Phosphorus Leaching Research Articles

Responses of total, reactive and dissolved phosphorus pools and crop yields to long-term fertilization

Maintaining an appropriate soil phosphorus level is key to ensure sustainable phosphorus management for crop production and to minimise phosphorus losses to water bodies. However, the effects of long-term fertilization on different soil phosphorus pools, crop yields and phosphorus loss risk remain unclear. This requires insights into the responses of soil phosphorus pools, crop phosphorus uptake with related crop yields and phosphorus loss to long-term phosphorus inputs. Changes in four soil phosphorus pools (PCACL2, POLSEN, POX and PTOTAL, respectively) and crop yield responses to various fertilization rates were examined in a 29-year long-term phosphorus fertilization experiment in China. Results showed that the increase in the four soil phosphorus pools was proportional to the accumulated phosphorus surplus, i.e., the input minus uptake. POLSEN and POX increased linearly with continuous phosphorus application and peaked at a phosphorus accumulation near 3200 kg P ha−1. Beyond this threshold, continuous phosphorus application caused a gradual increase in PTOTAL and a linear increase in PCACL2, which implies an increasing risk for leaching. The POX pool accounted for 87% of the accumulated phosphorus surplus until soil phosphorus saturation occurred. The crop yields of wheat and maize responded clearly to changes in PTOTAL, POX, POLSEN and PCACL2, with POX explaining most of the yield variation. Furthermore, POX was highly correlated with PCACL2, being a risk indicator for phosphorus leaching. Given that POX explains best how much of phosphorus surplus accumulates in soil, the variation in crop yield, and the risk for P leaching, it can be used as a valuable and reliable indicator to manage phosphorus sustainably.

Phosphorus leaching risk from black soil increased due to conversion of arid agricultural land to paddy land in northeast China

BackgroundLand-use change from arid agricultural land to paddy land may increase soil phosphorus (P) leaching in the black soil region. However, little information is available for soil P leaching risk assessment from soil profiles due to the land-use conversion in the black soil region of northeast China.ResultsThis study explored the effect of land-use change from arid agricultural land to paddy land on soil P leaching change point, P leaching risk and P fractions. Conversion from arid agricultural land to paddy land decrease soil P leaching change point (0–20 cm: 59.63 mg kg−1 vs. 35.35 mg kg−1; 20–40 cm: 24.31 mg kg−1 vs. 17.20 mg kg−1; 40–60 cm: 32.91 mg kg−1 vs. 10.45 mg kg−1); 30.9% of arid agricultural soils were at risk of P leaching into the shallow groundwater, compared to 87.5% of paddy soils, implying a high risk of P leaching after land-use conversion. P fraction analysis using the Hedley sequential extraction method showed that moderately active P, including NaOH-Pi, NaOH-Po, and HCl-Pi, were the dominant fractions in the tested soils. HCl-Pi and NaOH-Pi were the major P fraction of moderately active P in arid agricultural land and paddy land, respectively, indicating that land-use change leads to the conversion from Ca-bound P to P associated with Fe and Al.ConclusionsThe soil P leaching change point decreased due to land-use conversion from arid agricultural soils to paddy soils, which may lead to higher P leaching risk. Therefore, it is necessary to strengthen the management and control of soil P loss in areas with large-scaled conversion from arid agricultural land to paddy fields.Graphical

Preparation of a low-carbon plant-compatible ecological concrete with fertilizer self-release characteristics based on multi-solid waste co-recycling and its environmental impact

Plant-compatible ecological concrete is a new functional slope protection material that perfectly combines engineering protection and ecological restoration, and has significant superiority in ecological benefits. In this study, a high greenness low-carbon plant-compatible eco-concrete (LCPEC) with fertilizer self-release properties was developed via using multi-solid waste-based low-alkalinity cementitious materials (LACM) and self-ignited coal gangue aggregates (SCGAs). The physicochemical properties, hydration products and leaching characteristics of heavy metals and phosphorus of LACM under multi-components system were systematically investigated and reveal that phosphogypsum can be used as an excellent alkalic-reducing material but bring about a sharp reduction in strength, whereas the synergistic effect PG with the multi-components system is more conducive to the balanced development of alkalinity and strength. In addition, the optimal LACM component with the performance at pH 8.75 and 28-day compressive strength of 99.7 MPa was obtained based on the response surface analysis. Moreover, the fact that the continuous leaching of phosphorus and heavy metal leaching concentrations were lower than the standard limits suggested that LCPEC possess environmental friendliness and fertilizer self-release properties. Furthermore, the sustainable self-release of fertilizer in LCPEC is related to the long-term self-formation of CaHPO4·2H2O and Ca(H2PO4)2 in LACM matrix and the accumulation and micropore precipitation of nutrient elements due to the water absorption characteristics of porous structure on SCGAs surface. Finally, life cycle assessment and economic analysis indicated that LCPEC is more environmental-friendly, cost-saving and energy-efficient than traditional eco-concrete.

Chitosan and Zinc Oxide Nanoparticle-Enhanced Tripolyphosphate Modulate Phosphorus Leaching in Soil

Phosphorus (P) loss from agro-ecosystems impinges upon P use efficiency by plants and thereby constitutes both agronomic and environmental nuisances. Herein, we report on the potential for controlling P leaching loss and application in crop fertilization through repurposing and nano-functionalizing tripolyphosphate (TPP) as a sole P source. The developed TPP-Chitosan and TPP-Chitosan-ZnO nanofertilizers exhibited positive surface charges, 5.8 and 13.8 mV, and hydrodynamic sizes of 430 and 301 nm, respectively. In soil, nanoformulations of TPP-Chitosan and TPP-Chitosan-ZnO significantly reduced cumulative P leaching during 72 h, reaching 91 and 97% reductions, respectively, compared to a conventional fertilizer, monoammonium phosphate (MAP). Cumulative P leaching after 72 h from these nanofertilizers was, respectively, 84 and 95% lower than from TPP alone. TPP-Chitosan-ZnO was, overall, 65% more effective in reducing P leaching, compared to TPP-Chitosan. Relative to MAP, the wheat plant height was significantly increased by TPP-Chitosan-ZnO by 33.0%. Compared to MAP, TPP-Chitosan and TPP-Chitosan-ZnO slightly increased wheat grain yield by 21 and 30%, respectively. Notably, TPP-Chitosan-ZnO significantly decreased shoot P levels, by 35.5, 47, and 45%, compared to MAP, TPP, and TPP-Chitosan, respectively. Zn release over 72 h from TPP-Chitosan-ZnO was considerably lower, compared to a control, ZnO nanoparticles, and averaged, respectively, 34.7 and 0.065 mg/L, which was 534 times higher for the former. Grain Zn was significantly higher in the TPP-Chitosan treatment, relative to MAP. TPP-Chitosan also significantly mobilized the resident K, S, Mg, and Ca from soil into the plant, helping to improve the overall nutritional quality and supporting the role of chitosan in nutrient mobilization. Taken together, our data highlight the potential for repurposing a non-fertilizer P material, TPP, for agricultural and environmental applications and the effect of applying nanotechnology on such outcomes. Broadly speaking, the reduction in P loss is critical for controlling the eutrophication of water bodies due to nutrient overload and for sustaining the dwindling global P resources.

Metal oxide modified biochars for fertile soil management: Effects on soil phosphorus transformation, enzyme activity, microbe community, and plant growth

Metal oxide modified biochars are increasingly being used for intensive agricultural soil remediation, but there has been limited research on their effects on soil phosphorus transformation, soil enzyme activity, microbe community and plant growth. Two highly-performance metal oxides biochars (FeAl-biochar and MgAl-biochar) were investigated for their effects on soil phosphorus availability, fractions, enzyme activity, microbe community and plant growth in two typical intensive fertile agricultural soils. Adding raw biochar to acidic soil increased NH4Cl–P content, while metal oxide biochar reduced NH4Cl–P content by binding to phosphorus. Original biochar slightly reduced Al–P content in lateritic red soil, while metal oxide biochar increased it. LBC and FBC significantly reduced Ca2–P and Ca8–P properties while improving Al–P and Fe–P, respectively. Inorganic phosphorus-solubilizing bacteria increased in abundance with biochar amendment in both soil types, and biochar addition affected soil pH and phosphorus fractions, leading to changes in bacterial growth and community structure. Biochar's microporous structure allowed it to adsorb phosphorus and aluminum ions, making them more available for plants and reducing leaching. In calcareous soils, biochar additions may dominantly increase the Ca (hydro)oxides bounded P or soluble P instead of Fe–P or Al–P through biotic pathways, favoring plant growth. The recommendations for using metal oxides biochar for fertile soil management include using LBC biochar for optimal performance in both P leaching reduction and plant growth promotion, with the mechanisms differing depending on soil type. This research highlights the potential of metal oxide modified biochars for improving soil fertility and reducing phosphorus leaching, with specific recommendations for their use in different soil types.

Phosphorus Leaching Alleviated by Organic Carbon in Greenhouse Vegetable Production System

Phosphorus Leaching Alleviated by Organic Carbon in Greenhouse Vegetable Production System

Phosphorus behavior under long-term fertilization in the intensive rice cultivation system

Advocating proper phosphorus (P) fertilisation is necessary to save this limited natural resource and to save the investment in rice cultivation. This study aimed to evaluate changes in phosphorus availability, total phosphorus in soil, phosphorus buffering capacity, and phosphorus saturation in the long-term phosphorus fertilisation in the paddy rice system. Soil samples were collected in the harvest stage after seven consecutive crops over three years at Can Tho city, Vietnam. The applied phosphorus fertiliser rates were: no phosphorus fertilisation (P0), 17.4 kg P/ha (P17.4), and 26.2 kg P/ha as farmer’s practice (P26.2). The results showed that the soil phosphorus buffering capacity in P0, P17.4 and P26.2 treatments was 9.49, 9.08 and 9.04 mg/kg, respectively. The degree of phosphorus saturation of P17.4 and P26.2 treatments ranged from 17.7% to 25.5%, showing the medium to high risk of phosphorus leaching. This study indicated that the application of phosphorus rate higher than 17.4 kg P/ha might result in the reduced soil phosphorus buffering capacity in the intensive rice cropping system in the Vietnamese Mekong Delta region. Our results implied that the application of a rate lower than 17.4 kg P/ha/crop could be extended to the other rice-growing (double/triple rice) areas in the Vietnamese Mekong Delta region or other paddy rice on alluvial soils in Asia.

Mitigation of nutrient leaching from bioretention systems using amendments

Bioretention systems have been showcased to be effective in reducing stormwater quantity and improving stormwater quality. However, the systems can also leach nutrients especially during their initial operation, which needs to be mitigated to optimize their benefits. To examine the efficiency of six amendments selected primarily for reducing phosphorus (P) leaching, six amended and two control cells were constructed and monitored soon after their construction in the field of the 2020 growing season. The effects of the amendments on both the hydrological performance (in terms of water retention rate (WRR)) and water quality performance (in terms of the event mean concentration and pollutant removal rate) were investigated. The results showed that all amendments had the capability of preventing or mitigating P leaching from bioretention systems to varying degrees, with the water treatment residual (WTR) outperforming all other amendments, followed by the activated aluminum (AA) and sorptiveMEDIA (SM) amendments. In addition, some of the amendments (i.e., drywall (DRY), WTR, and SM) were also found to be beneficial in reducing the nitrogen (N) leaching to a slight degree, whereas eggshell (EGG) introduced an extra source of N leached. Furthermore, the temporal evolution of the P leaching of the amendment cells was found to be different from that of the control cells. The same result was not observed for the temporal evolution of the N leaching, implying that the amendments (except EGG) did not largely affect the N leaching. Among the amendments’ effect on WRR, there was no obvious difference. Whereas the observed differences between the control cells and some amendment cells in vegetation growth and antecedent media moisture condition might imply their potential impacts on the hydrologic performance. Overall, other than P leaching, the use of amendments affected other functions of bioretention systems, which should be taken into consideration when selecting an amendment for practice.

Indicator-based agri-environmental direct payments: Assessment of three systems of different complexity levels

This paper presents a scientifically sound set of environmental indicators for comprehensive description of farm environmental impact within a policy-driven framework that aims at achieving Swiss agri-environmental policy goals. The indicator system covers the following key environmental areas: greenhouse gas (GHG) and ammonia emissions, nitrate and phosphorus leaching, biodiversity, plant protection products, soil erosion, and humus accumulation. Novel indicators were developed through reviewing existing indicators and intensive consultation with experts. To provide a flexible and suitable indicator-based system, three systems of varying complexity (simple, medium, detailed) were developed.In-depth evaluation revealed specific advantages and disadvantages of the three novel indicator systems at different complexity levels. The simple system benefited from a low administrative burden, but may suffer from limited acceptance owing to its low flexibility regarding farmers’ scope for action. The detailed system may be very demanding to implement in terms of data acquisition, but benefited from more accurate representation of the key driving processes. Successful implementation of the system will require broad acceptance promoted through sufficient support and advice, good communication between participating stakeholders, a secure and simple data acquisition process, and a high degree of transparency.

Influence of Flue Gas Desulfurization Gypsum on Phosphorus Loss in Pine Bark Substrates

Flue-gas desulfurization (FGD) gypsum, a byproduct of coal-fired electrical utility plants, has been shown to effectively reduce phosphorus (P) leaching in many agricultural systems. However, its applications in horticultural production systems have been insufficiently researched resulting in limited industry adoption. To evaluate the efficacy of FGD gypsum to reduce P leaching in horticultural media, pine bark substrates were amended with FGD gypsum at 2.5, 5, and 10% (v/v). In accordance with industry practice, controlled release fertilizer (19N-3P-10K) was amply incorporated into all potting media treatments to support primary nutrient sufficiency of transplanted stock. The greatest P leaching occurred in the control substrates containing only pine bark and fertilizer. The standard pine bark substrate treatment, containing lime and micronutrients, reduced total P leaching by 35% and should be considered a best management practice. The addition of FGD gypsum at 2.5, 5, and 10% (v/v) reduced the total P collected in leachate by 47, 59, and 70%, respectively. Gypsum amendments increased potassium leachate concentrations but elevated potassium levels normalized after ~20 days. With little to no effect on substrate physical properties or pH, pine bark substrates can be amended with FGD gypsum to effectively reduce P leaching in short-term crops.

The Fate of Phosphorus in Experimental Burials: Chemical and Ultramicroscopic Characterization and Environmental Control of Its Persistency

The permanence of a buried body in soil always induces the formation of a decomposition island that can serve as a significant recording location to understand how the persistence of a clandestine grave affects soil. This study aims to analyze the elemental exchange from buried bodies to soil, with a focus on phosphorus content, and to determine the effects of environmental factors on its persistency. The experiment was carried out using eleven swine carcasses buried in an open site (northern Italy). The analyses were performed using the Olsen P method, which allowed for a recognition of the trend of the amount of phosphorus over time, due to the decomposition of phospholipids, followed by the transfer of the element from bone to soil. Additionally, microanalyses performed using a scanning electron microscope (SEM-EDS) on two different soil sample specimens (i.e., “dust” and “plug”) allowed for the identification of numerous phosphatic features (i.e., coatings, infillings, impregnations, and organo-mineral associations), which are the result of the interaction between soil and body fluids and can thus be used as indicators of the former presence of decomposing body (even in its absence). The ultramicroscopic analysis also shows increasing and decreasing amounts of P2O5 over time in the soil, which could be related to environmental conditions (i.e., soil moisture), due to the leaching of phosphorus induced by the percolation of natural rainwater. The study underlines the potential use of these methods to evaluate the possibility of a cadaver–soil linkage and of assessing the burial in the soil for a variable period. Moreover, the study may aid in analyzing the dynamics of phosphorus migration from buried bodies to soil during and after the decomposition process.

Seasonal nitrogen and phosphorus leaching in urban agriculture: Dominance of non-growing season losses in a Southern Swedish case study

Urban agriculture, as most agriculture, can potentially contribute to eutrophication via losses to ground and surface water. Few published studies have empirically measured nitrogen and phosphorus losses (including leaching) from urban agriculture, and even fewer have examined losses in real-world settings throughout the year. Here we investigated year-round (May 2020–2021) weekly nitrogen and phosphorus leaching from allotment gardens in Linköping, southern Sweden. We installed eight lysimeters (8 plots) and collected water 0.3 m below the soil surface in four gardens (2 plots per garden), each with their own gardening practices (organic fertilizers, irrigation, and crops). The gardens exhibited large nutrient leaching per area cultivated compared to observed nutrient leachate in rural agriculture in similar climates. There was a large variability among studied plots, where nitrogen leaching reached 39–191 kg ha−1 y−1 and phosphorus 0.9–2.4 kg ha−2 y−1. Importantly, the non-growing season, especially snowmelt, was a key period for leaching. Most of the nitrogen (78–91 %) and phosphorus (45–97 %) leaching occurred from November to April when the soil was bare, suggesting that mineralization of organic matter was important. Three of the gardens received high amounts of organic fertilizers, though no clear relation between inputs and leaching could be discerned. One plot deviated from the pattern, with less than 40 % of the nutrient leaching occurring in the non-growing season. This gardener had a fine net covering the plot to deter insects. This protected from precipitation as the water volume collected was the lowest, with only 26 % collected in the non-growing season, and nitrogen leaching was also the lowest. Our results illustrate that additional monitoring studies should occur year-round and in several gardens to account for high temporal and spatial heterogeneity and avoid under-estimating leaching losses from urban agriculture. Providing guidance on fertilization, irrigation, and soil covering may be a way to minimize leaching.

Genomic Analysis of Pseudomonas asiatica JP233: An Efficient Phosphate-Solubilizing Bacterium.

The bacterium Pseudomonas sp. strain JP233 has been reported to efficiently solubilize sparingly soluble inorganic phosphate, promote plant growth and significantly reduce phosphorus (P) leaching loss from soil. The production of 2-keto gluconic acid (2KGA) by strain JP233 was identified as the main active metabolite responsible for phosphate solubilization. However, the genetic basis of phosphate solubilization and plant-growth promotion remained unclear. As a result, the genome of JP233 was sequenced and analyzed in this study. The JP233 genome consists of a circular chromosome with a size of 5,617,746 bp and a GC content of 62.86%. No plasmids were detected in the genome. There were 5097 protein-coding sequences (CDSs) predicted in the genome. Phylogenetic analyses based on genomes of related Pseudomonas spp. identified strain JP233 as Pseudomonas asiatica. Comparative pangenomic analysis among 9 P. asiatica strains identified 4080 core gene clusters and 111 singleton genes present only in JP233. Genes associated with 2KGA production detected in strain JP233, included those encoding glucose dehydrogenase, pyrroloquinoline quinone and gluoconate dehydrogenase. Genes associated with mechanisms of plant-growth promotion and nutrient acquisition detected in JP233 included those involved in IAA biosynthesis, ethylene catabolism and siderophore production. Numerous genes associated with other properties beneficial to plant growth were also detected in JP233, included those involved in production of acetoin, 2,3-butanediol, trehalose, and resistance to heavy metals. This study provides the genetic basis to elucidate the plant-growth promoting and bio-remediation properties of strain JP233 and its potential applications in agriculture and industry.

Phosphorus Leaching Behavior from Extensive Green Roof Substrates

The substrate is the key component of a green roof system that directly influences the system’s stormwater mitigation performance; however, it is also identified as a potentially significant source of contaminants. It is interesting whether substrate phosphorus discharge behavior is predictable and, if so, whether the study of substrate phosphorus leaching behavior is representative of the green roof system performance. The substrates tested were extracted from a 4-year-old extensive green roof and a 1-year-old proprietary substrate from an agricultural (Ag) green roof. The column test for the extensive green roof substrate (comprised of 90% v/v pumice and 10% v/v compost) was designed to simulate 3 years of precipitation in a 3-month period, based on field monitoring of rainfall from 2018 to 2020, and assuming precipitation occurred equally each month. Double the amount of precipitation was applied to the Ag substrate to make up for the shorter duration field exposure before the laboratory experiment. Total phosphorus (TP) concentrations in the permeate from the extensive and the Ag substrates showed exponential decreases with cumulative water flow. The decreasing rates of TP concentrations were similar regardless of the initial phosphorus in the two different substrates. Field monitoring indicated that the TP discharge from the newly built green roof behaved differently compared with its substrate in the laboratory. However, substrate tests could be an extension of field monitoring to estimate the phosphorus discharge for aged green roofs.

Comparing methods for measuring egestion in aquatic animals

AbstractMost aquatic research on animal waste production evaluates excretion and not egestion, as it is difficult both to collect feces and to accurately analyze its nutrient content. This limits our understanding of how individuals process their dietary nutrients and how animal waste production impacts ecosystems. In this study, we systematically analyzed whether incubation experiments effectively quantify egestion (at high and low temperatures), estimated fecal phosphorus (P) leaching, and evaluated foregut‐hindgut analyses as a complementary method. Incubations were superficially effective but were flawed. Although 82% of fish in high‐temperature incubations and 75% of fish in low‐temperature incubations egested in 24 h, a minority of fish cleared their guts (38% at high temperatures and 6% at low temperatures), making analyzing full nutrient input and output impossible. Furthermore, feces leached P rapidly and variably; a field population's and an experimental population's feces leached 41% and 75% of their initial P respectively. This suggests that previous egestion research that does not measure leaching underestimates fecal nutrient content. Foregut‐hindgut analyses are unaffected by leaching and so effectively complemented incubations. These analyses provided enough hindgut material to estimate fecal %P and allowed us to estimate both dietary nutrient intake (when unknown) and the relative quantity of P in the diet and in the feces. Overall, we suggest that future researchers combine incubations and foregut‐hindgut analyses to estimate aquatic animal waste production.

Incorporation of calcium cyanamide and straw reduces phosphorus leaching in a flooded agricultural soil

Calcium cyanamide and straw additions coupled with one-month of flooding conditions can effectively inhibit soil diseases by generating anaerobic conditions and hydrolysing cyanamide during the summer fallow period in agricultural settings. However, the response of soil phosphorus (P) forms and mobility to the calcium cyanamide and straw additions under flooding conditions remain unknown. This study employed column leaching devices to monitor the P fractions and related movement in a flooded soil with six treatments: control, 0.5 g kg−1 calcium cyanamide (CC), 2 g kg−1 straw (S2), 0.5 g kg−1 calcium cyanamide coupled with 2 g kg−1 straw (CS2), 10 g kg−1 straw (S10) and 0.5 g kg−1 calcium cyanamide coupled with 10 g kg−1 straw (CS10). The results showed that the CC significantly reduced the cumulative P leaching by 26.3%, compared with the control, attributed to the fixation of dissolved P by calcium hydroxide hydrolyzed from calcium cyanamide. The S2, CS2, S10 and CS10 reduced the cumulative P leaching by 10.4%, 41.0%, 70.0% and 80.5%, and enhanced soil P adsorption maximum and the proportions of NaOH-P fraction, compared with the control, respectively. The reason for low P mobility in treatments with straw addition could be attributed to the strengthened association between dissolved P and poorly crystalline Al/Fe/Mn oxides in soils due to an acidification effect induced by decomposition of straw under flooded conditions. Such acidification further coupled with calcium hydroxide was responsible for the lowering of P mobility in CS2 and CS10 treatments. Redundancy analysis indicated that topsoil organic carbon is the most important factor explaining 32.9% of the variations in soil P fractions and cumulative leached P across the treatments. This study highlights that calcium cyanamide in combination with straw additions suppressed soil P leaching under flooded conditions during the summer fallow period, which provided a net water quality benefit slowing release of P to the environment. Future studies should be carried out in agricultural regions with various soil mineral matrices.

Influence of soil test phosphorus level and leaching volume on phosphorus leaching

Phosphorus (P) is an essential nutrient in agricultural production, yet its losses contribute to eutrophication in freshwater systems. To mitigate this, there is increasing interest in quantifying soluble P leaching losses and including them in P indices. The objectives of this research were to 1) evaluate water soluble P leaching loss from topsoils (0-15 cm) across a range of initial soil test P (STP) levels; 2) determine the effects of soil type, physiochemical soil properties, and leaching volume on P leaching loss; and 3) determine the predictability of P leaching losses from soil tests. Intact soil cores (3.81 cm in diameter, 0–15 cm deep) were collected from six agricultural fields in Minnesota and leached with deionized water offsite. Additional columns were collected to identify the influence of three leaching volumes on P leaching load. Phosphorus leaching loss was impacted by soil type, initial STP level, and the volume of the leaching event. Leachate P concentration increased with increasing STP level and remained consistent among leaching volumes. Concentrations were not diluted with increased leaching volumes. Consequently, leaching volume was the primary driver of total P load. Several linear and machine learning models were employed to predict P leachate concentration. Phosphorus concentration was best predicted using a Ridge Regression model using two soil tests: the degree of phosphorus sorption (DPSOP) and water extractable P (WEP) (R2 = 0.58, RMSE = 0.06). The model prediction of P leaching loss is promising, although further research on subsoil interactions is needed. This article is protected by copyright. All rights reserved

Electrochemical phosphorus leaching from digested anaerobic sludge and subsequent nutrient recovery

With the rising concern over the depletion of phosphorus rock, phosphorus recovery from wastewater has become a key step for sustainable economy. Herein, simultaneous phosphorus leaching and nutrient recovery were accomplished in an electrochemical nutrient recovery cell (ENRC) treating digested anaerobic sludge. The anode reaction of water electrolysis lowered the sludge pH from 8.0 to 2.0 at a current density of 25 A m−2, elevating the PO43−-P concentration from 27.72 to 253.47 mg L−1, comparable to that from direct acid leaching. The released PO43−-P was transferred to the cathode chamber for recovery, where PO43−-P recovery efficiency was enhanced from 42.0% to 90.3% by 0.26 M HCl catholyte acidification. The ENRC recovered 90-98% of the coexisting NH4+-N in the sludge. Increasing current density accelerated both phosphorus leaching and PO43−-P & NH4+-N recovery, but at the expense of a higher energy consumption. After five consecutive cycles of operation, the PO43−-P and NH4+-N concentrations reached 404.56 and 3493.56 mg L−1, respectively, at a normalized energy consumption of 229.20 ± 30.13 kWh kg−1 P or 25.67 ± 3.07 kWh kg −1 N. At pH 8.5, 99% of the recovered aqueous PO43−-P in the recovery solution precipitated, mainly as calcium phosphate that can have a good soil phosphorus availability. The results of this study have provided a foundation for further exploration of electrochemically leaching P from waste sludge with simultaneous nutrient recovery.

Highly efficient oxygen evolution reaction enabled by phosphorus-boron facilitating surface reconstruction of amorphous high-entropy materials

Efficient, cost-effective and durable electrocatalysts are highly required to overcome the slow kinetics and high overpotential of oxygen evolution reaction (OER). Here we report a series of novel amorphous high-entropy borophosphate catalysts FeCoNiMBPOx (M = Mg, Al, Cr, Mn) prepared by a low-temperature reduction method. The leaching of boron and phosphorus accelerates the surface self-reconstruction of FeCoNiMnBPOx, and the subsequently formed high-oxidation-state metal-OOH species is beneficial to improve the catalyst performance. Moreover, the unique amorphous structure with abundant defects provides more active sites for OER. As a return, all the samples exhibit excellent OER activity and stability. Among them, FeCoNiMnBPOx with the highest conductivity and the largest electrochemical active surface area (ECSA) exhibits the best electrocatalytic performance, requiring only low overpotentials of 248 mV and 294 mV to reach current densities of 10 mA cm−2 and 100 mA cm−2, respectively. This sample also shows an exceptional durability for 50 h without a significant increase in potential, which is superior to that of the benchmark RuO2 electrocatalyst. The combination of the adsorbate evolution mechanism (AEM) and the lattice oxygen-mediated mechanism (LOM) are responsible for the excellent catalyst performance. This work provides new ideas for designing high-activity multiple-element catalysts.

Retention of phosphorus and fluorine in phosphogypsum for cemented paste backfill: Experimental and numerical simulation studies

The solidification/stabilization of phosphogypsum using cemented paste backfill (OCPB) provides a low-cost and alternative in-situ technique for recycling phosphogypsum stockpiles. But the OCPB is far from obtaining steady states in which the pollutants would redistribute as a response to dynamic environmental conditions. Further, the associated chemical interactions and the mineralogy information of the solubility-controlling phases of contaminants (fluorine and phosphorus) have not been thoroughly studied or fully understood. In this study, a framework coupling the chemical, mineralogical, and morphological analyses is used to determine the fluoride and phosphate retention mechanisms of immobilized OCPB. Then the pH-dependent leaching tests and numerical simulation is applied as a useful tool to identify the minerals controlling stabilized OCPB leaching behavior. The overall findings proved that aluminate-rich calcium silicate hydrates play an essential role in fluoride and phosphate retention. Both experimental and simulational acid neutralization and leaching curves indicate that the cementitious matrix works as a strong buffering material ensuring high pH conditions that are necessary for fluorine and phosphorus retention. Although discrepancies were observed in absolute fluorine and phosphorus leaching values at highly acidic conditions, the simulations are able to describe highly amphoteric leaching behavior. The simulation suggests that the aluminum species and calcium phosphates governed the solubility of fluorine and phosphorus, respectively. The results of this work would have implications for predicting the leaching behavior of OCPB in detrimental and multiple environments.