Ammonia Loss Research Articles

Climate change may interact with nitrogen fertilizer management leading to different ammonia loss in China's croplands.

Despite research into the response of ammonia (NH3 ) volatilization in farmland to various meteorological factors, the potential impact of future climate change on NH3 volatilization is not fully understood. Based on a database consisting of 1063 observations across China, nonlinear NH3 models considering crop type, meteorological, soil and management variables were established via four machine learning methods, including support vector machine, multi-layer perceptron, gradient boosting machine and random forest (RF). The RF model had the highest R2 of 0.76 and the lowest RMSE of 0.82 kg NH3 -N ha-1 , showing the best simulation capability. Results of model importance indicated that NH3 volatilization was mainly controlled by total input of N fertilizer, followed by meteorological factors, human managements and soil characteristics. The NH3 emissions of China's cereal production (paddy rice, wheat and maize) in 2018 was estimated to be 3.3Mt NH3 -N. By 2050, NH3 volatilization will increase by 23.1-32.0% under different climate change scenarios (Representative Concentration Pathways, RCPs), and climate change will have the greatest impact on NH3 volatilization in the Yangtze river agro-region of China due to high warming effects. However, the potential increase in NH3 volatilization under future climate change can be mitigated by 26.1-47.5% through various N fertilizer management optimization options.

Features and Applications of Urine Stabilization Methods: A Review

The recovery of nutrients from unconventional water such as domestic sewage is considered as a sustainable solution to environmental sanitation, personal hygiene, water, and food safety issues. Source separation of urine and the sequenced treatment techniques are the promising approaches to recover the resources from this unconventional water. However, in the storage of urine, urea is hydrolyzed under the action of urease, resulting in odor, precipitation and the loss of ammonia, which is a challenge to be overcome in the process of urine recycling. This review collates research related to urine stabilization, and aims to summarize the characteristics and applications of existing urine stabilization methods, such as acidification, alkalization, electrochemistry, inhibitors and etc. Overall, acidification and alkalization have higher dosage requirements and have an attentional impact on the environment; electrochemical technology is suitable for decentralized sanitation facilities, but the inhibition duration is short; inhibitors are the least effective and are usually used to regulate urease activities in soil environment rather than for urine stabilization. Choosing the appropriate approaches of urine stabilization should focus on the overall perspective of urine resource utilization, consider the separation method and recovery form, and combine it with the concentration technology.

Conservation agricultural practices for minimizing ammonia volatilization and maximizing wheat productivity.

A large amount of ammonia volatilization from the agricultural system causes environmental problems and increases production costs. Conservation agriculture has emerged as an alternate and sustainable crop production system. Therefore, in the present study, ammonia losses from different agricultural practices were evaluated for the wheat crop under different tillage practices. The results of the present study showed that the cumulative emission of ammonia flux from the wheat field varied from 6.23 to 24.00 kg ha-1 (P ≤ 0.05) in conservation tillage (CA) and 7.03 to 26.58 kg ha-1 (P ≤ 0.05) in conventional tillage (CT) among different treatments. Application of basal 80% nitrogen resulted in the highest ammonia flux in conventional and conservation tillage practices. The ammonia volatilization followed the following trend: urea super granules with band placement > neem-coated urea with band placement > neem-coated urea with broadcast before irrigation > neem-coated urea with broadcast after irrigation > slow-release N fertilizer (urea stabilized with DCD and N(n-butyl)thiophosphoric triamide) with band placement. The conservation agricultural practices involving conservation tillage appear to be a sustainable approach for minimizing ammonia volatilization and improving wheat productivity.

Duromide increase NBPT efficiency in reducing ammonia volatilization loss from urea

ABSTRACT Novel fertilizer stabilization technologies are needed to decrease ammonia (NH3-N) losses and increase nitrogen use efficiency. Duromide + NBPT is a new technology that combines two molecules, Duromide and NBPT, whose propose is to increase the efficiency of the urease inhibitor NBPT in reducing NH3-N loss from urea. Preliminary results showed that Duromide + NBPT can be a more effective product than just NBPT, particularly under low soil pH and high-temperature conditions. This study aimed to compare the effects [...]

Strategies to mitigate ammonia and nitrous oxide losses across the manure management chain for intensive laying hen farms

Circular economy principle aims to achieve sustainable production systems, focusing on the waste valorisation and the reduction of gaseous losses to the atmosphere. Nitrogen (N) compounds in terms of ammonia (NH3) and nitrous oxide (N2O) represent the major losses to the atmosphere of laying hen manure management chain. We present a study aimed to evaluate NH3 and N2O emission and mitigation strategies at housing, storage and land spreading stages. The whole manure management chain was evaluated under different scenarios which combined mitigation strategies of each stage. Two intensive laying hen facilities were involved in the study. Evaluated mitigation strategies were: (i) frequency of manure removal from housing facility, (ii) dried manure storage after passing throughout a manure drying tunnel (MDT) compared to fresh manure storage and (iii) fresh or dried manure incorporation versus surface land application. Increasing the frequency of manure removal from 4 days to 1/3 daily, reduced N losses around 68%. Dried manure storage achieved around 75% reduction in N losses compared to fresh manure storage. Spreading dried manure on grassland surface reduced ≈77% NH3 losses in relation to the emission level reached by fresh manure. The reduction was similar when dried manure was incorporated compared to surface application of fresh manure (≈79%). A 40% reduction in N losses was achieved using the MDT compared to no drying strategy. In the whole manure management chain, the combination of strategies that most reduced N losses was: removal frequency of 1/3 daily, dry storage after passing through the MDT and incorporated land application. These strategies reduced N losses between 40 and 60% compared to the 4 days of removal frequency, fresh storage and surface application of fresh manure.

A novel approach to estimate the abatement of ammonia emissions from mitigation techniques at farm-scale slurry stores exemplified by a semifloating cover.

Ammonia (NH3 ) losses from livestock slurry stores substantially contribute to agricultural emissions to the atmosphere. Gas release from slurry storage facilities is driven by interactions between store operations and meteorological conditions. This study quantifies the abating effect of an impermeable semifloating cover as an emission mitigation technique at a farm-scale slurry storage tank. Emissions were measured over 1 yr and compared with the preceding 2 yr of measurements with the uncovered tank. In this novel approach, emission data were aggregated to categories within 1 h measuring intervals according to five key factors influencing emissions (time span after agitation and tank-filling level as surrogates for natural crust occurrence; the meteorological parameters precipitation, air temperature, and wind speed) for the two consecutive measurement campaigns with and without the cover. The emission abatement effect of the cover was determined by emission modeling of the entire measuring campaign based on measuring intervals of the uncovered and the covered tank where the aggregated categories of influencing factors were equal. The resulting average emission abatement was 48%. An average abatement of 37 and 54% was achieved during periods with and without a surface crust, respectively. The emission reduction was less with low tank filling level due to higher air exchange through openings of the cover. The presented approach is applicable to evaluate emission mitigation techniques for single farm-scale stores. With adequate measurement duration, it is appropriate to produce reliable emission data reflecting the complex interactions between emissions and influencing factors occurring at real-world storage facilities.

Disclosing the thermal reactions of aliphatic amines in the presence of TiO2 nanoparticles by multi-shot analytical pyrolysis

Analytical pyrolysis is a powerful tool to study the thermal behaviour of organic compounds, but relatively little information is available on the pyrolysis of amines, especially when bound to inorganic systems. In this study, we analysed aliphatic amines (propylamine, dipropylamine, tripropylamine, and tert-butylamine), both as pure compounds and bound to titania nanoparticles, using multi-shot analytical pyrolysis-gas chromatography coupled to mass spectrometry (Py-GC–MS) with a liquid nitrogen cryo-trap system. Desorption of amines was observed at 260 °C, while pyrolysis reactions were mostly observed at 600 °C. Pure amines underwent intermolecular reactions, generating heavier nitrogen-containing compounds. Conversely, amines bound to titania nanoparticles underwent loss of ammonia and hydrogen, and both inter- and intramolecular couplings generate unsaturated hydrocarbons and aromatics. Differences in the pyrolysis mechanisms were attributed to the catalytic effect of the nanoparticles. The present work provides fundamental information on the pyrolytic behaviour of aliphatic amines and on the catalytic effect of titania nanoparticles.

Aerated Buffalo Slurry Improves Spinach Plant Growth and Mitigates CO2 and N2O Emissions from Soil

Manure management is the main strategy for mitigating gas emissions from livestock farming. In this study, a laboratory-scale experiment was set up to identify suitable conditions to be applied in a farm-scale experiment. The liquid fraction (LF) of slurry was aerobically treated and greenhouse gas emissions from soil were evaluated. Furthermore, the value of treated LF as a fertilizer on spinach plants was also tested. The aeration of LF determined an increase in mean alkalinity due to ammonia loss. The mass fraction of heavy metals also decreased, likely due to the reduction in solubility. After being applied on soil, aerated LF determined lower CO2 and N2O emissions compared to untreated LF due to a reduced nitrogen load. Spinach plants fertilized with treated LF showed a lush growth and exhibited a lower heavy metal mass fraction as well as a higher content of antioxidants compared to plants fertilized with untreated slurry. Our results show that aeration might be an effective alternative for slurry management as it is able to produce an eco-friendly final product with a high fertilizing value.

Impacts of Low Disturbance Liquid Dairy Manure Incorporation on Alfalfa Yield and Fluxes of Ammonia, Nitrous Oxide, and Methane

Surface applied liquid dairy manure application (i.e., broadcasting) after alfalfa (Medicago sativa L.) harvest is a common practice. Low disturbance manure incorporation (LDMI) may offer multiple benefits including lower ammonia (NH3), greenhouse gas (GHG) and hydrologic nutrient losses compared to broadcast. However, few studies have simultaneously quantified LDMI impacts on alfalfa yield, NH3 and greenhouse gas (GHG) fluxes. We measured NH3, nitrous oxide (N2O), and methane (CH4) fluxes for liquid dairy manure treatments applied to alfalfa plots for broadcast and LDMI over three seasons (2014 to 2016) in central Wisconsin, USA. There were minor differences in alfalfa yield and nitrogen (N) uptake across treatments and years. Shallow disk injection and aerator/band reduced NH3 loss by 95 and 52% of broadcast, respectively, however both substantially increased N2O fluxes (6 and 4.5 kg ha−1 year−1 versus 3.6 kg ha−1 year−1 for broadcast, respectively). The magnitude and timing of N2O fluxes were related to manure application and precipitation events. Average CH4 fluxes were similar among methods and increased with soil moisture after manure application. Results highlight the importance of quantitatively evaluating agri-environmental tradeoffs of LDMI versus broadcast manure application for dairy farms.

Effect of Acid Flow Rate, Membrane Surface Area, and Capture Solution on the Effectiveness of Suspended GPM Systems to Recover Ammonia.

Ammonia losses from manure pose serious problems for ecosystems and human and animal health. Gas-permeable membranes (GPMs) constitute a promising approach to address the challenge of reducing farm ammonia emissions and to attain the EU’s Clean Air Package goals. In this study, the effect of NH3-N concentration, membrane surface area, acid flux, and type of capture solution on ammonia recovery was investigated for a suspended GPM system through three experiments, in which ammonia was released from a synthetic solution (NH4Cl + NaHCO3 + allylthiourea). The effect of two surface areas (81.7 and 163.4 cm2) was first evaluated using three different synthetic N emitting concentrations (3000, 6000, and 12,000 mg NH3-N∙L−1) and keeping the flow of acidic solution (1N H2SO4) constant (0.8 L·h−1). A direct relationship was found between the amount of NH3 captured and the NH3-N concentration in the N-emitting solution, and between the amount of NH3 captured and the membrane surface area at the two lowest concentrations. Nonetheless, the use of a larger membrane surface barely improved ammonia capture at the highest concentration, pointing to the existence of other limiting factors. Hence, ammonia capture was then studied using different acid flow rates (0.8, 1.3, 1.6, and 2.1 L∙h−1) at a fixed N emitting concentration of 6000 mg NH3-N∙L−1 and a surface area of 122.5 cm2. A higher acid flow rate (0.8–2.1 L∙h−1) resulted in a substantial increase in ammonia absorption, from 165 to 262 mg of NH3∙d−1 over a 14-day period. Taking the parameters that led to the best results in experiments 1 and 2, different types of ammonia capture solutions (H2SO4, water and carbonated water) were finally compared under refrigeration conditions (at 2 °C). A high NH3 recovery (81% in 7 days), comparable to that obtained with the H2SO4 solution (88%), was attained when chilled water was used as the capture solution. The presented results point to the need to carefully optimize the emitter concentration, flow rate, and type of capture solution to maximize the effectiveness of suspended GPM systems, and suggest that chilled water may be used as an alternative to conventional acidic solutions, with associated savings.

Gas-phase fragmentation reactions of a7 ions containing a glutamine residue.

The gas-phase fragmentation reactions of the a7 ions derived from glutamine (Q) containing model heptapeptides have been studied in detail with low-energy collision-induced dissociation (CID) tandem mass spectrometry (MS/MS). Specifically, the positional effect of the Q residue has been investigated on the fragmentation reactions of a7 ions. The study involves two sets of permuted isomers of the Q containing model heptapeptides. The first set contains the QAAAAAA sequence, and the second set involves of QYAGFLV sequence, where the position of the Q residue is changed from N- to C-terminal gradually for both peptide series. An intense loss of ammonia from the a7 ions followed by internal amino acid eliminations strongly supports forming the imine-amides structure via cyclization/rearrangement reaction for all studied a7 ions. This is in agreement with the pioneering study reported by Bythell et al. (2010, 10.1021/ja101556g). A novel rearrangement reaction is detected upon fragmentation of imine-amide structure, which yields a protonated C-terminal amidated hexapeptide excluding the Q residue. A possible fragmentation mechanism was proposed to form the protonated C-terminal amidated hexapeptide, assisted via nucleophilic attack of the side chain amide nitrogen of the Q residue on its N-protonated imine carbon atom of the rearranged imine-amide structure. HIGHLIGHTS: The gas-phase fragmentation reactions of a7 ions obtained from protonated model peptides containing glutamine residue were studied by ESI-MS/MS. A rearranged imine-amide structure is the predominant even for a7 ions. Novel rearrangement reaction is observed which forms a protonated C-terminal amidated hexapeptide excluding Q residue upon fragmentation of the imine-amide structure.

Evaluation of mass spectrometry MS/MS spectra for the presence of isopeptide crosslinked peptides.

Isopeptide crosslinked proteins can be the product of transglutaminase or of exposure to organophosphorus toxicants (OP). Transglutaminase links glutamine to lysine with loss of ammonia. OP toxicants induce a link between glutamic acid and lysine with loss of water. Our goal was to establish criteria to distinguish real from false isopeptide crosslinks reported by software searches of mass spectrometry data. We used fragmentation spectra of tryptic peptides from MAP-rich tubulin Sus scrofa as a test system for detection of naturally-occurring isopeptide crosslinks. Data were analyzed with Protein Prospector. Criteria for the assignments included the presence of at least 1 crosslink specific product ion, fragment ions from both peptides, Protein Prospector scores ≥20, and best fit of the MS/MS data to the crosslinked peptide as opposed to a linear peptide. Out of 301,364 spectra, 15 potential transglutaminase-type crosslinked peptide candidates were identified. Manual evaluation of these MS/MS spectra reduced the number to 1 valid crosslink between Q112 of NFH and K368 of Tau. Immunopurification with anti-isopeptide 81D1C2 confirmed that MAP-rich tubulin contained only one isopeptide. Support for this isopeptide bond was obtained by showing that transglutaminase was capable of incorporating dansyl-aminohexyl -QQIV into K368. A model of the KIETHK-QLEAHNR isopeptide was synthesized with the aid of transglutaminase. MS/MS spectra of the model validated our interpretation of the native isopeptide. An OP-induced isopeptide bond between K163 of tubulin alpha-1A and E158 of tubulin beta-4B was induced by treating MAP-rich tubulin with 100 μM chlorpyrifos oxon. This crosslink was supported by the criteria described above and by the presence of diethoxyphospho-lysine 163 in the tubulin alpha-1A peptide. The information obtained in this work is valuable for future studies that aim to understand why exposure to OP is associated with increased risk of neurodegenerative disease.

From Preassociation to Chelation: A Survey of Cisplatin Interaction with Methionine at Molecular Level by IR Ion Spectroscopy and Computations.

Methionine (Met) plays an important role in the metabolism of cisplatin anticancer drug. Yet, methionine platination in aqueous solution presents a highly complex pattern of interconnected paths and intermediates. This study reports on the reaction of methionine with the active aqua form of cisplatin, cis-[PtCl(NH3)2(H2O)]+, isolating the encounter complex of the reactant pair, {cis-[PtCl(NH3)2(H2O)]+·Met}, by electrospray ionization. In the unsolvated state, charged intermediates are characterized for their structure and photofragmentation behavior by IR ion spectroscopy combined with quantum-chemical calculations, obtaining an outline of the cisplatin–methionine reaction at a molecular level. To summarize the major findings: (i) the {cis-[PtCl(NH3)2(H2O)]+·Met} encounter complex, lying on the reaction coordinate of the Eigen-Wilkins preassociation mechanism for ligand substitution, is delivered in the gas phase and characterized by IR ion spectroscopy; (ii) upon vibrational excitation, ligand exchange occurs within {cis-[PtCl(NH3)2(H2O)]+·Met}, releasing water and cis-[PtCl(NH3)2(Met)]+, along the calculated energy profile; (iii) activated cis-[PtCl(NH3)2(Met)]+ ions undergo NH3 departure, forming a chelate complex, [PtCl(NH3)(Met)]+, whose structure is congruent with overwhelming S-Met ligation as the primary coordination step. The latter process involving ammonia loss marks a difference with the prevailing chloride replacement in protic solvent, pointing to the effect of a low-polarity environment.

Integrated application effects of biochar and plant residue on ammonia loss, heavy metal immobilization, and estrogen dissipation during the composting of poultry manure

Inadequate handling of poultry manure can cause significant releases of NH3, heavy metals, and estrogen, thereby impairing environmental quality. This study was a composting experiment involving the combination of poultry manure with plant residues (corn stalks, mushroom residues, and vegetable straw), as well as with either wheat stalk biochar (WB) or rice husk biochar (RB). The integrated effects of plant residues and biochar on NH3 loss, heavy metal (Cu, Zn, As, and Cd) stabilization, and 17β-estradiol (E2) dissipation were investigated during composting. The poultry manure co-composted with corn straw and mushroom residue showed the highest potential for E2 degradation. Biochar enhanced E2 dissipation and decreased estrogenic activity in all treatments, with RB showing a stronger effect than WB. Both biochars decreased microbial diversity and increased bacterial groups related to E2 and organic matter degradation·NH3 emission was reduced by 50-82% with 15% WB and 86-97% with 15% RB. The extractable fraction of As was reduced by 0-53% with WB and 50-84% with RB, while that of Cd was reduced by 5-28% for WB and 25-41% for RB in poultry manure compost. However, biochar showed little effect on Cu and Zn. Biochar appears to have a promotional effect and enhances the microbial degradation of E2. Specifically, the integration of corn stalks, mushroom residues, and RB in poultry manure compost had a positive effect by preventing nitrogen loss while reducing the bioavailability of heavy metals and hormones.

Fragmentation reactions of protonated α,ω-diamino carboxylic acids: The importance of functional group interactions.

Protonated members of a homologous series of biologically significant α,ω-diamino carboxylic acids were subjected to collision induced dissociation (CID). The resulting fragmentation patterns were studied using isotopic labeling, quantum mechanical computations, and pseudo MS3 experiments conducted primarily on an ion trap mass spectrometer. Each protonated α,ω-diamino acid showed a primary neutral loss of either ammonia or water; a clear explanation was developed for the observed variation of the two losses within the series. Protonated 2,3-diaminopropanoic acid, 2,4-diaminobutanoic acid, and 2,7-diaminoheptanoic acid gave secondary losses of water, carbon monoxide, and a loss of water plus carbon monoxide, respectively. In the parallel pathways characterized for the fragmentations of protonated ornithine and lysine, the α-nitrogen of the diamino acid was maintained in the cyclic iminium product formed by successive losses of NH3 and (H2 O + CO), whereas the side-chain nitrogen was retained by consecutive losses of H2 O and (CO, NH3 ). The 1-piperideine ion from protonated lysine was fragmented further, losing ethylene from carbons 4 and 5. Protonated 2,6-diaminopimelic acid fragmented by analogous reactions. Detailed mechanistic schemes for the fragmentation of both protonated 2,3-diaminopropanoic and ornithine were generated from MP2/DFT computations. This work highlights the participation of the side-chain amino group, which distinguishes the gas-phase chemistry of protonated α,ω-diamino acids from the well-documented fragmentation reactions of protonated α-amino acids bearing a hydrogen atom or an alkyl side chain. In general, the results further illustrate the importance of intramolecular separations affecting the specific interactions between functional groups leading to the fragmentation of multifunctional ions.

Ammonothermal Synthesis and Characterization of First Amidozincate Hydroxides

AbstractThe first alkali metal amidozincate hydroxides Na3[Zn(NH2)4](OH) and Na3[Zn(NH2)3](OH)2were obtained from supercritical ammonia under ammonobasic conditions at 823 K and 250 MPa, and 623 K and 159 MPa, respectively. Crystal structures have been refined against single crystal X‐ray diffraction intensity data. Coordination environments of the cations as well as the rather open crystal structure and low density of Na3[Zn(NH2)4](OH) suggest the initial formation of a monoammoniate, prior loss of ammonia during depressurizing and recovery of the product. While Na3[Zn(NH2)4](OH) contains mutually isolated amidozincate ions next to hydroxide ions, Na3[Zn(NH2)3](OH)2is the first amidozincate realizing a condensation of the complex anionic substructure so far. Both compounds are regarded possible intermediates in an ammonothermal zinc nitride synthesis and give insights into the action of impurities during ammonothermal processes. Raman spectroscopic measurements support the assignment of amide and hydroxide groups.

Impact of Urea and Ammoniacal Nitrogen Wastewaters on Soil: Field Study in a Fertilizer Industry (Bahía Blanca, Argentina).

Nitrogen compounds in industrial effluents are considered a serious threat to the environment. The aim of this work is to identify the effect produced by nitrogen-rich wastewater on alkaline soils from industrial land. Two plots were irrigated with wastewater as ammoniacal nitrogen (31 to 53g N m-2) and urea (167-301g N m-2) sources named P1 and P2, respectively. Inorganic nitrogen (N) concentrations (N-NH3 + N-NH4, N-NO2, N-NO3), soil pH, and N-NH3 volatilization were monitored during a 2-year period. Variations in the fate of N compounds were distinguished according to the quantity and source of N applied to the soil. A higher N input in the form of urea was related to a greater concentration of nitrates and soil acidification in the topsoil (0-30cm). Otherwise, ammoniacal N wastewater showed greater relative ammonia losses due to volatilization. Ammonia losses were estimated as 24.2% and 7.43% of the total N applied in P1 and P2, respectively. Besides, in P1 ammoniacal N predominated over nitrate, unlike results obtained in P2. The correct management of nitrogen-rich wastewaters in fertilizer industries could greatly reduce soil and groundwater degradation.

Comparison of Alum and Sulfuric Acid to Retain and Increase the Ammonium Content of Digestate Solids during Thermal Drying

Aluminum sulphate (alum, Al2(SO4)3·nH2O) has successfully been used to reduce ammonia loss from poultry litter, cattle feedlots and manure composting, but has not yet been utilized in the thermal drying process of digestate solids. The objectives of the present study were to evaluate the effects of alum addition on ammonium nitrogen (NH4+-N) content and phosphorus (P) solubility in dried digestate solids in comparison to the addition of concentrated sulfuric acid (H2SO4). Manure-based (MDS) and sewage sludge-based (SDS) digestate solids were chosen to conduct a drying experiment at four pH levels (original pH, 8.0, 7.5 and 6.5) and using two acidifying agents (alum, concentrated H2SO4). Alum addition increased the final NH4+-N content significantly from 1.4 mg g−1 in the non-acidified control up to 18 mg g−1 and 10.8 mg g−1 in dried MDS and SDS, respectively, which were higher levels than obtained with the addition of concentrated H2SO4. Moreover, alum considerably lowered the water extractable phosphorus (WEP) in raw and dried SDS by 37–83% and 48–72%, respectively, compared with the non-treated control. In contrast, concentrated H2SO4 notably increased WEP in raw and dried MDS by 18–103% and 29–225%, respectively. The comparison between the two acidifying agents indicated that alum had the potential to be an efficient and easy-handling alternative to concentrated sulfuric acid, resulting in higher NH4+-N content and lower P solubility.

Mechanistic Understanding of Nitrogen Behaviour in Floating Treatment Wetlands: Abatement of Ammonia Flux

Nitrogen behaviour in domestic wastewater was investigated to develop a mechanistic understanding of ammonia dynamics in Floating Treatment Wetlands (FTWs) and to improve design and operation. A critical FTW design (full coverage of the floating mat and maximum plant density) was evaluated to optimize treatment performance of a pilot-scale system in removing ammonia under different operational volumes. A system dynamics approach as a framework was employed for robust understanding of the treatment mechanisms and system performance in removing ammonia. The results revealed that ammonia removal was enhanced in FTWs and the magnitude of removal was controlled by the design examined. Findings suggest that a design code of full coverage of water surface with mat material, high plant density, and low water volume can be considered as a critical design for FTW system to remove ammonia from domestic wastewater. This design promoted nitrification as principal ammonia removal process even when plants were present. The contribution of nitrification to overall ammonia removal was estimated to be between 81 and 85%. Plant uptake contributed to 14-19% of the total N loss. Ammonia loss via volatilization was determined to be negligible in examined system. Kinetics parameters for ammonia removal were between 0.14-0.22 day-1 in FTWs compared to 0.01-0.02 day-1 in controls. Understanding the contribution of removal processes of N could be useful to improve treatment system design, and enhance treatment performance.

Reducing Ammonia Volatilization from Urea Fertilizer Applied in a Waterlogged Tropical Acid Soil via Mixture of Rice Straw and Rice Husk Biochars

Ammonia volatilization causes major nitrogen losses from the soil and applied urea which results in low urea-N usage efficiency. In line to this, laboratory incubation experiment was conducted to assess the effect of rice straw and rice husk biochar on ammonia volatilization, soil pH, exchangeable ammonium, and available nitrate in comparison to the urea without additives under waterlogged conditions. Application of mixture of rice straw and rice husk biochars at application rate 5-10 t ha-1 had significantly minimized ammonia volatilization by 30.86%-38.61% over T1. The biochar mixture also had increased retention of ammonium and nitrate ions with increment of soil pH over control. Hence, the findings suggest that urea amended with rice straw and rice husk biochar altered the nutrients level in soil by minimizing ammonia loss in a way that enhanced nitrogen availability in waterlogged conditions.