Phosphorus Ratio Research Articles

Characteristics of Soil Carbon, Nitrogen, Phosphorus, and Ecological Stoichiometry in Vegetable Fields and Orchard in the Coastal Area of Fuzhou

The soil ecological stoichiometric characteristics of different agricultural land use types have a certain indicator function for characterizing the level of soil nutrient supply and are of great significance to the management of nutrient resources in farmland ecosystems. In order to reveal the soil carbon (C), nitrogen (N), and phosphorus (P) contents and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land use types, this study took vegetable fields (taro field and jicama field) and orchards (citrus tree orchard, watermelon field, and pear tree orchard) as the research objects in the coastal area of Fuzhou City. The contents of soil C, N, and P and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land uses were measured and analyzed. The soil C and N contents were in the order of orchard>vegetable field (P<0.05). The C content in the citrus tree orchard was the highest (4.44 g·kg-1), and the N content in the watermelon field was the highest (1.46 g·kg-1). The soil P content was vegetable field>orchard (P<0.05), and the jicama field had the highest P content (0.19 g·kg-1). The soil carbon and nitrogen ratio (C/N), carbon and phosphorus ratio (C/P), and nitrogen and phosphorus ratio (N/P) were orchard>vegetable field (P<0.05). Among them, the citrus tree orchard had the highest C/N (7.40) and C/P (61.43), and the watermelon field had the highest N/P (10.27). Soil N content was significantly and negatively correlated with bulk density and conductivity (r=-0.49, r=-0.28, P<0.05), and there was a significant and positive correlation with soil water content (r=0.61, P<0.05). C/P and C/N were significantly and positively correlated with SOM (r=0.71, r=0.64, P<0.01). In the process of crop planting and management in the coastal area of Fuzhou City, it is necessary to reasonably add nitrogen fertilizer to compensate for the N limitation, and slow-release nitrogen fertilizer is better for promoting the sustainable supply of nitrogen nutrients in the growth and development of crops.

Global distributions of foliar nitrogen and phosphorus resorption in forest ecosystems

Nutrient resorption is an important mechanism for nutrient conservation and can maintain ecosystem stoichiometry. Here, we examined the global-scale variation of nitrogen resorption efficiency (NRE) and phosphorus resorption efficiency (PRE) by analyzing observations from 218 published papers. We used Pagel's λ to test the phylogenetic limitation on NRE and PRE and applied the random forest model to assess biotic and abiotic drivers, which included climate, soil, species characteristics, and topographical factors, and predicted the global NRE and PRE distributions. We found that NRE and PRE had oppositing trends among climatic zones, plant functional groups, and foliar nitrogen (N) to phosphorus (P) ratios. Nutrient resorption was higher in ectomycorrhizal trees than in arbuscular mycorrhizal trees. Moreover, foliar NRE and PRE were not linked to phylogeny. On average, the random forest overall explained 38 % (21 %–55 %) variation in NRE and 36 % (16 %–55 %) variation in PRE. Both NRE and PRE varied greatly with climate and soil organic carbon (SOC). The spatial variation of NRE and PRE was coupled to N-limitation and P-limitation, respectively. Our evaluation of the factors that influenced NRE and PRE and their global distributions, and our novel approach for evaluating plant utilization of nutrients, advances our understanding of the relative stability of ecosystem randomness in forest ecosystems and the global forest nutrient cycle.

Carbon Cycle Responses to Changes in Weathering and the Long‐Term Fate of Stable Carbon Isotopes

AbstractThe causes of CO2 variations over the past million years remain poorly understood. Imbalances between the input of elements from rock weathering and their removal from the atmosphere‐ocean‐biosphere system to the lithosphere likely contributed to reconstructed changes. We employ the Bern3D model to investigate carbon‐climate responses to step‐changes in the weathering input of phosphorus, alkalinity, carbon, and carbon isotope ratio (δ13C) in simulations extending up to 600,000 years. CO2 and climate approach a new equilibrium within a few ten thousand years, whereas equilibrium is established after several hundred thousand years for δ13C. These timescales represent a challenge for the initialization of sediment‐enabled models and unintended drifts may be larger than forced signals in simulations of the last glacial–interglacial cycle. Changes in dissolved CO2 change isotopic fractionation during marine photosynthesis. This causes distinct spatio‐temporal perturbations in δ13C and affects the burial flux of 13C. We force a cost‐efficient emulator, based on the Bern3D results, with contrasting literature‐based weathering histories over the last 800 thousand years. Glacial–interglacial amplitudes of up to 30 ppm in CO2, 0.05‰ in δ13C, and ∼15 mmol m−3 in deep ocean are emulated for changes in carbonate rock weathering. Plausible input from the decomposition of organic matter on shelves causes variations of up to 10 ppm in CO2, 0.09‰ in δ13C, and 5 mmol m−3 in , highlighting the non‐negligible effect of weathering‐burial imbalances.

Minerals and Glucose Among Patients With Vitamin (D) Deficiency

According to previous studies, vitamin D deficiency might increase the risk of mineral deficiency, and type 2 diabetes mellitus. The aim of this study was to evaluate the level of calcium, phosphorus, calcium to phosphorus ratio, magnesium, and fasting blood glucose in blood serum of patients with vitamin D deficiency. This case-control study comprised 71 patients, 30 subjects sufficient in vitamin D classified as control group (Mean value of vitamin D was 30.67. ± 5.94 ng/dl), and 41 patients suffering from vitamin D deficiency, and insufficiency chosen as the case group (Mean value of vitamin D was 9.79 ± 3.12 ng/dl) .There was lower significant difference in the level of calcium (Ca), calcium–to-phosphorus ratio (Ca/P), and magnesium (Mg) in cases compared to control, but there was higher significant difference in the level of phosphorus (P), and fasting blood glucose (FBG) in cases compared to controls. Serum vitamin D levels showed significantly positive correlations with Ca, and Ca/P ratio, and negative correlation with P. However, vitamin D demonstrated insignificant positive correlation with Mg, and insignificant negative correlation with FBG. The study concluded that, vitamin D deficiency associated with diabetes risk, in addition to mineral deficiency, which associated with various disorders, such as skeletal deformities, osteoporosis, Osteomalacia, cardiovascular diseases, and metabolic syndrome.

Ecological drivers of dissimilarity in multidimensional plant composition of early‐stage plantations in a loess hilly‐gully region

AbstractPlant diversity is an important link between forest ecosystems' structural composition and functional processes. The simple composition of young plantations is weakening the ecological function of restored forest ecosystems in arid regions. The ecological drivers of the plant composition and dissimilarity in plantations remain unclear, especially in the early restoration stage. To fill the gap in knowledge of the differences in species composition in early restored ecosystems, and to reveal the influencing factors of similar species numbers with different compositional structures, based on species' presence‐absence, abundance, and conspicuousness, we explored dissimilarity in the plant composition of young plantations in the loess hilly‐gully region. Our results showed that differences in alpha diversity among plantations were minimal, while the differences in beta diversity were significant. Even if the species diversity of a plantation was low, communities with similar species richness used to have large dissimilarities in their species composition. Turnover components and balanced variation often contributed significantly to species compositional dissimilarity. Co‐inertia analysis results showed species conspicuousness had the greatest consistency with observed environmental variables (RV = 0.65). The redundancy analysis and generalized diversity modeling results showed differences between the drivers of species diversity and dissimilarity. The primary influencing factors for alpha diversity were: soil water content, soil texture, soil total phosphorus, and soil organic carbon. Primary influencing factors for dissimilarity (beta diversity) were: soil nitrogen to phosphorus ratio, breast‐height diameter, soil water content, and stand density. Collectively, plant taxa dissimilarity was influenced by soil nutrient ratio and community structure and plant taxa abundance was influenced by soil nutrient content. Our findings improve the understanding of the plantation species composition and facilitate the prediction of ecological functions.

Patterns of carbon, nitrogen, and phosphorus stoichiometry of three life-form desert plants and responses to soil and microbial biomass factors in a hyper-arid desert ecosystem.

Plant, soil, and microbial biomass ratios of carbon (C), nitrogen (N), and phosphorus (P) are crucial in maintaining stability of desert ecosystems. Nevertheless, variation in relations of elemental ratios between different life forms of plants and soil and microbial biomass in desert ecosystems remains unclear. In a hyper-arid desert ecosystem, C, N, and P concentrations and ratios were analyzed in the plant-soil-microbial biomass system of three perennial desert species (Alhagi sparsifolia Shap. [Herb, Fabaceae], Karelinia caspica Pall. [Herb, non-Fabaceae], and Tamarix ramosissima Ledeb. [Shrub]). Concentrations of N and P in Alhagi sparsifolia leaf, stem, and root were significantly greater than those in Karelinia caspica and Tamarix ramosissima, whereas plant C and soil organic C (SOC) were highest with Tamarix ramosissima. Alhagi sparsifolia and Tamarix ramosissima were P-limited, whereas Karelinia caspica was N-limited. According to correlation analysis, SOC rather than soil total P (STP) regulated plant N:P ratios, and microbial biomass C, N, and P rather than SOC, soil total N, and STP regulated plant C:N:P ratios. Soil water content also affected plant nutrient balance. Thus, in a hyper-arid desert ecosystem, the plant-soil-microbial biomass system and the balance of C, N, and P are closely related, and the role of soil microbial biomass in affecting plant nutrient balance should receive increased attention.

Inconsistent stoichiometry and growth responses of two coexisting dominant species to various N and P supplies in a supratidal wetland of the Yellow River Delta

The availability and stoichiometry ratio of nitrogen (N) and phosphorus (P) play vital roles in plant trophic dynamics and primary production. However, the responses of these plant traits to varying N and P supplies remain largely unclear for supratidal wetland herbs. Here, we conducted a 4-year field manipulation experiment in a supratidal wetland in the Yellow River Delta. The changes in aboveground biomass, leaf N and P concentrations and N:P ratios of two dominant herbs (Suaeda glauca and Phragmites australis) were examined at 3 overall nutrient supply levels (low, medium and high) combined with 3 N:P supply ratios (5:1, 15:1 and 45:1). The results showed that the leaf trophic dynamics of the two dominant species rely on the overall supply level as well as on the N:P supply ratio, while the aboveground biomass of both species was only significantly influenced by the overall supply level. With the increase in supply level, S. glauca gained an advantage over P. australis in aboveground biomass competition. The leaf N and P concentrations of both species raised with the respective increasing nutrient inputs, and N:P improved with the increasing supply ratio. The leaf stoichiometry of S. glauca was more strongly influenced by the various N and P supplies than that of P. australis. Specifically, the gap of nutrient contents between the two species widened as nutrient availability improved, with the dominance of S. glauca increasing while that of P. australis decreasing. This species-specific response may explain the altered aboveground biomass of the two species. Our findings suggested that changing the N and P supply can potentially influence primary productivity by changing leaf nutrient status, indirectly affecting the shifts in plant dominance and community composition in supratidal wetland ecosystems.

Corrosion resistance of magnesium phosphate cement under long-term immersion in different solutions

Magnesium phosphate cement (MPC) is widely utilised in engineering. However, it may be subject to corrosion in the Western Chinese saline soil environment. This study analysed the factors of magnesium phosphorus ratio, borax content, water binder ratio and fly ash content. Mix proportions of MPC were devised through orthogonal testing. The corrosion performance of MPC specimens in water, 5% Na2SO4 solution, 5% NaCl solution and saline soil solution were analysed in terms of mass loss and the strength anti-corrosion coefficient. The corrosion mechanisms of MPC in different solutions were analysed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric and differential scanning calorimetry (TG-DSC) and Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). There were no obvious changes in MPC appearance or morphology after soaking in different solutions for 180 days. The mass loss was < 5% and the strength loss was < 25%, indicating that MPC has good resistance to saline soil and other saline solutions. The strength anti-corrosion coefficients of MPC soaked in various solutions for 180 days were > 0.75, and the influences on strength can be ranked as follows: 5% Na2SO4 solution > saline soil solution > water > 5% NaCl solution. On the basis of TG-DSC, FTIR and XRD analyses, when MPC was soaked in different solutions for 180 d, the contents of the hydration product MgKPO4·6H2O (MKP) were ranked as water > 5% NaCl solution > saline soil solution > 5% Na2SO4 solution. SEM-EDS analysis shows that MKP was corroded to varying degrees after the MPC was soaked in different solutions, with the 5% Na2SO4 solution causing the greatest corrosion.

Relationships between biomass of phytoplankton and submerged macrophytes and physicochemical variables of water in Lake Caohai, China: Implication for mitigation of cyanobacteria blooms by CO2 fertilization

Reducing nutrient input in aquatic ecosystems has been widely recognized as a way to mitigate eutrophication. The paradigm of nutrient limitation by N and P is pervasively accepted, without considering the possibility of C limitation. However, our assumption that C might affect the aquatic biological composition, lacks fieldwork support. We tested the co-limitation of C/N/P on the growth of submerged macrophytes and phytoplankton in the Caohai Lake, a typical shallow karst lake in southwestern China. This study documented the seasonal variations in the concentration and comparative availability of nutrients C/N/P, in addition to physicochemical parameters, submerged macrophytes biomass, and phytoplankton composition in the lake. Our results show that dissolved inorganic carbon plays a substantial role in enhancing the primary production of phytoplankton and macrophytes, which suggests that primary production can be suppressed not only by P and/or N (as generally believed) but also by C, owing to the unique physicochemical characteristics that prevail in typical karst regions. Additionally, submerged macrophytes have been found to inhibit phytoplankton growth. Further analysis showed that the proportion of Cyanobacteria over Chlorophyta and Bacillariophyta throughout the year was reduced at dissolved carbon dioxide/total nitrogen (CO2/TN) ratios (>0.2) and dissolved carbon dioxide/total phosphorus (CO2/TP) ratios (>10) in this study. Isotopic evidence further indicated that the abundance of Cyanobacteria was reduced when CO2 >30 µmol/L. In summary, the combined results suggest that when controlling N and P, CO2 fertilization may significantly affect both the growth and composition of phytoplankton communities/submerged macrophytes and carbon sequestration in karst surface water ecosystems. This implies a new “paradigm” in the mitigation of cyanobacteria blooms by adding more CO2 to aquatic ecosystems with low pCO2, during which carbon sequestration may also be enhanced.

Synergistic warming- and catchment-driven mid-Holocene cyanobacterial development: Pigment evidence from shallow eutrophic Lake Mayinghai on the Chinese Loess Plateau

The current lake environmental problem of harmful cyanobacterial blooms cannot be mitigated effectively despite numerous eutrophication control strategies, and climate warming may have been considered as a potential key driver. However, it is still unclear how climate change and associated natural processes influence cyanobacterial development. Here we use a sedimentary pigment record from a remote, alpine, small and eutrophic lake (Lake Mayinghai) on the Chinese Loess Plateau and take the mid-Holocene as an analog to explore the possible influences of temperature, precipitation and terrestrial vegetation on in-lake and catchment processes, algal compositional changes and cyanobacterial development. The pigment data indirectly suggest that a distinctly low β-carotene to chlorophyll a ratio during the mid-Holocene is likely due to an increase in non-nitrogen-fixing colonial coccoid cyanobacteria at the expense of nitrogen-fixing filamentous cyanobacteria. There are two probable synergistic driving mechanisms, of which one is high temperatures and associated increased lake thermal stratification and the other is high inorganic nitrogen supply and resultant increased lake nitrogen to phosphorus ratio. This study provides implications for the potential influences of future climate change on cyanobacterial development under a warmer, wetter and re-forested environment on the Chinese Loess Plateau.

Nitrate Pollution and Expansion of Free-Floating Plants in 3 Lower Wisconsin River Oxbow Lakes

Marshall DW, Wade K, Unmuth JL. 2023. Nitrate pollution and expansion of free-floating plants in 3 Lower Wisconsin River oxbow lakes. Lake Reserv Manage. XX:XX–XX. The Lower Wisconsin State Riverway (LWSR) in southwest Wisconsin is one of the highest quality large river floodplain ecosystems in the Midwest and is designated a Ramsar Wetland of International Importance. Oxbow lakes are important features of this floodplain ecosystem but many had become highly eutrophic by about 2011. Free-floating plants (FFP), comprised of duckweeds and filamentous algae, expanded in many groundwater-fed oxbow lakes along the LWSR. Beginning in 2013, we investigated possible causes of eutrophication. Our water pollution investigation indicated the primary oxbow water source is groundwater that flows beneath the cropland intensive Pleistocene sand terrace. The sand terrace aquifer delivers large amounts of NO3-N with concentrations that exceeded the federal and state Drinking Water Enforcement Standard (10 mg/L). Aquifer total phosphorus concentrations were orders of magnitude lower. NO3-N:total phosphorus (TP) ratios in terrace groundwater often exceeded 500:1. Estimated NO3-N loading rates were variable and ranged from 2989 kg/yr discharged to a 5.5 ha oxbow lake up to 33,091 kg/yr discharged to a 35 ha floodplain flowage. The results suggest coordinated groundwater and surface water quality protections are needed, and potentially Clean Water Act enforcement. Strategies designed to protect domestic water supplies beneath the sand terrace can reduce NO3-N pollution in the oxbow lakes. Addressing this issue could begin with adopting recommended surface water nitrogen criteria and developing FFP impairment criteria for LWSR oxbow lakes.

Nutrient Fate in the Full MAnure PHosphorus EXtraction (MAPHEX) System, and Design of a Simplified System (MAPHEX Lite)

Highlights The MAPHEX System removes and concentrates most of the P and other nutrients from liquid dairy manures. Most of the N and K are left in the liquid fraction for the beneficial use of the farmer. Design and expected performance of a simplified but much larger System is discussed. Abstract. The relatively recent concept of the manureshed highlights the problem of the broken nutrient cycle in modern animal agriculture and the low nitrogen:phosphorus ratio in manure relative to crop requirement that results in P accumulation in soils near source areas. One solution to avoid P accumulation is to transport the manure to soils with a deficit of P, but liquid manure’s bulkiness and low nutrient density present challenges for transport over great distances. While the full MAnure PHosphorus EXtraction (MAPHEX) System has shown to be capable of removing greater than 90% of the P from liquid manures while leaving much of the N in the liquid fraction for use on the farm, other nutrients present in manures in lesser amounts than N and P have not been reported on. This study indicates that both the full MAPHEX System and a newly designed MAPHEX Lite System, that not only conserves more N but is more efficient and less costly, are highly efficient at extracting and concentrating most nutrients in solid form while leaving most of the N and K in the liquid phase for beneficial use by the farmer near the manure source. Therefore, it seems clear that both Systems, and the components they include have the potential to play a significant role in manureshed management. Keywords: Chemical treatment, Liquid-solid separation, Manure, Nitrogen, Phosphorus, Potassium, Treatment systems.

Evaluation of Content and Ratio of Calcium and Phosphorus in Commercially Available Pet Food for Dogs and Cats

Evaluation of Content and Ratio of Calcium and Phosphorus in Commercially Available Pet Food for Dogs and Cats

Oxidation behavior of vanadium and phosphorus during simultaneous vanadium extraction and dephosphorization of hot metal

In this paper, the indirect equilibrium method was used to study the equilibrium distribution ratios of vanadium and phosphorus in the metal phase and the slag phase, and simultaneous vanadium extraction and dephosphorization experiments were carried out under different slag basicity (the mass ratio of CaO to SiO2) conditions to explore the oxidation behavior of vanadium and phosphorus during simultaneous vanadium extraction and dephosphorization of hot metal. The results show that with the increase of slag basicity, the equilibrium distribution ratio of V (lgLV) increases slightly and the equilibrium distribution ratio of P (lgLP) increases significantly. With slag basicity increasing from 0.5 to 2.5, lgLV and lgLP increase from 1.7 to 2.0 and 0.1 to 1.9, respectively. Both lgLV and lgLP decrease with the increase of temperature, and increase with the increase of FeO content. High MgO content is not conducive to vanadium extraction. MnO has less effect on lgLV and lgLP. lgLV increases with the increase of V2O3 content, and decreases with the increase of P2O5 content. lgLP decreases with the increase of V2O3 content, and increases with the increase of P2O5 content. Both lgLV and lgLP decrease with the increase of TiO2 content. When the slag basicity is 1.5, the oxidation rate of vanadium reaches 95% after 10 min of reaction. The total mass transfer coefficient of P is in the range of 0.0040–0.0084 cm/s, and increases obviously with the increase of slag basicity. However, the influence of slag basicity on the total mass transfer coefficient of V is not obvious. Both the rate-limiting step of vanadium extraction and dephosphorization are the mixed mass transfer in the metal phase and the slag phase.

Temporal and spatial characteristics of key indicators of nutritional level and control standards in Lake Poyang

本文研究2018—2020年鄱阳湖水质及营养水平关键指标——叶绿素a、总磷、总氮浓度时空特征，采用分位值法与压力-响应关系法等研究氮磷基准和适宜的控制标准。结果表明，2018—2020年鄱阳湖水质以Ⅳ类为主，超标污染物为总磷和总氮。近3年鄱阳湖处于“中偏富”营养水平，叶绿素a浓度均值为7.6 μg/L，总磷浓度均值为0.070 mg/L，总氮浓度均值为1.30 mg/L。所有水域在年内皆会出现富营养时段；年内各月份皆有水域处于富营养水平。总磷、总氮浓度枯水期高于丰水期；8月总磷浓度最低，8—9月总氮浓度最低。叶绿素a浓度较高的季节为秋季，尤以9月最高，9月全湖叶绿素a浓度均值和中位值分别为16和12 μg/L，皆超中-富营养界限值10 μg/L，原因在于9月“五河”退水与仍处汛期的长江干流顶托导致流速减缓。叶绿素a浓度较高的水域为入湖河流尾闾水域、浅水湖湾、碟形湖（如南湖村、金溪咀、南矶山、蚌湖等）。鄱阳湖平均N/P比为52，相对于藻类繁殖需求而言，氮、磷皆处于过量状态，总磷宜作为首要控制因子，总氮控制亦应考虑。鄱阳湖总磷基准范围为0.029~0.054 mg/L，总氮基准范围为0.50~0.81 mg/L。考虑当前水污染防治、社会经济发展所处的阶段和现实，目前鄱阳湖适宜的总磷控制标准在0.050~0.100 mg/L之间，适宜的总氮控制标准在1.00~1.50 mg/L之间。另外，对入湖河流控制断面，总磷控制标准应严于目前的0.20 mg/L，并建立适宜的总氮控制标准。;This work studied the key indicators of nutritional level of Lake Poyang in recent three years (2018-2020) including temporal and spatial characteristics of Chl.a, total phosphorus (TP) and total nitrogen (TN). The results showed that the water quality of Lake Poyang was mainly Class Ⅳ, and the pollutants exceeding national standard were TP and TN. The average concentrations of Chl.a, TP and TN during 2018-2020 were 7.6 μg/L, 0.070 mg/L and 1.30 mg/L, respectively. Presently, Lake Poyang is under medium-to-rich nutrient level. All the lake area had eutrophication periods in the year, and in all months of the year, there were regions that were eutrophic. The concentrations of TP and TN in dry seasons were higher than those in wet seasons. TP concentrations were the lowest in August and TN concentrations were lowest during August-September. The season with higher Chl.a concentration was mainly from September to November, especially in September when the mean and median values of Chl.a concentrations were 16 μg/L and 12 μg/L, exceeding the mesotrophic limit value of Chl.a, indicating that the whole lake was eutrophic. The reason was that the velocity of water in the lake slowed down due to the retreat of the Five Rivers in September and the mainstem of the Yangtze River still in the flood season. The waters with high Chl.a were the tail waters of rivers entering the lake, shallow lake bay and dished lake waters, such as Nanhu village, Jinxizui, Nanjishan, Banghu lake, etc. The ratio of nitrogen and phosphorus in Lake Poyang was 52, and both of TN and TP were excessive for algae production. TP should be controlled as a key point, and TN control should also be paid attention too. The reference of TP of Lake Poyang is in the range of 0.029-0.054 mg/L, and TN is in the range of 0.50-0.81 mg/L. Considering requirement of water pollution prevention and social and economic development, it is suggested that TP control objective of Lake Poyang is set in 0.050-0.100 mg/L, and TN in 1.00-1.50 mg/L. In addition, for the control section of rivers entering the lake, TP control objectives should be more strict than current 0.20 mg/L, and an appropriate TN standard should be properly established.

Study on flexural resistance and hydration mechanism of magnesium phosphate cement

Based on a large number of research data at home and abroad, this paper designed an experiment to complete the research on the mechanical properties and durability of magnesium phosphate cement by the ratio of magnesium phosphorus, fly ash content and pH value. On this basis, the effects of curing methods and different concentrations of hydrochloric acid on hydration products of magnesium phosphate cement were studied, and the mechanism of action was analyzed. Finally, when the M/P ratio was 4, with the increase of curing time, the strength of MPC increases gradually. When M/P is greater than 4, the flexural strength of MPC all shows a certain degree of shrinkage. In addition, fly ash can reduce the shrinkage of magnesium phosphate cement-based materials; The content of K-type struvite (KMgPO4ꞏ6H2O) in MPC can be increased under acid curing (pH=2) and water curing conditions.

Eficiência de uso de fósforo por genótipos de meloeiro

ABSTRACT This study aimed to evaluate the efficiency of phosphorus use with melon genotypes cultivated in a hydroponic system. Ten melon genotypes were evaluated in solutions with and without phosphorus restriction. A randomized block design in a 10 × 2 factorial scheme was used, with five replicates. The following characteristics were evaluated: leaf number, stem diameter, main branch length, root system length, root system volume, chlorophyll, root and shoot phosphorus concentration ratio, total phosphorus, root and shoot dry matter ratio, total dry matter, and phosphorus use, acquisition, and internal utilization efficiencies. The existence of variability among genotypes was verified for all evaluated characteristics, except for chlorophyll. Genotypes A-16, A-29, A-50, A-52, and Trinity were classified as efficient and responsive in the phosphorus-restricted solution and are promising for breeding studies.

Influence of net cages on water quality and trophic status of Lake Victoria, Kenya: The case of Kadimu Bay

AbstractWater quality is a critical component regulating ecosystem functioning in aquatic habitats, requiring regular monitoring for sustainable ecosystem services. Cage fish farming has the potential to affect water quality because of its rapid increase in many African waterbodies in response to dwindling wild fish stocks. Thus, there is a need for more studies to guide sustainable cage aquaculture in African lakes and reservoirs. This study evaluated the possible effects of cage farming of Nile tilapia (Oreochromis niloticus) on water quality parameters and the trophic state of Kadimu Bay, Lake Victoria, Kenya. Sampling for physicochemical and biological variables, including nutrient load, was conducted from January to October 2021, at five fish cage sites and a control site within the bay. In situ measurements of physical variables were undertaken in the field, while analysis of water samples for nutrient loads, biological and chemical variables was undertaken in the laboratory, following the methods described in APHA (American public health association standard methods for the examination of water and waste water. APHA‐AWWA‐WEF, 2005). The Carlson's Trophic State Index (CTSI) was used to classify the trophic state of the cage sites, while the total nitrogen:total phosphorus (TN:TP) ratio was used to determine the primary productivity limiting nutrient in the bay. The study results indicated electrical conductivity was significantly lower at the control (97.53 ± 4.17 μS/cm), compared to cage sites (105.42 ± 5.32 μS/cm at the Utonga cage site to 112.84 ± 1.94 μS/cm at the Oele cage site), indicating water of relatively lower quality at the cage sites. Similarly, the nitrite concentrations were higher at cage sites (6.35 ± .96 μg/L at the Uwaria cage site to 3.16 ± 2.25 μg/L at the Utonga cage site), and lower at the control site (2.68 ± 1.39 μg/L). In all, 14 physicochemical variables did not vary significantly between the cage and control sites, with nine variables (temperature, turbidity, electrical conductivity, total suspended solids, particulate organic matter, chlorophyll‐a, TP, nitrate and TN) being within the recommended thresholds for aquatic life processes. The bay was evaluated as being in a light eutrophic state, indicating moderate influence of the fish cages on the trophic state of the sites. There was a moderate relationship between chlorophyll‐a and TP concentration at the sampling sites (R2 = .50), compared to a stronger relationship with (R2 = .78). The TN:TP ratios were &lt;10 at the sampling sites, indicating nitrogen was the limiting factor for primary production in the bay. The calculated CTSI suggests that the bay exhibited a light eutrophic state. Overall, although the results of this study showed cage aquaculture is not a current challenge to the water quality of the bay, regular monitoring is nevertheless recommended to inform sustainable aquaculture development in the bay and lake.

Effect of multi-phase slag on dephosphorization in BOF steelmaking

In basic oxygen furnace double slag process, the slag shows a coexisting state of both liquid and solid. In order to study the effect of multi-phase slag on dephosphorization, heat experiments were conducted in this study, and the multi-phase slag was analyzed with the method of SEM-EDS. The results show that the mass fraction and size of solid solution increase with increasing basicity and decreasing FetO concentration. The distribution of P2O5 (LP2O5) between the solid solution and liquid phase increases with the T.Fe content in the liquid phase. While the increase of CaO content in liquid phase shows the opposite effect. A higher CaO content in liquid phase brought a decrease in γP2O5. The increase of T.Fe content in liquid slag has no notable effect on γP2O5 of dephosphorization slag, but increases γP2O5 of decarburization slag. The partition ratio of phosphorus between slag and steel (LP) increases with the increase of basicity, for conditions of FetO content in dephosphorization slag less than 25%. In the case of basicity of 3.0, LP reaches a maximum at FetO = 15%. When the basicity is 3.5 and 4.0, LP value is the largest at FetO of 15% or 20%.

Çubuk stream pollution and environmental effects

The water quality parameters of Çubuk Stream were examined in terms of physical and chemical aspects and the pollution level of Çubuk Stream was determined by comparing these parameters with the Surface Water Quality Regulation (SWQR). For this purpose; samples were taken from three different stations between August 2012 and April 2013, the water samples were compared with each other and with previous studies, the water quality of Çubuk Stream was determined according to the surface water quality regulation. In our study, the biological oxygen requirement of Çubuk Stream according to SWQR (BOD5: 22.5mg/l) IV. class, ammonium nitrogen element (NH4–N:2.34 mg/l) IV. class, nitrite nitrogen element (NO2–N: 0.035 mg/l) II. class, nitrate nitrogen element (NO3 –N:0.95 mg/l) Class I, according to phosphate value (PO4:0.075 mg/l) Class I and trace elements (Pb, Cd, Cr, Ni, Mn) values Class I. water quality. According to the ratio of NH4-N/PO4 (2.34/0.075=31.2 mg/l), the element that limits eutrophication in Çubuk Stream is P. Compared to previous studies, after the wastewater treatment plants established in the region, higher quality water is provided, especially in terms of NO3 and PO4. It has been determined that the nitrogen and phosphorus ratios are high because the region, which is dense in terms of organic matter, is close to industrial establishments.