Ammonia Nitrogen Concentration Research Articles

Predicting the adsorption of ammonia nitrogen by biochar in water bodies using machine learning strategies: model optimization and analysis of key characteristic variables.

Biochar adsorption technology has been widely used to remove ammonia nitrogen from water bodies. However, existing methods for predicting adsorption efficiency often lack sufficient accuracy and practical usability. This study evaluated eight machine learning models, including XGB, LR, KNN, DT, RF, GBR, SVR, and ANN, to predict the adsorption efficiency of ammonia nitrogen. The evaluation utilized a dataset comprising 770 instances of ammonia nitrogen adsorption by biochar. The models' prediction performances were systematically compared, and cross-validation was applied to enhance their generalization ability, leading to the selection of the best-performing model. The selected model's parameters were further optimized using Bayesian optimization to improve the prediction accuracy. The Bayesian-optimized XGB model achieved the highest predictive performance, with a coefficient of determination (R2) of 0.978. The R2 values of the other models ranged from 0.556 (LR) to 0.927 (RF). Key factors influencing ammonia nitrogen adsorption efficiency were identified using SHAP analysis. These factors included the amount of biochar, adsorption time, initial ammonia nitrogen concentration, solution pH, pyrolysis time, and O%. Their optimal ranges were further determined through partial dependency plots. This study developed a reliable machine learning tool for accurately predicting ammonia nitrogen adsorption efficiency. Additionally, it provided insights into optimizing the preparation processes and adsorption conditions of biochar, contributing to its practical application in treating ammonia nitrogen pollution in water bodies.

Phycocyanin Additives Regulate Bacterial Community Structure and Antioxidant Activity of Alfalfa Silage

Phycocyanin is a water-soluble pigment protein extracted from prokaryotes such as cyanobacteria and has strong antioxidant activity. As a silage additive, it is expected to enhance the antioxidant activity and fermentation quality of alfalfa silage. This study revealed the effects of different proportions of phycocyanin (1%, 3%, 5%) on the quality, bacterial community and antioxidant capacity of alfalfa silage. The results showed that 5% phycocyanin supplementation could maintain dry matter (DM), crude protein (CP) and water-soluble carbohydrate (WSC) content; increase lactic acid (LA) content; decrease pH and butyric acid (BA) and ammonia nitrogen (NH3-N) content; and improve fermentation quality. At the same time, the contents of total antioxidant capacity (TAOC), total phenol content (TP), polysaccharide content (P) and total flavonoid content (F) in the addition group were significantly increased, the antioxidant capacity was enhanced and the abundance of lactic acid bacteria was increased, which was positively correlated with silage quality. Phycocyanin can improve the metabolic function of carbohydrates and amino acids and promote the production of secondary metabolites. The application of phycocyanin broadens the variety of additives for alfalfa silage.

Hydrothermal treatment of septic sludge: Revealing temperature-sensitive dissolved organic matter and potential toxicity relationships in the hydrothermal liquid

Hydrothermal treatment of septic sludge can result in the transfer of significant amounts of dissolved organic matter (DOM) into the hydrothermal liquid (HL). However, there is a lack of research exploring the relationship between temperature-sensitive fractions of DOM in HL and ecological risks. In this study, spectroscopic techniques combining two-dimensional correlation spectroscopy (2D-COS), self-organizing maps (SOM) and structural equation modeling (SEM), respectively, were employed to investigate temperature-sensitive DOM and its potential correlation with phytotoxicity at five process temperatures (180–340 °C). The findings revealed that DOM content peaked at 260 °C, measuring 7625 mg·CL−1. At peak levels, the concentrations of chemical oxygen demand, ammonium nitrogen, total nitrogen, and total phosphorus in the HL reached 16900 mg L−1, 34.8 mg L−1, 1920 mg L−1 and 756 mg L−1, respectively. Results from EEM-PARAFAC-SOM indicated that temperature significantly influences the variations in fluorescent components within DOM. Additionally, 2D-COS analysis identified conjugated structures and critical turning points at 220 °C and 300 °C. Notably, the -CO-NH- functional group, which is closely associated with aromatic protein II, exhibited the highest sensitivity to temperature changes. Wheat seed germination experiments revealed that the DOM sample at 180 °C exhibited the most pronounced inhibition of wheat root length, while demonstrating the least effect on germination. In contrast, seed growth was most severely impaired at 340 °C. SEM analysis revealed the influence of temperature—both direct and indirect—on the properties of DOM, identifying aromatic protein I as the primary determinant limiting seed germination. This research provides valuable insights for the management and utilization of HL.

Meta-analysis of dietary supplementation with flavonoids in small ruminants: Growth performance, antioxidant status, nutrient digestibility, ruminal fermentation, and meat quality

This study aimed to evaluate the effects of dietary supplementation with flavonoids on growth performance, antioxidant status, nutrient digestibility, ruminal fermentation, and meat quality of small ruminants through a meta-analytic approach. The data used in the meta-analysis were extracted from 29 scientific articles identified through systematic searches following the PRISMA methodology. Der-Simonian and Laird, random effects models, were used to assess effect sizes using weighted mean differences. Dietary supplementation with flavonoids increased (P < 0.05) dry matter intake, average daily gain, hot carcass weight, hot carcass yield, Longissimus dorsi muscle area, and backfat thickness. In contrast, the feed conversion ratio decreased (P < 0.05) in response to dietary flavonoid supplementation. Dietary supplementation with flavonoids increased (P < 0.001) the serum concentration of superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity but decreased (P < 0.001) the serum concentration of malondialdehyde (MDA). The digestibility of dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber increased (P < 0.05) in response to dietary flavonoid supplementation. Dietary supplementation with flavonoids decreased (P < 0.001) the ruminal concentration of ammonia nitrogen and increased (P < 0.001) the ruminal concentration of total volatile fatty acids and acetate. Dietary supplementation with flavonoids decreased (P < 0.001) cooking loss, shear force, and MDA in meat. In conclusion, dietary supplementation with flavonoids can be used as a nutritional strategy to improve growth performance, antioxidant status in blood serum, nutrient digestibility, ruminal fermentation, and meat quality in small ruminants.

Supplementation of lysophospholipids in calf starter: effects on growth performance, blood metabolites, health, and ruminal ammonia nitrogen concentration

The aim of the current study was to evaluate the effects of a commercial mixture of Lysophospholipids (LPL) in calf starter on performance, blood metabolites, antioxidant capacity, liver enzymes concentration, and health status of pre-weaning dairy calves. Forty-eight newborn female Holstein calves (37.5 ± 2.9kg of body weight) were randomly assigned to four treatments (12 replicates), which included the control (CON, without additive) and a commercial blend of LPL at 0.5, 1, and 1.5g/kg of starter feed. The body weight of the calves was measured using a digital scale on days 15, 30, 45, and d 63 of the experimental period to calculate the average daily gain (ADG). The individual starter intake and fecal score were measured daily. Blood samples were collected at 30 and 63 days, while fecal samples were collected for four consecutive days after weaning to measure nutrient digestibility. The treatments did not significantly afffect the total dry matter and starter intake. However, the supplementation of LPL resulted in an increase in the ADG and improved feed efficiency (FE, from1-63 d) compared to the CON group. The addition of LPL did not have any significant impact on the apparent digestibility of dry matter (DM), and organic matter (OM). Eether extract (EE) digestibility tended to increase with the addition of LPL. Calves that received starter feed containing 0.5g/kg of LPL had higher superoxide dismutase activity at 30 d of age compared to the intake.CON group. Additionally, the average fecal score significantly decreased in calves fed 0.5 and 1.5g/kg LPL compared with the CON group. These findings suggest that the inclusion of LPL at an average dose of 1g/kg of calf starter can improve the performance of pre-weaning Holstein dairy calves.

Application of the River Habitat Survey Method in the Assessment of the Human Pressure Within the Lowland River Catchment: The Mollusc Biodiversity Versus Habitat Features

The objectives of our study were to analyse the degree of human pressure within the lowland river catchment in relation to the mollusc communities and to assess the usefulness of the River Habitat Survey as a field method in determining the human pressure in the mollusc biodiversity context. The River Habitat Survey (RHS), an essential method for hydromorphological studies of rivers under the requirements of the European Union Water Framework Directive, was applied. This study showed that the diversity of molluscs was impacted by several environmental factors acting simultaneously, including pH, concentration of ammonium nitrogen in water, and the habitat features depending on the degree of human pressure on the river. The result of the RHS method confirmed that the occurrence of molluscs including Unio crassus and Pseudanodonta complanata, the endangered species on a global scale, was associated with the extensive presence of several natural habitat features in the river channel. The RHS method proved to be an indispensable tool for assessing the relationships between the diversity of aquatic organisms and the degree of habitat anthropogenic modification of river environments. It seems innovative and necessary, especially in restoring the natural character of rivers.

Anaerobic decomposition of substandard pet food as a raw material source for producing hydrogen from methane

A potential raw material for producing hydrogen (the main carrier for the accumulation, storage and transportation of energy) is methane from biogas. An approach to producing biogas with a high methane content (69–72%) from waste commercial dry and wet food for dogs and cats under mesophilic conditions has been demonstrated. For 27–28 days under anaerobic conditions, the degree of biotransformation of waste was 60–88%. As a result of mineralization of watered organic waste, the content of ammonium nitrogen and phosphorus in the form of phosphates amounted to 676–887 mgNH4+/l and 77–160 mgPO43-/l, respectively. In anaerobically treated effluent, accumulation of sulfide ions up to 22 mg/l was observed. The solid sediment and anaerobically treated effluent (liquid fraction) obtained upon completion of the biotransformation of pet food waste are a potential organic fertilizer for agricultural needs, and methane from biogas is a raw material for producing hydrogen and pure carbon for the needs of the nanoindustry.

Unraveling the unique microbiota and metabolites in three different colors Jiangqu through multidimensional analysis

Tri-colored Jiangqu, including white (WQ), yellow (YQ), and black (BQ)-color Daqu, significantly influence fresh Baijiu yield and quality. The differences in attributes of these Jiangqu types, sourced from two renowned Baijiu enterprises, were investigated using multi-omics approaches. Color intensity negatively correlated with ammonia nitrogen content, but positively with pyroglutamic acid content. 182 volatiles and 291 non-volatiles were identified, with each types exhibiting unique metabolites. Esters, pyrazines, ketones and phenols were predominant in WQ, YQ, and BQ, respectively. The content of peptides, amines, and amino acids with derivatives also showcased the differences of microbiota and metabolic pathways among tri-colored Jiangqu. BQ's characteristic components of L-Tyrosine and acetyl tributyl citrate were closely associated with melanin formation. In YQ, Scopulibacillus and Rhizopus correlated positively with tetramethylpyrazine. Moreover, the bacterial community significantly influenced the metabolic profiles, and synergistic interactions between fungal and bacterial communities were crucial in determining metabolite abundance.

The Application of Straw Return with Nitrogen Fertilizer Increases Rice Yield in Saline–Sodic Soils by Regulating Rice Organ Ion Concentrations and Soil Leaching Parameters

Soil salinization is a severe environmental problem that restricts crop productivity. Straw amendment could increase the fertility of saline–sodic soils by improving soil physical properties and carbon sequestration; however, the chemical mechanism of saline soil improvement via straw reclamation is not clear. This study aimed to investigate the effects of straw return with nitrogen fertilizer on soil leaching characteristics, rice organ ion concentrations, and yield. Therefore, a soil column leaching experiment was conducted in 2021 in Baicheng, Jilin Province, using two straw application rate treatments (0 and 8 t hm−2) and three nitrogen application rate treatments (0, 180, and 360 kg hm−2). The results revealed the following: 1. The combination of straw return and nitrogen fertilizer significantly increased the soil leachate volume, leachate pH, Na+ concentration, and Na+/K+ ratio, thereby reducing Na+ stress on rice; 2. The application of nitrogen fertilizer during straw return effectively minimized soil nitrogen loss by lowering the ammonium and nitrate nitrogen concentrations in the soil leachate; 3. This combination also reduced plant Na+ concentrations while increasing plant K+ concentrations, thus improving the Na+/K+ ratio in the plants; 4. Straw return with nitrogen fertilizer significantly enhanced rice yield, which increased with higher nitrogen application rates. In summary, the integration of straw return with nitrogen fertilizer not only regulates rice salinity tolerance but also boosts rice yield, presenting a novel approach for improving saline–sodic soils.

Experimental treatment of pickled vegetable wastewater by electrofenton method based on modified PbO2 electrode

The pickle industry is acknowledged as one of the most environmentally harmful sectors within the food industry. The elevated concentrations of chemical oxygen demand (COD), total phosphorus (TP), ammonium nitrogen (NH4+-N), and salinity found in pickle wastewater present significant environmental challenges. To tackle these issues, this study investigates the efficacy of a La-doped Ti/SnO2-Sb2O5/La-PbO2 electrode employing an electro-Fenton method for the treatment of pickle wastewater. Experimental design was performed using response surface methodology to identify optimal operational parameters. Results demonstrate that all processes adhere to pseudo-first-order reaction kinetics. Under conditions where the degradation temperature is maintained at 65 °C, current density at 100 mA cm−2, pH at 4.1, FeSO4 concentration at 3.03 mmol L−1, and H2O2 concentration at 2.07 mmol L−1 with six additions over a degradation period of 240 minutes, COD removal achieved an impressive rate of 92.87 %, while ammonium nitrogen removal reached a remarkable rate of 95.26 %. In comparison to traditional electrochemical methods, both COD and ammonium nitrogen removal rates exhibited substantial improvements; furthermore, hydroxyl radicals (•OH) played a pivotal role in facilitating the radical quenching degradation process. The operation cost analysis shows that the electric Fenton process has a lower operation cost, which provides a good opportunity for the food industry to treat Pickled vegetables wastewater. The operating cost for COD removal rate is 1.262 $ m−3kg−1, and the operating cost for ammonia nitrogen removal rate is 1.355 $ m−3kg−1.

Thermodynamic characteristics of nitrifiers reveal the potential NOB inhibition strategies at low temperatures

Nitrification is a highly temperature-sensitive biological process, yet relatively little research has explored thermodynamic characteristics of enzyme-catalyzed nitrification processes in wastewater treatment systems. In this study, a variety of thermodynamic models were employed to evaluate thermodynamic characteristics of four activated sludge samples cultivated under various temperatures (10, 15, and 20 °C) and ammonia nitrogen concentration (40 mg/L and 300 mg/L). Results revealed a higher maximum temperature (Tmax) for ammonia oxidizing bacteria (AOB) compared to nitrite oxidizing bacteria (NOB), suggesting the robust resistance to high temperatures of AOB. Conversely, the lower minimum temperature (Tmin) of NOB indicated its stronger tolerance to low temperatures. Notably, both low temperatures and high-ammonia nitrogen concentrations are conducive to the competition of Nitrotoga over Nitrospira, resulting in Nitrotoga emerging as the dominant NOB within 10∼15 °C. Moreover, heat capacity (ΔCpǂ) of enzymes exhibited a similar trend across all samples, i.e. HAO > AMO > NOR, indicating that HAO exhibited the strongest thermodynamic stability, followed by AMO, and NOR has the worst thermodynamic stability. Additionally, the difference in optimal temperature (Topt) between dominant AOB-Nitrosomonas and dominant NOB-Nitrotoga cultivated at high nitrogen concentration and low temperature could reach up to +8.13 °C, enabling selective inactivation of NOR through thermal treatment at Topt,AOB ∼ Topt,NOB. However, despite insignificant differences in Topt,AOB and Topt,NOB under low-temperature and low-ammonia nitrogen concentration, the smaller the difference between Tmax and Top (Tmax-Topt) of NOB and smaller D-value of NOR made NOB more susceptible to inhibition than AOB. However, the presence of low-abundance Nitrospira renders thermal treatment alone inadequate for complete NOB inhibition, combing it with other strategies is necessary for effective inhibition. Therefore, the fundamental differences in thermodynamic characteristics of AOB and NOB determine the potential of NOB inhibition strategies at low temperatures.

Anthropogenic activities disturb phytoplankton taxa and functional groups in an urban river

Anthropogenic activities have substantial impacts on river ecosystems, yet how phytoplankton taxa and functional groups respond to varying levels of anthropogenic activity in urban rivers remains poorly understood. Herein, we investigated the sensitivity of phytoplankton taxa and functional groups to anthropogenic disturbances in the Bahe River, which experiences increased anthropogenic activity intensity from upstream to downstream. We found that both phytoplankton composition and niche breadth exhibited distinct variations among the three reaches with different anthropogenic disturbances. Notably, we observed a marked increase in the abundance of potential bloom-forming species in the river section with the highest anthropogenic disturbance, suggesting that anthropogenic activities might promote the growth and proliferation of these species. Compared to geographical and physiochemical factors, anthropogenic activities were identified as the primary driver of changes in phytoplankton taxa and functional groups. Increasing levels of anthropogenic activities potentially led to higher concentrations of ammonium nitrogen and total phosphorus, further influencing niche differentiation among phytoplankton taxa and functional groups. Our study offers profound insights into the impacts of anthropogenic disturbances on phytoplankton, emphasizing the necessity of integrating watershed-scale human activity management into strategies for controlling phytoplankton in urban rivers.

Effects of tannin-tolerant lactic acid bacteria in combination with tannic acid on the fermentation quality, protease activity and bacterial community of stylo silage.

Proteolysis during ensiling primarily occurs due to undesirable microbial and plant protease activities, which reduce the protein supply to ruminant livestock and cause a series of environmental problems. The objective of this study was to investigate the effects of the tannin-tolerant lactic acid bacterium strain Lactiplantibacillus plantarum 4 (LABLP4) in combination with tannic acid (TA) on protein preservation in stylo (Stylosanthes guianensis) silage. The stylos were either ensiled without additives (control) or treated with LABLP4 (106 colony-forming units per gram of fresh matter), 1% (fresh matter basis) TA, 2% TA, LABLP4 + 1% TA and LABLP4 + 2% TA. Fermentation quality, protein composition, protease activity and bacterial diversity were determined at 3, 7, 14 and 31 days of ensiling. The combination of LABLP4 and TA decreased the pH, coliform bacteria count, non-protein nitrogen, ammonia-nitrogen (NH3-N) content and protease activities (P < 0.05) and increased the true protein content (P < 0.05) compared to the control. LABLP4 + TA led to a lower pH and NH3-N content than LABLP4 or TA alone (P < 0.05). On the last day (31 days) of ensiling, LABLP4 + TA increased the relative abundances of Firmicutes and Lactiplantibacillus (P < 0.05), except for the LABLP4 treatment, and decreased the relative abundance of Actinobacteria (P < 0.05). The combination of tannin-tolerant LABLP4 and TA effectively improved the fermentation quality of stylo silage and reduced protein degradation by altering the bacterial community structure. © 2024 Society of Chemical Industry.

Potential use of Wolffia globosa powder supplementation on in vitro rumen fermentation characteristics, nutrient degradability, microbial population, and methane mitigation

This study examined the potential of duckweed powder (DWP) on in vitro fermentation characteristics, nutrient degradability, microbial change, and methane (CH4) production using in vitrostudy technique. This investigation used a 2 × 6 factorial arrangement in a completely randomized design (CRD) by different roughage-to-concentrate (R: C) ratios of 60:40 and 40:60 combined with DWP supplementation levels at 0, 2, 4, 6, 8, and 10% of the total dry matter (DM) substrate, respectively. There was an interaction effect by R: C ratios combined with DWP supplementations that changed gas production rate, pH value (4 h; h), volatile fatty acid (VFA) (8 h), in vitro dry matter degradability (IVDMD) at 12 h, and concentration of ammonium nitrogen (NH3-N) (p < 0.05). Furthermore, the R: C ratio (40:60) significantly decreased CH4 production (4 and 8 h), pH (8 h), and Ruminococcus albus (8 h) (p < 0.05), while it significantly increased total VFA (8 h), and nutrient degradability (p < 0.05). DWP 4% significantly increased to the highest of gas production, improved nutrient degradability (IVDMD at 24 h and in vitro organic matter degradability; IVOMD at 12 h), whereas significantly decreased Methanobacteriales (8 h) and CH4 production. DWP 4% has potential as a ruminant feed additive for reducing Methanobacteriales and CH4 emission and enhancing rumen fermentation.

Root morphology, nitrogen metabolism and amino acid metabolism in soybean under low phosphorus stress.

Phosphorus deficiency is a major influence on growth and development of soybean. Therefore, improving phosphorus utilization efficiency in soybean is a research priority for the soybean community. In this experiment, Liaodou 13 (high phosphorus utilization: HPE) and Tiefeng 3 (low phosphorus utilization: LPE) were used as test varieties. We investigated changes in root morphology, amino acid content, and content of key substances of the nitrogen metabolic pathway with normal phosphorus (0.5 mM) and low phosphorus (0.005 mM) treatments. The results showed that the root length, root surface area and number of lateral roots of HPE roots were higher than those of LPE roots under normal and low phosphorus conditions. The contents of different types of amino acids showed different trends in two varieties. The HPE showed small change in the content of total hydrolyzed amino acids under the low phosphorus condition when compared to the normal phosphorus treatment by a 6.67% decrease, on the contrary LPE showed a drastic decrease by 20.36%. However, HPE exhibited similar decreasing trends in the contents of hydrolyzed and free aspartic acid with the low phosphorus treatment. Moreover, the contents of free histidine and valine in LPE were significantly increased by 657.84% and 149.29% respectively, in contrast to significant decreases in HPE. In aspects of major nutrient elements, the contents of phosphorus, total nitrogen and ammonia nitrogen in both HPE and LPE varieties decreased to dramatic levels. However, the nitrate nitrogen content significantly increased 78.51% for HPE and 65.12% for LPE. Compare to the normal condition, the GOGAT activity in HPE decreased by 5.18% but increased by 33.10% in LPE. Compare to the normal condition, the GS activity in HPE increased by 7.26% but decreased by 21.72% in LPE under phosphorus deficiency. In summary, the phosphorus-efficient soybean variety HPE exhibited superior tolerance to low phosphorus deficiency through advantageous root morphology, phosphorus uptake and transfer capability, and balanced amino acid metabolism and nitrogen metabolism pathways.

Food Waste as Feedstock for Anaerobic Mono-Digestion Process

There is a growing recognition that food waste (FW) comprises a significant amount of unused energy. Indeed, FW shows great potential to produce methane (CH4)-rich biogas via an anaerobic digestion (AD) process. Nevertheless, to ensure high AD process performance, deepening the knowledge of FW characteristics is required. Furthermore, the biogas yield is strongly influenced by several operational parameters. Taking into account the above, in the current study, based on the data in the literature, the physicochemical parameters of FW generated throughout the world are presented and discussed. In addition, the performance profile of the single-stage anaerobic mono-digestion process with the use of FW as a feedstock was investigated. The performed analysis clearly demonstrated that FW is characterized by significant variations in several parameters, such as pH, the total solid (TS) and volatile solid (VS) contents, the volatile solids to total solids ratio (VS/TS), soluble chemical oxygen demand (sCOD), the concentrations of VFAs and ammonium nitrogen (NH4+-N), and the carbon-to-nitrogen ratio (C/N). Moreover, it was shown that the selected operational parameters, such as temperature, pH, the ratio of food waste to inoculum (I) (FW/I), and the organic loading rate (OLR), may have the most significant impact on the performance of the single-stage anaerobic mono-digestion process. In addition, it was found that most of the experimental investigations presented in the literature were conducted on a laboratory scale. Hence, in future research, more effort should be made to determine the biogas yield with the use of full-scale systems. To summarize, it should be clearly highlighted that the analysis presented in this study may have important implications for the management and application of FW as feedstock for an anaerobic mono-digestion process on an industrial scale.

Effects of Rice Root Development and Rhizosphere Soil on Methane Emission in Paddy Fields.

Paddy fields are important anthropogenic emission sources of methane (CH4). However, it is not clear how rice root development and rhizosphere soil properties affect CH4 emissions. Therefore, we selected rice varieties with similar growth periods but different root traits in the local area. We measured CH4 emission fluxes, cumulative CH4 emissions, root dry weight, root length, and the dissolved organic carbon (DOC), microbial biomass carbon (MBC), redox potential (Eh), ammonium nitrogen (NH4+-N), and nitrate nitrogen (NO3--N) contents in rhizosphere soil. Methanogens and methanotrophs are crucial factors influencing CH4 emissions; thus, their abundance and community composition were also assessed. The result showed that CH4 fluxes of each rice variety reached the peak at tillering stage and jointing-booting stage. The CH4 emissions in tillering stage were the largest in each growth period. CH4 emissions had negative correlations with root length, root dry weight, Eh NO3--N, methanotroph abundance, and the pmoA/mcrA ratio, and positive correlations with NH4+-N, MBC, DOC, and methanogen abundance. Path analysis confirmed methanogens and methanotrophs as direct influences on CH4 emissions. Root development and rhizosphere soil properties affect CH4 emissions indirectly through these microbes. This study suggests that choosing rice varieties with good root systems and managing the rhizosphere soil can effectively reduce CH4 emissions.

Lipase pretreatment enhances biochar‐assisted anaerobic digestion of food waste

AbstractAnaerobic digestion is a promising technology for the treatment of food waste (FW) but it requires optimization to improve its performance. This study investigated whether combining the addition of biochar with lipase pretreatment could improve the anaerobic digestion of FW. The results showed that biochar stimulated the release of soluble substances, resulting in an increase in the methane yield of groups with added biochar by 16.24% to 19.36% in comparison with the group without biochar. Lipase pretreatment substantially shortened the fermentation time required to complete the anaerobic digestion, from 15 to 9 days. Lipase pretreatment further improved microbial abundance and promoted the enrichment of functional microbes in the anaerobic digestion of FW mediated by biochar. It also changed the methane production pathway from acetotrophic to hydrogenotrophic, thereby ensuring the stability of the anaerobic digestion system in the presence of a high ammonia nitrogen concentration.

Is the response of plant root systems to precipitation primarily driven by the rhizosphere soil?

BackgroundChanges in precipitation alter soil moisture, thereby affecting the aboveground and belowground ecological processes. However, it remains unclear whether plant root systems alter these effects through rhizospheric processes. In this study, a precipitation control experiment was conducted in the alpine grassland of northern Tibet to simulate precipitation changes with a 50% decrease and 50% increase in precipitation. Nutrient and microbial biomass, root traits, and survival strategies in the rhizosphere and bulk soils of the dominant plant, Stipa purpurea, were analyzed for alterations under precipitation changes.ResultsIncreased precipitation (IP) significantly decreased the rhizosphere soil total phosphorus and bulk soil ammonium nitrogen and increased the rhizosphere soil total potassium. Decreasing precipitation (DP) significantly increased the rhizosphere soil total potassium and decreased the bulk soil total potassium. DP significantly reduced microbial biomass carbon, nitrogen and phosphorus in rhizosphere soil, while IP significantly increased the bulk soil MBC:MBP, soil C:P imbalance, and soil N:P imbalance. Along the PC1 axis, where the contribution of the traits was relatively large, it was possible to define the root economic spectrum. The root system of Stipa purpurea from the DP treatment was distributed on the conservative side of the economic spectrum, whereas that from the control and IP treatments were clustered on the acquisition side.ConclusionsIncreasing and decreasing precipitation mainly affected the contents of total phosphorus and total potassium in rhizosphere soil and the contents of ammonium nitrogen and total potassium in bulk soil of Stipa purpurea. The microbial biomass carbon, nitrogen and phosphorus were mainly affected by a decrease in precipitation. Decreasing precipitation significantly reduced microbial biomass carbon, nitrogen and phosphorus, but the rhizosphere MBC:MBN, MBC:MBP and MBN:MBP remained stable under the change of precipitation. Increasing precipitation exacerbated the C:P imbalance and N:P imbalance in bulk soil, and increased the demand for phosphorus by bulk microorganisms. Increased precipitation promoted root access to resources. The root system of Stipa purpurea in the context of precipitation changes was driven by rhizosphere nutrients and bulk microorganisms. This study is important for revealing plant–microbe–soil interactions in terrestrial ecosystems.

Biomass Accumulation, Contaminant Removal, and Settling Performance of Chlorella sp. in Unsterilized and Diluted Anaerobic Digestion Effluent

Microalgae demonstrate significant efficacy in wastewater treatment. Anaerobic digestion effluent (ADE) is regarded as an underutilized resource, abundant in carbon, nitrogen, phosphorus, and other nutrients; however, the presence of inhibitory factors restricts microalgal growth, thereby preventing its direct treatment via microalgae. The purpose of this study was to dilute ADE using various dilution media and subsequently cultivate Chlorella sp. to identify optimal culture conditions that enhance microalgal biomass and water quality. The effects of various dilution conditions were assessed by evaluating the biomass, sedimentation properties, and nutrient removal efficiencies of microalgae. The results demonstrate that microalgal biomass increases as the dilution ratio increased. The microalgae biomass in the treatments diluted with simulated wastewater was significantly higher than that with deionized water, but their effluent quality failed to meet discharge standards. The treatment diluted with deionized water for 10 times exhibited abundant microbial biomass with strong antioxidant properties. The corresponding total phosphorus concentration in the effluent (6.96 mg/L) adhered to emission limits under the Livestock and Poultry Industry Pollutant Emission Standards (8 mg/L), while ammonia nitrogen concentration (90 mg/L) was near compliance (80 mg/L). The corresponding microbial biomass, with a sludge volume index (SVI30) of 72.72 mL/g, can be recovered economically and efficiently by simple precipitation. Its high protein (52.07%) and carbohydrate (27.05%) content, coupled with low ash (10.75%), makes it a promising candidate for animal feed and fermentation. This study will aid in understanding microalgal growth in unsterilized ADE and establish a theoretical foundation for cost-effective ADE purification and microalgal biomass production.