Total Phosphorus Concentrations Research Articles

The Spatial Evolution Characteristics of Phytoplankton and the Impact of Environmental Factors in a Harbor-Construction-Formed Reservoir

Phytoplankton are an important part of aquatic ecosystems and substantially contribute to primary productivity. Under certain conditions, phytoplankton can grow or cluster in large numbers, resulting in enormous economic losses and serious threats to human life and health. In this study, complex causative species of algal blooms were examined and regulatory factors were determined in a reservoir formed by harbor construction. The reservoir is isolated from the harbor by sluice gates, forming a separate water region. Twelve species of phytoplankton, including normally and abnormally blooming species, were identified to be causing blooms in this continuous water. Different from the areas where simple algae caused blooms, multiple bloom-causative species, which were completely different, occurred at several stations. In this study area, whereas the abundance of algal cells was above 10 million cells/L, the total phosphorus concentration was higher than 0.2 mg/L. When the total phosphorus concentration was lower than 0.2 mg/L, there was no algal bloom. In waters with total algal cell abundance over 10 million, the N/P ratios were all ˂8. This study indicates that the occurrence of algal blooms in this water was influenced by the concentrations of total nitrogen and phosphorus, and total phosphorus plays a more important role.

Distribution of soil fertility indices in aggregate size fractions under different land-use types for coarse-textured soils of the derived savannah

The research investigated the distribution of soil fertility indices among aggregate-size fractions across three land-use types (forested, cultivated, and fallow lands) for loamy sand at Ede-Oballa, a derived savannah in southeastern Nigeria. Surface soil samples from these land-use types were air-dried and separated into <0.25 mm, 0.25-0.5 mm, 0.5-1.0 mm, 1.0-2.0 mm, 2.0-4.0 mm, and 4.0-8.0 mm aggregates before analyses. There were significant interaction effects of land-use type and aggregate-size fraction on the distribution of soil particle sizes (sand, silt, and clay) and contents of total nitrogen, available phosphorus, exchangeable bases (Mg2+ and Na+), and exchangeable acidity as well as apparent cation exchange capacity (CEC). Land-use type affected soil pH, K+, Ca+, and percent base saturation but not soil organic carbon (SOC), which was rather unevenly distributed among the aggregate-size fractions. The distribution of most fertility indices, those defining CEC, and SOC content favoured >2.0 mm (large), 0.25-0.5 mm and <0.25 mm (micro-) aggregates, respectively, under cultivated land. However, soil total nitrogen and exchangeable acidity contents were best improved in the largest (4.0-8.0 mm) aggregates under forested and fallow lands, respectively. The study highlights the potential of land-use types generally and arable-crop cultivation specifically to engender aggregates of different sizes with specific roles in improving soil quality and fertility.

High-performance Multi-stage Baffled A2O Treatment Process for Domestic Sewage on Plateaus

At high altitudes, the low air pressure, low atmospheric oxygen content, and cryogenic environment during the cold season greatly limit the treatment efficiency of wastewater treatment plants (WWTPs). A novel pilot-plant configuration of the multi-stage baffled A2O wastewater treatment process was proposed and tested in Xizang. Different operational conditions involving at different influent loads and at low temperatures (10.0–11.0°C) were tested. When the influent flowrate increased to 4 m3∙d−1, the hydraulic retention time (HRT), internal and external reflux ratio, dissolved oxygen (DO), and aeration demands (gas to water ratio) all decreased to 34.2 h, 3.5/7, a stable 2.0–2.5 mg∙L−1, and 17.5, respectively. The effluent chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH+4−N), and total phosphorus (TP) all met the requirements of Class 1 Grade A of the China National Municipal Wastewater Discharge Standards (GB 18918-2002). The contribution of denitrifying phosphorus removal (DPR) to the removal of both nitrogen and phosphorus was over 50%. The alpha diversity and abundance of the top genera in the microbial community structure were both higher than the plateau WWTP. The reaction activity of the DPR process was significantly enhanced via the increased abundance of key functional genes within the metabolism pathway of ammonia-oxidizing bacteria (AOB) and nitrogen-oxidizing bacteria (NOB). The special multi-stage baffled structure featured a strategy of high sludge storage that improved the system tolerance for low temperatures and ensured favorable and stable performance for nitrogen and phosphorus removal at low temperatures. A short, periodic, and cyclically intermittent operation mode, with each cycle lasting only 20 minutes, effectively inhibited filamentous bacteria sludge bulking, resulting in a sludge volume index (SVI) that decreased to within 120 mL∙g−1 during the first 15 days of system start-up. A long sludge retention time (SRT) with no sludge discharging over 169 days and reduced aeration demands contributed to lower operation costs. The investigation revealed that the system had a high capacity for storing sludge phosphorus, possessing a TP content within a range of 23.45–28.99 mg∙g−1. This study provides a feasible solution for efficiently and economically treating wastewater in high-altitude areas.

Phosphorus dynamics in volcanic soils of Weizhou Island, China: implications for environmental and agricultural applications

The dynamics of phosphorus are intricately governed by geological and ecological processes. Examining phosphorus dynamics in volcanic islands can enhance our comprehension of its behavior within such unique geological systems. However, research on phosphorus dynamics in volcanic islands remains limited. We investigated the phosphorus content of volcaniclastic rocks and basalt soils from Weizhou Island, China, to understand the influencing factors on phosphorus dynamics. The results indicate that in the volcaniclastic profile, phosphorus concentrates at 20–40 cm (17 mg/kg), decreases at 40–60 cm (11.9 mg/kg), and increases at 80–200 cm up to 46.4 mg/kg proximate to the bedrock, for the basalt profile, phosphorus content increases from the surface (80.2 mg/kg) towards the bedrock (83.9 mg/kg). The differences in phosphorus distribution between volcaniclastic rocks and basalts reflect the influence of parent material, rock weathering degree, carbonate content, topographic elevation, sea level changes, and geological activities. A strong positive correlation (R = 0.96907) between total and available phosphorus has been observed, suggesting that total phosphorus content effectively predicts available phosphorus content. Volcaniclastic rocks in wharves and high-elevation areas show low total phosphorus, while forest land with dense vegetation and neutral to alkaline soil supports higher total phosphorus due to enhanced bioavailability for plant absorption and utilization. Overall, the basalt soil of the volcanic island Weizhou Island demonstrates superior long-term fertility compared to the volcaniclastic soil. Despite its low total phosphorus content, it mainly exists in a highly bioavailable form, facilitating plant absorption, which is crucial for enhancing agricultural yields and ecosystem restoration on volcanic islands.

Diversity and community distribution of soil bacterial in the Yellow River irrigation area of Ningxia, China.

The bacterial community performs an essential ecological role in maintaining agriculture systems. The roles of bacteria in the forest, marine, and agricultural systems have been studied extensively and intensively. However, similar studies in the areas irrigated by the Yellow River remain limited. In this study, we used Illumina sequencing analysis with the 16S rRNA method to analyze the bacterial diversity, community structure, and influencing factors in soil samples from eight regions of the Yellow River irrigation area in northwestern China. The bacterial community structure and diversity varied among samples from the eight regions. The samples differed significantly in terms of the bacterial community composition. Proteobacteria (approximately 12.4%-55.7%) accounted for the largest proportion and was the dominant bacteria, followed by Actinobacteria (approximately 9.2%-39.7%), Bacteroidetes (approximately 1.8%-21.5%), and Chloroflexi (approximately 2.7%-12.6%). Among the physicochemical variables, the soil pH in the eight regions was mildly alkaline, and the total nitrogen, total phosphorus, and total potassium contents in the soils differed significantly. However, the trend in the variations of the above variables was essentially similar. Soil bacteria in Yongning county had greater Chao1, Shannon-Wiener, and Simpson indices than those in the other regions. Notably, soil moisture, organic matter, and total nitrogen were recognized as the primary factors influencing the bacterial community in the Yellow River irrigation area. Our results revealed the laws of variation in soil bacterial diversity and community composition in the Yellow River irrigation area. Our findings could be beneficial for maintaining sustainable ecological practices in the Yellow River irrigation area.

Removal and recovery of phosphorus and fluorine in process water from water based direct physical lithium-ion battery recycling

In the present work, the recovery of phosphorus and fluorine from process water generated in a water based direct physical recycling process of Li-ion batteries has been studied. The recycling process considered in this work produces significant amounts of process water, which is generated during the opening of the batteries by means of electro-hydraulic fragmentation and the subsequent sorting of the components in aqueous solution. This process produces between 21.6 L and 30.3 L of process water per kg of batteries with a total phosphorus and a total fluorine concentration of 60–85 mg/L and 120–470 mg/L, respectively. Currently, the process water has to be disposed of as hazardous waste. The goal is to discharge the wastewater into the sewer system. For this the total phosphorus and total fluorine concentration must be reduced. The process water is mainly contaminated by the released electrolyte consisting of organic carbonates and conducting salts. 31-P and 19-F NMR shows conclusively that no hydrolysis takes place in this process water. The phosphorus is present exclusively in the form of the complex anion PF6- and fluorine as F-, namely as FSI- from the conducting salt LiFSI and PF6- from the conducting salt LiPF6. In order to meet the regulatory requirements for discharge into the sewage system, 70.4% of the phosphorus and 89.3% of the fluorine must be removed. The conducting salts are hydrolyzed by adding acid and thereby phosphate and fluoride are precipitated. After critical and valuable materials are recovered the process water can be discharged into the sewer system.

Characteristics and Drivers of Soil Ecological Stoichiometry in Saline–Alkali Areas of Western Jilin Province, Northeast China

ABSTRACTSoil ecological stoichiometry (SES) provides an important approach in exploring chemical element balance relationships and ecosystem structure and function, but the characterization, significance, and drivers of SES in saline–alkali areas have not been well studied. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured and their SES ratios were calculated from 155 soil samples collected at a depth of 20 cm in the saline–alkali soil zone of western Jilin Province, China. The results showed that SOC, TN, and TP contents and SES ratios (52:4:3) were lower in this region than in terrestrial ecosystems both in China as a whole and globally. The distribution of SOC, TN, and TP in saline–alkali soil varied significantly across land use types, with high concentrations mainly in woodland, grassland, and cropland. SOC, TN, and TP were tightly coupled, with significant positive correlations (p < 0.01), and C:N was significantly negatively correlated (p < 0.01) with the other SES ratios, indicating that saline–alkali soils are susceptible to carbon and nitrogen limitation. The distribution patterns of SOC, TN, TP, and their eco‐chemometrics on the environmental gradient were variable, mainly in the form of significant decreases with increasing mean annual precipitation, mean annual temperature, and elevation. Cropland was most affected by environmental factors, and all SES except TP were affected by environmental factors. Soil nutrient (44.9%) and soil texture (9.8%) contributed the most to explaining SES in the saline–alkali soil zone, while climate (1.6%) and vegetation (0.4%) contributed the least to the explanation. All land use types were most explained by AN, except for woodland SES, which was most explained by AP. Elevation (17.4%) possessed a high degree of explanation for SES on underutilized land, except for the soil itself. Grassland is the land category most affected by climatic factors (12.7%). By applying biochar, nitrogen fertilizer, and planting saline‐tolerant crops such as Leymus chinensis, the soil structure can be effectively improved and the content of carbon and nitrogen in the soil can be increased, which has a positive effect on the improvement of saline–alkali soil. The results of the study provide information that can be used to help saline–alkali areas cope with environmental and climate change and restore degraded ecosystems.

Effect of abrupt post‐fire ash inputs on water quality and the phytoplankton community in lentic freshwaters

Abstract One of the major threats to biodiversity is changing fire regimes, particularly increasingly frequent fires, especially during the dry season. However, studies on the direct and indirect effects of fire on biotic responses in aquatic ecosystems are still scarce. In this study, we investigated how water quality and phytoplankton community structure were affected by different ash concentrations from burning vegetation of a tropical savanna. We used a microcosm experiment to simulate the aquatic ecosystem with different ash concentration scenarios and evaluated the water quality and the composition, richness and density of phytoplankton over time. We found increased total phosphorus and ammoniacal nitrogen concentrations after ash addition, in addition to changes in electrical conductivity. We identified 242 phytoplankton taxa throughout the experiment and identified changes in species composition among treatments. We identified changes in the taxonomic richness of total phytoplankton, green algae and desmids over time. The density of total phytoplankton, diatoms, green algae, desmids and cyanobacteria also changed over time. Our results suggest that ash from terrestrial fires affects water quality and phytoplankton communities depending on the proportion of ash input. Our results serve as a basis for further investigations of the effects of fire on abiotic conditions in aquatic ecosystems and their communities over long periods of time. Finally, longer‐term experiments are needed to evaluate delayed responses by the phytoplankton community.

Quantitative Analysis of the Influence of Temperature Factors on Total Phosphorus Content in Water

Quantitative Analysis of the Influence of Temperature Factors on Total Phosphorus Content in Water

Multivariate Statistical Approach and Assessment of Pollution of Water and Sediments in Karstic Springs of Transboundary Aquifer Žumberak–Samoborsko Gorje Mountain (Croatia/Slovenia)

This study highlights the geochemistry of water and sediments of the karstic springs of the transboundary aquifer (TBA) Žumberak–Samoborsko Gorje Mt. (NW Croatia). After calculating pollution indices, the analysis showed that the sediments are unpolluted. The geo-accumulation index (Igeo) showed only the elements Ba and Rb, indicating moderate levels of pollution, with the highest values in springs Vapnik and Bistrac. Statistical analysis confirmed their natural origin. The water of these springs is under possible anthropogenic influence as indicated by elevated concentrations of total nitrogen (TN) and total phosphorus (TP). According to a principal component analysis (PCA) for elements in sediments, PC1 described a combined lithogenic and oxidative–reductive influence, PC2 described a combined geological background including total organic carbon (TOC) content and oxidative–reductive influence, while TOC had the greatest influence on PC3. Depending on element composition, the factor scores related to PC1 and PC2 resulted in two different groups of sites, while the factor scores concerning PC1 and PC3 did not show separation in two groups. The hierarchical cluster analysis showed three clusters in relation to the content of the elements. The correlation coefficient between the sediment and related water samples showed that the springs placed in a low-permeability formation (dolomite) had a strong positive coefficient of correlation.

Synchrotron-based P K-edge XANES spectroscopy reveals the transition of phosphorus cycling in the early Cambrian ocean

Phosphorus, as a long-term limiting nutrient, is essential for the rapid animal diversification in the early Cambrian ocean. However, the widespread occurrence of phosphorites during this period indicates anomalous phosphorus cycling mechanisms that remain inadequately explored. To investigate the interplay between marine redox conditions and phosphorus cycling, we used geochemical proxies and synchrotron-based P K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy to analyze the Cambrian Terreneuvian Yurtus Formation (Fortunian to Stage 2) from the Tarim Block. Redox-sensitive elements, iron speciation and nitrogen isotopes reveal an expansion of the surface oxygenated waters, despite persistent ferruginous bottom waters. Moreover, a shift of phosphorus speciation was observed in bedded cherts via P K-edge XANES, suggesting a transition of phosphorus cycling. Specifically, the samples exhibit low total phosphorus contents with a high rate of carbonate-fluorapatite authigenesis in the lower Yurtus Formation. This is followed by an increase in the proportion of terrestrial-derived fluorapatite and iron-bound phosphorus, corresponding to the expansion of surface oxygenated waters. Our findings reveal a significant shift in dominant phosphorus speciation in the early Cambrian marine sediments, which is intricately linked to the coupled phosphorus‑iron‑carbon‑oxygen cycles in the Cambrian ocean.

Stochastic processes driving cyanobacterial temporal succession in response to typhoons in a coastal reservoir

Typhoons associated with heavy rainfall events, potentially triggering harmful algal blooms (cyanoHABs) dominated by cyanobacteria in coastal reservoirs. These blooms deteriorate water quality and produce toxins, posing a threat to aquatic ecosystems. However, the ecological mechanisms driving cyanobacteria communities in response to typhoons remain unclear. To address this gap, we investigated a coastal reservoir with high-frequency sampling during two typhoon seasons. We employed comprehensive statistical methods under neutral and evolutionary theories to analyze environmental dynamics and cyanobacterial genus succession. Our findings revealed a significant increase in nutrient loads following typhoons, with concentrations of total nitrogen (TN), total phosphorus (TP), and ammonia-nitrogen (NH4+-N) rising from 0.4 mg/L to 1.0 mg/L, 0.02 mg/L to 0.63 mg/L, and 0.03 mg/L to 0.26 mg/L, respectively. These changes coincided with fluctuations in other physicochemical parameters under changing hydrometeorological conditions. Despite significant environmental disturbances, the cyanobacterial community exhibited a remarkable recovery within 15–25 days following the typhoons. This recovery progressed through four distinct successional phases, with a notable shift in community composition from Raphidiopsis and Pseudoanabaena to Aphanocapsa, subsequently replaced by Raphidiopsis and Microcystis, before reverting to the pre-typhoon community structure. During the entire successional phase, the availability of TN and the TN/TP ratio played a dominant role, as indicated by PLS-PM analysis (total effects = -0.6; p < 0.05). Pre-typhoon, environmental factors primarily influenced community structure (54 %) based on modified stochasticity ratio. However, following the typhoons, stochastic fluctuations took precedence (71 %-91 %). The rapid recovery of cyanobacterial communities and the shift in driving mechanisms from deterministic to stochastic processes underscore the complex ecological responses to typhoon events. This study provides essential insights for biodiversity preservation and ecosystem restoration, emphasizing the need to consider both stochastic and deterministic processes in ecological management strategies.

Linking fine‐root diameter across root orders with climatic, biological and edaphic factors in the Northern Hemisphere

The importance of fine‐root diameter for ecosystem functioning is increasingly recognized, yet much remains to be learned about the variation in fine‐root diameter at large scales. We conducted an analysis of fine‐root diameter for five root orders for 1163 plant species to detect patterns in relation to resource availability (e.g. carbon, nitrogen, water and net primary production (NPP)), stress intensity (e.g. plant/soil biodiversity and soil bulk density) and temperature. First‐ to fourth‐order root diameters showed non‐linear relationships with mean annual temperature (except for first‐order root diameter) and/or with latitude. The diameters of the five root orders decreased with increasing mean annual precipitation, but increased with greater NPP, which was the strongest determinant of fine‐root diameter. Increasing soil biodiversity was associated with decreasing diameters of fourth‐ and fifth‐order roots, while greater plant biodiversity was associated with decreasing diameters of first‐ to third‐order roots. Soil total nitrogen concentration had a positive effect on first‐order root diameter but a negative effect on fourth‐ and fifth‐order root diameters. The patterns reversed for soil total phosphorus concentration. First‐ to third‐order and fifth‐order root diameters increased with greater soil bulk density. Second‐ to fourth‐order root diameters increased with higher soil pH. Overall, the variables related to climatic, biological and edaphic factors explained 44–63% of the total variance in the diameters of the different root orders. The unique patterns of plasticity observed in fine‐root diameter across root orders in response to varying environmental conditions contributes to a diversification of plant strategies for nutrient/water acquisition and transport under climate change.

A probabilistic hazard assessment for cyanobacterial toxins accounting for regional geography and water body trophic status

Under climate change scenarios freshwater eutrophication is expected to increase, and with it the occurrence of cyanobacterial toxin-producing harmful algal blooms. In the current study, microcystin toxin occurrence data from literature sources and a long-term provincial monitoring program were used to conduct a probabilistic hazard assessment for Alberta, Canada. The large temporal and spatial range of data makes Alberta a model system for identifying regional geography and water body trophic status factors driving toxin concentrations. Environmental exposure distributions of microcystin concentrations were plotted and used to identify the likelihood of a given sample exceeding water guideline values as a function of regional geography, total phosphorus and chlorophyll-a concentration. This process identified regions with intensive cultivation and those most prone to water deficits associated with climate change to be most associated with exceedances of regulatory guideline values. Elevated phosphorus and chlorophyll-a concentrations were also drivers of toxin occurrence. This assessment can be used to identify water bodies of greatest risk to human and animal populations from cyanotoxins and thereby inform regulators as to most effective monitoring strategies.

Change in leaf C:N:P stoichiometry and its correlations with soil available nutrients and dry matter yield in common vetch/oat intercropping under N fertilization

AbstractC, N, and P concentrations and stoichiometric ratios of the leaf are important for adaptive plant growth and nutrient utilization. However, our knowledge of how these traits change with N fertilization in intercropping systems remains limited. Hence, a 2‐year experiment was conducted with four cropping patterns, including two‐row common vetch (Vicia sativa L.) intercropping with one‐row oat (Avena sativa L.), one‐row common vetch intercropping with two‐row oat as well as sole oat and common vetch cropping with 0, 50, and 100 kg N/ha fertilization. Leaf total nitrogen (LTN) and phosphorus (LTP) concentrations and C:N:P stoichiometric ratios were measured and their linkages with soil nutrient availability were analysed. N fertilization significantly increased LTN, N:P, and C:P, while significantly decreasing LTP and C:N. Intercropping affected leaf nutrient concentrations and stoichiometric ratios, which were affected by N fertilization, basic soil fertility, and crop species. Intercropping and N fertilization affected soil nitrate nitrogen (SNN), available phosphorus (SAP) content, and dry matter (DM) yield. There were strong correlations between the leaf nutritional traits of oats and SNN, SAP, and DM, but few correlations were observed with common vetch. In conclusion, intercropping led to contrasting changes in leaf nutrient concentrations and stoichiometric ratios, which varied with N fertilization and crop species. We failed to reveal solid and direct effects of intercropping ratio on leaf nutritional traits. These findings contribute to a better understanding of crop nutritional traits and the link between leaves and soil in response to intercropping and N fertilization.

Inter-algal associations and nutrients linked by Scenedesmus and Desmodesmus structure eukaryotic algal communities.

Eutrophication reduces the variability of the community composition of plankton. However, the mechanisms underlying the diversity and restructuring of eukaryotic algal communities remain unknown. This study analysed the diversity and compositional patterns of algal communities in shallow eutrophic lakes. It investigated how these communities were modified by key genera through mediating inter-algal associations under the influence of abiotic factors. Inter-algal associations explained more variance in algal communities than environmental variables, and variation in composition and diversity was primarily derived from Scenedesmus, Desmodesmus and Cryptomonas, rather than nutrients. Scenedesmus and Desmodesmus were positively correlated with the genera of Chlorophyta and formed the hub of the algal association network. When the relative abundance of Scenedesmus and Desmodesmus increased from 0.41% to 13.74%, communities enriched in biomarkers of Bacillariophyta, Chrysophyceae and Cryptophyta transitioned to communities enriched in biomarkers of Chlorophyta. Moreover, negative associations between the Chlorophyta hub genera and other non-Chlorophyta genera increased. High concentrations of total phosphorus altered the composition of algal communities by increasing the abundance of Scenedesmus and Desmodesmus, which in turn had cascading effects through inter-algal associations. Additionally, algal communities with higher abundances of Scenedesmus and Desmodesmus were more susceptible to the effects of total phosphorus. Our study suggested that inter-algal associations, centred on Scenedesmus and Desmodesmus, had a greater influence on algal diversity and community structure than other factors. Nutrient levels were not a direct driver of algal diversity and community structure adjustments, but acted indirectly by enhancing the influence of Scenedesmus and Desmodesmus.

Dry season irrigation promotes nutrient cycling by reorganizing Eucalyptus rhizosphere microbiome

In southern China, seasonal droughts and low soil phosphorus content constrain the productivity of Eucalyptus trees. To understand the rhizosphere microbiome response to the dry season, metagenomic sequencing analysis was used to investigate the 6-year-old Eucalyptus rhizosphere microbiome under four different irrigation and fertilization treatments. The results showed that irrigation and fertilization during the dry season significantly altered the composition of microbiome in the rhizosphere soil of Eucalyptus plantations. The soil physicochemical properties and enzyme activity explained 30.73 % and 29.75 % of the changes in bacterial and fungal community structure in Eucalyptus rhizosphere soil, respectively. Irrigation and fertilization during the dry season significantly altered the physicochemical properties of rhizosphere soil. Compared with the seasonal drought without fertilizer treatment (CK), the dry season irrigation with fertilizer treatment (WF) significantly increased the content of total nitrogen (46.34 %), available nitrogen (37.72 %), available phosphorus (440.9 %), and organic matter (35.34 %). Soil organic matter (OM), pH, and available phosphorus (AP) were key environmental factors influencing the microbial community composition. Moreover, irrigation and fertilization promoted carbon fixation and nitrogen and phosphorus mineralization, increasing soil OM content and the availability of inorganic nitrogen and phosphorus. Meanwhile, compared to the CK, the increase of acid phosphatase (16.81 %), invertase (146.89 %)and urease (59.45 %) in rhizosphere soil under irrigation (W) treatment further proves that dry season irrigation promote the soil carbon, nitrogen and phosphorus cycles. Irrigation and fertilization treatment alleviated the constraints of low phosphorus in southern China's soil, which promoted Eucalyptus productivity. In conclusion, we suggest implementing reasonable irrigation and fertilization strategies in the production practice of Eucalyptus and utilizing microbial resources to improve soil fertility and Eucalyptus productivity.

Elevated effect of hydrothermal treatment on phosphorus transition between solid-liquid phase in swine manure

The morphology and composition of phosphorus in biomass wastes are key factors in determining its potential for utilization. However, the morphological distribution and evolutionary mechanism of phosphorus during the hydrothermal conversion of biomass wastes are still unclear. In this study, swine manure was investigated as the research subject, and the changes in its solid-phase organic components, such as lignocellulose, and inorganic constituents, including metals and phosphorus, during the hydrothermal carbonization (HTC) processes were analyzed in relation to hydrothermal reaction severity (LnR0). A significant linear correlation in Phase II was observed between the solid-phase yield of swine manure and the LnR0. The rapid decline in the solid-phase yield during the initial phase (LnR0 < 9.72) was primarily attributed to the hydrolysis of hemicellulose and similar components. Similarly, solid phase phosphorus showed a very significant phase II with the decrease of solid phase yield. In the first stage, inorganic phosphorus and metal ions (calcium ions, magnesium ions) transferred to the liquid phase (LnR0<9.41). When LnR0 > 9.41, and the driving force of inorganic phosphorus and metal ions into solid phase is enhanced. As the LnR0 was further increased, the HTC could fix over 90 % of the total phosphorus content. XANES analysis indicated that hydroxyapatite emerged as the predominant phosphorus fraction in the solid-phase products, comprising more than 60 %, while magnesium ammonium phosphate components also appeared. This research elucidates the underlying mechanisms of component interaction and phosphorus transformation, providing a solid foundation for enhancing the reuse efficiency of phosphorus in wastes.

Effects of Phosphorus Application Levels on Its Uptake and Utilization in Foxtail Millet

Foxtail millet is a traditional minor crop in China, known for its strong resistance to stress, tolerance to barren lands, and wide adaptation. Phosphorus is an essential element for crop growth and development, and the appropriate application of phosphorus can enhance crop yield and quality. However, the optimal phosphorus fertilization levels for the growth of foxtail millet have yet to be determined. This study aims to explore the effects of different phosphorus application levels (T1, T2, T3, and T4), on phosphorus accumulation and use efficiency and crop yield and quality in the foxtail millet cultivars ‘B376’ and ‘B27’, which have different phosphorus efficiencies. Additionally, we investigated the effects of phosphorus accumulation and use efficiency on the heading and filling stages of these cultivars. The results show that the total phosphorus content and accumulation levels in the ‘B376’ and ‘B27’ cultivars vary at different developmental stages and in different plant parts. Furthermore, crop yield and quality in both cultivars vary in response to the different phosphorus application levels. In terms of yield, the phosphorus-tolerant variety ‘B376’ reaches its highest at T2, while the phosphorus-sensitive variety ‘B27’ achieves its maximum yield at T3. For quality, ‘B376’ exhibits the highest moisture and crude fat content under T4, and the highest protein and the lowest amylose content under T3. On the other hand, ‘B27’ achieves its highest moisture content under T4, its highest crude fat and protein levels under T3, and its lowest amylose content under T2. Therefore, the response to different phosphorus application levels differs between the two cultivars with different phosphorus use efficiencies. Moreover, under different phosphorus fertilization levels, the average crop yield, moisture, fat, and amylose content averages of the phosphorus-tolerant ‘B376’ cultivar are 16.1%, 1.2%, 7.0%, and 4.1% higher than those of the phosphorus-sensitive ‘B27’ cultivar. Additionally, phosphorus use efficiency is positively correlated with the moisture and crude fat contents of foxtail millet. In conclusion, the phosphorus-tolerant cultivar demonstrates superior phosphorus accumulation, absorption, and utilization capacities compared to the phosphorus-sensitive cultivar. These results suggest that in the phosphorus-tolerant ‘B376’, optimal phosphorus fertilization levels enhance the development of roots, stems, and leaves at the T2 (P45) level, and promote the accumulation of moisture and crude fat in foxtail millet grains, thereby improving their taste and quality. Our findings provide a theoretical basis for phosphorus fertilizer utilization in foxtail millet cultivation and will help determine the optimal fertilization levels for foxtail millet growth.

Assessment of water quality and identification of priority areas for intervention in Guanabara Bay basin, Rio de Janeiro, Brazil, using nonparametric and multivariate statistical methods.

The Guanabara Bay hydrographic region (GBHR) has served as a central hub for human settlement and resource utilization throughout Brazil's history. However, the region's high population density and intense industrial activity have come at a cost, leading to a significant decline in water quality. This work aimed to identify homogeneous regions in GBHR according to water quality parameters in dry and rainy periods. The following water quality monitoring variables were monitored at 49 gauge stations: total phosphorus (TP), nitrate (NO3-), dissolved oxygen (DO), hydrogenionic potential (pH), turbidity (Turb), thermotolerant coliforms (TCol), total dissolved solids (TDS), biochemical oxygen demand (BOD), water temperature (Tw), and air temperature (Ta). The statistical analysis consisted of determining principal components, cluster analysis, seasonal differences, and Spearman's correlation. The water quality parameter correlations were not expressively influenced by seasonality, but there are differences in the concentrations of these parameters in the dry and rainy periods. In the dry period, urban pressure on water quality is mainly due to fecal coliforms. The resulting clusters delimited areas under urban, agricultural, and forestry influence. Clusters located in areas with high demographic density showed high concentrations of TCol and TP, while clusters influenced by forestry and agriculture had better water quality. In the rainy season, clusters with urban influence showed problems with TCol and TP, in addition to some characteristics in each group, such as high TDS, NO3-, and BOD. Forested areas showed high DO, and clusters under agricultural influence had higher concentrations of TCol, BOD, and NO3- concerning forested regions. The troubling state of sanitation in GBHR occurs in metropolitan regions due to lack of a formal sanitation system.