Phosphorus Release Research Articles

Phosphorus and cadmium release and distribution characteristics in environmental microinterfaces of biochar based on DGT technology

Phosphorus and cadmium release and distribution characteristics in environmental microinterfaces of biochar based on DGT technology

Effects of Phosphate-Solubilizing Bacteria on Phosphorus Release from Coastal Sediments and the Growth of ‘Green Tide’ Chaetomorpha linum

Effects of Phosphate-Solubilizing Bacteria on Phosphorus Release from Coastal Sediments and the Growth of ‘Green Tide’ Chaetomorpha linum

Potential Release of Phosphorus by Runoff Loss and Stabilization of Arsenic and Cadmium in Mining-Contaminated Soils with Exogenous Phosphate Fertilizers

Phosphate has been proven to be effective in remediating soils contaminated with potentially toxic elements (PTEs); however, the potential release of phosphorus (P) through runoff and the impact on PTEs’ transport in this process have never been assessed. A rainfall simulation study was conducted to investigate P runoff loss and its impact on the stability of arsenic (As) and cadmium (Cd) after applying potassium dihydrogen phosphate (PDP), superphosphate (SSP), and ground phosphate rock (GPR) in soil trays packed with As–Cd-contaminated soil. The phosphorus loss through runoff and sedimentary phases followed the order of SSP > PDP > GPR > control. Phosphate fertilizers’ application reduced the mobility of As and Cd. In the first rainfall, the enrichment ratios (ERs) of As and Cd in the sedimentary phase after PDP, SSP, and GPR treatment were 0.12, 0.04, and 0.08 and 0.24, 0.16, and 0.07 units lower than the control, respectively. The <53 μm fraction in the sedimentary phase accounted for 53.06–75.95%, and phosphate fertilizers significantly enhanced the As and Cd stability in this fraction. The XPS analysis showed that the conversion of As(III) to As(V) and the generation of Cd–phosphate compounds were important reasons for enhancing As and Cd stability. This study demonstrated that PDP might be capable of the remediation of As–Cd contamination with the least release of P to watersheds.

Enhancing phosphorous release and recovery from waste activated sludge by citric acid treatment and cyclic extraction

Waste activated sludge (WAS) is a potential alternative supply of non-renewable phosphorus. However, improving phosphorus release from WAS is challenged by the elution of phosphorus in metal-bound phosphorous (mainly Fe-P or Al-P) due to the extreme pH condition requirement and the slow disintegration of sludge flocs. In this study, the role of citric acid (CA) in enhancing phosphorus release from WAS was investigated. Owing to its intensive chelating function, CA addition rapidly increased phosphorus release to its peak within 24 h. With the CA dosage increasing from 0.08 g/gTS to 0.32 g/gTS, the concentration of total dissolved P in the supernatant reached 698 ± 17 mg/L, significantly higher than that of the control group (154 ± 2.3 mg/L). The relative release efficiency of Fe-P and Al-P was substantially enhanced, contributing to 60.1 % − 82.4 % and 76.0 % − 85.6 %, respectively. Apatite P was almost completely released under acidic conditions (pH < 5), with the relative release efficiency achieving 78.5 % − 93.1 %. Additionally, compared to adjusting pH to 3 alone, the synergistic effect of adjusting pH to 3 combined with 0.08 g/gTS CA addition boosted total solid P (TSP) release efficiency by 16 %, primarily due to the cheating function of CA with released iron and aluminum ions. Furthermore, after three continuous acid (pH = 3) recycling cycles, the release efficiency of TSP finally increased to 73.0 ± 0.9 % with the average PO43−-P recovery efficiency achieved 98 %, and the average content of P2O5 in recovered phosphorus precipitates was more than 20 %. Therefore, this study provided a research basis for the efficient recovery of phosphorus from real WAS by a cost-effective and environmentally friendly method in practice.

Insights into multivalent metal removal-assistant anaerobic fermentation of waste activated sludge: Impact factor identification and mechanism clarification of metal removal

The study investigated the impact factors of metal removal and their role in enhancing anaerobic fermentation of waste activated sludge (WAS), aiming to identify key mechanisms. By optimizing the sludge concentration, it found that a sludge suspension solid range of 10–30 g/L significantly improved the efficiency of anaerobic fermentation, and yielded SCOD of 93.8–177.1 mg/g volatile suspension solid after 8 h, respectively, which was 3.67–4.77 times higher than the control. Correspondingly, the production of short-chain fatty acids (SCFAs) was significantly enhanced. At the optimal sludge suspension solid of 10–30 g/L, the SCFAs were 1.28–1.51 times higher than that of the control. Furthermore, the study evaluated the performance of different metal removal reagents and discovered that microporous COOH reagent outperformed gel SO3H and macroporous SO3H reagent. The macroporous COOH reagent achieved 1.54 and 1.22 times higher SCOD values and significantly enhanced the production of SCFAs, demonstrating its superiority in metal removal and fermentation enhancement. Moreover, the research revealed that sludge concentration and metal removal agent types influenced the activities of key enzymes involved in anaerobic fermentation. Additionally, the macroporous COOH reagent showed the most efficient ability to remove metal ions, contributing to increased nutrient recovery in terms of nitrogen (NH4+-N) and total phosphorus (TP) release during the acidification process. In summary, the enhancing mechanism of metal removal-assistant anaerobic fermentation was discussed from the sludge floc concentration, the skeleton structure and the ion exchange group type. The identified mechanism significantly improves fermentation efficiency and facilitate the organic recovery, representing an innovative approach for wide application in WAS management and resource recovery.

Long-term effects of dead algal deposition on sediment surfaces: behavior of endogenous phosphorus release in sediments

Long-term effects of dead algal deposition on sediment surfaces: behavior of endogenous phosphorus release in sediments

Water quality and pollution source apportionment responses to rainfall in steppe lake estuaries: A case study of Hulun Lake in northern China

Hulun Lake, the largest inland steppe lake in China, is encountering severe water quality degradation. Estuaries play important roles in material and energetic exchange between rivers and lakes. The water quality at the estuaries of Hulun Lake directly reflects the impact of both human activities and natural factors on the lake’s overall water quality, especially during rainfall events. From July 28, 2021, to August 4, 2021, water samples from 62 sites were collected in the three estuaries of Hulun Lake before and after a moderate rainfall event. 13 water parameters, including dissolved oxygen (DO), Turbidity (Tur), Total Nitrogen (TN), Total Phosphorus (TP), Total Organic Nitrogen (TON), and Total Organic Phosphorus (TOP) were measured. The spatio-temporal distribution of water quality in the estuaries was assessed based on water quality index (WQI). Besides, an improved approach integrating stepwise linear regression (SLR) and principal component analysis (PCA) was utilized to construct a WQImin model for an effective assessment of water quality in these estuaries. Furthermore, the absolute principal component scores-multiple linear regression (APCS-MLR) model was employed to identify and quantify the environmental drivers underlying the water quality in the estuaries. The results of WQI indicated that the water quality of the sites in the estuaries of Hulun Lake was “medium” or “poor”, both before and after the rainfall, with a general deterioration in water quality in response to the rainfall. The simplified WQImin model consisted of 5 crucial parameters (i.e., TN, TP, ammonium (NH4+-N), Tur, and permanganate index (CODMn)), and it performed well without parameter weights. Spatial differences in some water parameters among the estuaries were detected, which were attributed to the natural factors and human activities upstream. The principal environmental factors affecting the water quality in the estuaries consisted of hydrodynamic processes, internal phosphorus release, external phosphorus input, external nitrogen input, nitrification in the estuaries, and external organic input and internal organic release. Therefore, we propose basin management strategies such as limiting grazing pressure, adopting enclosed pasture, wetland restoration, optimizing water renewal cycle in Hulun Lake, and transboundary water quality management to tackle water contamination in Hulun Lake.

Promoting effect of submerged plants on phosphorus source and sink in sediments: Response of phosphorus release and microbial community to Vallisneria natans and Potamogeton malaianus growth

Promoting effect of submerged plants on phosphorus source and sink in sediments: Response of phosphorus release and microbial community to Vallisneria natans and Potamogeton malaianus growth

Preparation of a slow-release fertilizer from MgO-modified biochar and struvite and its capacity for cadmium passivation

This study investigates the development of a slow-release coated fertilizer using magnesium oxide-modified coconut shell biochar (MgO-BC), struvite, and urea. The performance of this coated fertilizer in terms nitrogen and phosphorus release and cadmium (Cd) passivation in Cd-contaminated soil was evaluated through soil column leaching tests and pot experiments. The coated fertilizer, prepared with a mass 6: 2: 1 ratio of MgO-BC: urea: struvite, achieved a compressive strength of 38.6 N/grain. The nitrogen and phosphorus release rates from Cd-contaminated soil treated with the coated fertilizer were 887.391 μg/d and 2.884 μg/d, respectively, representing decreases of 5.0 % and 32.8 % compared to soil treated with struvite and urea. The coated fertilizer demonstrated a good Cd fixation effect in Cd-contaminated soil. The coated fertilizer effectively reduced Cd mobility, with the total accumulated Cd leached from the soil decreasing by 73.2 % after ten leaching cycles. Furthermore, the coated fertilizer significantly inhibited Cd uptake by peas (Pisum sativum L.), with Cd content in the above-ground and under-ground parts of the plants decreasing by 82.78 % and 68.04 %, respectively, compared to the control. The transport coefficient (TFS/R) of Cd for peas decreased by 46.12 %. The Cd passivation efficiency of the coated fertilizer was 37.76 %, attributed to the transformation of acid extractable/exchangeable Cd to residual Cd. These results demonstrate that the coated fertilizer, prepared from MgO-modified biochar and struvite, effectively combines slow releasing nutrient properties with Cd passivation capabilities.

Kitchen Waste Digestate and Digestate Biochar Fertilizer for Turfgrass Management and Nutrient Leaching

Slow-release fertilizer is generally used in turfgrass management to maintain quality turf without inducing excess vertical growth, to avoid frequent mowing. This study was designed to verify whether kitchen waste digestate and digestate biochar could serve as slow-release fertilizers to promote turf quality and reduce nutrient leaching risk in two turfgrass species over two years in controlled pot experiments. The results showed that the nutrient release of granular fertilizers made from kitchen waste digestate and digestate biochar was a two-phase process (an initial rapid phase, followed by a slow-release phase). The kitchen waste digestate showed higher nitrogen and phosphorus release ratios than the biochar and sheep manure. Compared to the reference sheep manure, fertilization with kitchen waste digestate and biochar increased the leaf chlorophyll content by 48.6% and 27.9%, and reduced senescent leaves by 15.6% and 11.1%, respectively, at 23 d after fertilization, leading to higher turf quality. Fertilization with kitchen waste digestate biochar significantly reduced the nutrient leaching risk compared to fertilization with kitchen waste digestate and sheep manure. Our results demonstrated the potential of reusing kitchen waste digestate and digestate biochar as slow-release fertilizers for promoting turf quality in turfgrass management.

Delving into nitrogen and phosphorus dynamics in shallow eutrophic lakes: Multi-interface response to freeze-thaw cycles

Assessing the impact of freeze-thaw cycles on nutrient transfer in lakes is crucial for addressing the global eutrophication of freshwater ecosystems in cold and arid regions. However, available information about the dynamics of nitrogen (N) and phosphorus (P) release during intact freeze-thaw cycles, especially in the sediment–porewater–water column continuum of lakes, is limited. This study collected the samples during ice-covered (January) and non-ice-covered (April, July, and October) periods. The changes in total nitrogen (TN) and total phosphorus (TP) were analyzed to estimate their release fluxes from the sediment-water interface. Both redundancy analysis (RDA) and variance partitioning analysis (VPA) were used to explore the effects of environmental variables on N and P. The results indicated that during the ice-covered period (ICP), the surface water content of different forms of N and P was lower than that of the overlying water, whereas the opposite was true during the non-ice-covered period (NICP). The overall trend for the different forms of N was TN > DIN > NH4-N > NO3-N > NO2-N, and for P, it was TP > PP > DTP > DOP>DIP. The vertical profiles of the porewater TN and TP generally demonstrated an increase followed by a decrease from the surface to the bottom, with an inflection point at 15 cm. Sediment TN and TP trends over time matched porewater trends, with both being spatially highest at the lake inlet. ICP sediments acted as sinks for TN and TP, and NICP sediments acted as sources. N and P in the water column were significantly correlated mainly with physicochemical indicators, whereas sediment contributed positively to TN and TP in the porewater. VPA indicated that environmental factors explained 46.45 % of the variation in TN and TP in the porewater. These findings emphasize the importance of freeze-thaw cycling processes in driving N and P nutrient enrichment, source-sink effects, and multi-media coupling in shallow lakes in arid plateau regions.

Assessing the influence of thermal structure variation on Fe and P mobility in sediments cores using Yellow Spring Instrument, diffusive gradient technology, and HR Peeper for sustainable water quality management.

The freshwater ecological characteristics in terms of the daily inventory of thermal stratification, spatial variation of O2 distribution, and the mobility of potentially toxic elements (PTEs) at the water sediment interface (WSI) are prudent freshwater assessment indices for water quality management protocol. The study conducted daily observations within a monsoon-influenced region, utilizing high-resolution techniques such as HR Peeper, Yellow Spring Instrument (YSI), and ZrO-Chelex diffusive gradient technology (DGT) to analyze PTEs, specifically phosphorus (P) and iron (Fe),within the water-sediment interface (WSI) under different temperatures and oxygen conditions. The 66-day field study showed that high thermal structure contributed significantly to production Fe ions and P from sediment under reductive dissolution of FeOOH. The study also revealed that P and Fe exhibited comparable spatial distribution patterns at the WSI, indicating a linked relationship between these PTEs. This correlation was reinforced by high Pearson correlation coefficients ranging from 0.7 to 0.9 (bilateral, p < 0.05) indicating that the concentrations of labile P were predominantly influenced by the release of phosphorus bound to iron. The fluxes of the PTEs were positive with a range of Fe, 3.3-81.5 mg/m2 day and P, 0.03-0.5 mg/m2 day showing the sediments liberated the PTEs into the benthic water. Again, high positive fluxes (Fe≈60 mg/m2 day, P≈0.5 mg/m2 day) for PTEs were obtained when stratification was high (anoxic conditions) and low (Fe≈5 mg/m2 day, P≈0.08 mg/m2 day) when stratification did not exist. This depicts that Fe/P dynamics were hinged mainly on hypoxic conditions in the benthic water under the reductive dissolution of FeOOH. The findings showed that organic materials (both solid and dissolved) correlated (> 0.7) significantly with (positive high values) Fe. This indicates that their interaction contributed to the reservoir water deterioration. However, Ca2⁺ and Mg2⁺ had little impact on the liberation of Fe-DOC-P from sediments due to their inability to compete with Fe for binding to DOC and P, as shown by their low correlation values. The research provides in-depth insights into the dynamics of PTEs on a daily timescale and offers valuable information for water management practices in inland reservoirs, particularly concerning the cycling of phosphorus (P) and its effects on ecosystem health.

Blocking endogenous phosphorus release in sediments by a hydrotalcite mixture synthesized with natural sepiolite and discarded cans

Pure hydrotalcite (LDH) materials prepared from chemical reagents have been investigated as solid-phase phosphorus (P) inactivation materials (SPIM) to manage endogenous P loading in sediments. However, the efficacy and mechanism of LDH mixtures prepared by natural minerals and solid wastes in controlling sediment P release are unclear. Therefore, a Ca/Mg-Al-LDH (CMA-LDH) material was synthesized using sepiolite and cans, and its efficacy, mechanism, and ecological impact in controlling sediment P release were investigated. CMA-LDH-p was prepared as a control material using pure chemical reagents. The CMA-LDH and CMA-LDH-p were both composed of hydrotalcite and hydrocalumite. The maximum P adsorption capacity of CMA-LDH was 123.01 mg/g, comparable to that of CMA-LDH-p. The adsorbed P by CMA-LDH was mostly in the stable P form, accounting for 87.2 % of the total P. The adsorption capacity and immobilization ability of CMA-LDH for P were superior to other reported LDH-based SPIM. Both the CMA-LDH addition and capping successfully blocked sediment P release under anaerobic conditions. Passivation of mobile P in the sediment and DGT-labile P in the interstitial water was critical to preventing sediment P release by the CMA-LDH addition. The CMA-LDH capping inhibited sediment P release through the effective adsorption of CMA-LDH on DGT-labile P at the sediment/overlying water interface. The CMA-LDH addition and capping affected the abundance of microbial communities associated with iron and sulfur cycling, which might affect the stability of endogenous P. These results confirmed that CMA-LDH addition and capping treatments were effective methods for managing sediment P loading.

Cascaded reservoirs promote phosphorus bioavailability of surface sediments in the Upper Mekong River

As a key nutrient for primary productivity in freshwater ecosystems, the effect of upper cascade reservoirs on the downstream phosphorus (P) loading is subject to an ongoing scientific debate in the Mekong River. To investigate the effects of cascade reservoirs on the forms of P and its bioavailability in surface sediment, two rounds of field research were carried out both in a free-flowing river (Nu River) and in the Upper Mekong River (Lancang River) during winter and summer. Results showed that while the P was trapped with sediments and environmental parameters changed significantly, high relative abundance of bioavailable phosphorus (BioP, generally include Fe-bound P, Al-bound P, and Organic P) in sediment was detected in reservoirs and at near the border between China and Myanmar. The increased Bio-P in reservoirs may be caused by sediments sorting, anaerobic surface sediments, appropriate temperature, longer residence time and algae-nutrient positive feedback loops. Accumulated Bio-P in sediments may elevate the phosphorus release to overlying water and exacerbate eutrophication in reservoirs. Considered the intense anthropogenic phosphorus loading, nutrients enrichment risk in the lower Mekong River should receive more attention in further research.

Study on Phosphorus Variability Characteristics and Response Mechanism of Microbial Community during Sediment Resuspension Process

Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism of the microbial community were studied. The results indicated that the total phosphorus (TP) content increased from 678.875 to 1019.133 mg/kg and from 1126.017 to 1280.679 mg/kg in sediments and suspended solids (SSs) during the sediment resuspension process, respectively. Organic P (OP) increased by 127.344 mg/kg and 302.448 mg/kg in sediments and SSs after the disturbance, respectively. The microbial communities in the sediments and the leaves of V. natans had higher Chao values after the disturbance, while Shannon values decreased after the disturbance compared to the control in SSs. Proteobacteria had the highest abundance with the value of 51.1% after the disturbance in the sediments and SSs, and the abundance values of Proteobacteria in rhizomes and leaves of V. natans could reach 73.2% on average. Chloroflexi, Acidobacteria, and Firmicutes were also the main phyla in the sediment resuspension system. Sodium hydroxide extractable P (NaOH-P) in sediments could reduce the bioavailability of this P fraction under disturbance conditions. The decrease in the abundance of Bacteroidetes and Nitrospirae indicated that they were more sensitive to the disturbance, and the rotational speed changed the survival conditions for the Bacteroidetes and Nitrospirae. The response mechanism of microbial community during the sediment resuspension process could reflect the influence of the microbial community on the changing characteristics of P and could provide a theoretical foundation for P control at the micro level.

Fe(II)-Catalyzed Recrystallization Drives Phosphorus and Aluminum Release from Goethite.

Goethite often harbors impurities, such as phosphorus (P) and aluminum (Al), which are incorporated into its structure through direct substitution or coprecipitation with nanocrystalline phases. Understanding the processes that drive the release of P and Al from goethite is of paramount importance for the iron ore industry and for managing nutrient and pollutant behavior in the environment. This study investigates the impact of Fe(II)-catalyzed recrystallization on the release of P and Al from goethite. We evaluated the solubility and extractability of P and Al in suspensions of Al- and P-coprecipitated goethite, treated with 57Fe-enriched Fe(II)aq under oxygen-free conditions for 30 days at neutral pH and room temperatures. The addition of Fe(II)aq induced the recrystallization of goethite dominant initial synthetic phases (i.e., low P- and Al-containing phases) and the transformation of higher P- and/or Al-bearing starting material that was actually a mixture of goethite and minor amounts of lepidocrocite and feroxyhyte. Our results reveal that Fe(II)-catalyzed mineral and structural evolution led to the repartitioning of P and, to a lesser extent, Al throughout the crystal structure, mineral surface, and aqueous solution. Following a 30 day reaction with Fe(II)aq, we extracted approximately 80, 68.8, 73.9, and 83.2% of P from P-only, low, medium, and high P + Al goethite, respectively. Additionally, we observed total Al removals of approximately 17, 27, and 25% from low, medium, and high P + Al goethite, respectively. The results demonstrate that treating both P-only and P + Al goethite with Fe(II) at room temperature, followed by a 24 h extraction using 1 M NaOH, significantly enhances the overall extractability of P and Al, including both aqueous and surface-adsorbed fractions, compared to Fe(II)-free controls. These findings advance our understanding of the recrystallization process and impurity substitution in goethite, offering promising avenues for developing new environmentally friendly methods to extract P and other impurities from goethitic iron ores at lower temperatures.

Biochar-based fertilizers from co-pyrolysis of algae and hazelnut shell with triple superphosphate: Physicochemical properties and slow release performance.

Phosphorus (P) is a vital nutrient for plant growth and food production. Excessive amounts of P fertilizers to a greater extent of crop P offtake are inevitably applied due to low utilization efficiency, causing environmental pollution. This study aimed to evaluate biochar-based fertilizers (BBFs) produced by co-pyrolyzing algae (A) and hazelnut shell (H) biomasses with triple superphosphate (TSP) at a ratio of 4:1 (w/w). The potential of the slow-release performance of BBFs was studied during kinetics experiments. The co-pyrolysis of biomasses with TSP yielded BBFs with significantly different properties, including electrical conductivity, pH, elemental ratios, functional groups, specific surface area and pore size characteristics. Phosphorus release from all biochars and BBFs followed the Elovich model, except for TSP and H+TSP. Kinetic studies revealed prolonged P-release times and slower release rates for BBFs compared to conventional TSP. So that, TSP released 100% of the total P, whereas H+TSP and A+TSP biochars released only 3.14% and 5.14% of the total P, respectively, during a 240-hour experiment. The slow-release performance of BBFs suggests their potential as promising alternatives to conventional phosphate fertilizers. BBFs have the potential to enhance P utilization efficiency, increase crop yield and mitigate the environmental impact of P fertilizer runoff.

Long-term organic fertilization increases phosphorus content but reduces its release in soil aggregates

There is currently limited published information on the coupling correlation between phosphorus (P) redistribution and release in soil aggregates. To fulfill this gap, we conducted a 10-year field experiment of soil amended with organic fertilizer to investigate phosphorus transformation and immobilization during the organic fertilization process. Microbial communities, functional genes and enzymes were analyzed to elucidate the multi-mechanisms of the conversion among phosphorus fractions. Phosphorus content in soil aggregates was determined as follows: FeP (34 % ~ 45 %) > Ca-P (16 % ~ 27 %) > Oc-P (15 % ~ 17 %) > Or-P (13 % ~ 19 %) > Al-P (4 % ~ 5 %) ≈ Ex-P (2 % ~ 4 %). Compared to a control with only chemical fertilizer, a 13 % ~ 38 % increase in P availability of experimental treatments mixed with chemical and organic fertilizers was attributed to the mineralization of Or-P, but not to the dissolution of inorganic P. Following organic fertilization, the phnF gene was dominant factor to promote the mineralization of Or-P, because it encodes CP lyases that pyrolyzes the CP bounds in organophosphate esters. Overall, organic fertilization decreased P release risk in soil aggregates, especially for the micro-aggregates that showed a higher capacity to activate non-available P and immobilize endogenous P in farmland soil. These results provide a theoretical guidance for the source control of P pollution in agro-ecosystems.

12375 Rhabdomyolysis As A Cause Of PTH-independent Hypocalcemia In A Child With Acute Influenza Infection

Abstract Disclosure: S. Bhattarai: None. K. Halpin: None. Introduction: Hypocalcemia is characterized by low blood calcium level. Normal range for calcium for ages 12- 19-year is 8.5-10.6 mg/dli . Severe hypocalcemia is considered as serum calcium level of &amp;lt;7 mg/dl. Hypoparathyroidism, pseudohypoparathyroidism and Vitamin D deficiency are some of the most common causes encountered by pediatrician endocrinologists. Rhabdomyolysis with hypocalcemia and elevated PTH is a rare presentation that should be considered, particularly for children presenting with acute viral illness. We present a rare case of rhabdomyolysis associated with hypocalcemia not related to hypoparathyroidism. Case: A 12-year-old female presented to the ED with body ache, poor oral intake and vomiting. She was found to be influenza positive. Labs showed hypocalcemia (4.8 mg/dl). She had an undetectable 25-OH vitamin D level (&amp;lt;5 ng/ml) and elevated iPTH level (609 pg/ml). We discussed the possibility of her etiology of hypocalcemia as Vitamin D deficiency although her presentation was atypical at an older age with negative imaging for rickets, hyperphosphatemia (6.0 mg/dl), and normal ALP (334 unit/L). She did not have any phenotypic features of Albright’s hereditary osteodystrophy with normal renal function. She had elevated CK (4829 U/L) supporting rhabdomyolysis secondary to acute influenza as a cause of her hypocalcemia. Rhabdomyolysis, a known complication of influenza infection, causes cell membrane destruction which impairs the normal function of Na-K-ATPase channel leading to increase in intracellular sodium activating Na/Ca exchanger. This in turn causes influx of calcium intracellularly causing hypocalcemia. Additionally, any injury leads to high phosphorus release from cells due to its lysis. High phosphorus is also caused by reduced oxidative metabolism in muscles impairing phosphate use. This excess of phosphate then combines with calcium and causes calcium-phosphate complex in soft tissues. Hyperphosphatemia additionally inhibits 1 alpha hydroxylase limiting formation of calcitriol leading to hypocalcemia. iiConclusion: Our patient had severe hypocalcemia due to influenza-related rhabdomyolysis. Rhabdomyolysis is an important cause of hypocalcemia in children, especially with acute viral illness. Accordingly, it is also important to obtain serum electrolytes in patients presenting with rhabdomyolysis as hypocalcemia may lead to complications like seizures and cardiac arrhythmia. Endnotes:i Roizen, Jeffrey &amp; Shah, Vipul &amp; Levine, Michael &amp; Carlow, Dean. (2013). Determination of Reference Intervals for Serum Total Calcium in the Vitamin D-Replete Pediatric Population. The Journal of clinical endocrinology and metabolism. 98. 10.1210/jc.2013-3105.ii Ding LN, Wang Y, Tian J, Ye LF, Chen S, Wu SM, Shang WB. Primary hypoparathyroidism accompanied by rhabdomyolysis induced by infection: A case report. World J Clin Cases. 2019 Oct 6;7(19) Presentation: 6/2/2024

Effects of Polyethylene Terephthalate Microplastics on Anaerobic Mono-Digestion and Co-Digestion of Fecal Sludge from Septic Tank.

Anaerobic digestion (AD) is one of the most significant processes for treating fecal sludge. However, a substantial amount of microplastics (MPs) have been identified in septic tanks, and it remains unclear whether they impact the resource treatment of feces. To investigate this, polyethylene terephthalate (PET) was used as an indicator of MPs to study their effect on the anaerobic digestion of fecal sludge (FS). Two digestion systems were developed: FS mono-digestion and FS co-digestion with anaerobic granular sludge. The results indicated that the effects of PET varied between the two systems. PET inhibited volatile fatty acid synthesis in both systems, but the inhibition period differed. During mono-digestion, PET slightly increased gas and methane production, in contrast to the co-digestion system, where PET reduced methane production by 75.18%. Furthermore, in the mono-digestion system, PET increased soluble chemical oxygen demand and ammonia nitrogen concentrations while blocking phosphorus release, whereas the co-digestion system showed the opposite effects. Ultimately, the choice of digestion method is crucial for the resource utilization of septic tank sludge, and the impact of MPs on AD cannot be ignored.