Eutrophic Water Research Articles

Meta-analysis revealed the factors affecting the functions of ecological floating bed in removing nitrogen and phosphorus from eutrophic water.

Ecological floating bed (EFB) has been widely used to remove nitrogen and phosphorus from eutrophic water. However, its effects on nitrogen and phosphorus removal are different in various studies. Presently it has not been systematically clear what factors produce effects on EFB removing nitrogen and phosphorus from eutrophic water. In this study, we performed a meta-analysis of 169 articles to discuss the effects of EFB characteristics and experimental conditions on EFB removing nitrogen and phosphorus. Results showed that EFB generally decreased nitrogen and phosphorus concentrations in eutrophic water regardless of EFB characteristics and experimental conditions. EFB showed better effects on simultaneously removing TN, NH4+-N, and TP when it had one of the characteristics: constructed by monocots, 2-3 plant species, an area of 1.1-3.0 m2, and the coverage of 21%-40%. However, NO3--N removal by EFB was complicated due to the effects of nitrification and denitrification. Moreover, EFB plant density also showed different effects on nitrogen and phosphorus removal. Experimental conditions produced evident effects on EFB removing nitrogen and phosphorus, and it showed better effects under one of the conditions: water temperature of 16-25℃, experimental duration of 31-60days, long hydraulic retention time, and aeration. This study indicates that EFB can significantly remove nitrogen and phosphorus from eutrophic water, and itis an effective technology to control water eutrophication, but the effects ofEFB characteristics and environmental conditions on EFB functionshould be considered in application.

Enhancing phosphorus removal: the impact of alkaline environment in eutrophic water systems

Abstract Excessive phosphorus input leads to poor water quality and eutrophication. However, limited research has directly explored the influence of pH on phosphorous in actual aquatic systems. This study investigated the effect of pH on phosphorus removal in synthetic, eutrophic, and black-odorous water. The pH levels ranging from 3.5 to 12.0 were adjusted using H2SO4, NaOH, and cement with a 0.5 ± 0.03 interval, followed by a 25 ± 1 °C static water bath for 24 h. Results showed that NaOH-adjusted pH removed >65% TP from eutrophic water (pH ≥9.50) and black-odorous water (pH ≥11.0). Meanwhile, cement-adjusted pH removed >84%, >90%, and >82% TP from the synthetic solution (pH ≥11.0), eutrophic water (pH ≥9.5), and black-odorous water (pH ≥9.5), respectively. The alkaline environment enhanced the formation of Ca-P in eutrophic water and black-odorous water, and cement strengthened the chemical precipitation of phosphorus by providing additional Ca2+. This study lays the groundwork for pH adjustment strategies in eutrophic water, holding significant implications for water resource management and environmental protection.

An efficient polyaluminum lanthanum silicate coagulant for phosphorus removal and algal bloom control

Due to the advantages of convenient operation and low cost, the use of coagulants is considered a promising method for algae bloom harvesting. However, large dosages, poor algal bloom control rates, and limited phosphorus removal efficiency restrict the usage of most coagulants. In this study, a novel polyaluminum lanthanum silicate (PALS) coagulant was used to remove phosphorus and control algal bloom. The results of isotherm study showed that phosphorus adsorption on PALS fitted Freundlich model, indicating chemisorption and heterogeneous multilayer adsorption were the mechanisms of phosphorus adsorption by PALS. The maximum phosphorus adsorption capacity of PALS by Langmuir model was 485.30mg/g. According to the algal bloom control experiments, the removal of algae and phosphorus was slight at low dosages of PALS (2mg/L and 5mg/L). Short-term control of the algal bloom was observed within 2 days in PALS-10 group, but the bloom recovered afterward, while phosphorus and algae were almost completely removed in PALS-15 and PALS-20. When the dosage of PALS was ≤ 10mg/L, PALS coated the algal cell surfaces and induced mild oxidative stress, showing a little damage to cell integrity. However, the PALS dose over 15mg/L could effectively capture algal cells through charge neutralization, cause severe oxidative stress, strongly upregulate the expression of selected five genes, significantly damage cell integrity, and lead to algae lysis. These findings demonstrated that PALS is a promising coagulant for phosphorus removal and algal bloom control in eutrophic waters, and the minimum threshold of its usage was 15mg/L.

Exploring the potential of Typha Populations for biorefineries: Opportunities in Peru

Abstract Typha species have been used for energy crops in constructed wastewater. They have a great capacity to bioremediate eutrophic waters and produce biomass. Typha represents a potential source for biobased materials, solid biomass, or cellulosic bioethanol for circular bioeconomy. The objective of this paper is to present current knowledge regarding the critical characteristics of the Typha and identify promising applications and potential for its use in Peru. Results of this work show that all plant fractions of Typha biomass (leaves and shoots, roots, and rhizomes) have a high potential for biorefinery.

Preparation of ZnAlLa-LDHs by one-step hydrothermal method and its adsorption properties for phosphate

Abstract Phosphate is one of the main limiting factors of water eutrophication, and the effective removal of phosphate is essential to control the eutrophication of the aquatic environment and meet the increasingly stringent phosphate discharge regulations. This study successfully prepared ZnAlLa-LDHs materials using a simple hydrothermal method using triethanolamine as a soft template, which SEM, XRD, and FT-IR characterized. The results show that ZnAlLa-LDHs is a kind of two-dimensional porous structure material; the adsorption isotherm of ZnAlLa-LDHs on phosphate conforms to the Langmuir model, and the maximum adsorption capacity is 83.333 mg g−1; the adsorption kinetics conforms to the pseudo-second-order kinetic model, and the adsorption rate is mainly controlled by chemical adsorption; the adsorption mechanism of ZnAlLa-LDHs on phosphate is mainly ion exchange and electrostatic adsorption. ZnAlLa-LDHs have an excellent effect on phosphorus in wastewater from sewage treatment plants.

One stone two birds: Simultaneous control of eutrophication and microplastic pollution via surface functionalized nano-Fe3O4

Microplastics (MPs) aggregate with phytoplankton to form aggregates that impede light and oxygen penetration, and the adsorbed nitrogen and phosphorus are either taken up by algae or released into the water column, thereby exacerbating water eutrophication. Therefore, it is imperative to simultaneously control nutrients (N and P) and MPs pollution in water. To address this, nano-Fe3O4 with different surface modifications (–COOH, –NH2, and –OH) was developed to control these mixed pollutants. The results showed that the surface modification can enhance the affinity for NH4+, PO43- and polyethylene microplastic (PE-MP), which can achieve exceptional adsorption capacities for NH4+-N (18.45 mg/g), PO43--P (30.04 mg/g), and PE-MP (1611 mg/g). OH-Fe3O4 efficiently removed NH4+-N (2 mg/L), PO43--P (5 mg/L), and PE-MP (1 g/L, 13 μm) from two types of water, achieving removal rates of 80 %, 95 %, and 62 % in freshwater, and 78 %, 94 %, and 70 % in seawater, respectively. FTIR, XPS, kinetic analysis, and density functional theory (DFT) calculations revealed that nano-Fe3O4 provides abundant active sites for MPs and PO43- through electrostatic adsorption and hydrogen bonding, while there is a Fe-O-P bond with PO43-. The NH4+ can be adsorbed on MPs via ion exchange. In addition, –COOH enhances affinity for NH4+, –NH2 increases the holding capacity for PO43-, and –OH strengthens PE-MP adsorption. The environmental impact of the production of nano-Fe3O4 demonstrates the economic feasibility and environmental friendliness of this process. The findings of this study offer promising data that can inform the future development of sustainable and cost-effective materials to combat eutrophication and MPs pollution.

Different patterns of bacterioplankton in response to inorganic and organic phosphorus inputs in freshwater lakes - a microcosmic study

Phosphorus (P) is a limiting factor in fresh waters and is also the main cause of water eutrophication and deterioration, However, the practical effect of elevated P level on bacterioplankton is less evaluated. In this study, we investigated the bacterioplankton in a 96 hours microcosm experiment with P additions in two forms (organic/inorganic P, OP/IP) and three levels (final conc., 0.040, 0.065 and 0.125 g/L), aiming to find out the response pattern of bacterioplankton in coping with the increasing P levels. Results showed a more dramatic change of water properties and bacterioplankton between P forms (OP and IP) than among the addition levels, and a more remarkable effect of OP addition than the IP. Both OP and IP treatments significantly decreased the water pH, dissolved oxygen (DO), Electrical Conductivity (EC), Nitrate Nitrogen (NO3--N) and Total Organic Carbon (TOC), and reduced the α-diversity of bacterioplankton and relative abundance of Cyanobacteria, but increased the abundance of Proteobacteria. The IP addition decreased Actinobacteria abundance (especially for HgcI) and showed higher denitrification potentials, while the OP addition depressed the Bateroidota and exhibited lowed methylotrophic functions, but such trends decreased with increasing addition concentrations. The network analysis showed that both IP and OP additions increased the proportion of positively correlated edges and reduced the network complexity and stability, but the OP network was more stable than the IP network. The study clarifies the response pattern of bacterioplankton to the P input with different forms and levels, and deepens our understanding of the eutrophication process, which provides a scientific basis for the management and control of freshwater lakes facing eutrophication.

Corn stover waste preparation cerium-modified biochar for phosphate removal from pig farm wastewater: Adsorption performance and mechanism

The high phosphorus content in livestock and poultry wastewater is a significant factor contributing to water eutrophication. It is imperative to seek an economically efficient method for phosphate recovery. This study employed cerium-modified biochar to recover phosphate from pig farm wastewater. An investigation was conducted to examine the adsorption performance and removal mechanism of phosphate. Among the different samples, 0.1CeB-500℃ was selected for subsequent experiments. It exhibited a phosphate adsorption capacity of 9.58 mg/g and a removal efficiency of 95.75 %. The results showed that the phosphate adsorption process followed not only the pseudo-second-order kinetic model, but also the Langmuir isotherm model. It suggested that the adsorption of phosphate onto the biochar occurred in a monolayer chemical manner, with a maximum adsorption capacity of 10.86 mg/g. Phosphate adsorption was minimally affected within the pH range of 2–9, with Cl- having negligible impact, NO3- slightly inhibiting, and HCO3- and CO32- significantly hindering phosphate adsorption. A series of characterization results indicated that phosphate removal occurred through surface precipitation forming CePO4, ligand exchange between carbonate and phosphate, inner-sphere complexation, and electrostatic attraction. The phosphate removal efficiency from pig farm wastewater was 43.25 %, demonstrating promising potential for practical application.

Potential Linkages Between Submarine Groundwater (Fresh and Saline) Nutrient Inputs and Eutrophication in a Coastal Aquaculture Bay

AbstractSubmarine groundwater discharge (SGD) plays a crucial role in nutrient budgets of coastal systems, encompassing both submarine fresh groundwater discharge (SFGD) and recirculated saline groundwater discharge (RSGD). Despite its significance, the specific importance of these components in mariculture bays has not been thoroughly assessed. Here, utilizing Ra isotopes and water‐salt mass balance model, we show that SFGD flux (1.1 ± 0.4 cm d−1) represented only 17% of the SGD in the Zhenzhu Bay, a typical mariculture bay along the South China Sea. Interestingly, the nutrient contribution from SFGD surpassed that from RSGD, accounting for 82% of the dissolved inorganic nitrogen (DIN) flux within the SGD. Analysis of the monthly satellite Chlorophyll‐a (Chl‐a) data confirmed that the decline in phytoplankton biomass can be linked to the limited dissolved silicate (DSi) transported by SFGD. Additionally, the elevated nitrogen to phosphorus ratio (241:1) and reduced silicon to nitrogen ratio (0.5:1) in SFGD compared to the Redfield ratio suggested that SFGD characterized by nitrogen excess and silica deficient, which likely played a role in transitioning from biogenic element constraints in coastal water. This shift may impact the proportions and functionality of the phytoplankton community, potentially mitigating water eutrophication. These findings underscore the significant influence of SGD on nutrient dynamics and the ecological environment in the Zhenzhu Bay.

White rot fungi as a multifaceted biocontrol agent: Metabolic disruption and algal inhibition in Microcystis aeruginosa

Microcystis aeruginosa is a prevalent cyanobacterium linked to water eutrophication and harmful algal blooms. While bacterial control strategies are well-studied, the effects of white rot fungi on Microcystis aeruginosa are less understood. This study examines the impact of whole fungal liquid, its centrifuged supernatant, and sterilized solutions on the algae’s physiological and biochemical traits. Metabolomics and multivariate analysis identified significant changes in 47 metabolic markers, including carbohydrates, amino acids, and fatty acids, across treatments. The complete fungal liquid exhibited the strongest algicidal effect, likely due to synergistic solubilization mechanisms mediated by extracellular enzymes such as manganese peroxidase, catalase, and laccase. Notably, algicidal activity persisted even after sterilization, suggesting the presence of non-proteinaceous compounds like polysaccharides or lipids. The metabolic disturbances included downregulation of the TCA cycle and reduced fatty acid synthesis, leading to inhibited photosynthesis and compromised nucleic acid integrity in the algal cells. This research enhances our understanding of how white rot fungi disrupt Microcystis aeruginosa metabolism, providing a theoretical basis for their potential use in bioremediation of eutrophic aquatic environments.

The impact of organic matter and iron/calcium coupling on phosphorus retention in the hyporheic zone of the Danjiangkou area tributary: Evidence from bonding recognition

The coupling between organic matter (OM) and minerals considerably influences the phosphorus (P) cycle within the hyporheic zone, but the role of different geological mineral-organic complexes (MOCs) on P burial during hyporheic exchange remains under-explored. This study investigates the effects of OM and iron (Fe)/calcium (Ca) coupling on P migration within the hyporheic zone of an agricultural tributary to the Danjiangkou Reservoir. These relationships were explored by measuring hyporheic flow (q), organic and inorganic P forms, and sediment PO4-P adsorption capacity [following treatment with fulvic acid (FA), Fe-OM, or Ca-OM]. Multivariate statistical analysis, X-Ray Diffraction, Fourier-transform Infrared Spectroscopy, and X-ray Photoelectron Spectroscopy were employed to elucidate the underlying mechanisms. Results indicate that upward hyporheic flow transports dissolved porewater P into surface water, contributing 11.27–12.13 % of the total P flux. MOCs associated with Fe(III)/Ca silicate minerals, along with FA and labile OM, were identified as key OM fractions influencing P migration, contributing 5–24 %, 10–11.7 %, and 6–14.9 % to the overall flux, respectively. FA and labile OM facilitate P release, whereas MOCs enhance P retention. Ca-OM is the most efficient PO4-P adsorption [adsorption capacity (AC): 0.8980–0.9524 mg/g], followed by Fe-OM (AC: 0.5120–0.7020 mg/g), original sediment (AC: 0.4368–0.5596 mg/g), and FA (AC: 0.2657–0.2769 mg/g). Cation bridges, primarily formed by -OH and -NH2 groups within Ca-OM (outer-sphere complexes), promote greater P adsorption than Fe-OM (inner-sphere complexes, mainly associated with -COOH). However, Fe-OM-P exhibits a more stable structure. In high P environments, P adsorption onto Ca-OM may induce the release of labile OM, temporarily retaining P through resorption onto labile OM. Hyporheic flow with higher pH and Eh values promotes MOC formation, underscoring their significant P retention capacity. Therefore, strategic MOC use within the hyporheic zone is crucial for mitigating surface water eutrophication.

Integrating water quality model and aeration with IoT technology in water quality management: A conceptual framework

Eutrophication poses a significant threat to both human population growth and aquatic life. It gives rise to a range of issues, including algae blooms, loss of habitat, reduced self-purification capacity, and changes in the biodiversity system. In order to restore the ecosystem, it is imperative to implement water quality management measures to combat eutrophication. Common methods for mitigating eutrophication include the use of water quality models, aeration, and IoT technology. Water quality model simulations have been demonstrated to accurately predict future water quality. Aeration, on the other hand, increases oxygen concentration in water through dispersion. Furthermore, the utilization of IoT in water quality monitoring provides users with precise and real-time data. Despite research findings that suggest the effectiveness of water quality models, aeration, and IoT technologies in addressing eutrophication, their current integration is inadequate. Therefore, the aim of this paper is to develop a conceptual framework that incorporates water quality models, aeration, and IoT technology to regulate water quality, with a specific focus on preventing the eutrophication issue. The conceptual framework was created by studying existing research on frameworks for water treatment, water quality modelling, aerators, and IoT technologies. Several adjustments were made to tailor the general framework to the specific requirements of this study. The discussion emphasizes the advantages of conceptual framework development in managing water quality, which integrates water quality models, aerators, and IoT technologies. This framework is expected to serve as an effective tool for managing eutrophication in water, while also promoting sustainable measures to address water contamination.

Enhanced aqueous phosphorus removal and mechanism by water spinach (Ipomoea aquatica Forsk) pretreated with lanthanum nitrate.

Excess nutrients such as phosphate (PO43-) entering surface waters promote eutrophication, and phosphorous (P) removal is important to clear the water. Phytoremediation efforts have been used to improve water quality by varieties of P removal plants, such as water spinach (Ipomoea aquatica Forsk). Water spinach can reduce both internal and external resources of phosphorus from waterbody. The ion of lanthanum (La), one rare earth element (REE), is an immobilization substance for aqueous phosphate and also a fertilizer for plants. Therefore, lanthanum nitrate La (NO3)3 was used further to improve the phytoextraction of P from the polluted water. This study investigated the effects of La on the aqueous P removal by two genotypes of water spinach, green stem large leaves (GSLL) and green stem willow leaves (GSWL). The low concentration La (NO3)3 helped the plant to remove more phosphorous from eutrophic water, but La at high concentration lowered the removal of P. Under La (NO3)3 treatments, the optimum concentration for maximum P removal in GSLL is 3mg/L, and for GSWL, it is 10mg/L and P removal rates were enhanced to 95% and 96%, respectively. When the concentration of La (NO3)3 is 100mg/L, the removal percentage of P was only 10% for both genotypes. The very high concentration of La will impose toxicity and even cause the death of the water spinach and produce secondary pollution; for example, under some specific circumstances, the bond between lanthanum and nitrates dissociates into lanthanum ions (La3⁺) and nitrate ions (NO₃⁻). If the concentration is high, then it accumulates in the aquatic water organisms and plants and causes toxicity in their bodies. If humans eat up these plants and fish, it causes toxic effects in humans. The La (NO3)3 positively affects different parameters of plants. La (NO3)3 increases the growth, pigments, enzyme activity, and malondialdehyde (MDA) of plants which were also discussed in this study. The biological mechanism should be responsible for the enhanced aqueous phosphorus removal by water spinach using lanthanum nitrate.

The relationship between chlorophyll fluorescence and polarized light field: Polarization-Curve Fluorescence Height

The impact of the un-polarized nature of chlorophyll fluorescence, which causes a dip in the degree of polarization of the underwater light field matching the fluorescence spectrum, led to the development of a theoretical relationship indicating that the resulting fractional reduction in observed polarization is linearly proportional to the magnitude of the fluorescence causing it. To evaluate this relationship, we used a vector radiative transfer code (VRTE) for the coupled atmosphere-ocean system using measured inherent optical properties (IOPs) for a variety of oligotrophic and eutrophic waters as inputs. The VRTE was used to simulate elastic components of the underwater reflectance as well as the degree of linear polarization (DoLP) for these different conditions. These values were compared with the underwater reflectances and the DoLPs measured by a multi-angular hyperspectral polarimeter to determine the magnitude of the fluorescence component in the reflectance spectra at 685 nm, and the decrease of the DoLP due to the fluorescence impact at the same wavelength. Fluorescence magnitudes retrieved from the differences between simulated and measured reflectances were found to match well the magnitudes estimated through the relationship based on the drop of the DoLP. It is noted that retrieval accuracies increase for both larger fluorescence and larger underlying DoLP values. Furthermore, a new method is evolved from the measured polarization analysis, Polarization-Curve Fluorescence Height (PCFH). Measured polarization were used to approximate the elastic signal and derive the inelastic un-polarized signal (fluorescence) from the difference in the fluorescence vicinity. These results open possibilities for estimating the magnitude of natural fluorescence using polarization measurements below or above the water surface, .in-situ, or remotely from aircraft or future satellites. Results of ongoing work on potential sensitivities and retrieval accuracies for these applications will be reported.

Artificial Cultivation of Aquatic Plants Promotes Nitrogen Transformation and the Abundance of Key Functional Genes in Agricultural Drainage Ditch Sediments in the Yellow River Irrigation Area in China

Excess nitrogen in agricultural drainage poses a serious threat to the water quality safety of the Yellow River basin. Utilizing aquatic plants to modify the rhizosphere microbial community structure and facilitate nitrogen transformation is a crucial strategy for mitigating regional water eutrophication. We here compare key processes of nitrogen transformation occurring in the rhizosphere of sediments of a ditch artificially planted with a mix of species (Phragmites australis, Typha orientalis, Nymphaea tetragon) with the rhizosphere of a ditch occupied by naturally occurring aquatic vegetation, dominated either by P. australis or T. orientalis. Our results revealed a species effect, with an increased denitrification rate (DR) and dissimilatory nitrate reduction to ammonium rate (DNRAR) in the cultivated ditch for P. australis, compared to the naturally occurring T. orientalis vegetation. The nitrogen fixation rate (NFR) increased in the artificial setting with T. orientalis in comparison to natural P. australis vegetation. The richness of the bacterial community and the relative abundances of Bacteroidota, Firmicutes, and Geobacter were significantly greater in the rhizosphere of the artificially cultivated ditch due a greater availability in nitrogen and organic carbon. In the artificially cultivated ditch, the dominant functional genes affecting DRNARs in the rhizosphere sediments of P. australis were nrfC and nrfA, whereas DRs were driven mainly by norB and napA, which were influenced by the nitrogen and carbon levels. The dominant functional genes affecting NFRs in the rhizosphere sediments of T. orientalis were nifD, nifK, and nifH. Our results provide a scientific basis for the use of aquatic plants for mitigating excess nitrogen levels in agricultural drainage.

CALLUS INDUCTION FROM THE FRONDS OF GREATER DUCKWEED (<i>Spirodela polyrhiza </i>(L.) Schleid) AND ASSESSMENT OF ITS ANTIMICROBIAL EFFICACY

Greater duckweed (Spirodela polyrrhiza (L.) Schleid. are known to propagate excessively in stagnant eutrophic water bodies resulting in the contamination of daughter fronds which can affect their secondary metabolite profile. The present study was aimed in establish organogenic callus from the fronds of greater duckweeds; to optimize a protocol by utilizing different plant growth regulators for future use and to screen the antimicrobially potent metabolites present in callus. The induction of callus was successful using sterile fronds of Spirodela polyrrhiza (L.) Schleid as explants in MS, B5 and SH media fortified with plant growth regulators namely IBA and BAP. SH basal medium fortified with IBA and BA in 2:1 ratio was most effective in callus induction. B5 medium fortified with 2.0 µM IBA + 4.0 µM BAP showed highest callus induction in S. polyrrhiza with lower days to callus induction as reflective in their overall biomass. The callus extract showed efficient antimicrobial effect on Pseudomonas aeroginosa (MTCC accession No. 3451) with ampicillin and chloramphenicol as reference antibiotics. Presence of flavonoids like orientin, genistin and apigetrin were indicated in the LC-MS data which might be responsible for antimicrobial activity in a synergistic manner.

Paleo-redox conditions during the demise of a carbonate platform in the Tethyan ocean: Evidence from phosphatized and metals (Mn and Fe) rich hardgrounds

Phosphatized Mn and Fe rich hardgrounds and condensed pelagic deposits in carbonate platform successions are precious archives of abrupt climate and environmental changes (redox conditions and phosphorous availability) in the past shallow-water marine environment. While numerous examples have been documented in the Cretaceous successions of the Northern Tethys, the scarcity of similar descriptions from the southern margins suggests differences in sedimentary processes or preservation conditions.In this work we study three phosphatized Mn and Fe rich hardgrounds and pelagic condensed deposits that mark the repetitive demise of the Panormide carbonate platform developed in the Southern Tethyan margin during the Cretaceous. The integration of SEM-EDS, PXRD, and Micro-Raman spectroscopy data shows that these hardgrounds consist of fine-grained Fe (goethite and hematite) and Mn (birnessite and/or vernadite) oxides dispersed in a calcite and apatite matrix. Micro-Raman spectroscopy shows the presence of oxidized Mn species: Mn3+ and Mn4+. The oxidation of Mn2+ → Mn3+/4+ and/or Fe2+ → Fe3+ occurred at the sediment-seawater interface under oxic conditions (where both Mn and Fe oxidize) or suboxic conditions (where only Fe oxidizes). The paleoenvironmental perturbations that triggered the formation of both hardgrounds and condensed pelagic deposits were likely related to pCO2 cycle, upwelling of P-Mn-Fe-rich water masses, eutrophication and phosphatization related to the Cretaceous climate oscillations during the main Oceanic Anoxic Events. These perturbations were likely enhanced by tectonic activity. Moreover, we show that the formation of the phosphatized metals-rich hardgrounds and the recovery of shallow-water sedimentation occurred after long-term periods (6–12 Ma). Thus, the Panormide serves as a remarkable example of resilience amidst significant climatic changes.

Synthesis of a novel biomass-based flame retardant featuring vinyl-terminated chemical cross-linking and application in flame retardancy, smoke suppression, toxicity reduction and mechanical enhancement of PAN composite fibers

To develop green and efficient polyacrylonitrile (PAN) fibers with excellent fire safety properties, a new biomass-based flame retardant (PPC@VA) with vinyl-terminated groups was prepared based on the reaction of hexachlorocyclotriphosphonitrile, teat polyphenols, ethylenediamine and vinylphosphonic acid. Subsequently, it was mixed with spinning solution to obtain PPC@VA/PAN through wet spinning, which were then chemically cross-linked via thermal initiation to achieve CC-PPC@VA/PAN fibers. CC-PPC@VA/PAN showed a significant improvement in flame retardancy with a limiting oxygen index value of 32.5 %. The peak of smoke production rate, total smoke production and CO production rate were lowered by 81.9 %, 77.8 % and 91.3 %. Besides, the hazardous gas HCN was greatly suppressed. Owing to the macromolecular entanglement, hydrogen bonding and covalent cross-linking, CC-PPC@VA/PAN improved elongation at break and tensile strength by 19.2 % and 72.1 %. Also, chemical cross-linking contributed to decrease the migration of P/N-based flame retardants, lower the potential risk of water eutrophication and increased the service life of the fibers.

Dissolved organic matter (DOM) rather than warming and eutrophication directly affects partial pressure of CO2 (pCO2) in mesocosm systems

Environmental warming and eutrophication pose significant challenges to shallow lake systems, where dissolved organic matter (DOM) serves as a diverse and intricate mixture of organic macromolecules, playing a pivotal role in aquatic ecosystems. Despite its complexity, comprehending the interplay between environmental changes and DOM composition alterations and their subsequent impacts on aqueous CO2 partial pressure (pCO2) is essential for a better understanding of carbon cycling. Yet, our current understanding in this realm remains limited. To address this gap, mesocosm systems were established to investigate how elevated water temperature and eutrophication, alongside changes in DOM composition, influence pCO2 dynamics. Results indicate that while temperature and nutrient levels do not directly influence pCO2 fluctuations, they indirectly affect aqueous pCO2 through their modulation of DOM composition. Elevated temperature and nutrient concentrations notably enhance both the production and degradation of indigenous protein-like organic matter and increase the accumulation of humic-like organic compounds, with phosphorus released from sediment playing a particularly significant role. Furthermore, the degradation rate of protein-like organic matter significantly exceeds its accumulation rate. On the other hand, the impact of water eutrophication on DOM composition surpasses that of temporal temperature variations, with a 2∼4 °C temperature rise showing minimal effects on DOM composition. Notably, the degradation of protein-like organic matter markedly increases aqueous pCO2, while the rise in humic-like organic matter in water exerts minimal influence on pCO2 concentrations. A comprehensive understanding of carbon cycling processes under environmental changes will facilitate effective management of lake ecosystems and the advancement of carbon mitigation technologies.

Calcium carbonate is a liming product as good as calcium hydroxide in eutrophic CO2-rich waters

Currently, there is still much debate over the correct liming procedures to perform in shrimp ponds, concerning product, dosage, and timing, especially about the use of hydrated lime. The objective of this work was to determine the dissolution rates of Ca(OH)2 and CaCO3 in eutrophic CO2-rich waters with increasing Langelier saturation indexes (LSI), and discuss its importance to the rational liming of shrimp ponds. Three dilutions of seawater were prepared with increasing LSI values, namely −2.0, −1.0 and ≈ 0.0. The study was carried out in three consecutive phases of 5 weeks each. In the first, second and third phases, the flasks were filled with the LSI-2, LSI − 1 and LSI0 waters, respectively. In each phase, eight 2000-mL Erlenmeyer flasks received 1.0 g Ca(OH)2 p.a. and eight flasks received 1.0 g CaCO3 p.a. In four of the flasks that received Ca(OH)2 or CaCO3, one gram of a highly degradable organic matter (HDOM) was added. There were also four control flasks with no liming product but HDOM. The waters' temperature, pH, specific conductance, total alkalinity (TA), total hardness (TH), and the concentrations of Ca+2 and Mg+2 were monitored once a week. HDOM has moderated the increasing effect of Ca(OH)2 on the waters' pH. Regardless the water's LSI, and the liming product, the increase rate of TA was significantly greater in the HDOM-flasks. In all LSI-1 and LSI0 flasks, TH has decreased after the application of the liming products, despite the addition of HDOM. After one week, there was a marked Ca+2 drop in the Ca(OH)2 flasks with no HDOM. In all waters, the concentrations of Mg+2 have decreased significantly after the applications of Ca(OH)2 or CaCO3. Only the HDOM treatments have increased their initial LSI over time. The applications of Ca(OH)2 and CaCO3 in eutrophic CO2-rich waters have produced a total alkalinity higher than 100 mg L−1. Therefore, the anecdotal knowledge that hydrated lime is a superior liming product than agricultural limestone for shrimp ponds has not been supported by the present work.