conducted a seven-year field experiment (2011–2017) and examined the effects of different fertilization on plant biodiversity and soil belowground (prokaryotic and eukaryotic) communities in the alpine meadow of the Tibetan Plateau, based on data collected in 2017. Our results indicate that nitrogen addition promoted total plant biomass but reduced the plant species richness. Conversely, phosphorus enrichment did not promote plant biomass and exhibited an unimodal pattern with plant richness. In the belowground realm, distinct responses of soil prokaryotic and eukaryotic communities were observed under fertilizer application. Specifically, soil prokaryotic diversity decreased with nitrogen enrichment, correlating with shifts in soil pH. Similarly, soil eukaryotic diversity decreased with increased phosphorous inputs, aligning with the equilibrium between soil available and total phosphorus. We also established connections between these soil organism communities with above-ground plant richness and biomass. Overall, our study contributes to a better understanding of the sustainable impacts of human-induced nutrient enrichment on the natural environment. Future research should delve deeper into the long-term effects of fertilization on soil health and ecosystem functioning, aiming to achieve a balance between agricultural productivity and environmental conservation.

Circular economy approach: Nutrient recovery and economical struvite production from wastewater sources by using modified biochars

The enrichment of phosphorus (P) and nitrogen (N) in aquatic systems can cause eutrophication. Moreover, P rocks may become exhausted in the next 100 years. A slow-release fertilizer called struvite (MgNH4PO4.6H2O) can reduce surface runoff. However, the high cost of raw material or chemicals is a bottleneck in their economical production. Therefore, incinerated sewage sludge ash, food wastewater, and bittern were combined as the sources of P, N, and Mg, respectively. Sawdust biochar was used to enhance the adsorptive recovery of nutrients. First, recovery kinetics was studied by comparing bittern-impregnated biochar (BtB) with the Mg-impregnated biochar (MgB). Subsequently, the synergistic physical and chemical interactions were observed for P and N recovery. Almost complete PO43–P recoveries were achieved within 10 min for both biochars. However, NH4+-N recovery was stable after 2 h, with 26% recovery by MgB and 20% recovery by BtB. Biochars activated with steam (steam-activated biochar) and KOH (KOH-activated biochar) gave superior activities to those of unactivated biochars and activated carbon (AC) nutrient recovery and struvite purity. Moreover, the activated biochars showed a lower risk of surface runoff, similar to that of AC. Therefore, activated biochars can be used as an alternative to AC for economical struvite production from a combination of wastewater sources.

Cyanotoxin accumulation and growth patterns of biocrust communities under variable environmental conditions

Biocrusts dominate the soil surface in deserts and are composed of diverse microbial communities that provide important ecosystem services. Cyanobacteria in biocrusts produce many secondary metabolites, including the neurotoxins BMAA, AEG, DAB, anatoxin-a(S) (guanitoxin), and the microcystin hepatotoxins, all known or suspected to cause disease or illness in humans and other animals. We examined cyanobacterial growth and prevalence of these toxins in biocrusts at millimeter-scales, under a desert-relevant illumination gradient. In contrast to previous work, we showed that hydration had an overall positive effect on growth and toxin accumulation, that nitrogen was not correlated with growth or toxin production, and that phosphorus enrichment negatively affected AEG and BMAA concentrations. Excess illumination positively correlated with AEG, and negatively correlated with all other toxins and growth. Basic pH negatively affected only the accumulation of BMAA. Anatoxin-a(S) (guanitoxin) was not correlated with any tested variables, while microcystins were not detected in any of the samples. Concerning toxin pools, AEG and BMAA were good predictors of the presence of one another. In a newly conceptualized scheme, we integrate aspects of biocrust growth and toxin pool accumulations with arid-relevant desertification drivers.

Postfire Phosphorus Enrichment Mitigates Nitrogen Loss in Boreal Forests.

Net nitrogen mineralization (Nmin) and nitrification regulate soil N availability and loss after severe wildfires in boreal forests experiencing slow vegetation recovery. Yet, how microorganisms respond to postfire phosphorus (P) enrichment to alter soil N transformations remains unclear in N-limited boreal forests. Here, we investigated postfire N-P interactions using an intensive regional-scale sampling of 17 boreal forests in the Greater Khingan Mountains (Inner Mongolia-China), a laboratory P-addition incubation, and a continental-scale meta-analysis. We found that postfire soils had an increased risk of N loss by accelerated Nmin and nitrification along with low plant N demand, especially during the early vegetation recovery period. The postfire N/P imbalance created by P enrichment acts as a "N retention" strategy by inhibiting Nmin but not nitrification in boreal forests. This strategy is attributed to enhanced microbial N-use efficiency and N immobilization. Importantly, our meta-analysis found that there was a greater risk of N loss in boreal forest soils after fires than in other climatic zones, which was consistent with our results from the 17 soils in the Greater Khingan Mountains. These findings demonstrate that postfire N-P interactions play an essential role in mitigating N limitation and maintaining nutrient balance in boreal forests.

Migration behavior of iron and phosphorus during gas-based reduction for high-phosphorus iron ore

With the depletion of high-grade iron ore, it is necessary to develop low-quality high-phosphorus iron ore through economical and sustainable solutions. In this study, we presented simultaneous enrichment of iron (Fe) and phosphorus (P) to recover P from high-phosphorus iron ore and clarified the migration of P from the original apatite to reduced iron during the direct reduction process. To capture the migration route, gas-based reduction at a relatively slow rate was conducted on two typical iron ores samples (low-grade and high-grade) at different temperatures and times. Results indicate that there are concentration gradients for P and Fe of reaction products in the low-grade iron ore at 1400 °C. The P content continuously increased in the sequence from metallic iron (Fe), wustite (FeO), and fayalite (Fe2SiO4), to apatite (Ca3(PO4)3F). Conversely, the content of Fe gradually decreased. During this process, P dissolved from apatite entered and formed P-bearing fayalite. For the high-grade iron ore, P-bearing fayalite with a metastable structure disappeared as the reduction progressed, and P was released and then reduced to a gaseous state, finally absorbed by metallic iron. Furthermore, when metallic iron was not formed in the initial 60 min at 1300 °C, the P migrated from the apatite to the fayalite and gas phase. As the reduction time increased from 60 min to 240 min, the formed metallic iron provided a site for gasified P, which inhibited the volatilization of P and contributed to Fe and P enrichment.

Pedipalp anatomy of the Australian black rock scorpion, Urodacus manicatus, with implications for functional morphology

Pedipalps – chelate ‘pincers’ as the second pair of prosomal appendages – are a striking feature of scorpions and are employed in varied biological functions. Despite the distinctive morphology and ecological importance of these appendages, their anatomy remains underexplored. To rectify this, we examined the pedipalps of the Australian black rock scorpion, Urodacus manicatus, using a multifaceted approach consisting of microcomputed tomography, scanning electron microscopy, energy dispersive X-ray spectroscopy, and live pinch force measurements. In doing so, we document the following aspects of the pedipalps: (1) the musculature in three dimensions; (2) the cuticular microstructure, focusing on the chelae (tibial and tarsal podomeres); (3) the elemental construction of the chelae teeth; and (4) the chelae pinch force. We recognise 25 muscle groups in U. manicatus pedipalps, substantially more than previously documented in scorpions. The cuticular microstructure – endo-, meso-, and exocuticle – of U. manicatus pedipalps is shown to be similar to other scorpions and that mesocuticle reinforces the chelae for predation and burrowing. Elemental mapping of the chelae teeth highlights enrichment in calcium, chlorine, nickel, phosphorus, potassium, sodium, vanadium, and zinc, with a marked lack of carbon. These elements reinforce the teeth, increasing robustness to better enable prey capture and incapacitation. Finally, the pinch force data demonstrate that U. manicatus can exert high pinch forces (4.1 N), further highlighting the application of chelae in subduing prey, as opposed to holding prey for envenomation. We demonstrate that U. manicatus has an array of adaptions for functioning as a sit-and-wait predator that primarily uses highly reinforced chelae to process prey.