Ammonia Loss Research Articles

Aerobic Polishing of Liquid Digestate for Preparation of Hydroponic Fertiliser

Nutrient pollution—mainly nitrogen and phosphorus—caused by organic waste continues to impact the environment. The implementation of a circular economy is integral to alleviating these effects. Liquid digestate, which is a byproduct of anaerobic digestion (a waste-valorising process), is a nutrient-dense organic fertiliser with vast applications in agriculture. Using an aerobic polishing unit, this study developed a viable method for the preparation of a hydroponic fertiliser by investigating the effect of pH on the nutrient recycling capabilities of said system. The heterotrophic bacteria present in the biofilm, identified by 16S gene sequencing, are responsible for 90% of organic carbon (as TOC) removal with minimal ammonium loss. This is ideal for promoting optimal nitrification in hydroponic systems in the absence of organic carbon to ensure plant growth is not affected. Although pH 8 was found to be ideal for batch operation, this pH condition resulted in decreased microbial longevity and, therefore, increased ammonification due to microbial decay. Therefore, continuous operation at pH 7 proved to be a better option owing to the ammonium-rich effluent (>220 mg/L) which was produced, which is on par with the nitrogen concentration of a Hoagland solution. The continuous carbon polishing of liquid digestate provides an efficient way of utilising organic fertilisers in hydroponic systems.

High sugarcane yield and large reduction in reactive nitrogen loss can be achieved by lowering nitrogen input

Nitrogen (N) fertilisation is critical for sugarcane crop production. Consequently, overuse of N fertiliser in sugarcane is widespread and it is most prevalent in China. Yet, a comprehensive analysis of sugarcane N balance accounting for different reactive N (Nr) loss pathways, crop N use and soil N retention using 15N labelled fertilisers under commercial high-input cropping conditions is lacking. A two-year field experiment with 5 N levels (0–560 kg N ha−1; N0, N210, N300, N390, N560) was conducted to quantify the effect of N rate on sugarcane yield, Nr loss through different loss pathways, crop N use and soil N retention, and to identify an optimal N rate that sustain high yield whilst reducing Nr loss in Southern China. The results showed that optimal N rate (N300) had similar yield compared with farmer practice (N560) for the plant crop and the ratoon crop. Nitrogen leaching and ammonia loss were increased significantly with increase in N rate, with farmer practice recording the highest Nr loss. Compared with farmer practice, under optimal N application, N leaching was reduced from 211 kg ha−1 to 107 kg ha−1 and from 244 kg ha−1 to 165 kg ha−1 for the plant and ratoon crops, respectively. The ammonia volatilization from the plant crop and the ratoon crop in the optimal N treatment was 24.8 kg ha−1 and 27.0 kg ha−1, respectively, which are considerably less compared with the emission from the farmer practice. There was no significant difference in nitrous oxide emission between optimal N rate and farmer practice. 15N labelling studies showed that crop N recovery, soil N residue and fertiliser N lost at the optimal N rate were 20.9%, 24.9% and 54.2%, respectively, as opposed to 12.5%, 14.8% and 72.7%. respectively, under farmer practice. To the best of our knowledge, this study forms the first comprehensive evaluation of sugarcane N balance accounting Nr loss, N use and native N soil stock covering a wide range of N supply simultaneously in the plant and ratoon crops under commercial crop production condition. This study thus provides very valuable new knowledge not only for crop N supply optimisation in high-input sugarcane production systems as in China but also for sugarcane greenhouse gas accounting studies particularly from climate change mitigation and bioenergy production context.

Comparing the adsorption of micropollutants on activated carbon from anaerobically stored, organics-depleted, and nitrified urine

Separate collection and treatment of urine optimizes nutrient recovery and enhances micropollutant removal from municipal wastewater. One typical urine treatment train includes nutrient recovery in three biological processes: anaerobic storage, followed by aerobic organics degradation concurrently with nitrification. These are usually followed by activated carbon adsorption to remove micropollutants. However, removing micropollutants prior to nitrification would protect nitrifiers from potential inhibition by pharmaceuticals. In addition, combining simplified biological treatment with activated carbon adsorption could offer a cheap and robust process for removing micropollutants where nutrient recovery is not the first priority, as a partial loss of ammonia occurs without nitrification. In this study, we investigated whether activated carbon adsorption could also take place between the three biological treatment steps. We tested the effectiveness of micropollutant removal with activated carbon after each biological treatment step by conducting experiments with anaerobically stored urine, organics-depleted urine, and nitrified urine. The urine solutions were spiked with 19 pharmaceuticals: amisulpride, atenolol, atenolol acid, candesartan, carbamazepine, citalopram, clarithromycin, darunavir, diclofenac, emtricitabine, fexofenadine, hydrochlorothiazide, irbesartan, lidocaine, metoprolol, N4-acetylsulfamethoxazole, sulfamethoxazole, trimethoprim, venlafaxine, and two artificial sweeteners, acesulfame and sucralose. Batch experiments were conducted with powdered activated carbon (PAC) to determine how much activated carbon achieve which degree of micropollutant removal and how organics, pH, and speciation change from ammonium to nitrate influence adsorption. Micropollutant removal was also tested in granular activated carbon (GAC) columns, which is the preferred technology for micropollutant removal from urine. The carbon usage rates (CUR) per person were lower for all urine solutions than for municipal wastewater. The results showed that organics depletion would be needed when micropollutant removal was the sole aim of urine treatment, as the degradation of easily biodegradable organics prevented clogging of GAC columns. However, CUR did hardly improve with organics-depleted urine compared to stored urine. The lowest CUR was achieved with nitrified urine. This resulted from the additional organics removal during nitrification and not the lower pH or the partial conversion of ammonium to nitrate. In addition, we showed that the relative pharmaceutical removal in all solutions was independent of the initial pharmaceutical concentration unless the background organics matrix changed considerably. We conclude that removal of micropollutants in GAC columns from organics-depleted urine can be performed without clogging, but with the drawback of a higher carbon usage compared to removal from nitrified urine.

Rice yield in Costa Rican Central Pacific did not improve with a urease inhibitor

Urea is widely used as nitrogen (N) source for rice fertilization in Costa Rica, despite its low efficiency linked to ammonia losses. To assess urea management alternatives, two field experiments were conducted in the Central Pacific region of Costa Rica to study the effect of N-(n-butyl) thiophosphoric triamide (NBPT) on rice yield and N use efficiency (NUE). In Experiment 1 (Exp1) three tillage treatments (commercial-CT-, reduced-RT-, and reduced tillage with previous subsoiler-RTS-) were evaluated with three N managements: control (without N), urea at 124 kg N ha-1 with and without NBPT. In Experiment 2 (Exp2), a 100 kg N ha-1 rate (with and without NPBT) was evaluated along with a control (without N). NUE was estimated using 15N urea isotopic labeling technique for both trials. In Exp1, a significant difference of 4.8% in NUE for grain was observed among urea with and without NBPT, but no tillage effect was observed. No statistically significant differences were observed in yield among the fertilization treatments (Exp1: 3.56 ± 0.98 t ha-1 for urea and 3.85 ± 0.85 t ha-1 for urea with NBPT; Exp2: 3.38 ± 0.39 t ha-1 for urea and 3.40 ± 0.58 t ha-1 for urea with NBPT) or due to different tillage practices (CT: 3.33 ± 0.79 t ha-1, RT: 3.56 ± 0.74 t ha-1, and RTS: 4.23 ± 0.98 t ha-1). Although the NBPT is a viable option to reduce ammonia losses, its adoption in tropical conditions might be restricted by the small impact on yield.

Measurement of Light-Duty Vehicle Exhaust Emissions with Light Absorption Spectrometers

Light-duty vehicle emission regulations worldwide set limits for the following gaseous pollutants: carbon monoxide (CO), nitric oxides (NOX), hydrocarbons (HCs), and/or non-methane hydrocarbons (NMHCs). Carbon dioxide (CO2) is indirectly limited by fleet CO2 or fuel consumption targets. Measurements are carried out at the dilution tunnel with “standard” laboratory-grade instruments following well-defined principles of operation: non-dispersive infrared (NDIR) analyzers for CO and CO2, flame ionization detectors (FIDs) for hydrocarbons, and chemiluminescence analyzers (CLAs) or non-dispersive ultraviolet detectors (NDUVs) for NOX. In the United States in 2012 and in China in 2020, with Stage 6, nitrous oxide (N2O) was also included. Brazil is phasing in NH3 in its regulation. Alternative instruments that can measure some or all these pollutants include Fourier transform infrared (FTIR)- and laser absorption spectroscopy (LAS)-based instruments. In the second category, quantum cascade laser (QCL) spectroscopy in the mid-infrared area or laser diode spectroscopy (LDS) in the near-infrared area, such as tunable diode laser absorption spectroscopy (TDLAS), are included. According to current regulations and technical specifications, NH3 is the only component that has to be measured at the tailpipe to avoid ammonia losses due to its hydrophilic properties and adsorption on the transfer lines. There are not many studies that have evaluated such instruments, in particular those for “non-regulated” worldwide pollutants. For this reason, we compared laboratory-grade “standard” analyzers with FTIR- and TDLAS-based instruments measuring NH3. One diesel and two gasoline vehicles at different ambient temperatures and with different test cycles produced emissions in a wide range. In general, the agreement among the instruments was very good (in most cases, within ±10%), confirming their suitability for the measurement of pollutants.

Experimental and theoretical study on reactive oxygen and nitrogen species generation in plasma bubbles with ammonia solution

AbstractLow‐temperature plasma‐assisted nitrogen fixation is a promising method for organic‐polluted soil/water remediation, that improves N‐fertilizer performance and mitigates ammonia emission. Our study explores a novel approach: plasma bubbles‐assisted ammonia treatment, and investigates the role played by various reactive substances in the oxidation of ammonia. The specific reaction pathways and the contribution of OH radicals in the ammonia oxidation process in O2 plasma treatment are determined. Air emerges as the optimal feed gas owing to a positive feedback loop in the reaction between NO2− and H2O2. Air plasma treatment enriches N in the ammonia solution and minimizes ammonia loss during treatment. This study offers new insights into an advanced plasma‐assisted ammonia treatment method.

Ammonia Retention in Biowaste via Low-Temperature-Plasma-Synthesized Nitrogen Oxyacids: Toward Sustainable Upcycling of Animal Waste.

Sustainable fertilizer production is a pressing challenge due to a growing human population. The manufacture of synthetic nitrogen fertilizer involves intensive emissions of greenhouse gases. The synthetic nitrogen that ends up in biowaste such as animal waste perturbs the nitrogen cycle through significant nitrogen losses in the form of ammonia volatilization, a major human health and environmental hazard. Low-temperature air-plasma treatment of animal waste holds promise for sustainable fertilizer production on farmlands by enabling nitrogen fixation via ionization, forming nitrogen oxyacids. Although the formation of nitrogen oxyacids in plasma treatment of water is well-established, the extent of nitrogen oxyanion enrichment in animal waste and its downstream effects on acidifying the waste remain elusive because many compounds found in complex biowaste media may interfere with absorbed NOx species. This work aims to establish that plasma treatment of dairy manure can suppress ammonia loss by volatilization via acidification of animal waste while enriching the waste in total nitrogen due to nitrogen retained in ammonia as well as adding nitrogen oxyacids by reacting NOx with the aqueous slurry. To this end, air-plasma effluent containing NOx is bubbled through dairy manure, which is then analyzed for changes in the nitrogen oxyanion content and pH. Increasing the plasma treatment time results in more acidic manure, reduced ammonium content in the downstream acid trap, and increased nitrogen oxyanion content, where the yield of nitrogen oxyanion from absorbed NOx species is approximately 100%. Increased plasma treatment also led to an increase in the total Kjeldahl nitrogen and the total nitrogen. These results indicate that plasma treatment of animal waste can significantly suppress ammonia pollution from animal husbandry facilities such as dairy farms while upcycling animal waste as a rich organic source of nitrogen.

Enhanced internal circulation for struvite crystallization in a novel air-lift circulation reactor with Venturi structure for ammonium recovery from wastewater

Nutrient recovery as struvite from wastewater in is quite feasible. The mystery of ammonia loss has received much attention, and inadequate struvite purity is frequently present. A struvite fluidized bed reactor (FBR) was constructed and operating conditions were optimized in order to minimize ammonia nitrogen loss. The properties of the struvite produced by the reactor and the optimum operating conditions for ammonia recovery were also assessed. According to simulations, the Venturi tube increased turbulent flow energy to 4.5 × 10−2 m2·s−2. This significantly improved the mass transfer efficiency. A significant difference between the wall shearing rate (50–319 s−1) and the fluid shearing rate (2–10 s−1) prevented the crystal particles from colliding with the vessel wall. The reactor reached stable operation under conditions of N/P = 1:1 and pH = 9.0. The purity of the obtained struvite was 96.5 %, with an ammonia nitrogen conversion rate of 89.67 %, where the struvite crystals could grow to 82 μm within 24 h. It was concluded that the new FBR with air-lift internal circulation function was feasible for improving struvite crystal growth and purification. It is possible to achieve high ammonia nitrogen recovery efficiency at low cost.

Optimizing Nitrogen Sources in Top Dressing for Wheat: Field Study on Growth, Yield, and Ammonia Volatilization.

In alkaline calcareous soils, ammonia volatilization is the primary nitrogen (N) loss process, resulting in the reduced N use efficiency of crops. This study aimed at assessing the impact of different N sources for top dressing on ammonia volatilization, as well as their effects on wheat growth and yield over two years. In each year, half of the recommended N was applied as a basal dose using diammonium phosphate (DAP) and urea. The remaining half was top-dressed 35 days after sowing with various sources: prilled urea (PU), granular urea (GU), ammonium sulfate (AS), and calcium ammonium nitrate (CAN) in the first year; PU, urea coated with a urease inhibitor from 20 g (VnU-20) and 40 g (VnU-40) leaves of Vachellia nilotica, biochar-coated urea (BU), and urease inhibitor paraphenylenediamine-coated urea (PPDU) in the second year. Ammonia volatilization losses were tracked for up to 12 weeks from sowing. Ammonia losses from basal-applied N remained consistent in both years, comprising around 4% of the applied N. In the first year, top-dressed AS resulted in the highest losses, followed by GU, while losses from urea and CAN were statistically similar. In the second year, coated fertilizers showed lower ammonia losses compared to PU, with VnU-40 displaying the least losses, 48% less than PU. Nitrogen concentration in wheat grain and straw exhibited a negative correlation with ammonia losses. The choice of top-dressed N source influenced tillering, biological, straw, and grain yields of wheat. In the first year, CAN provided maximum yield benefits, and in the second year, VnU-20 exhibited 27% more grain yield than PU. These findings suggest that top dressing with coated urea, especially VnU-20, has the potential to reduce ammonia losses, improve crop nitrogen status, and enhance economic yield compared to other nitrogen sources.

Construction and Evaluation of The Wind Tunnel Technique for Estimating Ammonia Volatilization from Land

Agriculture is mainly responsible for ammonia (NH3) volatilization. Among all agricultural activities, livestock and especially animal manures are the most important sources of NH3 emissions. Manure application which not only exacerbate greenhouse gas emissions, but also leads to eutrophication of water bodies. Many studies have shown that surface application of manure can lead to large ammonia losses and run off, on the other hand that tillage can substantially reduce these losses. It is necessary to determine ammonia flux from manure-amended soils to improve management manure handling practices for minimizing agriculture’s impact on the environment. From this point of view, one of the direct measured method was used to determine this volatilization. The objections of this work were: i) The design, construction, physical calibration, and operation of the little wind tunnels. ii) Recover ammonia loss from bovine slurry by little wind tunnel method. iii) Determine the effect of slurry application depth on ammonia emission. The little wind tunnel system consisted of plastic canopy covering the treatment area (2 m long by 0.5 m wide). By was using a fan, it was imitated the natural wind speed in the test area (1-1.5 m/s). Nitrogen losses were measured with this method in surface application, 50 mm and 100 mm subsurface. In the surface application, the highest ammonia emission was observed. It was approximately 68% higher in compared to another methods. There is significantly (P=0.05) different in the ammonia emission, between the surface apply method and injection manure in soil methods. But There isn’t any significantly different between ammonia emission amount in injection subsurface methods (100 mm and 50 mm deep).

Urease inhibitors technologies as strategy to mitigate agricultural ammonia emissions and enhance the use efficiency of urea-based fertilizers

Experiments were conducted to evaluate the stability and degradation of NBPT under storage conditions and to quantify urease activity, ammonia losses by volatilization, and agronomic efficiency of urea treated with different urease inhibitors, measured in the field. Experiments included urea treated with 530 mg NBPT kg−1 (UNBPT) in contact with six P-sources (monoammonium phosphate-MAP; single superphosphate; triple superphosphate; P-Agrocote; P-Phusion; P-Policote), with two P-concentrations (30; 70%); the monitoring four N-technologies (SoILC; Limus; Nitrain; Anvol); and the application of conventional urea (UGRAN) or urea treated with urease inhibitors as topdressing in three maize fields, at three N rates. It is concluded that: the mixture of UNBPT and P-fertilizers is incompatible. When MAP granules were coated to control P-release (P-Agrocote), the degradation of NBPT was moderate (approximately 400 mg kg−1 at the end of the storage test). SoILC and Limus solvent technologies extended the NBPT half-life by up to 3.7 and 4.7 months, respectively. Under field, each inhibition technology reduced urease activity, and lowered the intensity of ammonia emission compared to UGRAN by 50–62%. Our results show that the concentration of NBPT is reduced by up to 53.7% for mixing with phosphates. In addition, even with coatings, the storage of mixtures of urea with NBPT and phosphates should be for a time that does not reduce the efficiency of the inhibitor after application, and this time under laboratory conditions was 168 h. The reduction of NBPT concentration in urea is reduced even in isolated storage, our results showed that the half-life time is variable according to the formulation used, being 4.7, 3.7, 2.8 and 2.7 days for Limus, SoILC, Nitrain and Anvol, respectively. The results of these NBPT formulations in the field showed that the average losses by volatilization in the three areas were: 15%, 16%, 17%, 19% and 39% of the N applied, for SoILC, Anvol, Nitrain, Limus and urea, respectively. The rate of nitrogen application affected all agronomic variables, with varied effects in Ingaí. Even without N, yields were higher than 9200 kg ha−1 of grains. The increase in nitrogen rates resulted in linear increases in production and N removal in Luminárias and Ingaí, but in Lavras, production decreased above 95.6 kg ha−1 of N. The highest production in Lavras (13,772 kg ha−1 of grains) occurred with 100 kg ha−1 of N. The application of Anvol reduced the removal of N in Ingaí.

Ammonium loss microbiologically mediated by Fe(III) and Mn(IV) reduction along a coastal lagoon system

Anaerobic ammonium oxidation, associated with both iron (Feammox) and manganese (Mnammox) reduction, is a microbial nitrogen (N) removal mechanism recently identified in natural ecosystems. Nevertheless, the spatial distributions of these non-canonical Anammox (NC-Anammox) pathways and their environmental drivers in subtidal coastal sediments are still unknown. Here, we determined the potential NC-Anammox rates and abundance of dissimilatory metal-reducing bacteria (Acidomicrobiaceae A6 and Geobacteraceae) at different horizons (0–20 cm at 5 cm intervals) of subtidal coastal sediments using the 15N isotope-tracing technique and molecular analyses. Sediments were collected across three sectors (inlet, transition, and inner) in a coastal lagoon system (Bahia de San Quintin, Mexico) dominated by seagrass meadows. The positive relationship between 30N2 production rates and dissimilatory Fe and Mn reduction provided evidence for Feammox’s and Mnammox’s co-occurrence. N loss through NC-Anammox was detected in subtidal sediments, with potential rates of 0.07–0.62 μg N g−1 day−1. NC-Anammox process in vegetated sediments tended to be higher than those in adjacent unvegetated ones. NC-Anammox rates showed a subsurface peak (between 5 and 15 cm) in the vegetated sediments but decreased consistently with depth in the adjacent bare bottoms. Thus, the presence/absence of seagrasses and sediment characteristics, particularly the availability of organic carbon and microbiologically reducible Fe(III) and Mn(IV), affected the abundance of dissimilatory metal-reducing bacteria, which mediated NC-Anammox activity and the associated N removal. An annual loss of 32.31 ± 3.57 t N was estimated to be associated with Feammox and Mnammox within the investigated area, accounting for 2.8–4.7% of the gross total import of reactive N from the ocean into the Bahia de San Quintin. Taken as a whole, this study reveals the distribution patterns and controlling factors of the NC-Anammox pathways along a coastal lagoon system. It improves our understanding of the coupling between N and trace metal cycles in coastal environments.

A physics-informed long short-term memory (LSTM) model for estimating ammonia emissions from dairy manure during storage

Manure management on dairy farms impacts how farmers maximize its value as fertilizer, reduce operating costs, and minimize environmental pollution potential. A persistent challenge on many farms is minimizing ammonia losses through volatilization during storage to maintain manure nitrogen content. Knowing the quantities of emitted pollutants is at the core of designing and improving mitigation strategies for livestock operations. Although process-based models have improved the accuracy of estimating ammonia emissions, complex systems such as manure storage still need to be solved because some underlying science still needs work. This study presents a novel physics-informed long short-term memory (PI-LSTM) modeling approach combining traditional process-based with recurrent neural networks to estimate ammonia loss from dairy manure during storage. The method entails inverse modeling to optimize hyperparameters to improve the accuracy of estimating physicochemical properties pertinent to ammonia's transport and surface emissions. The study used open data sets from two on-farm studies on liquid dairy manure storage in Switzerland and Indiana, U.S.A. The root mean square errors were 1.51 g m−2 h−1 for the PI-LSTM model, 3.01 g m−2 h−1 for the base compartmental process-based (Base-CPBM) model, and 2.17 g m−2 h−1 for the hyperparameter-tuned compartmental process-based (HT-CPBM) model. In addition, the PI-LSTM model outperformed the Base-CPBM and the HT-CPBM models by 20 to 80 % during summer and spring, when most annual ammonia emissions occur. The study demonstrated that incorporating physical knowledge into machine learning models improves generalization accuracy. The outcomes of this study provide the scientific basis to improve policymaking decisions and the design of suitable on-farm strategies to minimize manure nutrient losses on dairy farms during storage periods.

Intramolecular interactions and the neutral loss of ammonia from collisionally activated, protonated ω-aminoalkyl-3-hydroxyfurazans.

Gas phase fragmentation reactions of monoprotonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan were investigated to examine potential interactions between functional groups. The two heterocyclic alkyl amines were ionized by electrospray ionization (ESI, positive mode) and fragmented using tandem mass spectrometry (MS/MS). The fragmentation pathways were characterized using pseudo MS3 experiments, precursor-ion scans, and density functional computations. For both heterocyclic ions, loss of ammonia was the only fragmentation process observed at low collision energies. Computational analysis indicated that the most feasible mechanism was intramolecular nucleophilic displacement of ammonia from the protonated ω-aminoalkyl side chain by N5 of the furazan ring. The alkylated nitrogen in the resulting bicyclic product ion facilitated N-O bond cleavage; subsequent neutral losses of nitric oxide (NO) and carbon monoxide (CO) occurred by homolytic bond cleavages. Next in the multistep sequence, neutral loss of ethylene from a radical cation was observed. A less favorable, competing fragmentation pathway of protonated 4-(3-aminopropyl)-3-hydroxyfurazan was consistent with cleavage of the 3-hydroxyfurazan ring and losses of NO and CO. Overall, the similar fragmentation behavior found for protonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan differed from that previously characterized for furazan analogs with shorter alkyl chains. These observations demonstrate that a small change in the structure of multifunctional, heterocyclic alkyl amines may significantly influence interactions between distinct functional groups and the nature of the fragmentation process.

Experimental and model-based comparison of wind tunnel and inverse dispersion model measurement of ammonia emission from field-applied animal slurry

Volatilization of ammonia from field-applied animal slurry is a significant problem. Accurate emission measurements are needed for inventories and research, but are not provided by all measurement methods. Wind tunnels may give emission values substantially above or below micrometeorological results, which have been shown to be accurate. This limitation reduces the utility of wind tunnel results, which make up a large fraction of available measurements. The present work focused on understanding wind tunnel measurement error by comparing micrometeorological and wind tunnel measurements with the aid of a semi-empirical model. Ammonia loss from digestate after field application was measured in high time resolution in three field trials using wind tunnels and the backward Lagrangian stochastic (bLS) dispersion technique simultaneously. Differences in measured emission were interpreted using the ALFAM2 model, and measurements were used to evaluate the model. Results showed that wind tunnel and bLS methods provided different cumulative emission estimates, although there were similarities in measured emission dynamics. The ALFAM2 model was generally able to reproduce emission dynamics for both measurement methods, but only when differences in mass transfer between the two methods were incorporated in an experimental parameter set. This important result suggests that: 1) the simple structure of the ALFAM2 model captures the essential physical and chemical processes controlling emission and 2) the two measurement methods differ only (or mainly) through mass transfer above the slurry/soil surface and rain. Therefore, with careful selection of wind tunnel air flow it should be possible to approximately match emission that occurs under open-air conditions. But without temporal variation in air flow, actual emission dynamics cannot be captured. This work provides a template for integrating and comparing measurements from different methods, and suggests it is possible to use wind tunnel measurements for model evaluation and even parameter estimation.

Effect of a Prolonged-Release System of Urea on Nitrogen Losses and Microbial Population Changes in Two Types of Agricultural Soil.

Urea is the nitrogen-containing fertilizer most used in agricultural fields; however, the nutrient given by the urea is lost into the environment. The aim of this research was to determine the effect of two soil textures by applying a prolonged-release system of urea (PRSU) on the N losses. This research shows an important decrease of the nitrate and ammonium losses from 24.91 to 87.94%. Also, the microbiological population increases after the application of the PRSU. It was concluded that both soil textures presented the same loss-reduction pattern, where the N from the nitrates and ammonium was reduced in the leachates, increasing the quality of the soil and the microbial population in both soil textures after the PRSU application.

Capture of NH3 using air plasmas to form NH4NO3 for N recycling: Impact factors and mechanisms

Ammonia loss results in significant resource waste and environmental pollution. In this study, we proposed and explored the way of using air plasmas to capture NH3 to form NH4NO3 for N recycling under different reaction modes, discharge powers, and gas flow rates. The reaction mechanisms under different modes were also revealed. A needle-needle discharge driven by AC power was used and ammonia gas was utilized to simulate the volatilized ammonia. Notably, white particles were observed during Mode 1 and Mode 2 (these particles gradually disappeared over time in Mode 2), while no particles or significant NOx were detected in Mode 3 throughout the process. The quantitative NH4NO3 yield was significantly influenced by discharge power and NH3 flow rate, reaching its highest value in Mode 1 at 24 W and 20 sccm in this investigation. Directly mixing the air discharge products with NH3 in Mode 1 under the threshold decomposition temperature of NH4NO3 leads to the stable formation of NH4NO3. Discharging in the NH3/air mixture will inhibit the generation of NOx and further restrain the NH4NO3 formation in Mode 2 and 3. Additionally, the temperature rises during discharge and also decomposes NH4NO3, resulting in unstable NH4NO3 formation in Mode 2.

Glauconitic Siltstone: additive for ammonia retention and reduction of nitrogen volatilization loss

Glauconitic siltstone is sedimentary rock used as raw material to produce a multinutrient fertilizer that can combine with urea to increase their agronomic efficiency. The purpose of this study was to evaluate glauconitic siltstone as additive to reduce nitrogen losses by ammonia volatilization in nitrogen fertilizers. The experiment used randomized block, in a portion subdivided over time, following a 6 x 8 factorial with four replications and treatments comprising glauconitic siltstone mixture at a dose of 100 kg N ha-1 (control, without the application of nitrogen; conventional urea – 45% N; commercial fertilizer registered with the trade name of Super N®; urea with addition of glauconitic siltstone: 9% N; 20 and 31% N) and the remaining portion divided in the collection time at 3, 6, 9, 12, 15, 18, 24 and 30 days after fertilizer application. The collection of the volatilized ammonia was made in a semi-opened free static chamber. The use of glauconitic siltstone associated with urea provided a reduction in loss by volatilization from 10 to 27% in relation to conventional urea. The treatments with application of urea with the urease inhibitor showed the lowest volatilization rate and delay in the volatilization peak, which occurred 17 days after fertilizer application. In addition to providing nutrients to the plants, glauconitic siltstone reduces ammonia losses.

Modelling potential human exposure to the urease inhibitor NBPT through the environment-food pathway

The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) has recently attracted a lot of attention attributing to its efficiency in reducing ammonia loss from urea fertiliser applied to temperate grassland soils. Ammonia gas lost to the environment causes soil acidification, eutrophication and contributes to global warming through increased greenhouse gas emissions and ozone layer depletion. The active chemical NBPT blocks the soil microbial enzyme (urease) and reduces ammonia emission. Furthermore, NBPT’s use in agriculture might benefit farmers by reducing reliance on expensive nitrate fertiliser and aiding in a shift to more urea-based fertiliser (using NBPT co-applied with urea is more cost-effective). The present study was carried out to characterise the potential transfer of NBPT from grass to liquid milk and compute the associated human health risks. Using probabilistic risk assessment techniques, an exposure assessment model was developed to calculate the Estimated Daily Intake (EDI) of NBPT from milk, following co-application of NBPT with a urea N-fertiliser. Results show that the predicted mean concentration of NBPT in milk is 2.5 × 10−8 mg NBPT/kg milk, while the mean daily intake (EDI) of NBPT is 5 × 10−11 mg NBPT /kg BW/day). Back-calculations revealed that, under the studied conditions, for the EDI to exceed ADI of 3 × 10−2 mg NBPT/kg BW/ day, the NBPT application rate would need to exceed the NBPT fertiliser limit (0.09–0.2% by mass of urea nitrogen) set in the Commission Regulation (EC) No 1107/2008, and the bio-transfer factor would need to be over 100% (implausible). Sensitivity analysis revealed soil pH (SPH), phytoaccumulation factor (PF), NBPT permissible levels in fertiliser (NBPT%), pasture cover (P), and grazing rotation length (t) as critical factors influencing the EDI of NBPT. The present study concludes that NBPT presents negligible risk to human health under the conditions and assumptions studied.

Artefacts in Field Trial Research—Lateral Ammonia Fluxes Confound Fertiliser Plot Experiments

Agricultural ammonia (NH3) emissions can have serious environmental impacts, lower fertiliser nitrogen-use efficiencies, and cause economic losses. NH3 losses may not only occur directly from organic fertilisers such as biogas digestates when applied to crops, the crops themselves may also be a source of ammonia emissions. Wheat yields from 14 years of an organic small plot fertiliser trial fertilised with biogas digestate were analysed to determine if there was significant lateral N transfer between plots. A simple NH3 loss/gain model was developed to calculate possible N gains and losses via NH3 volatilisation from the applied digestate. This model was tested using NH3 volatilisation measurements. In addition, 15N isotope measurements of crop biomass were used to analyse plant N uptake. While digestate fertilisation increased wheat yields, yield patterns indicated that NH3 emissions from plots fertilised with biogas digestate affected yields in neighbouring unfertilised plots. Measurements of ammonia losses and gains in the field validated our modelling results, showing that 55% of digestate NH4+-N was volatilised. 15N isotope analysis indicated that crops took up as much as 30 kg ha−1 NH3-N volatilised from digestate, and that plots closer to fertilised plots took up more of this NH3-N than crops further away from fertilised plots. Our results imply that neither the results from the fertilised plots nor from the unfertilised plots are without bias. To avoid inadvertently introducing artefacts into fertiliser field trials, plot sizes need to be increased and treatments situated further apart.