Eutrophication Of Water Bodies Research Articles

Interception of internal phosphorus release from sediments by lanthanum-modified shrimp shell biochar in two application modes

Lanthanum (La)-modified biochar has been widely investigated as a phosphate adsorbent material. However, its effectiveness and mechanism as an amendment material to manage sediment internal phosphorus (P) release under anoxic conditions is still unclear. Thus, a lanthanum carbonate-modified shrimp shell biochar (LBC-1) was synthesized for controlling sediment P release, and the efficacy, mechanism, and sediment microbial community impact of LBC-1 under two application modes (addition and capping) were investigated. The maximum adsorption capacity of LBC-1 for phosphate was 79.5 mg/g, superior to most La-modified biochar materials. The generation of LaPO4 and Ca5(PO4)3(OH) precipitates and the formation of inner-sphere complexes were the main adsorption mechanisms of LBC-1 for phosphate. Both the LBC-1 addition and capping treatments successfully blocked sediment P release under anoxic conditions, with the removal efficiencies of DGT-labile P in the overlying water being 97.7–99.7% and 97.5–99.5%, respectively. The conversion of the mobile P forms to the stable HCl-P form in sediments played an important role in the interception of internal P release by the LBC-1 addition treatment. Furthermore, the LBC-1 addition treatment also prevented internal P release by effectively adsorbing DGT-labile P in the interstitial water due to the excellent P adsorption capacity of LBC-1. However, the prevention of P release from sediments by the LBC-1 capping treatment was mainly attributed to the efficient adsorption of DGT-labile P by LBC-1 at the sediment/overlying water interface. The release of P driven by sulfate-reducing bacteria (SRB) was a key mechanism for the migration of P from sediment to interstitial water. The LBC-1 addition treatment reduced the relative abundance of SRB in the surface sediment and might inhibit the release of sediment P into the interstitial water, whereas the LBC-1 capping treatment had little effect on the relative abundance of SRB. In practice, the LBC-1 capping was easier to manipulate than the LBC-1 addition. These findings confirmed that sediment remediation using the LBC-1 capping treatment has great potential to manage internal P loading in eutrophic water bodies.

Modulation of soil nitrous oxide emissions and nitrogen leaching by hillslope hydrological processes

Soil nitrous oxide (N2O) emissions and nitrogen (N) leaching are key pathways for soil N loss in hillslope ecosystem, with potential implications for global warming and water body eutrophication. While soil N loss in hillslope ecosystem has been extensively studied, there is limited understanding of the spatiotemporal distribution patterns and factors driving soil N2O emissions and N leaching from a hillslope hydrology perspective. This study investigated N concentrations in leachate and soil N2O fluxes and their responses to soil hydrological factors on a tea plantation (TP) hillslope and a bamboo forest (BF) hillslope. Four distinct precipitation patterns—spring rainfall (SR), plum rain (PR), summer flood rain (SF), and drought period (DR)—were identified based on precipitation intensity, duration, and cumulative precipitation. Results showed that, soil N2O flux and leachate N concentrations were 8.2 times and 18.0 times higher On TP hillslope compared to the BF hillslope. The greatest soil N2O fluxes occurred during the PR period, while the lowest were observed during the DR period. Precipitation increased soil water content (SWC) and water-filled pore space, stimulating soil N cycling for N2O production. Fertilization activities and precipitation led to peak N concentration in leachate during the SR period. Additionally, soil wetness index (SWI) shaped spatial patterns of SWC, resulting in distinct spatial patterns of N2O emissions and nitrate leaching. Locations with higher SWI exhibited greater soil N2O flux and higher nitrate concentrations in leachate. This study emphasizes the significant effect of soil hydrological processes on soil N2O emissions and N leaching in hillslope ecosystems, providing valuable insights for N management in these environments.

Hitting two birds with one stone: A ce-modified Fe-based bi-functional material reinforced fenton-like system for complete removal of organophosphorus pesticides

Organophosphorus pesticides, widespread and hazardous to ecosystems and human health, were mainly decomposed thoroughly by advanced oxidation processes (AOPs). However, the generated inorganic phosphate (IP) was prone to accumulation and led to eutrophication of water bodies. Herein, a Fe/Ce bimetallic-loaded biochar (FeCe@BC-400–5) with excellent H2O2 activation and IP adsorption properties was designed and used to treat glyphosate (GLY)-contaminated water. Results showed that ∼ 92 % of GLY (20 mg P/L) was removed in the FeCe@BC-400–5/H2O2 system within 120 min, and the converted IP was almost completely adsorbed onto FeCe@BC-400. Experiment and theoretical calculations revealed that Ce doping facilitated the capture of H2O2 by the iron-based catalysts and promoted the activation of H2O2 to produce more reactive oxygen species (•OH and O2•-). Meanwhile, the released IP was adsorbed onto FeCe@BC-400–5 via inner-sphere complexation to avoid secondary contamination. Intriguingly, toxicity tests showed that the degraded GLY solution in FeCe@BC-400–5/H2O2 system promoted germination rate, root and stem growth of Solanum nigrum L (herbaceous plant). This study provided a new idea on constructing oxidation-adsorption bifunctional materials for the comprehensive removal of organophosphorus in the Fenton-like field.

Uncovering the genomic basis of symbiotic interactions and niche adaptations in freshwater picocyanobacteria

BackgroundPicocyanobacteria from the genera Prochlorococcus, Synechococcus, and Cyanobium are the most widespread photosynthetic organisms in aquatic ecosystems. However, their freshwater populations remain poorly explored, due to uneven and insufficient sampling across diverse inland waterbodies.ResultsIn this study, we present 170 high-quality genomes of freshwater picocyanobacteria from non-axenic cultures collected across Central Europe. In addition, we recovered 33 genomes of their potential symbiotic partners affiliated with four genera, Pseudomonas, Mesorhizobium, Acidovorax, and Hydrogenophaga. The genomic basis of symbiotic interactions involved heterotrophs benefiting from picocyanobacteria-derived nutrients while providing detoxification of ROS. The global abundance patterns of picocyanobacteria revealed ecologically significant ecotypes, associated with trophic status, temperature, and pH as key environmental factors. The adaptation of picocyanobacteria in (hyper-)eutrophic waterbodies could be attributed to their colonial lifestyles and CRISPR-Cas systems. The prevailing CRISPR-Cas subtypes in picocyanobacteria were I-G and I-E, which appear to have been acquired through horizontal gene transfer from other bacterial phyla.ConclusionsOur findings provide novel insights into the population diversity, ecology, and evolutionary strategies of the most widespread photoautotrophs within freshwater ecosystems.62j11owDS1FAqTqkQkf7rCVideo

QPCR-based phytoplankton abundance and chlorophyll a: A multi-year study in twelve large freshwater rivers across the United States

Phytoplankton overgrowth, which characterizes the eutrophication or trophic status of surface water bodies, threatens ecosystems and public health. Quantitative polymerase chain reaction (qPCR) is promising for assessing the abundance and community composition of phytoplankton. However, applications of qPCR to indicate eutrophication and trophic status, especially in lotic systems, have yet to be comprehensively evaluated. For the first time, this study correlates qPCR-based phytoplankton abundance with chlorophyll a (the most widely used indicator of eutrophication and trophic status) in multiple freshwater rivers. From early summer to late fall in 2017, 2018, and 2019, we evaluated phytoplankton, chlorophyll a, pheophytin a, and the Trophic Level Index (TLI) in twelve large freshwater rivers in three regions (western, midcontinent, and eastern) in the United States. qPCR-based phytoplankton abundance had positive allometric correlations with chlorophyll a concentration (adjusted R2 = 0.5437, p-value < 0.001), pheophytin a concentration (adjusted R2 = 0.3378, p-value <0.001), and TLI (adjusted R2 = 0.4789, p-value < 0.001). Thus, a greater phytoplankton abundance suggests a higher trophic status. This work also presents the numerical values of qPCR-based phytoplankton abundance defining the boundaries among trophic statuses (e.g., oligotrophic, mesotrophic, and eutrophic) of freshwater rivers. The sampling sites in the midcontinent rivers were more eutrophic because they had significantly higher chlorophyll a concentrations, pheophytin a concentrations, and TLI values than the sites in the western and eastern rivers. The higher phytoplankton abundance at the midcontinent sites confirmed their higher trophic status. By linking qPCR-based phytoplankton abundance to chlorophyll a, this study demonstrates that qPCR is a promising avenue to investigate the population dynamics of phytoplankton and the trophic status (or eutrophication) of freshwater rivers.

Temporal variations in dissolved organic matter properties in a eutrophic lake under water dilution and aquatic plant litter decomposition: A simulated microcosm study revealing the environmental and microbial driving factors

Dilution by importing external clean water and restoration of aquatic vegetation are widely applied strategies for improving water quality of eutrophic lakes, while the influence of dilution or aquatic plant litter decomposition on dissolved organic matter (DOM) properties, which is closely associated with the health of aquatic ecosystems, is rarely known. In this study, the temporal variations of DOM properties in the overlying water of a eutrophic lake (Yilong lake in Yunnan, southwest China) under water dilution and aquatic plant litter decomposition were comparatively investigated via a simulated microcosm study using in situ samples. The results showed that water dilution reduced DOM concentration and bioavailability in the overlying water in a short term (about 45 d), and increased DOM humification, but such effect diminished over time. DOM concentration increased substantially during aquatic plant litter decomposition, and reed litter released much more amounts of DOM than that of cattail litter, which dominated by protein-like substances and characterized by high bioavailability and low humification degree. Nutrient (available phosphorus (AP), NH4+-N and TN) contents in the sediment indirectly affected DOM properties by remarkably influencing microbial community compositions and enzyme activities. The strong correlations between the relative abundances of dominant genera Bacillus and Clostridium and concentrations of DOM components implied the important roles of these taxa in DOM transformations. Our findings highlighted the effects and potential mechanisms of dilution and aquatic plant litter decomposition on DOM properties in eutrophic water bodies, and the necessity of proper water diversion and plant litter harvest to reduce endogenous organic pollution in lakes.

Ironstone and red mud barriers to reduce subsurface movement of soil phosphorus.

Loss of phosphorus in seepage may contribute to eutrophication of downstream water bodies. This study examined the potential use of pedogenic ironstone and untreated red mud (bauxite refining residue) as P sorbents in a permeable reactive barrier (PRB) to mitigate such loss. Effects of ironstone and red mud on P sorption (batch), transport (columns), saturated hydraulic conductivity (KS), and growth of common bermudagrass (Cynodon dactylon; greenhouse) were examined. Both materials had sorption maxima of ∼30mmol Pkg-1 or about five times that of a P-enriched sandy soil; however, sorption by red mud greatly increased with decreasing pH. Transport of P through columns of ironstone and red mud (diluted with nonreactive sand) was similar and slower compared to soil+sand. However, when red mud was mixed with soil, increased sorption at lower pH resulted in greater P retention compared to ironstone+soil (76%vs. 13%). Although addition of ironstone to soil up to 20% did not reduce KS, red mud at even 5% did. Soil amendment with red mud increased bermudagrass growth and P uptake. Given long-term neutralization of red mud in an acidic soil and increased P sorption, it may be suitable in a PRB if incorporated at a low rate and/or co-incorporated with a coarser material.

Inhibition of JNK transcription via the Nrf2/Keap1a pathway to resist microcystin-induced oxidative stress and apoptosis in freshwater mussels Cristaria plicata

With global warming and increasing eutrophication of water bodies, a variety of algal toxins, including microcystin (MC), released into water by cyanobacterial blooms pose a serious threat to the survival of aquatic organisms. To investigate the mechanism of the Nrf2/Keap1a pathway on resisting MC-induced oxidative stress and apoptosis in Cristata plicata, we cloned the full-length cDNA of CpBcl-2. The cDNA full-length of CpBcl-2 was 760 bp, encoded a 177 amino acid peptide, and contained a highly conserved Bcl-2-like superfamily domain. MC stimulation increased the expression and activity levels of related antioxidant enzymes. After CpNrf2 knockdown, the transcription levels of NAD(P)H quinone redox Enzyme-1 (NQO1) and related antioxidant enzymes activity in the gills and kidney of C. plicata were significantly down-regulated upon MC stress, but that was significantly upregulated after knockdown of CpKeap1a. Additionally, Upon MC stress, the mRNA levels of CpBcl-2 were increased in the gills and kidney after knockdown of CpNrf2 at 24 h, and that of CpBcl-2 were decreased at 72 and 96 h in the CpKeap1a-siRNA+MC group. Moreover, MC stimulation significantly inhibited CpJNK expression in the gills and kidney, but which regulated the Nrf2/Keap1a pathway in C. plicata. However, the JNK inhibitor SP600125 promoted the expression of CpNrf2 and related enzymes with antioxidant response element (ARE-driven enzyme) in the gills and kidney. Then, we speculated that CpKeap1a was a negative regulator of CpNrf2, and C. plicata resisted MC-induced oxidative damage and apoptosis by inhibiting JNK transcription via the Nrf2/Keap1a pathway.

How to Achieve a 50% Reduction in Nutrient Losses From Agricultural Catchments Under Different Climate Trajectories?

AbstractUnder persistent eutrophication of European water bodies and a changing climate, there is an increasing need to evaluate best‐management practices for reducing nutrient losses from agricultural catchments. In this study, we set up a daily discharge and water quality model in Hydrological Predictions of the Environment for two agricultural catchments representative for common cropping systems in Europe's humid continental regions to forecast the impacts of future climate trajectories on nutrient loads. The model predicted a slight increase in inorganic nitrogen (IN) and total phosphorus (TP) loads under RCP2.6, likely due to precipitation‐driven mobilization. Under RCP4.5 and RCP8.5, the IN loads were forecasted to decrease from 16% to 26% and 21%–50% respectively, most likely due to temperature‐driven increases in crop uptake and evapotranspiration. No distinct trends in TP loads were observed. A 50% decrease in nutrient loads, as targeted by the European Green Deal, was backcasted using a combination of management scenarios, including (a) a 20% reduction in mineral fertilizer application, (b) introducing cover crops (CC), and (c) stream mitigation (SM) by introducing floodplains. Target TP load reductions could only be achieved by SM, which likely results from secondary mobilization of sources within agricultural streams during high discharge events. Target IN load reductions were backcasted with a combination of SM, fertilizer reduction, and CC, wherein the required measures depended strongly on the climatic trajectory. Overall, this study successfully demonstrated a modeling approach for evaluating best‐management practices under diverging climate change trajectories, tailored to the catchment characteristics and specific nutrient reduction targets.

SYSTEMATIC ANALYSIS OF EUROPEAN ENVIRONMENTAL QUALITY THROUGH THE PRISM OF ENVIRONMENTAL AND ECONOMIC INDICATORS

The main objective of the article is to study the anthropogenic impact on the state of environmental quality by using ecological and economic indicators to further determining the level of necessary environmental protection actions. A systematic analysis of the indicators that identify the dynamics of changes in environmental quality in the current conditions of transformation of the European economy under the globalisation processes is carried out. It is determined that the sustainability of modern production depends on the efficiency of resource use, which provides economic growth and prevents increased pressure on the environment. It is proved that the rate of carbon dioxide emissions in highly developed countries is constantly decreasing, which is associated with the flexible environmental policy and transformation of the energy sector. It is established that in order to achieve the status of a climate-neutral country, Ukraine needs to use a modern system for monitoring greenhouse gas emissions, optimise the СО2 tax and implement a more intensive decarbonisation policy. When introducing organic farming mechanisms, it is necessary to take into consideration the effect of all exogenous and endogenous factors and the potential benefits of using inorganic fertilisers in the short term. The level of phosphate pollution of rivers in European countries and their influence on water quality are determined, and effective mechanisms for reducing this harmful effect are proposed. The reasons that cause eutrophication of water bodies, the consequences of its influence on the state of water and living organisms are investigated, and the areas of marine areas with eutrophic waters are established. The influence of the energy factor on the state of environmental quality is determined by analysing the indicator of final energy consumption by households per capita in oil equivalent. The efficiency of the European waste management policy is analysed and the level of waste packaging recycling in the Scandinavian countries is determined. The algorithm for calculating the gross value added of the environmental goods and services sector and its place in the GDP structure is identified. It is recommended that Ukraine implement the experience of the EU countries in fundamental approaches to resource conservation and sustainable development.

Mixotrophic aerobic denitrification facilitated by denitrifying bacterial-fungal communities assisted with iron in micro-polluted water: Performance, metabolic activity, functional genes abundance, and community co-occurrence

Low-dosage nitrate pollutants can contribute to eutrophication in surface water bodies, such as lakes and reservoirs. This study employed assembled denitrifying bacterial-fungal communities as bio-denitrifiers, in combination with zero-valent iron (ZVI), to treat micro-polluted water. Immobilized bacterial-fungal mixed communities (IBFMC) reactors demonstrated their ability to reduce nitrate and organic carbon by over 43.2 % and 53.7 %, respectively. Compared to IBFMC reactors, IBFMC combined with ZVI (IBFMC@ZVI) reactors exhibited enhanced removal efficiencies for nitrate and organic carbon, reaching the highest of 31.55 % and 17.66 %, respectively. The presence of ZVI in the IBFMC@ZVI reactors stimulated various aspects of microbial activity, including the metabolic processes, electron transfer system activities, abundance of functional genes and enzymes, and diversity and richness of microbial communities. The contents of adenosine triphosphate and electron transfer system activities enhanced more than 5.6 and 1.43 folds in the IBFMC@ZVI reactors compared with IBFMC reactors. Furthermore, significant improvement of crucial genes and enzyme denitrification chains was observed in the IBFMC@ZVI reactors. Iron played a central role in enhancing microbial diversity and activity, and promoting the supply, and transfer of inorganic electron donors. This study presents an innovative approach for applying denitrifying bacterial-fungal communities combined with iron enhancing efficient denitrification in micro-polluted water.

Impact of Gas-to-Water Ratio on Treatment Efficiency of Submerged-Macrophyte Constructed Wetland Systems

Constructed wetland systems employing submerged macrophytes are increasingly utilized for treating municipal and industrial wastewater, as well as odoriferous and eutrophic water bodies. However, the pollutant removal efficiency of these systems needs further enhancement. In this study, we examined the impact of the gas-to-water ratio on the treatment efficiency of the constructed wetland of Vallisneria. We also examined the extracellular polymeric substances (EPSs) of the floating biofilm and the structure of the microbial community in this system. Our findings showed that the gas-to-water ratio significantly affects the total nitrogen (TN) removal rate within the Vallisneria wetlands, with an optimum removal at a gas-to-water ratio of 15:1, while the removal efficiencies for chemical oxygen demand (COD), NH4+-N, and total phosphorus (TP) remain relatively unaffected. Increased gas-to-water ratios corresponded to a notable decrease in biofilm EPSs. High-throughput sequencing analysis demonstrated a shift in biofilm-denitrifying bacteria from anoxic heterotrophic to aerobic denitrifiers, alongside a significant rise in the abundance of denitrifying bacteria, whereas excessively high gas-to-water ratios inhibited the growth of these bacteria. A gas-to-water ratio of 15:1 constituted the optimal condition for ecological restoration of the water body within the Vallisneria wetland systems. These results could contribute to the optimization of submerged-macrophyte constructed wetland system design and the enhancement of treatment efficiency.

Effect of lactose as a co-substrate in the biodegradation of an anionic surfactant “LAS” by anaerobic digestion

Sodium alkylbenzenesulfonate (LAS) is the most widely used anionic surfactant in the manufacture of commercial detergents due to its excellent detergent properties and low cost. However, they are highly polluting products due to their chemical composition, causing a serious problem of pollution and eutrophication in natural bodies of water, if the amount dumped and the frequency with which they are dumped is taken into account. In addition, damage to health and ecosystems by remaining in the environment for a long time, is a relevant issue of immediate attention. This article presents the results found when using lactose as a co-substrate on the simultaneous biodegradation of the LAS surfactant in an arrangement of UASB-type anaerobic reactors in two stages; with a hydraulic retention time of 0.25 days in the acidogenic reactor in which two surfactant concentration rates were evaluated: 200 ± 0.49 mg/L with an organic load of 5.92 ± 0.5 KgCOD/m3.d (experiments II, III and V) and 300 ± 0.05 mg/L with organic loading. of 6.8 ± 0.11 KgCOD/m3.d (experiment VI) and of one day, in the methanogenic reactor. The results showed that the acidogenic reactor was able to eliminate COD by 42.24% and biodegrade LAS by 86.65% (experiment V). At 300 mg/L (experiment VI), these values are reduced to 36.6 and 55% respectively. For its part, the methanogenic reactor fed with the effluent of the acidogenic reactor (experiment V) with a lower concentration of COD, LAS and organic load, showed a COD removal and LAS biodegradation efficiency of 83.17 and 13.85% respectively.

Microbial alchemists: unveiling the hidden potentials of halophilic organisms for soil restoration.

Salinity, resulting from various contaminants, is a major concern to global crop cultivation. Soil salinity results in increased osmotic stress, oxidative stress, specific ion toxicity, nutrient deficiency in plants, groundwater contamination, and negative impacts on biogeochemical cycles. Leaching, the prevailing remediation method, is expensive, energy-intensive, demands more fresh water, and also causes nutrient loss which leads to infertile cropland and eutrophication of water bodies. Moreover, in soils co-contaminated with persistent organic pollutants, heavy metals, and textile dyes, leaching techniques may not be effective. It promotes the adoption of microbial remediation as an effective and eco-friendly method. Common microbes such as Pseudomonas, Trichoderma, and Bacillus often struggle to survive in high-saline conditions due to osmotic stress, ion imbalance, and protein denaturation. Halophiles, capable of withstanding high-saline conditions, exhibit a remarkable ability to utilize a broad spectrum of organic pollutants as carbon sources and restore the polluted environment. Furthermore, halophiles can enhance plant growth under stress conditions and produce vital bio-enzymes. Halophilic microorganisms can contribute to increasing soil microbial diversity, pollutant degradation, stabilizing soil structure, participating in nutrient dynamics, bio-geochemical cycles, enhancing soil fertility, and crop growth. This review provides an in-depth analysis of pollutant degradation, salt-tolerating mechanisms, and plant-soil-microbe interaction and offers a holistic perspective on their potential for soil restoration.

Sustainable agricultural practices: Volcanic rock potential for soil remineralization

Brazil is one of the world's largest importers of agricultural inputs, with 84% of fertilizers used in the country originating from imports. The widespread use of soluble chemical fertilizers leads to various adverse environmental impacts, such as the eutrophication of water bodies. The development and improvement of techniques and agricultural products capable of providing a variety of macro and micronutrients to crops with the least negative environmental impact have been intensified. Soil remineralization through the addition of ground rocks represents a low-negative environmental impact alternative and clean food production, aligning with the second goal of sustainable development proposed by the United nations agenda 2030. This study aimed to determine the viability of outcropping andesitic in the municipality of Jaguarão, in the extreme south of Brazil, for soil remineralization. For this purpose, mineralogical and geochemical characterization, as well as an analysis of availability of nutrients using citric acid as an extracting solution indicated a significant availability of macronutrients (Ca, K, Mg, and Mn) and micronutrients (Fe and Cu), essential for the development of various crops., were performed. The free quartz content and the levels of K2O, MgO, As, Cd, Hg, and Pb comply with the parameters established by Normative Instruction No. 5 of 2016 from the Ministry of Agriculture, Livestock, and Supply (MAPA), which regulates the commercialization of soil remineralizers. The analysis of availability of nutrients using citric acid as an extracting solution indicated a significant availability of macronutrients (Ca, K, Mg, and Mn) and micronutrients (Fe and Cu), essential for the development of various crops.

Phosphorus flow characteristics in the waste system of Poyang Lake Watershed over the past 70 years

With the intensification of human activities, the amount of phosphorus (P)-containing waste has increased. When such waste is not recycled, P is released into the environment, leading to environmental issues such as the eutrophication of water bodies. In this study, based on the material flow analysis method, a P Waste Flow analysis model (P-WFA) was developed to analyze the P flow in the waste system of Poyang Lake, the largest freshwater lake in China. To address the research gap in long-term P flow analysis at the watershed scale, this study quantified the P content in the waste system of the Poyang Lake Watershed from 1950 to 2020. The analysis revealed that from 1950 to 2020, the total P input into the waste system increased from 5.49 × 104 tons in 1950 to 2.28 × 105 tons in 2020. The breeding industry system was identified as the primary source, accounting for 25.19–41.59 % of the total waste system. Over the past 70 years, P loss to surface water from waste systems has been primarily facilitated by manure from the breeding industry, as well as drainage from crop farming systems (77.74 % in 2020). At the same time, the P recycling rate (PRR) of the waste system exhibited an initial increase followed by a decrease, increasing from 44.14 % to 47.75 % before dropping to 44.41 %. Population growth, urbanization, and changes in consumption levels in Jiangxi Province have led to changes in the dietary structure and fertilizer use, consequently affecting the P cycling pattern. This study presents a comprehensive P flow model for waste systems in the Poyang Lake Watershed. This model can be used as a reference to enhance P cycling and manage P loss in other large freshwater lakes.

The eutrophication-related index of drinking water sources based on the oxidation-reduction potential

Eutrophication caused by excessive nitrogen and phosphorus is an important factor affecting water quality in drinking water sources. Convenient monitoring of eutrophication in water bodies can reduce the use of pesticides and reduce energy consumption, helping to promote ecological and economic development. This study examined the relationship between water eutrophication and the oxidation-reduction potential (ORP). The results showed that various parameters related to eutrophication, such as ammonia nitrogen, total nitrogen, total phosphorus, chlorophyll-a, and cyanobacteria, had correlations with ORP. There is a close relationship between eutrophication and the concentration of cyanobacteria. When cyanobacteria blooms occur in the drinking water source, it may contaminate the drinking water. Because the conventional eutrophication index does not include the concentration of cyanobacteria, principal component analysis (PCA) was utilized to comprehensively analyze these eutrophication-related parameters and obtain the eutrophication-related index, with the cumulative contribution of principal components reaching 81.8%. Different mathematical methods such as neural network model and mathematical fitting were used to study the relationship between ORP and the eutrophication-related index. A three-segment relationship between the ORP and the index was established. This three-stage relationship was confirmed in different reservoirs.

Effect of surfactant's charge properties on behavior, physiology, and biochemistry and the release of microcystins of Microcystis aeruginosa

Surfactant pollution is escalatitheng in eutrophic waters, but the effect of surfactant charge properties on the physiological and biochemical properties of toxin-producing microalgae remains inadequately explored. To address this gap, this study explores the effects and mechanisms of three common surfactants―cetyltrimethylammonium bromide (CTAB, cationic), sodium dodecyl sulfate (SDS, anionic), and Triton X-100 (nonionic)―found in surface waters, on the agglomeration behavior, physiological indicators, and Microcystin-LR (MC-LR) release of Microcystis aeruginosa (M. aeruginosa) by using UV–visible spectroscope, Malvern Zetasizer, fluorescence spectrometer, etc. Results suggest that charge properties significantly affect cyanobacterial aggregation and cellular metabolism. The CTAB-treated group demonstrates a ∼5.74 and ∼9.74 times higher aggregation effect compared to Triton X-100 and SDS (300 mg/L for 180 min) due to strong electrostatic attraction. Triton X-100 outperforms CTAB and SDS in polysaccharide extraction, attributed to its higher water solubility and lower critical micelle concentration. CTAB stimulates cyanobacteria to secrete proteins, xanthohumic acid, and humic acids to maintain normal physiological cells. Additionally, the results of SEM and ion content showed that CTAB damages the cell membrane, resulting in a ∼90% increase in the release of intracellular MC-LR without cell disintegration. Ionic analyses confirm that all three surfactants alter cell membrane permeability and disrupt ionic metabolic pathways in microalgae. This study highlights the relationship between the surface charge properties of typical surfactants and the dispersion/agglomeration behavior of cyanobacteria. It provides insights into the impact mechanism of exogenous surfactants on toxic algae production in eutrophic water bodies, offering theoretical references for managing surfactant pollution and treating algae blooms.

Simultaneous removal of calcium, phosphorus, and bisphenol A from industrial wastewater by Stutzerimonas sp. ZW5 via microbially induced calcium precipitation (MICP): Kinetics, mechanism, and stress response

The biological treatment of complex industrial wastewater has always been a research hotspot. In this experiment, a salt-tolerant strain Stutzerimonas sp. ZW5 with aerobic denitrification and biomineralization ability was screened, and the optimum conditions of ZW5 were explored by kinetics. The removal efficiencies of nitrate (NO3--N), bisphenol A (BPA), phosphorus (PO43--P), and calcium (Ca2+) were 94.47 %, 100 %, 98.87 %, and 83.04 %, respectively. The removal mechanism of BPA was the adsorption of microbial induced calcium precipitation (MICP) and extracellular polymeric substances (EPS). Moreover, BPA could weaken the electron transfer ability and growth metabolism of microorganisms and affect the structure of biominerals. At the same time, the stress response of microorganisms would increase the secretion of EPS to promote the process of biomineralization. Through nitrogen balance experiments, it was found that the addition of BPA would lead to a decrease in the proportion of gaseous nitrogen. This experiment offers novel perspectives on the treatment of industrial effluents and microbial stress response.

Genotoxicity detected during cyanobacteria bloom in a water supply reservoir

The aquatic ecosystems are susceptible to cyanobacterial blooms due to the eutrophication of water bodies caused by human activities. In this study, phytoplankton and cyanotoxins analysis, as well as cellular and genetic biomarkers of toxicity (Allium cepa test - higher plant test system), were evaluated in water samples of Alagados Reservoir during a cyanobacterial bloom in South Brazil. The water samples were collected during the wet season at two sites in the Reservoir. Paralytic shellfish toxins (PSTs) were detected in both samples (sites 1 and 2); however, the levels of PSTs were higher in site 1. Gonyautoxin 2 was the major cyanotoxin found in the Reservoir. Both samples were able to induce cytotoxic effects (reduced Mitotic Index) and damage the genetic material (i.e., increased frequencies of chromosome aberration and micronuclei) of meristematic cells of A. cepa. The cellular and genetic damages were higher in the sample site 1, wherein high levels of PSTs were verified. Thus, our findings suggested that cyanotoxins-contaminated waters may damage the genetic material of living organisms, and therefore this group of contaminants should be assessed for their potential genotoxicity.