NH3 Concentration Research Articles

Atmospheric NH3 in urban Beijing: long-term variations and implications for secondary inorganic aerosol control

Abstract. Ammonia (NH3) has major effects on the environment and climate. In situ measurements of NH3 concentrations taken between June 2009 and July 2020 at an urban site in Beijing were analyzed to study its long-term behavior, responses to meteorological conditions, and influences on the formation of secondary inorganic aerosols (SIAs). The 11-year average NH3 mixing ratio was 26.9±19.3 ppb (median 23.5 ppb). The annual average NH3 mixing ratio increased from 2009 to 2017 by 50 % and then decreased by 49 % from 2017 to 2020. Notably, the long-term trend for NH3 at the ground level did not align with the trends derived from satellite observations and emission estimates. The NH3 concentration exhibited a stronger correlation with the daily variation in water vapor (H2O) concentration than with air temperature. Thermodynamic modeling revealed the nonlinear response of SIAs to NH3, with increased sensitivity when its concentration was reduced to 40 % of the initial level. Although reducing NH3 concentrations can improve air quality during winter, controlling acid gas concentrations has a greater effect than controlling NH3 concentrations on reducing SIA concentrations, until NH3 and acidic gas concentrations are reduced below 80 % of their current levels. Nevertheless, the increased mass proportion of ammonium salts in SIAs during the observation period indicates that future control measures for NH3 concentrations may need to be prioritized in Beijing.

Assessing the effects of high-carvacrol oregano oil on rumen microbial fermentation, gas production, and methane production in vitro

The objective of this in vitro study was to assess the effects of high-carvacrol oregano oil (ORE; 50 g/kg oregano oil, 800-802 g/kg carvacrol), on microbial fermentation and CH4 production. In the experiment (a complete randomized block design), treatments included a negative control (CTL, no additive), a positive control (monensin, MON, 10 mg/L), and ORE (20, 40, 80, 120, 200, 160, and 1000 mg/L). Compared with CTL, MON shifted (p < 0.05) volatile fatty acid (VFA) profile from acetate and butyrate to propionate production, thereby reducing (p < 0.05) CH4 production (-26%). Monensin decreased (p < 0.05) NH3 and branched-chain VFA concentrations. Of the doses evaluated, only the highest dose (1000 mg/L) affected ruminal microbial fermentation and CH4 production. At this dose, ORE reduced (p < 0.05) gas production, total VFA, acetate, propionate and NH3 concentrations, and CH4 production (-22%). The reduced gas production and total VFA is an indication of feed digestion inhibition. These results suggest that ORE may decrease CH4 production and improve ruminal N utilization. However, these findings need to be validated in vivo to determine the optimal dose to benefit from the positive effects while avoiding the negative impact of ORE on feed digestion.

Portable Sensing Probe for Real-Time Quantification of Ammonia in Blood Samples.

The detection of ammonia levels in blood is critical for diagnosing and monitoring various medical conditions, including liver dysfunction and metabolic disorders. However, traditional diagnostic methods are slow and cumbersome, often involving multiple contact-based steps such as ammonia separation in alkali conditions followed by distillation or microdiffusion, leading to delays in diagnosis and treatment. Herein, we developed a colorimetric assay capable of rapid detection of ammonia in whole blood or plasma samples, utilizing 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TCNC) coupled with gold nanoparticles (AuNPs). The basis of our assay relies on either (i) the interaction between the carboxylate group (-COO) of TEMPO and ammonium ions or (ii) the manipulation of AuNPs surface plasmon resonance (SPR) through the formation of Au(NH3)43+, which displaces a redox mediator, resazurin, resulting in observable multicolor displays at various concentrations of ammonia. The colorimetric assay exhibits a wide linear detection range for dissolved NH4+ (0.1-37 μM) with a low limit of detection (LOD) of 0.1 μM. Additionally, it effectively measures NH3(g) concentrations in the range of 0.5-144 μM. The fabricated electrochemical nose (E-nose) device demonstrates excellent analytical performance for plasma ammonia sensing (0.05-256 μM). Experimental results demonstrate a linear detection range suitable for clinical applications, with excellent correlation to standard laboratory methods, offering a practical solution for point-of-care (PoC) testing. We anticipate that this approach can be applied broadly to improve patient monitoring and treatment by providing immediate and accurate ammonia measurements in a clinical setting.

Effects of Paddy Rain-Flood Storage on Rice Growth Physiological Indices and Nitrogen Leaching under Organic Planting in Erhai Lake Basin.

In order to address the increasingly prominent issues of water resource protection and agricultural non-point source pollution in the Erhai Lake Basin, this study conducted a two-year field experiment in Gusheng Village, located in the Erhai Lake Basin. In 2022, two irrigation treatments were set up: conventional flooding irrigation (CK) and controlled irrigation (C), with three replicates for each treatment. In 2023, aiming to enhance the utilization rate of rainwater resources and reduce the direct discharge of dry-farming tailwater from upstream into Erhai Lake. The paddy field was used as an ecological storage basin, and the water storage depth of the paddy field was increased compared to the depth of 2022. Combined with the deep storage of rainwater, the dry-farming tailwater was recharged into the paddy field to reduce the drainage. In 2023, two water treatments, flooding irrigation with deep storage and controlled drainage (CKCD) and water-saving irrigation with deep storage and controlled drainage (CCD) were set up, and each treatment was set up with three replicates. The growth and physiological index of rice at various stages were observed. Nitrogen leaching of paddy field in surface water, soil water, and groundwater under different water treatments after tillering fertilizer were observed. The research results show that the combined application of organic and inorganic fertilizers under organic planting can provide more reasonable nutrient supply for rice, promote dry matter accumulation and other indices, and also reduce the concentration of NH4+-N in surface water. Compared with CK, the yield, 1000-grain weight, root-to-shoot ratio, and leaf area index of C are increased by 4.8%, 4.1%, 20.9%, and 9.7%, respectively. Compared with CKCD, the yield, 1000-grain weight, root-to-shoot ratio, and leaf area index of CCD are increased by 6.5%, 3.8%, 19.6%, and 21.9%, respectively. The yield in 2023 is 19% higher than that in 2022. Treatment C can increase the growth indicators and reduce the net photosynthetic rate to a certain extent, while CCD rain-flood storage can alleviate the inhibition of low irrigation lower limit on the net photosynthetic rate of rice. Both C and CCD can reduce nitrogen loss and irrigation amount in paddy fields. CCD can reduce the tailwater in the Gusheng area of the Erhai Lake Basin to Erhai Lake, and also can make full use of N, P, and other nutrients in the tailwater to promote the formation and development of rice. In conclusion, the paddy field rain-flood storage methodology in the Erhai Lake Basin can promote various growth and physiological indicators of rice, improve water resource utilization efficiency, reduce direct discharge of tailwater into Erhai Lake, and decrease the risk of agricultural non-point source pollution.

Operando Investigation of WS2 Gas Sensors: Simultaneous Ambient Pressure X-ray Photoelectron Spectroscopy and Electrical Characterization in Unveiling Sensing Mechanisms during Toxic Gas Exposure.

Ambient pressure X-ray photoelectron spectroscopy (APXPS) is combined with simultaneous electrical measurements and supported by density functional theory calculations to investigate the sensing mechanism of tungsten disulfide (WS2)-based gas sensors in an operando dynamic experiment. This approach allows for the direct correlation between changes in the surface potential and the resistivity of the WS2 sensing active layer under realistic operating conditions. Focusing on the toxic gases NO2 and NH3, we concurrently demonstrate the distinct chemical interactions between oxidizing or reducing agents and the WS2 active layer and their effect on the sensor response. The experimental setup mimics standard electrical measurements on chemiresistors, exposing the sample to dry air and introducing the target gas analyte at different concentrations. This methodology applied to NH3 concentrations of 100, 230, and 760 and 14 ppm of NO2 establishes a benchmark for future APXPS studies on sensing devices, providing fast acquisition times and a 1:1 correlation between electrical response and spectroscopy data in operando conditions. Our findings contribute to a deeper understanding of the sensing mechanism in 2D transition metal dichalcogenides, paving the way for optimizing chemiresistor sensors for various industrial applications and wireless platforms with low energy consumption.

CHARACTERIZATION OF LEACHATES FROM UNCONTROLLED OPEN DUMPSITE IN AHIAEKE, ISIEKE AND NSUKWE UMUAHIA, ABIA STATE

This study aimed to characterize the chemical in the leachates from uncontrolled open dumpsite in Ahiaeke, Isieke and Nsukwe in Umuahia, Abia State. Air, soil and leachate samples were analysed using an absolute instrument system, AIS (Aerocet model 5315) and standard procedures to measure the concentration of SO4, NH3, O3, CO2, VOC, PM10, PM2.5, H2S and CO in the air and some selected physicochemical and heavy metal content. From the result, SO4 ranges from 0.02 - 0.19 mg/m3, NH3(1.11 - 14.05), O3(0.01 - 0.15), CO2(618.50 - 832.50), VOC (1889.50 - 6343.50), PM10(46.19 -751.50), PM2.5(14.03 - 344.72), H2S (0.02 - 5.91), CO (1.91 - 6.91 mg/m3),For leachate and soil analysis, pH ranges from 8.75 - 9.01, Potassium (2.04 - 6.93 mg/l),Iodine (1.24 - 7.86), Fluorine (0.32 - 31.96), Acidity (344.70 - 821.65), Magnesium (209.70 - 498.66), Nitrate (0.34 - 2.07), DO (1.95 - 6.82), COD (3181.29 - 19090.56), Phosphate (13.42 - 57.35), Boron (0.79 - 3.15), Ammonia (0.85 - 3.55), Lead (0.00 - 3.76 mg/kg),Mercury (0.12 - 0.88), Cadmium (0.21 - 1.49), Manganese (2.13 - 14.72) , Chromium (0.10 - 0.61), Nickel (2.14 - 8.12), Iron (1.13 - 6.28), Zinc (0.15 - 1.22),Barium (24.15- 172.02), Copper (1.18 - 9.56 mg/kg). In this study, concentration of all air parameters was higher at distance closer to the dumpsites. The level of ammonia, PM10, PM2.5 and some heavy metals exceeded WHO guidelines. Hence, the waste dumps were observed to be the major contributors of increase in chemical and heavy metal levels in the leachate.

Effect of elemental sulfur on anaerobic ammonia oxidation: Performance and mechanism

Biological nitrogen removal processes provide effective means to mitigate nitrogen-related issues in wastewater treatment. Previous studies have highlighted the collaborative efficiency between sulfur autotrophic denitrification and Anammox processes. However, the trigger point induced the combination of nitrogen and sulfur metabolism is unclear. In this study, elemental sulfur (S0) was introduced to Anammox system to figure out the performance and mechanism of S0-mediated autotrophic denitrification and Anammox (S0SAD-A) systems. The results showed that the nitrogen removal performance of the Anammox reactor decreased with the increasing concentrations of NH4+-N and NO2−-N in influent, denitrification occurred when NH4+-N concentration reached 100 mg/L. At stage ⅳ (150 mg/L NH4+-N), the total nitrogen removal efficiency in S0SAD-A system (95.99%) was significantly higher than that in the Anammox system (77.22%). Throughout a hydraulic retention time, the consumption rate of NH4+-N in S0SAD-A was faster than that in Anammox reactor. And there existed a nitrate-concentration peak in S0SAD-A system. Metagenomic sequencing was performed to reveal functional microbes as well as key genes involved in sulfur and nitrogen metabolism. The results showed that the introduction of S0 elevated the abundance of Ca. Brocadia. Moreover, the relative abundance of Anammox genes, such as hao, hzsA and hzsC were also stimulated by sulfur. Notably, unclassified members in Rhodocyclaceae acted as the primary contributor to key genes involved in the sulfur metabolism. Overall, the interactions between Anammox and denitrification were stimulated by sulfur metabolism. Our study shed light on the potential significance of Rhodocyclaceae members in the S0SAD-A process and disclosed the relationship between anammox and denitrification.

A multimodal sensing network based on synergistically sensitized polyaniline composites strategy for safety monitoring in pesticide spraying

Ensuring the safety of farmers during pesticide spraying is crucial in smart agricultural practices due to the potential risks of pesticide poison and the associated irreversible damages. However, there is a notable deficiency of efficient monitoring strategies for providing timely and cost-effective safety warnings. In this study, we have devised an advanced and real-time sensing network using polyaniline (PANI) composites to address this pressing concern. To enhance sensing performance, diverse quantum dots (QDs) sensitizers and rigid or flexible substrates are strategically integrated with PANI, resulting in sensors tailored to different sensing capabilities. Specifically, the proton conduction is heightened by incorporating carboxyl graphene QDs (GQDs) into PANI, obtaining the superior gas-sensing performance for NH3 detection. Moreover, a strain sensor employing Ti3C2Tx QDs (MQDs) and a flexible thermoplastic polyurethane (TPU) substrate has been developed for real-time monitoring of physical biosignals. Finally, a smart sensing network with real-time display integrated with the above sensors is designed to detection NH3 concentration released from pesticide volatilization and physiological tracking in cases of mild pesticide poisoning. This sensing network can wirelessly interface with a laptop for convenient safety monitoring of farmers engaged in smart agriculture. The proof of concept demonstrated by this sensing network holds promise for enhancing safety monitoring in smart agriculture.

Role of ectomycorrhizal colonization in enhancement of nutrients for survival of plants collected from mountainous cold stress areas

BackgroundEctomycorrhizal (ECM and ECM-like) structures associated with plant root systems are a challenge for scientists. The dispersion pattern of roots within the soil profile and the nutritional conditions are both favourable factors to motivate the plants to make ECM associations.ResultsThis study discusses the colonization of mycorrhizal associations in Kobresia and Polygonum species including Polygonum viviparum, Kobresia filicina, K. myosuroides, Alnus nitida, Betula pendula, Pinus sylvestris, and Trifolium repens grown naturally in cold stressed soils of Gilgit-Baltistan (high-altitude alpine Deosai plains), Hazara, Swat, Dir, and Bajaur. Sieved soil batches were exposed to +5 °C (control), -10, -20, -30, -40, -50, -125 °C for 5 h, and selected plants were sown to these soils for 10 weeks under favourable conditions for ECM colonization. Ectomycorrhizal associations were examined in the above mentioned plants. Some ECM fungi have dark mycelia that look like the mantle and Hartig net. Examples of these are Kobresia filicina, K. myosuroides, and Polygonum viviparum. Findings of this study revealed that K. myosuroides excelled in ECM root tip length, dry mass, and NH4 concentration at -125 °C. Contrarily, A. nitida demonstrated the lower values, indicated its minimum tolerance. Notably, T. repens boasted the highest nitrogen concentration (18.7 ± 1.31 mg/g), while P. sylvestris led in phosphorus (3.2 ± 0.22 mg/g). The B. pendula showed the highest potassium concentration (9.4 ± 0.66 mg/g), emphasising species-specific nutrient uptake capabilities in extreme cold conditions. The PCA analysis revealed that the parameters, e.g., NH4 in soil mix (NH4), NO3 in soil mix (NO3), phosphorus in soil in species of Polygonum viviparum, Kobresia filicina, K. myosuroides, Alnus nitida, Betula pendula, Pinus sylvestris, and Trifolium repens are most accurately represented in cases of + 5 °C, -10 °C, and -20 °C temperatures. On the other hand, the parameters for ECM root tips (ECM) and Dry Mass (DM) are best described in -40 °C, -50 °C, and − 125 °C temperatures. All parameters have a strong influence on the variability of the system indicated the efficiency of ECM. The heatmap supported the nutrients positively correlated with ECM colonization with the host plants.ConclusionAt lower temperatures, hyphae and spores in roots were reduced, while soluble phosphorus concentrations of leaves were increased in cold stress soils. Maximum foliar nutrient concentrations were found in K. myosuroides at the lowest temperature treatments due to efficient functioning and colonization of ECM.

Feeding or pen surface application of clinoptilolite with different particle sizes: impact on nitrogen utilization and manure ammonia emissions in feedlot cattle.

This study investigated the effects of feeding clinoptilolite (CLN; 2.5% of diet dry matter) with a particle size of either 30- or 400-µm on ruminal fermentation characteristics, measures of nitrogen (N) utilization, and manure ammonia-N (NH3) emissions in feedlot cattle. The impact of directly applying 30- or 400-µm CLN to the pen surface (2,250kg/ha) on manure NH3-N emissions was also evaluated. Six beef heifers were used in a replicated 3 × 3 Latin square design with 21-d periods. Dietary treatments were 1) finishing ration with no supplement (CON), 2) CON + 30-µm CLN (CLN-30), and 3) CON + 400-µm CL (CLN-400). Intake was measured daily. To evaluate fermentation characteristics, ruminal fluid was collected on day 19. Indwelling pH loggers were used to measure ruminal pH from days 15 to 21. Blood was collected 3-h post-feeding on day 21 for metabolite analysis. Fecal grab and urine spot samples were also collected from days 19 to 21 to measure nutrient digestibility, route of N excretion, and in vitro NH3 emissions. There was no diet effect (P ≥ 0.12) on nutrient intake and apparent total tract digestibility, and ruminal short-chain fatty acid profile and pH. Ruminal NH3 concentration, which was lower (P = 0.04) for CLN-30 than CON heifers, did not differ between CON and CLN-400 heifers. Although there was no diet effect (P = 0.50) on plasma urea-N (PUN) concentration, proportion of urea-N excreted in urine was lower (P = 0.01) for CLN-30 than CON and CLN-400 heifers. Urinary NH3-N excretion, which was greater (P ≤ 0.04) for CLN-400 than CON heifers, did not differ between CLN-30 and CLN-400 heifers. Feeding CLN also increased (P ≤ 0.02) fecal excretion of potassium (K) and iron (Fe) and reduced (P = 0.01) urinary excretion of calcium (Ca). There was a treatment × time interaction (P = 0.01) for NH3 emission rate, which was greatest within the first 36h of incubation and was lower for manure from CLN-400 compared to CON and CLN-30 heifers and pen surface application treatments. Cumulative NH3 emissions were lower (P < 0.01) for manure from CLN-400 compared to CON and CLN-30 heifers and the pen surface application treatments. Although surface application was ineffective, feeding 400-µm CLN to finishing cattle could result in a beneficial decrease in manure NH3 emissions. However, changes in fecal and urine excretion of minerals like K and Ca, which suggest a decrease in bioavailability, need to be considered when feeding CLN in finishing cattle diets.

Multi-time Scale Variation of Atmospheric Ammonia Concentration and Dry Deposition in a Paddy Rice Region in Subtropical China

Meteorological factors and anthropogenic activities significantly affect atmospheric ammonia （NH3） concentration and its dry deposition. Former studies have examined the spatial and temporal variability in atmospheric NH3 concentrations at monthly scales. However, the characteristics of atmospheric concentrations at finer time scales such as hourly and daily scales and the influencing factors remain unclear. In this study, atmospheric NH3 concentration and related meteorological factors were continuously monitored online for one year in a double cropping rice region in subtropical China, and atmospheric NH3 concentration and its meteorological influencing factors as well as dry deposition were analyzed at different time scales （hourly, daily, and monthly）. The main results were as follows： The annual average daily concentration of NH3 in the rice area varied from 0.01 to 58.0 μg·m-3 （in N, same below）, and the annual average concentration was 5.3 μg·m-3. On the hourly scale, the 24-hour dynamics of atmospheric NH3 concentration showed a unimodal pattern, and the time of the NH3 peak appearance in different seasons was different； the time of the peak that appeared in winter lagged behind that in the other seasons. From the perspective of daily scale, NH3 concentration was mainly affected by fertilization in the paddy fields, peaking at 1-3 days after fertilization and then gradually decreasing. On the monthly scale, NH3 concentration peaked at 12.8 μg·m-3 in July and was the lowest in October at 1.6 μg·m-3. On the hourly scale, NH3 concentration varied seasonally due to the influences of meteorological factors, mainly as follows： NH3 concentration showed significant positive correlations with air temperature and solar radiation in all four seasons and with wind speed in spring and summer, whereas it showed significant negative correlations with relative humidity except in winter. On the daily scale, NH3 concentration showed a significant positive correlation with air temperature, rainfall, and solar radiation, whereas it showed a significant negative correlation with relative humidity. On the monthly scale, no significant correlation existed between each meteorological factor and NH3 concentration. The annual dry deposition flux （in N） calculated from the hourly average NH3 concentration was 8.5 kg·（hm2·a）-1, which was 11.6% higher than the annual flux calculated from the daily average and 12.4% higher than the annual flux calculated from the monthly average. In summary, there were significant daily and seasonal variations in atmospheric NH3 concentration in the paddy rice region in subtropical China, and conducting hourly-scale observations of NH3 concentration can help to reveal the multi-time scale variations in NH3 concentration and to quantify NH3 dry deposition more accurately.

Role of Ammonia in Aerosol Liquid Water, pH, and Secondary Inorganic Aerosols Formation at an Ammonia-rich City in Changzhou

Ammonia （NH3） is an important alkaline reactive nitrogen, which, as a precursor of fine particulate matter, raises public health issues. In this study, online NH3, SO2, NO2, PM2.5, and its water-soluble inorganic ions were detected to deduce the influence of NH3 on aerosol liquid water content （AWC） and aerosol pH, including the formation of water-soluble secondary ions in PM2.5 in winter in Changzhou, an ammonia-rich city in the Yangtze River Delta area in winter. The results showed that NH4+ mainly existed in the form of NH4NO3 and （NH4）2SO4, and the remaining NH4+ existed as NH4Cl. Owing to the NH3-NH4+ buffer system, the aerosol pH values were found at 4.2 ± 0.4, which was positively correlated with the NH3 content. The aerosol pH value variation narrowed with the increase in PM2.5 concentration and tended to be between 4 to 5. AWC increased exponentially with the increase in humidity and SNA content, among which NH4NO3, （NH4）2SO4, and NH4Cl contributed 58.5%, 18.4%, and 8.3%, respectively, due to their hygroscopicity. Aerosol pH, AWC, and NH3-NH4+ conversion promoted the gas-to-particle conversion of SO2 and NO2. In Changzhou, rich NH3-NH4+ were found to maintain relatively high pH values, push up AWC, and promote the heterogeneous reaction of SO2, whereas NO3- generation was dominated by a homogeneous reaction, which was accelerated by NH3. According to the simulation results, relatively noticeable changes in aerosol pH and AWC could be found by the reduction of up to 30% of NH3.

The Effect of Mixture Variation and Initial Temperature On the NH2* Thickness of Spherically Propagating Laminar Ammonia Flames

Abstract Interest in ammonia (NH3) in combustion has increased recently as a carbon-free fuel alternative. Understanding its combustion characteristics is crucial. One way to increase knowledge of ammonia combustion is by investigating the flame zone of a laminar flame. Using a high-spatial-resolution flame zone measurement technique developed by the current research group, the flame zone of different NH3-containing mixtures was measured experimentally. These measurements were achieved by investigating spherically propagating flames using a chemiluminescence imaging diagnostic with a focus on NH2* profiles. The effect of the fuel mixture on the profile shape was examined by investigating two different mixtures: an oxy-ammonia mixture consisting of NH3 + oxygen-enriched oxidizer with varying O2 concentrations from 25% to 40%, and a blend of NH3-H2 with NH3 concentrations (XNH3) varied from 0.5 to 0.8. Additionally, the effect of the initial temperature was investigated by varying it from 293 to 373 K. In all investigated mixtures, the initial pressure was fixed at 1 atm and the equivalence ratio at 1.0. The study revealed that increasing the O2 concentration in the oxy-ammonia mixture produced thinner flames, while increasing XNH3 in the NH3-H2 blend produced slightly thicker flames. Varying the initial temperature had different effects: it thinned the flame in the oxy-ammonia mixture and NH3-H2 blend, but slightly thickened the flame in the H2-NH3-N2 blend. The predicted NH2* profile thicknesses from chemical kinetics agreed with measurements, except for the H2-NH3-N2 blend.

Novel flexible chemiresistive ammonia sensors based on rGO/ZIF-8 composites deposited on conductive graphite sheets

This work presents novel investigations on room temperature chemiresistive ammonia (NH3) gas sensing capability of composite materials based on reduced graphene oxide (rGO) and ZIF-8 metal organic framework (MOF), deposited on flexible graphite substrate. These rGO/ZIF-8 composites synthesized via a facile one-pot wet chemical route were found to exhibit a fast, highly sensitive and reversible response over successive exposure cycles towards various concentrations of NH3. The enhanced response is attributable to the synergistic performance of the appreciably conductive rGO and the highly porous ZIF-8. ZIF-8 with its high specific surface area, microporous structure and hydrophobicity, serves to provide greater gas adsorptive capacity as well as resistance to effects of ambient moisture. rGO, on the other hand, has limited specific surface area due to π-π restacking of its sheets but it is capable of providing a conductive template to the hybrid material. Consequently, the NH3 gas sensing performance parameters of rGO/ZIF-8 were measured to be exceedingly better than those of bare rGO and ZIF-8 synthesized separately. A response of 15.98 % was recorded towards 10 ppm NH3 with response/recovery times as 2.8/6 s for the rGO/ZIF-8 composites. The enhanced gas sensing performance is credited to the formation of hierarchical pore structure which allows for greater adsorption at the micropore sites and faster diffusion through the mesopores. The effect of rGO loading in the hybrid materials was also assessed. The composite materials exhibited appreciable stability with respect to ambient aging. The adsorption behaviors and the resultant gas sensing mechanisms have also been discussed for the investigated materials.

Tracing N2O from dairy processing sludge amended soil with visualizing microscale heterogeneity of NH3 and pH (Short Communication)

Nitrous oxide (N2O) emissions from organic waste and animal slurry contribute to climate change and endanger our ecosystems. For the development of efficient mitigation technologies, in-depth knowledge of emission processes is needed. This can be obtained by non-destructive, temporal measurements of in-situ soil profiles and the transformation of ammonium (NH4+) during events of emissions. Planar optode imaging is a non-destructive measuring method that can be used to visualize spatiotemporal changes of ammonia (NH3) and pH in soil systems. In this study, soil amended with dairy processing sludge (DPS) was incubated in static chambers for 23 days, and GHG emissions, NH3 concentrations and pH in the soil were measured simultaneously over time. The aim was to investigate the potential of applying different planar optodes to provide information that gives insight into processes of N2O emissions. The DPS was applied to the soil as a surface layer (SL), with untreated soil as a control (CK). We were able to measure N2O emissions while monitoring spatiotemporal changes of soil pH and NH3 concentrations. The visualized microscale heterogeneity of the soil contributed to a better understanding of N2O emission processes. While technical challenges (e.g., humidity sensitivity of the NH3 optode and airtightness of the chambers) still need to be overcome, the method is a promising non-destructive method to study soil processes after application of different types of soil amendments.

NITRINET: A predictive model for nitrification in reclaimed water distribution in pressurised irrigation networks

In this work, a new model (NITRINET) to simulate nitrification processes in pressurised irrigation distribution networks fed with reclaimed water is developed and applied to the Tintín Irrigation District distribution network as case study (Montilla, southern Spain). The importance of this model relies on the fact that the nutrient chemical composition of reclaimed water varies spatially along the network. The water quality analyses carried out in the Irrigation District have shown that nitrate concentrations increase along the distribution network in contrast to the reduction observed in the ammoniacal forms. This confirms that nitrification processes occur inside the pipes. Thus, the model combines the hydraulic simulation of the distribution network and the modelling of nitrification processes to predict the concentration of ammoniacal nitrogen (NH4+-N) and nitric nitrogen (NO3--N) in water arriving at farms. This model is of great applicability to the irrigation sector, given that to carry out precision fertigation strategies and optimise the amount of fertiliser applied, it is necessary to determine the concentration of nutrients present in water arriving at farms. The nutrients that reclaimed water already carries must be considered when planning fertilisation. This allows for a reduction in the amount of fertiliser applied to the soil, which has a positive impact both on the environment and on farmers’ incomes. Simulations performed with NITRINET have shown promising results, predicting the concentration of NH4+-N and NO3--N in irrigation water with mean absolute errors of 1.49 mg·L−1 and 1.25 mg·L−1, respectively.

Soybean molasses can be used as a substitute for corn in grazing beef cattle supplements during the rainy season.

Soybean molasses (SBMO) is a byproduct derived from the production of soy protein concentrate, obtained through solubilization in water and alcohol. The utilization of SBMO as an animal feed ingredient shows promising potential, primarily due to its low cost and as a potential energy concentrate. This study aimed to assess the intake, digestibility, ruminal parameters (pH and ruminal ammonia - NH3), nitrogen retention (NR) and microbial protein synthesis in grazing beef cattle supplemented with SBMO as a substitute for corn during the rainy season. Five Nellore (10-month-old) bulls with an average initial weight of 246 ± 11.2kg were utilized in a 5 × 5 Latin square design. The animals were housed in five paddocks, each consisting of 0.34ha of Marandu grass (Urochloa brizantha). Five isonitrogenous protein-energy supplements (300g crude protein [CP]/kg supplement) were formulated, with SBMO replacing corn at varying levels (0, 0.25, 0.50, 0.75, or 1.00g-1g). The supplements were provided daily at a quantity of 2.0kg-1 animal. The inclusion of SBMO at any level of corn substitution did not significantly affect the intake of pasture dry matter or total dry matter (P > 0.10). Likewise, the intake of CP and, consequently, the ruminal concentration of NH3 did not differ among the SBMO levels. Increasing the inclusion of SBMO did not have a significant impact on NR (P > 0.10), indicating that animals receiving supplements containing 100% SBMO as a substitute for corn may perform similarly to animals receiving supplements with 100% corn (0% SBMO). Soybean molasses represents a viable alternative energy source for grazing beef cattle during the rainy season and can entirely replace corn without adversely affecting animal nutritional performance.

Preparation of slow-release carbon source fillers from agricultural solid waste for efficient nitrogen removal from municipal wastewater: Removal performance, microbial community and mechanisms

In this study, five types of agricultural wastes, were used as alternative materials for slow-release carbon source, alternative materials were prepared as slow-release carbon source fillers (ZCF) using a no-sintering method, and studied by leaching elements, carbon release, nitrification and denitrification potential, and bio-attachment performance, walnut shell-based filler was found to have better performance in terms of persistence of carbon release, impact stability, carbon biochemistry and green safety. When HRT was 8 h in H-O, 12 h in H-A, and R was 100 % and C/N was 2 in H-Z BAF, the average concentrations of effluent NH4+-N and TN were only 0.4 and 12.2 mg/L, which achieved the high efficiency and economy of H-Z BAF under low C/N conditions. The newly prepared ZCF had a rougher outer surface, a uniformly distributed flocculent structure and numerous microporous channels on the inner surface, and the carbon source inside the filler was degraded or transformed by microorganisms, as compared to the filler in H-O and H-A at the later stage of use. The abundance of nitrifying bacteria, denitrifying bacteria was increased in the H-Z BAF, and that functional CAZymes were enriched and involved in the degradation of cellulose and hemicellulose, can be efficiently utilized by microorganisms. This study provides technical support for the development of cheap, stable and efficient slow-release carbon sources and their application in denitrification of municipal wastewater plant tailwater.

Comparative effects of ammonium nitrogen on perchlorate degradation performance under heterotrophic condition with different carbon sources

Perchlorate (ClO4-) mainly exists in the form of ammonium perchlorate in industrial production. However, the degradation mechanisms of different concentrations of ammonium nitrogen (NH4+-N) and ClO4- mixed pollutants in the environment are not well understood. This study aims to explore the potential of different types of carbon sources for ClO4- and NH4+-N biodegradation. Experimental results showed that the concentration and type of carbon sources are decisive to simultaneous removal of NH4+-N and ClO4-. Under condition of C(COD)/C(ClO4-) ratio of 21.15 ± 4.40, the simultaneously removal efficiency of ClO4- and NH4+-N in acetate (Ace) was relatively higher than that in methanol (Met). C(NH4+-N)/C(ClO4-) ratio of 9.66 ± 0.51 and C(COD)/C(ClO4-) ratio of 2.51 ± 0.87 promoted ClO4- reduction in glucose-C (Glu-C). However, high concentration of Glu could cause pH decrease (from 7.57 to 4.59), thereby inhibiting ClO4- reduction. High-throughput sequencing results indicated that Proteobacteria and Bacteroidetes have made a major contribution to the simultaneous removal of NH4+-N and ClO4-. They are two representative bacterial phyla for participating in both ClO4- reduction and denitrification. Notably, the abundance of main ClO4- degrading bacteria (such as Proteobacteria, Chloroflexi, and Firmicutes) significantly increased by 528.57 % in Glu-C. It can be inferred that the concentration of carbon source and NH4+-N were the most important factors determining the removal efficiency of ClO4- by influencing changes in the core microbial community. This study will provide new techniques and mechanistic insights for the simultaneous removal of mixed ClO4- and nitrogen pollutants, which can also provide theoretical support for innovation in future biological treatment processes.

Polyaniline/ZnO heterostructure-based ammonia sensor self-powered by electrospinning of PTFE-PVDF/MXene piezo-tribo hybrid nanogenerator

Self-powered sensors are receiving increasing attention for their environmental friendliness and energy efficiency. In this work, self-powered polyaniline/zinc oxide (PANI/ZnO) heterostructure-based ammonia (NH3) sensor was driven by polytetrafluoroethylene (PTFE)-polyvinylidene fluoride/Ti3C2Tx (PVDF/MXene) piezo-tribo hybrid nanogenerator (PTNG) at room temperature. PVDF/MXene nanofiber membranes were prepared using electrospinning technology to construct a PTFE-PVDF/MXene PTNG. This enhances the effective contact area and dielectric properties of the composite film, thereby increasing the surface charge density. Additionally, the synergy between the triboelectric and piezoelectric effects significantly improves the output performance of the PTNG, effectively enabling energy harvesting for wearable devices. In addition, ZnO/PANI composite materials with a large specific surface area and high active sites were prepared, and a self-powered ammonia sensor was constructed based on the impedance matching effect. Furthermore, by constructing a PANI/ZnO p-n heterojunction, the number of active sites has been increased, significantly enhancing the sensing performance. The sensor has a minimum detection limit of 0.1 ppm, and at an NH3 concentration of 10 ppm, the response rate reaches 96.1 %. This study provides insights for the development of self-powered gas detection systems and holds significant research and practical value in enhancing the performance of NH3 sensors.