[Effects of Biochar on Growth and Pollutant Accumulation of Lettuce in Soil Co-contaminated with Tetracycline and Copper].

Through lettuce potting experiments, the effects of different types of biochar (apple branch, corn straw, and modified sorghum straw biochar with phosphoric acid modification) on lettuce growth under tetracycline (TC) and copper (Cu) co-pollution were investigated. The results showed that compared with those under CK, the addition of biochar treatment significantly increased the plant height, root length, shoot fresh weight, and root fresh weight of lettuce (P < 0.05). The addition of different biochars significantly increased the nitrate nitrogen, chlorophyll, and soluble protein content in lettuce physiological indicators to varying degrees, while also significantly decreasing the levels of malondialdehyde, proline content, and catalase activity. The effects of biochar on lettuce physiological indicators were consistent during both the seedling and mature stages. Compared with those in CK, the addition of biochar resulted in varying degrees of reduction in the TC and Cu contents of both the aboveground and underground parts of lettuce. The aboveground TC and Cu levels decreased by 2.49%-92.32% and 12.79%-36.47%, respectively. The underground TC and Cu levels decreased by 12.53%-55.64% and 22.41%-42.29%, respectively. Correlation analysis showed that nitrate nitrogen, chlorophyll, and soluble protein content of lettuce were negatively correlated with TC content, whereas malondialdehyde, proline content, and catalase activity were positively correlated with TC content. The resistance genes of lettuce were positively correlated with TC content (P < 0.05). In general, modified biochar was found to be more effective in improving lettuce growth quality and reducing pollutant accumulation compared to unmodified biochar, with modified sorghum straw biochar showing the best remediation effect.

Acute toxicity of total ammonia to Macrobrachium rosenbergii postlarvae at different salinity levels.

Nitrogen compounds, particularly ammonium, nitrite and nitrate, are a major problem in shrimp production systems. These compounds can accumulate in the aquatic environment and reach harmful or even lethal levels. Thus, monitoring the levels of nitrogenous compounds such as ammonia and studying their effects on the animals are essential. One tool used for this purpose is acute toxicity testing based on the evaluation of LC50 values. Furthermore, tools that can help improve the performance of aquatic organisms in culture are needed. The present study aimed to evaluate the effect of salinity on the toxicity of total ammonia to postlarvae of the freshwater prawn Macrobrachium rosenbergii. For this purpose, acute toxicity testing (LC50-96h) was performed using 540 postlarvae with a mean weight of 0.13 g and a mean total length of 2.47 cm, divided into 54 experimental units of two liters each. A completely randomized design in a 3×6 factorial scheme was used, combining three salinities (0, 5, and 10 g.L-1) and six total ammonia concentrations (0, 8, 16, 32, 64, and 128 mg.L-1), with three replicates per combination. The LC50 values for M. rosenbergii postlarvae at 24, 48, 72, and 96 h and their respective confidence intervals (95%) were estimated using the trimmed Spearman-Karber method. The results showed that salinities of 5 or 10 g.L-1 did not reduce the acute toxicity of total ammonia.

Groundwater hydrochemical signatures, nitrate sources, and potential health risks in a typical karst catchment of North China using hydrochemistry and multiple stable isotopes.

Nitrate pollution in aquatic ecosystems has received growing concern, particularly in fragile karst basins. In this study, hydrochemical compositions, multiple stable isotopes (δ2H-H2O, δ18Ο-Η2Ο, δ15Ν-ΝΟ3-, and δ18Ο-ΝΟ3-), and Bayesian stable isotope mixing model (MixSIAR) were applied to elucidate nitrate pollution sources in groundwater of the Yangzhuang Basin. The Durov diagram identified the dominant groundwater chemical face as Ca-HCO3 type. The NO3- concentration ranged from 10.89 to 90.45 mg/L (average 47.34 mg/L), showing an increasing trend from the upstream forest and grassland to the downstream agricultural dominant area. It is worth noting that 47.2% of groundwater samples exceeded the NO3- threshold value of 50 mg/L for drinking water recommended by the World Health Organization. The relationship between NO3-/Cl- and Cl- ratios suggested that most groundwater samples were located in nitrate mixed endmember from agricultural input, soil organic nitrogen, and manure & sewage. The Self-Organizing Map (SOM) and Pearson correlations analysis further indicated that the application of calcium fertilizer, sodium fertilizer, and livestock and poultry excrement in farmland elevated NO3- level in groundwater. The output results of the MixSIAR model showed that the primary sources of NO3- in groundwater were soil organic nitrogen (55.3%), followed by chemical fertilizers (28.5%), sewage & manure (12.7%), and atmospheric deposition (3.4%). Microbial nitrification was a dominant nitrogen conversion pathway elevating NO3- levels in groundwater, while the denitrification can be neglectable across the study area. The human health risk assessment (HHRA) model identified that about 88.9%, 77.8%, 72.2%, and 50.0% of groundwater samples posing nitrate's non-carcinogenic health hazards (HQ > 1) through oral intake for infants, children, females, and males, respectively. The findings of this study can offer useful biogeochemical information on nitrogen pollution in karst groundwater to support sustainable groundwater management in similar human-affected karst regions.

Long-term exposure to fine particulate matter constituents in relation to chronic kidney disease: evidence from a large population-based study in China.

The effects of long-term exposure to fine particulate matter (PM2.5) constituents on chronic kidney disease (CKD) are not fully known. This study sought to examine the association between long-term exposure to major PM2.5 constituents and CKD and look for potential constituents contributing substantially to CKD. This study included 81,137 adults from the 2018 to 2019 baseline survey of China Multi-Ethnic Cohort. CKD was defined by the estimated glomerular filtration rate. Exposure concentration data of 7 major PM2.5 constituents were assessed by satellite remote sensing. Logistic regression models were used to estimate the effect of each PM2.5 constituent exposure on CKD. The weighted quantile sum regression was used to estimate the effect of mixed exposure to all constituents. PM2.5 constituents had positive correlations with CKD (per standard deviation increase), with ORs (95% CIs) of 1.20 (1.02-1.41) for black carbon, 1.27 (1.07-1.51) for ammonium, 1.29 (1.08-1.55) for nitrate, 1.20 (1.01-1.43) for organic matter, 1.25 (1.06-1.46) for sulfate, 1.30 (1.11-1.54) for soil particles, and 1.63 (1.39-1.91) for sea salt. Mixed exposure to all constituents was positively associated with CKD (1.68, 1.32-2.11). Sea salt was the constituent with the largest weight (0.36), which suggested its importance in the PM2.5-CKD association, followed by nitrate (0.32), organic matter (0.18), soil particles (0.10), ammonium (0.03), BC (0.01). Sulfate had the least weight (< 0.01). Long-term exposure to PM2.5 sea salt and nitrate may contribute more than other constituents in increasing CKD risk, providing new evidence and insights for PM2.5-CKD mechanism research and air pollution control strategy.

Human health risk of nitrate in groundwater of Tehran-Karaj plain, Iran.

Groundwater pollution by nitrate has is a major concern in the Tehran-Karaj aquifer, Iran, where the wells provide up to 80% of the water supply for a population of more than 18 million-yet detailed human health risks associated with nitrate are unknown due to the lack of accessible data to adequately cover the aquifer in both place and time. Here, using a rich dataset measured annually in more than 75 wells, we mapped the non-carcinogenic risk of nitrate in the aquifer between 2007 and 2018, a window with the most extensive anthropogenic activities in this region. Nitrate concentration varied from ~ 6 to ~ 150 mg/L, around three times greater than the standard level for drinking use, i.e. 50 mg/L. Samples with a non-carcinogenic risk of nitrate, which mainly located in the eastern parts of the study region, threatened children's health, the most vulnerable age group, in almost all of the years during the study period. Our findings revealed that the number of samples with a positive risk of nitrate for adults decreased in the aquifer from 2007 (17 wells) to 2018 (6 wells). Although we hypothesized that unsustainable agricultural practices, the growing population, and increased industrial activities could have increased the nitrate level in the Tehran-Karaj aquifer, improved sanitation infrastructures helped to prevent the intensification of nitrate pollution in the aquifer during the study period. Our compilation of annually mapped non-carcinogenic risks of nitrate is beneficial for local authorities to understand the high-risk zones in the aquifer and for the formulation of policy actions to protect the human health of people who use groundwater for drinking and other purposes in this densely populated region.

Nitrate denitrification rate response to temperature gradient change during river bank infiltration.

Nitrate attenuation during river bank infiltration is the key process for reducing nitrogen pollution. Temperature is considered to be an important factor affecting nitrate attenuation. However, the magnitude and mechanism of its impact have not been clear for a long time. In this study, the effects of temperature and temperature gradient on the nitrate denitrification rate were investigated via static batch and dynamic soil column simulation experiments. The results showed that temperature had a significant effect on the denitrification rate. Temperature effects were first observed in denitrifying bacteria. At low temperatures, the microorganism diversity was low, resulting in a lower denitrification rate constant. The static experimental results showed that the denitrification rate at 19 °C was approximately 2.4 times that at 10 °C. The dynamic soil column experiment established an exponential positive correlation between the nitrate denitrification decay kinetic constant and temperature. The affinity of denitrifying enzymes for nitrate in the reaction substrate was ordered as follows: decreasing temperature gradient (30 °C → 10 °C) > zero temperature gradient (10 °C) > increasing temperature gradient condition (0 °C → 10 °C). This study provides a theoretical basis for the biogeochemical processes underlying river bank infiltration, which will help aid in the development and utilization of groundwater resources.

Photoprotection by photoinhibitory and PSII-reaction centre quenching controls growth of Ulva rigida (Chlorophyta) and is a pre-requisite for green tide formation.

MAIN CONCLUSION: The combined photoinhibitory and PSII-reaction centre quenching against light stress is an important mechanism that allows the green macroalga Ulva rigida to proliferate and form green tides in coastal ecosystems. Eutrophication of coastal ecosystems often stimulates massive and uncontrolled growth of green macroalgae, causing serious ecological problems. These green tides are frequently exposed to light intensities that can reduce their growth via the production of reactive oxygen species (ROS). To understand the physiological and biochemical mechanisms leading to the formation and maintenance of green tides, the interaction between inorganic nitrogen (Ni) and light was studied. In a bi-factorial physiological experiment simulating eutrophication under different light levels, the bloom-forming green macroalga Ulva rigida was exposed to a combination of ecologically relevant nitrate concentrations (3.8-44.7 µM) and light intensities (50-1100 µmol photons m-2 s-1) over three days. Although artificial eutrophication (≥ 21.7 µM) stimulated nitrate reductase activity, which regulated both nitrate uptake and vacuolar storage by a feedback mechanism, nitrogen assimilation remained constant. Growth was solely controlled by the light intensity because U. rigida was Ni-replete under oligotrophic conditions (3.8 µM), which requires an effective photoprotective mechanism. Fast declining Fv/Fm and non-photochemical quenching (NPQ) under excess light indicate that the combined photoinhibitory and PSII-reaction centre quenching avoided ROS production effectively. Thus, these mechanisms seem to be key to maintaining high photosynthetic activities and growth rates without producing ROS. Nevertheless, these photoprotective mechanisms allowed U. rigida to thrive under the contrasting experimental conditions with high daily growth rates (12-20%). This study helps understand the physiological mechanisms facilitating the formation and persistence of ecologically problematic green tides in coastal areas.

Nitrate and oxygen significantly changed the abundance rather than structure of sulphate-reducing and sulphur-oxidising bacteria in water retrieved from petroleum reservoirs.

Sulphate-reducing bacteria (SRB) are the main culprits of microbiologically influenced corrosion in water-flooding petroleum reservoirs, but some sulphur-oxidising bacteria (SOB) are stimulated when nitrate and oxygen are injected, which control the growth of SRB. This study aimed to determine the distributions of SRB and SOB communities in injection-production systems and to analyse the responses of these bacteria to different treatments involving nitrate and oxygen. Desulfovibrio, Desulfobacca, Desulfobulbus, Sulfuricurvum and Dechloromonas were commonly detected via 16S rRNA gene sequencing. Still, no significant differences were observed for either the SRB or SOB communities between injection and production wells. Three groups of water samples collected from different sampling sites were incubated. Statistical analysis of functional gene (dsrB and soxB) clone libraries and quantitative polymerase chain reaction showed that the SOB community structures were more strongly affected by the nitrate and oxygen levels than SRB clustered according to the sampling site; moreover, both the SRB and SOB community abundances significantly changed. Additionally, the highest SRB inhibitory effect and the lowest dsrB/soxB ratio were obtained under high concentrations of nitrate and oxygen in the three groups, suggesting that the synergistic effect of nitrate and oxygen level was strong on the inhibition of SRB by potential SOB.

Exploring the Impact of Alternative Sources of Dietary Nitrate Supplementation on Exercise Performance.

An increase in the level of nitric oxide (NO) plays a key role in regulating the human cardiovascular system (lowering blood pressure, improving blood flow), glycemic control in type 2 diabetes, and may help enhance exercise capacity in healthy individuals (including athletes). This molecule is formed by endogenous enzymatic synthesis and the intake of inorganic nitrate (NO3-) from dietary sources. Although one of the most well-known natural sources of NO3- in the daily diet is beetroot (Beta vulgaris), this review also explores other plant sources of NO3- with comparable concentrations that could serve as ergogenic aids, supporting exercise performance or recovery in healthy individuals. The results of the analysis demonstrate that red spinach (Amaranthus spp.) and green spinach (Spinacia oleracea) are alternative natural sources rich in dietary NO3-. The outcomes of the collected studies showed that consumption of selected alternative sources of inorganic NO3- could support physical condition. Red spinach and green spinach have been shown to improve exercise performance or accelerate recovery after physical exertion in healthy subjects (including athletes).

Zinc(II) Iminopyridine Complexes as Antibacterial Agents: A Structure-to-Activity Study.

Antibiotic resistance is currently a global health emergency. Metallodrugs, especially metal coordination complexes, comprise a broad variety of candidates to combat antibacterial infections. In this work, we designed a new family of Schiff base zinc(II) complexes with iminopyridine as an organic ligand and different inorganic ligands: chloride, nitrate, and acetate. The antibacterial effect of the Zn(II) complexes was studied against planktonic bacterial cells of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) strains. The results showed a moderate biocide activity in both types of planktonic bacteria, which arises from the metal complexation to the Schiff base ligand. Importantly, we confirmed the crucial effect of the metal, with Zn(II) improving the activity of Cu(II) counterparts previously reported. On the other hand, the impact of the inorganic ligands was not significant for the antibacterial effect but was relevant for the complex solubility. Finally, as proof of concept of topical antibacterial formulation, we formulated an emulsion containing the most lipophilic Zn(II) complex and confirmed a sustained release for 24 h in a vertical cell diffusion assay. The promising activity of iminopyridine Zn(II) complexes is potentially worth exploring in more detailed studies.

Reactive oxygen species (ROS) modulate nitrogen signaling using temporal transcriptome analysis in foxtail millet.

Reactive oxygen species (ROS) is a chemically reactive chemical substance containing oxygen and a natural by-product of normal oxygen metabolism. Excessive ROS affect the growth process of crops, which will lead to the decrease of yield. Nitrogen, as a critical nutrient element in plants and plays a vital role in plant growth and crop production. Nitrate is the primary nitrogen source available to plants in agricultural soil and various natural environments. However, the molecular mechanism of ROS-nitrate crosstalk is still unclear. In this study, we used the foxtail millet (Setaria italica L.) as the material to figure it out. Here, we show that excessive NaCl inhibits nitrate-promoted plant growth and nitrogen use efficiency (NUE). NaCl induces ROS accumulation in roots, and ROS inhibits nitrate-induced gene expression in a short time. Surprisingly, low concentration ROS slight promotes and high concentration of ROS inhibits foxtail millet growth under long-term H2O2 treatment. These results may open a new perspective for further exploration of ROS-nitrate signaling pathway in plants.

Metagenomics reveals the variations in functional metabolism associated with greenhouse gas emissions during legume-vegetable rotation process.

Legume-based rotation is commonly recognized for its mitigation efficiency of greenhouse gas (GHG) emissions. However, variations in GHG emission-associated metabolic functions during the legume-vegetable rotation process remain largely uncharacterized. Accordingly, a soybean-radish rotation field experiment was designed to clarify the responses of microbial communities and their GHG emission-associated functional metabolism through metagenomics. The results showed that the contents of soil organic carbon and total phosphorus significantly decreased during the soybean-radish process (P < 0.05), while soil total potassium content and bacterial richness and diversity significantly increased (P < 0.05). Moreover, the predominant bacterial phyla varied, with a decrease in the relative abundance of Proteobacteria and an increase in the relative abundance of Acidobacteria, Gemmatimonadetes, and Chloroflexi. Metagenomics clarified that bacterial carbohydrate metabolism substantially increased during the rotation process, whereas formaldehyde assimilation, methanogenesis, nitrification, and dissimilatory nitrate reduction decreased (P < 0.05). Specifically, the expression of phosphate acetyltransferase (functional methanogenesis gene, pta) and nitrate reductase gamma subunit (functional dissimilatory nitrate reduction gene, narI) was inhibited, indicating of low methane production and nitrogen metabolism. Additionally, the partial least squares path model revealed that the Shannon diversity index was negatively correlated with methane and nitrogen metabolism (P < 0.01), further demonstrating that the response of the soil bacterial microbiome responses are closely linked with GHG-associated metabolism during the soybean-radish rotation process. Collectively, our findings shed light on the responses of soil microbial communities to functional metabolism associated with GHG emissions and provide important insights to mitigate GHG emissions during the rotational cropping of legumes and vegetables.

Performance evaluation of deep learning based stream nitrate concentration prediction model to fill stream nitrate data gaps at low-frequency nitrate monitoring basins.

Accurate and frequent nitrate estimates can provide valuable information on the nitrate transport dynamics. The study aimed to develop a data-driven modeling framework to estimate daily nitrate concentrations at low-frequency nitrate monitoring sites using the daily nitrate concentration and stream discharge information of a neighboring high-frequency nitrate monitoring site. A Long Short-Term Memory (LSTM) based deep learning (DL) modeling framework was developed to predict daily nitrate concentrations. The DL modeling framework performance was compared with two well-established statistical models, including LOADEST and WRTDS-Kalman, in three selected basins in Iowa, USA: Des Moines, Iowa, and Cedar River. The developed DL model performed well with NSE >0.70 and KGE >0.70 for 67% and 79% nitrate monitoring sites, respectively. DL and WRTDS-Kalman models performed better than the LOADEST in nitrate concentration and load estimation for all low-frequency sites. The average NSE performance of the DL model in daily nitrate estimation is 20% higher than that of the WRTDS-Kalman model at 18 out of 24 sites (75%). The WRTDS-Kalman model showed unrealistic fluctuations in the estimated daily nitrate time series when the model received limited observed nitrate data (less than 50) for simulation. The DL model indicated superior performance in winter months' nitrate prediction (60% of cases) compared to WRTDS-Kalman models (33% of cases). The DL model also better represented the exceedance days from the USEPA maximum contamination level (MCL). Both the DL and WRTDS-Kalman models demonstrated similar performance in annual stream nitrate load estimation, and estimated values are close to actual nitrate loads.

Occurrence and concentrations of traditional and emerging contaminants in onsite wastewater systems and water supply wells in eastern North Carolina, USA.

Onsite wastewater treatment systems (OWTSs) and private wells are commonly used in Eastern North Carolina, USA. Water from private wells is not required to be tested after the initial startup, and thus persons using these wells may experience negative health outcomes if their water is contaminated with waste-related pollutants including bacteria, nitrate or synthetic chemicals such as hexafluoropropylne oxide dimer acid and its ammonium salt (GenX). Water samples from 18 sites with OWTSs and groundwater wells were collected for nitrate, Escherichia coli (E. coli), total coliform, and GenX concentration analyses. Results showed that none of the 18 water supplies were positive for E. coli, nitrate concentrations were all below the maximum contaminant level of 10 mg L-1, and one well had 1 MPN 100 mL-1 of total coliform. However, GenX was detected in wastewater collected from all 18 septic tanks and 22% of the water supplies tested had concentrations that exceeded the health advisory levels for GenX. Water supplies with low concentrations of traditionally tested for pollutants (nitrate, E. coli) may still pose health risks due to elevated concentrations of emerging contaminants like GenX and thus more comprehensive and routine water testing is suggested for this and similar persistent compounds.

Nitrate increases the capacity of an aerobic moving-bed biofilm reactor (MBBR) for winery wastewater treatment.

We used bench-scale tests and mathematical modeling to explore chemical oxygen demand (COD) removal rates in a moving-bed biofilm reactor (MBBR) for winery wastewater treatment, using either urea or nitrate as a nitrogen source. With urea addition, the COD removal fluxes ranged from 34 to 45 gCOD/m2-d. However, when nitrate was added, fluxes increased up to 65 gCOD/m2-d, twice the amount reported for aerobic biofilms for winery wastewater treatment. A one-dimensional biofilm model, calibrated with data from respirometric tests, accurately captured the experimental results. Both experimental and modelling results suggest that nitrate significantly increased MBBR capacity by stimulating COD oxidation in the deeper, oxygen-limited regions of the biofilm. Our research suggests that the addition of nitrate, or other energetic and broadly used electron acceptors, may provide a cost-effective means of covering peak COD loads in biofilm processes for winery or another industrial wastewater treatment.

Quantification of Major Inorganic Contaminants in a Mediterranean Coastal Lagoon with a Large Dystrophic Crisis.

In August 2021, the Mar Menor, a saltwater lagoon located in the Region of Murcia (Spain), suffered a tragic environmental episode of dystrophic crisis and anoxia. The appearance of numerous dead fish in different areas of the lagoon over the course of days put all the authorities and the population of the area on alert. This paper shows a case study of what happened in the lagoon in terms of the presence of the most common inorganic pollutants. Measurements of the concentration of nitrogen species, phosphates and main heavy metals were carried out at different sampling sites in the Mar Menor from May 2021 to November 2022. Chemical analyses were carried out for each of the species under study. These analyses provide valuable information about the dystrophic crisis caused by a classic eutrophication process that began with the excessive nutrient input into the Mar Menor. Ion chromatography and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were used as instrumentation for the quantification of these samples. The species whose values were greatly increased after the tragic episode described above were nitrates. The concentration varied significantly at the different sampling sites throughout the study. On the last sampling date, decreased concentrations of all the species were measured at each of the sampling sites, coinciding with the apparent good state of the lagoon.

Transceptor NRT1.1 and receptor-kinase QSK1 complex controls PM H+-ATPase activity under low nitrate.

NRT1.1, a nitrate transceptor, plays an important role in nitrate binding, sensing, and nitrate-dependent lateral root (LR) morphology. However, little is known about NRT1.1-mediated nitrate signaling transduction through plasma membrane (PM)-localized proteins. Through in-depth phosphoproteome profiling using membranes of Arabidopsis roots, we identified receptor kinase QSK1 and plasma membrane H+-ATPase AHA2 as potential downstream components of NRT1.1 signaling in a mild low-nitrate (LN)-dependent manner. QSK1, as a functional kinase and molecular link, physically interacts with NRT1.1 and AHA2 at LN and specifically phosphorylates AHA2 at S899. Importantly, we found that LN, not high nitrate (HN), induces formation of the NRT1.1-QSK1-AHA2 complex in order to repress the proton efflux into the apoplast by increased phosphorylation of AHA2 at S899. Loss of either NRT1.1 or QSK1 thus results in a higher T947/S899 phosphorylation ratio on AHA2, leading to enhanced pump activity and longer LRs under LN. Our results uncover a regulatory mechanism in which NRT1.1, under LN conditions, promotes coreceptor QSK1 phosphorylation and enhances the NRT1.1-QSK1 complex formation to transduce LN sensing to the PM H+-ATPase AHA2, controlling the phosphorylation ratio of activating and inhibitory phosphorylation sites on AHA2. This then results in altered proton pump activity, apoplast acidification, and regulation of NRT1.1-mediated LR growth.

Stable continuous flow CANDAN process transitioning from anammox UASB reactor by facilitating indigenous nitrite-producing denitrification community.

The emerging nitrogen removal process known as CANDAN (Complete Ammonium and Nitrate removal via Denitratation-Anammox over Nitrite) has been developed in Sequencing Batch Reactors (SBRs). Yet, starting up and maintaining stability in continuous-flow reactors remain challenging. This study explores the feasibility of transitioning the CANDAN process from an anammox-dominated process by introducing appropriate external organics to facilitate indigenous nitrite-producing denitrification community in an Upflow Anaerobic Sludge Blanket (UASB) reactor. 150-day operation results indicate that under feeding rates of domestic wastewater at 0.54 L/h and nitrate-containing wastewater at 1.08 L/h, excellent N removal was achieved, with effluent TN below 10.0 mg N/L. Adding external sodium acetate at a COD/NO3--N = 2.0 triggered denitratation, ex-situ denitrification activity tests showed increased nitrite production rates, maintaining the nitrate-to-nitrite transformation ratio (NTR) above 90 %. Consequently, anammox activity was consistently maintained, dominating Total Nitrogen (TN) removal with a contribution as high as 78.3 ± 8.0 %. Anammox functional bacteria, Brocadia and Kuenenia were identified and showed no decrease throughout the operation, indicating the robustness of the anammox process. Notably, the troublesome of sludge flotation, did not occur, also contributing to sustained outstanding performance. In conclusion, this study advances our understanding of the synergistic interplay between anammox and denitrifying bacteria in the Anammox-UASB system, offering technical insights for establishing a stable continuous-flow CANDAN process for simultaneous ammonium and nitrate removal.

Continuous planting of Chinese fir monocultures significantly influences dissolved organic matter content and microbial assembly processes.

Monoculture plantations in China, characterized by the continuous cultivation of a single species, pose challenges to timber accumulation and understory biodiversity, raising concerns about sustainability. This study investigated the impact of continuous monoculture plantings of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) on soil properties, dissolved organic matter (DOM), and microorganisms over multiple generations. Soil samples from first to fourth-generation plantations were analyzed for basic chemical properties, DOM composition using Fourier transform ion cyclotron resonance mass spectrometry, and microorganisms via high-throughput sequencing. Results revealed a significant decline in nitrate nitrogen content with successive rotations, accompanied by an increase in easily degradable compounds like carbohydrates, aliphatic/proteins, tannins, Carbon, Hydrogen, Oxygen and Nitrogen- (CHON) and Carbon, Hydrogen, Oxygen and Sulfur- (CHOS) containing compounds. However, the recalcitrant compounds, such as lignin and carboxyl-rich alicyclic molecules (CRAMs), condensed aromatics and Carbon, Hydrogen and Oxygen- (CHO) containing compounds decreased. Microorganism diversity, abundance, and structure decreased with successive plantations, affecting the ecological niche breadth of fungal communities. Bacterial communities were strongly influenced by DOM composition, particularly lignin/CRAMs and tannins. Continuous monoculture led to reduced soil nitrate, lignin/CRAMs, and compromised soil quality, altering chemical properties and DOM composition, influencing microbial community assembly. This shift increased easily degraded DOM, accelerating soil carbon and nitrogen cycling, ultimately reducing soil carbon sequestration. From environmental point of view, the study emphasizes the importance of sustainable soil management practices in continuous monoculture systems. Particularly the findings offer valuable insights for addressing challenges associated with monoculture plantations and promoting long-term ecological sustainability.

Driving mechanism of different nutrient conditions on microbial mediated nitrate reduction in magnetite-present river infiltration zone.

Significant research is focused on the ability of riparian zones to reduce groundwater nitrate contamination. Owing to the extremely high redox activity of nitrate, naturally existing electron donors, such as organic matter and iron minerals, are crucial in facilitating nitrate reduction in the riparian zone. Here, we examined the coexistence of magnetite, an iron mineral, and nitrate, a frequently observed coexisting system in sediments, to investigate nitrate reduction features at various C/N ratios and evaluate the response of microbial communities to these settings. Additionally, we aimed to use this information as a foundation for examining the effect of nutritional conditions on the nitrate reduction process in magnetite-present environments. These results emphasise the significance of organic matter in enabling dissimilatory nitrate reduction to ammonium (DNRA) and enhancing the connection between nitrate reduction and iron in sedimentary environments. In the later phases of nitrate reduction, nitrogen fixation was the prevailing process in low-carbon environments, whereas high-carbon environments tended to facilitate the breakdown of organic nitrogen. High-throughput sequencing analysis revealed a robust association between C/N ratios and alterations in microbial community composition, providing insights into notable modifications in essential functioning microorganisms. The nitrogen-fixing bacterium Ralstonia is more abundant in ecosystems with scarce organic matter. In contrast, in settings rich in organic matter, microorganisms, such as Acinetobacter and Clostridia, which may produce ammonia, play crucial roles. Moreover, the population of iron bacteria grows in such an environment. Hence, this study proposes that C/N ratios can influence Fe(II)/Fe(III) conversions and simultaneously affect the process of nitrate reduction by shaping the composition of specific microbial communities.