NH3 Flux Research Articles

NH3 release during the snow evaporation process in typical cities in Northeast China

NH3 is the most important alkaline gas in the atmosphere and functions as a precursor to secondary ammonium salts. Therefore, identifying its sources and quantifying its emissions is imperative. NH4+ represents a principal component of atmospheric particulate pollutants. As particulate matter acts as a condensation nucleus for wet deposition, the NH4+ concentrations in precipitation are typically elevated. During the evaporation process of wet deposition, NH4+ is likely to be re-emitted as a gas (NH3). In Northeast China, heavy and frequent snowfall occurs, making it crucial to elucidate the NH3 release flux and the factors influencing this release during the snow evaporation process in representative cities of this region. This study collected snow samples from five notable snowfall events in Changchun, Jilin Province that occurred from November 2023 to March 2024, to conduct indoor simulated evaporation experiments (among them, the actual phase changes of two snowfall events consisted mainly of evaporation, whereas those of the other three events consisted mainly of sublimation). The results indicated that during the snow evaporation process, the average ratio (R) of NH4+ re-emitted as NH3 was 39.28 ± 12.07%. The average release flux (F) was 1624.58 ± 2064.5 μg/m2, and the average release rate (V) was 361.33 ± 465.31 ng/(m2·s). Within the 100-m atmospheric boundary layer, the total NH3 flux that was released subsequently during the evaporation of all snowfall events in Changchun during the study period was 46.97 mg/m2. The average release flux for individual snowfall events was 688.66 μg/m2, which constituted approximately 2.44% of the NH3 concentration documented in the winter atmosphere of Changchun. During the snow evaporation or sublimation process, R was positively correlated with the environmental temperature (P < 0.05) and negatively correlated with both the environmental wind speed and snowfall amount (P < 0.05). Significant variations in R were observed across multiple functional areas, which were ranked in descending order as follows: commercial areas (R = 26.16%), residential areas (R = 22.01%), cultural and educational areas (R = 20.7%), and industrial areas (R = 18.01%). The influence of a snow-melting agent (NaCl) on the conversion rate of NH3 initially increased but then subsequently decreased as the dose increased. The lowest measured value (R = 22.02%) was 0 mg/L, whereas the peak measured value (R = 30.31%) was attained at a concentration of 200 mg/L. The findings of this research are important for illuminating the cycling process of NH3 in the atmosphere and for the comprehensive management of air quality.

A simple and accurate Dosi-Tube method for estimating ammonia loss from in-season nitrogen application in corn fields

Ammonia (NH3) volatilization is a major nitrogen (N) loss pathway for surface-applied fertilizers containing urea. The Dosi-Tube method developed by Van Andel et al. on manured fields without a crop canopy measures NH3 volatilization using wind speed and Dosi-Tubes. Here, we adapted the Dosi-Tube method to accurately and inexpensively measure NH3 volatilization from fertilizer N applied within corn canopies. NH3 losses were measured from surface-applied UAN and urea, with or without a urease inhibitor, via both Dosi-Tube and wind tunnel methods over two seasons in Woodslee, Ontario. A newly developed empirical model demonstrated improved accuracy in predicting NH3 fluxes.

Assessing Ammonia (NH₃) Emissions, Precursor Gas (SO2, NOx) Concentrations, and Source Contributions to Atmospheric PM2.5 from a Commercial Manure Composting Facility

Increased ammonia (NH3) emissions from intensive agriculture negatively affect environmental and ecosystem health, contributing to formation of particulate matter (PM) and the potent greenhouse gas, N2O. Better understanding NH3 emissions from the manure composting process and their behavior as a constituent of the atmospheric aerosol load is a crucial element in creating better farm management systems, improving public health outcomes, and mitigating the broader environmental and climatic impacts of agriculture. Retarded generation of PM with a major constituent source of NH3 is a primary mechanism for evaluating the effects of agricultural contribution to PM. This study aimed to quantify NH3 emissions, examine the influence of environmental factors, and investigate the relationship between precursor gases (SO2, NOx, NH3) and PM2.5 at a modern manure composting facility in Paju, South Korea. Over 35 days, average internal concentrations of NH3, SO2, and NOx were significantly higher than external levels. NH3 concentrations reached 3.64 ± 0.06 mg m−3 at 3 m height and 2.43 ± 0.16 mg m−3 at ground level, while the total NH3 flux from the facility was 24.47 ± 1.39 NH3-N kg d−1. Internal PM2.5 concentrations (36.9 ± 2.6 µg m−3) were about 50% higher than external levels (23.7 ± 2 µg m−3), with a moderate correlation (r = 0.341) suggesting some contribution of external PM2.5 to internal levels. Despite large quantities of internal emissions, the facility’s sealed design with a negative pressure ventilation system effectively minimized external emissions. These results suggest that while manure composting facilities are significant sources of NH3 and PM2.5, advanced systems like high-volume ventilation and scrubbing technologies can effectively reduce their impact on regional air pollution, contributing to better environmental management in agriculture.

Reducing ammonia volatilization in rice paddy: the importance of lower fertilizer rates and soil incorporation

In rice paddies, which exhibit higher ammonia (NH₃) emission factors than upland soils, identifying key drivers of NH₃ flux intensity is crucial. Contrary to the commonly held view that NH₃ flux is primarily governed by soil ammonium (NH₄⁺) concentrations, we found no significant relationship between NH₃ flux and NH₄⁺ levels in the soil during rice cultivation. To pinpoint a primary factor influencing NH₃ flux intensity under conventional rice cropping practices, we conducted a 2-year field study applying four nitrogen (N) fertilization rates (0, 45, 90, and 180 kg N ha⁻¹) using urea [(NH₂)₂CO], the most common N fertilizer. NH₃ emissions were tracked using the ventilation method. Following N application, NH₃ flux sharply increased but rapidly returned to baseline. Half of the N applied as a basal fertilizer was incorporated within the soil, contributing only 10% of total NH₃ emissions. In contrast, top-dressed applications—20% of total N at the tillering stage and 30% at panicle initiation—accounted for approximately 90% of NH₃ loss. Seasonal NH₃ flux increased quadratically with rising N application rates, correlating strongly with NH₄⁺ concentrations in floodwater rather than soil. Grain yield responded quadratically to N levels, peaking at 120 kg N ha⁻¹ with a 37% increase over control yields. NH₃ flux intensity, defined as seasonal NH₃ flux per unit of grain yield, showed a quadratic response to N fertilization, decreasing with initial fertilizer additions (up to 38 kg N ha⁻¹) but then sharply increased with further N fertilization increase. Hence, reducing NH₄⁺ concentrations in floodwater through moderated N application and deeper fertilizer placement could be essential for minimizing NH₃ volatilization in rice systems.

Annual emissions of N2O, NO, HONO, and NH3 from maize-wheat fields in the North China Plain

Fertilized agricultural soil is a significant source of gaseous nitrogen compounds (GNCs), including N2O, NO, HONO, and NH3. The North China Plain (NCP) is the “hot region” for the release of these GNCs due to intensive fertilization practices. However, existing research has primarily focused on N2O emissions from fertilized farmland in the NCP, lacking comprehensive observational studies on other GNCs. Therefore, a continuous cumulative sampling technique (open-top dynamic chamber system) was utilized in this study to simultaneously measure the exchange fluxes of N2O, NO, HONO, and NH3 over summer maize-winter wheat rotation fields in the NCP. Results showed that GNC emissions from the soil displayed distinct diurnal variations, with higher emissions during the day attributed to elevated soil temperature. However, N2O emissions remained consistent between day and night, potentially influenced not only by soil temperature but also by soil humidity. Annual cumulative emissions and emission factors (EFs) for four GNCs were determined, indicating that N2O, NO, and NH3 emissions during the maize season were 1.38–2.37 times higher than those during the wheat season, with 98 % of HONO emissions occurring in the maize season. Additionally, the study first presented the annual HONO EFs of 0.36 ± 0.03 % in fertilized farmland. Furthermore, a comparison revealed that the fluxes of N2O, NO, NH3, and HONO using the conventional single-point sampling method were 26.4 %, 13.9 %, and 8.10 % lower, and 7.86 % higher compared to the continuous cumulative sampling method recommended in this study. In general, this study provided precise measurements of GNC emissions from farmland, offering essential foundational data for modeling parameters and contributing to the formulation of regional air pollution prevention and control policies.

Tempo-spatial Variations in Nitrogen and Phosphorus Loads in Jianli-Hankou Reach of the Middle Yangtze River During the Past 20 Years

Ammonia nitrogen （NH4+-N） and total phosphorus （TP） were the major control pollutants in the Yangtze River Basin. Based on measured data from 2003 to 2020, the temporal and spatial variations in concentrations and fluxes of NH4+-N and TP in the Jianli to Hankou （JL-HK） reach of the Middle Yangtze River were studied, and the impacts of flow-sediment factors, tributary inflows, and others on variations in NH4+-N and TP fluxes were discussed. The results showed that： ① In recent years, NH4+-N and TP concentrations in the mainstream have declined significantly, with annual NH4+-N and TP concentrations at each monitoring station in 2020 averagely decreasing by 41% and 34% compared to those in 2003, respectively. Spatially, NH4+-N and TP concentrations decreased and then increased along the mainstream. NH4+-N and TP concentrations of tributary inflows, which include the Dongting Lake and Han River, were generally lower than that of the mainstream. The multi-year average values of NH4+-N and TP concentrations were both averaged at 0.12 mg·L-1 in the mainstream and were averaged at 0.11 mg·L-1 and 0.09 mg·L-1 in the tributary inflows. ② The flux differences between the upper and lower sections net of tributary confluences showed that NH4+-N and TP fluxes were lost in the Jianli to Luoshan （JL-LS） sub-reach and increased in the Luoshan to Hankou （LS-HK） sub-reach in most years. NH4+-N and TP fluxes decreased in the JL-LS sub-reach, which was related to the lower NH4+-N and TP concentrations in lateral inflows, such as Dongting Lake, and thus lowered the NH4+-N and TP concentrations in the mainstream. The LS-HK sub-reach showed the opposite trends, and the water and sediment loads increased in this sub-reach. Across the whole JL-HK reach, TP flux as well as water and sediment loads were recharged along the reach, whereas NH4+-N flux was reduced greatly, which could be attributed to the pollution abatement conducted in the Yangtze River Basin, which mainly focused on NH4+-N. ③ The correlation analysis results showed that NH4+-N fluxes had the strongest correlation with NH4+-N concentrations but not significantly correlated with discharges and sediment transport rates, indicating that NH4+-N was mainly controlled by point source pollution in the study reach. TP fluxes had higher correlations with discharges and sediment transport rates in high flow level periods, and the correlations between TP fluxes and TP concentrations were better in low flow level periods, reflecting that point source pollution contributed more to TP in dry seasons compared to flood seasons.

Mitigating nitrogen loss in paddy field microcosms through indigenous arbuscular mycorrhizal fungi assemblage

AbstractWhether farmers should consider the role of arbuscular mycorrhizal fungi (AMF) in agriculture is a hotly debated topic. We aimed to investigate the role of indigenous AMF in reducing nitrogen (N) loss from paddy fields via runoff, leaching, NH3 volatilization, and N2O emission. We conducted a pot experiment employing a mycorrhiza‐defective rice mutant (non‐mycorrhizal) as the control, grown in soil containing indigenous AMF. The corresponding AMF treatment used the progenitor of this mutant with the same soil. The plants were fertilized with nitrogen, phosphorus and potassium 6 weeks after sowing. The root colonization was 23% in mycorrhizal rice, and no typical AMF structures were observed in the roots of non‐mycorrhizal rice. Our findings indicated that the mycorrhizal system exhibited lower N concentrations of runoff and leachate further compounded by reduced fluxes of N2O and NH3. This led to 14% decrease (mycorrhizal rice 111 kg N ha−1; the non‐mycorrhizal rice: 129 kg N ha−1) in cumulative N loss within 3 days post‐fertilization. While this AMF effect was consistent across the four tested N loss pathways, differences were observed between NH4+‐N and NO3−‐N in the runoff pathway. Notably, our results revealed no evidence of trade‐offs in AMF effect on N loss among the tested pathways. Additionally, mycorrhizal rice had larger shoots and roots than their non‐mycorrhizal counterparts. Our study underscores the potential benefits of indigenous AMF in paddy fields for mitigating water pollution and reducing greenhouse gas emission.

Evaluation of optimized flux chamber design for measurement of ammonia emission after field application of slurry with full-scale farm machinery

Abstract. Field-applied liquid animal manure (slurry) is a significant source of ammonia (NH3) emission, which is harmful to the environment and human health. To evaluate mitigation options, reliable emission measurement methods are needed. A new system of dynamic flux chambers (DFCs) with high-temporal-resolution online measurements was developed. The system was investigated in silico with computational fluid dynamics and tested using three respective field trials, with each trial assessing the variability in the measured emission after application with trailing hose at different scales: manual (handheld) application, a 3 m experimental slurry boom, and a 30 m farm-scale commercial slurry boom. For the experiments with machine application, parallel NH3 emission measurements were made using an inverse dispersion modeling method (backward Lagrangian stochastic, bLS, modeling). The lowest coefficient of variation among replicate DFC measurements was obtained with manual application (5 %), followed by the 3 m slurry boom (14 %), and lastly the 30 m slurry boom (20 %). Conditions in DFCs resulted in a consistently higher NH3 flux than that measured with the inverse dispersion technique, but both methods showed a similar emission reduction by injection compared with the trailing hose: 89 % by DFC and 97 % by bLS modeling. The new measurement system facilitates NH3 emission measurement with replication after both manual and farm-scale slurry application with relatively high precision.

Effect of agricultural management system (“cash crop”, “livestock” and “climate optimized”) on nitrous oxide and ammonia emissions

AbstractThe study aimed to measure soil-atmosphere N2O fluxes and their controlling factors, as well as NH3 emissions and yields for two soils (silt loam and clay loam) in three management systems over two years under subsequent wheat and maize cultivation. The management systems were characterized as follows: (1) cash crop (C) with mineral fertilizer and conventional tillage; (2) livestock (L) with biogas residue fertilization and its incorporation prior to sowing in maize and reduced tillage; and (3) climate optimized (O) with minimum tillage, 8-year crop rotation, with biogas residue fertilization, in maize without incorporation in clay loam soil or incorporation by strip-tillage prior to seeding in silt loam soil. Stable isotope ratios of N2O and mineral N were determined to identify N2O processes. Within the organically fertilized maize treatments, cumulative N2O fluxes were highest in the O-system treatments of both sites (4.0 to 9.4 kg N ha− 1 a− 1), i.e. more than twice as high as in the L-system (1.5 to 3.1 kg N ha− 1 a− 1). Below root-strip till fertilizer application did not enhance N2O fluxes. Fluxes with mineral fertilization of wheat (1.1 to 3.1 kg N ha− 1 a− 1) were not different from those with organic fertilization. Isotopic values of emitted N2O revealed that bacterial denitrification dominated most of the peak flux events, while the N2O/(N2 + N2O) ratio of denitrification was mostly between 0.1 and 0.5. It can be concluded that, contrary to the intention to lower greenhouse gas fluxes by the O-system management, the highest N2O fluxes occurred in the O-system without biogas digestate incorporation in maize. With respect to NH3 fluxes, we could confirm that the application of digestate application in growing crops without incorporation or late incorporation in fertilization before sowing induces high fluxes. The beneficial aspects of the O-system including more stable soil structure and resource conservation, are thus potentially counteracted by increased N2O and NH3 emissions.

Effect of fertilizer deep placement and nitrification inhibitor on N2O, NO, HONO, and NH3 emissions from a maize field in the North China Plain

Fertilized soil is an essential source of atmospheric gaseous nitrogen compounds (GNC, including N2O, NO, HONO, and NH3) that play important roles in global warming and regional air pollution. However, there is still a lack of comprehensive research on the exchange fluxes of these gases between soil and the atmosphere, let alone exploration of mitigation measures. Herein, the fluxes of N2O, NO, HONO, and NH3 under different fertilization treatments (surface fertilization (SF), deep fertilization (DF), DF with added nitrification inhibitor (DN), and control (CK, non-fertilization)) were comparatively investigated by open-top dynamic chambers in a maize field in the North China Plain (NCP) in 2022. The results showed that fertilization significantly promoted soil GNC emissions under SF and DF treatments, while there was no significant increase in GNC emissions except for NH3 under the DN treatment after fertilization. In comparison to the SF treatment, the cumulative emissions under the DF treatment exhibited a significant reduction, amounting to 80.8% for N2O, 89.4% for NO, 88.3% for HONO, 84.8% for NH3, and 83.9% for the total emissions of these four gases. These results emphasize the effect of fertilizer deep placement in mitigating soil GNC emissions, and further reductions were observed when using nitrification inhibitors like dicyandiamide (DCD). Compared with the cumulative emissions under the SF treatment, the DN treatment showed reductions exceeding 95% for N2O, NO, and HONO, and 77.1% for NH3 due to the inhibition of ammonia oxidation by DCD, resulting in an overall reduction of 88.8% for the four gases. Therefore, we advocate deep placement of fertilizer with or without nitrification inhibitors during crop cultivation to achieve a comprehensive reduction in GNC emissions and improve regional air quality.

Nitrous Oxide Emissions and Ammonia Volatilization from Pasture after Cattle Dung and Urine Applications in the Dry and Rainy Seasons of the Brazilian Cerrado

An important source of greenhouse gases in Brazil is the nitrous oxide (N2O) emission from pasture, and microorganisms play an important role in nitrogen transformations in the soil. This study aimed to evaluate N2O emission and NH3 volatilization from bovine excreta in pasture in an integrated crop–livestock system (ICL) in the Brazilian Cerrado. Three treatments (urine, dung and control) were performed in two pastures (Area 1—three-year pasture of Urochloa ruziziensis and Area 2—one-year pasture of Urochloa brizantha cv. Piatã), with two application times of the excreta (dry and rainy season), during two successive years of application. Compared to the control, the excreta deposition on ICL increased soil N2O and NH3 fluxes. In the dry season, N2O fluxes were associated with higher ammonium (NH4+) availability. In the rainy season, these fluxes were related to NO3− availability and water-filled pore space (WFPS). In both areas, NH3 volatilization was higher after urine than dung application, especially in the dry season. The highest N2O emission factors were obtained for urine (0.32%), the rainy season (0.36%), and older pasture (Area 1: 0.24%). All these values were below the mean IPCC default values (0.77%). These results indicate that N2O emissions in pasture should be evaluated in regional conditions.

Impact of gas dry deposition parameterization on secondary particle formation in an urban canyon

This study investigates the impact of the parameterization of dry deposition on the local gas-particle partitioning between ammonium nitrate NH4NO3 and its precursor gases (ammonia, NH3 and nitric acid, HNO3) through chemistry-coupled large-eddy simulations on the dispersion of reactive gaseous and particulate pollutant in an idealized street canyon. A key factor in the parameterization of dry deposition is the effective Henry's Law constant H*. Three distinct characterizations of H* are compared: two drawn from existing literature (referred to as Model 1 and Model 2) and one typical of low pH conditions (referred to as Model 3), which could be more representative of urban areas. Model 3 shows contrasting gas-particle partitioning results between NH3, HNO3, and NH4NO3 with Model 1 and Model 2. In detail, the NH4NO3 concentrations in the street of Model 1 and Model 2 are smaller than the background NH4NO3 concentration. However, Model 3 shows higher NH4NO3 concentration in the street than the background NH4NO3 concentration. This is because the dry deposition fluxes of NH3 and HNO3 are higher in Model 1 and Model 2 than in Model 3, resulting in less available NH3 and HNO3 for NH4NO3 formation. These findings highlight the importance of selecting an appropriate H* characterization that is tailored to the specific environmental conditions under investigation.

An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production

Abstract. Ammonia (NH3) emissions can negatively affect ecosystems and human health, so they should be monitored and mitigated. This study presents methodology for the estimation of uncertainties in NH3 emissions measurements using the solar occultation flux (SOF) method. The reactive nature of NH3 makes its measurement challenging, but SOF offers a reliable open-path passive method which utilizes solar spectrum data, thereby avoiding gas adsorption within the instrument. To compute NH3 gas fluxes, horizontal and vertical wind speed profiles, as well as plume height estimates and spatially resolved column measurements, are integrated. A unique aspect of this work is the first-time description of plume height estimations derived from ground and column NH3 concentration measurements aimed at uncertainty reduction. Initial validation tests indicated measurement errors between −31 % and +14 % on average, which was slightly larger than the estimated expanded uncertainty ranging from ± 12 % to ± 17 %. Application of the methodology to assess emission rates from farms of various sizes showed uncertainties between ± 21 % and ± 37 %, generally influenced by systematic wind uncertainties and random errors. The method demonstrates the capacity to measure NH3 emissions from both small (∼ 0.5–1 kg h−1) and large (∼ 100 kg h−1) sources in high-density farming areas. Generally, the SOF method provided an expanded uncertainty below 30 % in measuring NH3 emissions from livestock production, which could be further improved by adhering to best application practices. This paper's findings offer the potential for broader applications, such as measuring NH3 fluxes from fertilized fields and in the oil and gas sector. However, these applications would require further research to adapt and refine the methodologies for these specific contexts.

NH3 and greenhouse gas emissions during co-composting of lignite and poultry wastes and the following amendment of co-composted products in soil

ABSTRACT Ammonia (NH3) and greenhouse gas (GHG) emissions are substantial contributors to C and N loss in composting. Lignite can increase N retention by absorbing N H 4 + and NH3. However, the effects of co-composting on NH3 and GHG emissions in view of closing nutrient cycle are still poorly investigated. In the study, poultry litter was composted without (CK) or with lignite (T1) or dewatered lignite (T2), and their respective composts N H 4 + Com_CK, Com_T1, and Com_T2) were tested in a soil incubation to assess NH3 and GHG emission during composting and following soil utilization. The cumulative NH3 flux in T1 and T2 were reduced by 39.3% and 50.2%, while N2O emissions were increased by 7.5 and 15.6 times, relative to CK. The total GHG emission in T2 was reduced by 16.8% compared to CK. Lignite addition significantly increased nitrification and denitrification as evidenced by the increased abundances of amoA, amoB, nirK, and nirS. The increased reduction on NH3 emission by dewatered lignite could be attributed to reduced pH and enhanced cation exchangeable capacity than lignite. The increased N2O was related to enhanced nitrification and denitrification. In the soil incubation experiment, compost addition reduced NH3 emission by 72%∼83% while increased emissions of CO2 and N2O by 306%∼740% and 208%∼454%, compared with urea. Com_T2 strongly reduced NH3 and GHG emissions after soil amendment compared to Com_CK. Overall, dewatered lignite, as an effective additive, exhibits great potential to simultaneously mitigate NH3 and GHG secondary pollution during composting and subsequent utilization of manure composts.

Observational relationships between ammonia, carbon dioxide and water vapor under a wide range of meteorological and turbulent conditions: RITA-2021 campaign

Abstract. We present a comprehensive observational approach that aims to establish relationships between the surface–atmosphere exchange of ammonia (NH3) and CO2 uptake and transpiration by vegetation. In doing so, we study relationships useful for the improvement and development of NH3 flux representations in models. The NH3 concentration and flux are measured using a novel open-path miniDOAS (differential optical absorption spectroscopy) measurement setup, taken during the 5-week Ruisdael Land–Atmosphere Interactions Intensive Trace-gas and Aerosol measurement (RITA-2021) campaign (25 August until 12 October 2021) at the Ruisdael Observatory in Cabauw, the Netherlands. After filtering for unobstructed flow, sufficient turbulent mixing and CO2 uptake, we find the diurnal variability in the NH3 flux to be characterized by daytime emissions (0.05 µgm-2s-1 on average) and deposition at sunrise and sunset (−0.05 µgm-2s-1 on average). We first compare the NH3 flux to the observed gross primary production (GPP), representing CO2 uptake, and latent heat flux (LvE), representing net evaporation. Next, we study the observations following the main drivers of the dynamic vegetation response, which are photosynthetically active radiation (PAR), temperature (T) and the water vapor pressure deficit (VPD). Our findings indicate the dominance of the stomatal emission of NH3, with a high correlation between the observed emissions and both LvE (0.70) and PAR (0.72), as well as close similarities in the diurnal variability in the NH3 flux and GPP. However, efforts to establish relationships are hampered by the high diversity in the NH3 sources of the active agricultural region and the low data availability after filtering. Our findings show the need to collocate meteorological, carbon and nitrogen studies to advance our understanding of NH3 surface exchange and its representation.

Modern analogs for ammonia flux from terrestrial hydrothermal features to the Archean atmosphere

The isotopic composition of nitrogen in the rock record provides valuable evidence of reactive nitrogen sources and processing on early Earth, but the wide range of δ15N values (− 10.2 to + 50.4‰) leads to ambiguity in defining the early Precambrian nitrogen cycle. The high δ15N values have been explained by large fractionation associated with the onset of nitrification and/or fractionation produced by ammonia-ammonium equilibrium and water–air flux in alkaline paleolakes. Previous flux sensitivity studies in modern water bodies report alkaline pH is not a prerequisite and temperature can be the dominate parameter driving water–air flux. Here, I use the chemical and physical components of 1022 modern hydrothermal features to provide evidence that water–air NH3 flux produced a significant source of fixed nitrogen to early Earth’s atmosphere and biosphere. With regard to the modeled average NH3 flux (2.1 kg N m−2 year−1) and outlier removed average flux (1.2 kg N m−2 year−1), the Archean Earth’s surface would need to be 0.0092, and 0.017% terrestrial hydrothermal features, respectively, for the flux to match the annual amount of N produced by biogenic fixation on modern Earth. Water–air NH3 flux from terrestrial hydrothermal features may have played a significant role in supplying bioavailable nitrogen to early life.

Spatial Distribution of Ammonia Concentrations and Modeled Dry Deposition in an Intensive Dairy Production Region.

Agriculture generates ~83% of total US ammonia (NH3) emissions, potentially adversely impacting sensitive ecosystems through wet and dry deposition. Regions with intense livestock production, such as the dairy region of south-central Idaho, generate hotspots of NH3 emissions. Our objective was to measure the spatial and temporal variability of NH3 across this region and estimate its dry deposition. Ambient NH3 was measured using diffusive passive samplers at 8 sites in two transects across the region from 2018-2020. NH3 fluxes were estimated using the Surface Tiled Aerosol and Gaseous Exchange (STAGE) model. Peak NH3 concentrations were 4-5 times greater at a high-density dairy site compared to mixed agriculture/dairy or agricultural sites, and 26 times greater than non-agricultural sites with prominent seasonal trends driven by temperature. Annual estimated dry deposition rates in areas of intensive dairy production can approach 45 kg N ha-1 y-1, compared to <1 kg N ha-1 y-1 in natural landscapes. Our results suggest that the natural sagebrush steppe landscapes interspersed within and surrounding agricultural areas in southern Idaho receive NH3 dry deposition rates within and above the range of nitrogen critical loads for North American deserts. Finally, our results highlight a need for improved understanding of the role of soil processes in NH3 dry deposition to arid and sparsely vegetated natural ecosystems across the western US.

313 Efficacy of Vermifiltration to Treat Liquid Cattle Manure to Mitigate Carbon and Nitrogen Emissions

Abstract The objective was to determine the efficacy of a vermifiltration system that treats liquid cattle manure to alter methane (CH4), nitrous oxide (N2O), ammonia (NH3) emissions, and nutrient composition (potassium-K; phosphorus-P; nitrogen-N). Liquid manure was sampled as it entered the worm-bed (influent) and as it exited from the worm-bed (effluent) to measure changes in nutrient composition. Worm-bed surface fluxes of CH4 and N2O were measured in real-time for three distinct environmental temperatures (0 ˚C, 10 ˚C, and 20 ˚C) to examine seasonal variation at several locations in the 3.64 ha worm-bed using isolation chambers and cavity ring-down spectrometry. NH3 flux was measured from the chambers using a ChemComb 3500 Speciation Collection Cartridge and coated honeycomb denuders. NH3 samples were eluted within 4 h of collection and stored at -20 ˚C until colorimetric analysis. Duplicate NH3 measurements were made for each chamber location at each temperature. Examination of the influx and efflux data indicates reductions of 25% in K, 96% in P, 99% in total suspended solids, 92% in volatile solids, and 92% in total Kjeldahl N. Chamber CH4 concentrations at 0 ˚C (0.51 to 1.18 ppm) tended to be less at 10 ˚C (2.17 to 2.67 ppm) and 20 ˚C (1.6 to 2.45 ppm) but were not different across temperatures (P &amp;lt; .077) and reflected ambient concentrations (2.44 ppm). N2O concentrations at 0 ˚C (157.00 to 224.00 ppb) and 10 ˚C (86.3 to 176.5 ppb) were not different than ambient (358.5 ppb), but at 20 ˚C (400.0 to 655.0 ppb) concentrations tended to be greater (P &amp;lt; 0.07). NH3 concentrations at 0 ˚C (0.06 to 0.33 ppm) and 20 ˚C (1.35 and 2.21 ppm) were not different but at 10 ˚C (11.8 to 28.7 ppm) were greater (P &amp;lt; 0.05). Fluxes were calculated for each sampling period. During 0 ˚C flux densities were 1.61 ± 0.17 mg· m-2· day-1 for N2O, 2.5 0.57mg m-2· day-1 for CH4, and 0.007± 0.00 mg m-2· day-1 for NH3. At 20°C flux densities were 1.98± 0.63 mg· m-2day-1 for N2O, 2.88± 0.755 mg m-2· day-1 for CH4, and 25.4 ± 0.0 mg· m-2· day-1 for NH3.Flux calculations and extrapolation of emission rates to the entire system indicates that vermifiltration is an effective strategy to alter nutrient concentrations and reduce CH4 emissions but not emissions of N2O and NH3.

Development of a CFD model to simulate the dispersion of atmospheric NH3 in a semi-open barn

The dispersion of atmospheric NH3 constitutes the most common passive polluting system in cattle stables. Although the studies carried out through computational fluid dynamics (CFD) are focused on improving the environmental conditions in situ to increase the productivity of stables, they do not refer to determining the environmental impact of NH3 emissions into the atmosphere. This work evaluated the distribution of the NH3 flux inside a barn using CFD and its relationship with environmental conditions through probabilistic analysis by the K2 algorithm. The initial data on environmental conditions were wind speed and direction, maximum temperature, and humidity from the nearest weather station in a region characterized by hot weather conditions during summer. The vertical trajectory was used to analyze the impact of long-range transport on the spatial distribution, where 75% is between 0 and 5 m in height, and 25% is between 10 and 20 m outside the eaves. The work concluded that temperature is the main parameter of influence.

Improving nitrogen cycling in a land surface model (CLM5) to quantify soil N2O, NO, and NH3 emissions from enhanced rock weathering with croplands

Abstract. Surficial enhanced rock weathering (ERW) is a land-based carbon dioxide removal (CDR) strategy that involves applying crushed silicate rock (e.g., basalt) to agricultural soils. However, unintended biogeochemical interactions with the nitrogen cycle may arise through ERW increasing soil pH as basalt grains undergo dissolution that may reinforce, counteract, or even offset the climate benefits from carbon sequestration. Increases in soil pH could drive changes in the soil emissions of key non-CO2 greenhouse gases, e.g., nitrous oxide (N2O), and trace gases, e.g., nitric oxide (NO) and ammonia (NH3), that affect air quality and crop and human health. We present the development and implementation of a new improved nitrogen cycling scheme for the Community Land Model v5 (CLM5), the land component of the Community Earth System Model, allowing evaluation of ERW effects on soil gas emissions. We base the new parameterizations on datasets derived from soil pH responses of N2O, NO, and NH3 in ERW field trial and mesocosm experiments with crushed basalt. These new capabilities involve the direct implementation of routines within the CLM5 N cycle framework, along with asynchronous coupling of soil pH changes estimated through an ERW model. We successfully validated simulated “control” (i.e., no ERW) seasonal cycles of soil N2O, NO, and NH3 emissions against a wide range of global emission inventories. We benchmark simulated mitigation of soil N2O fluxes in response to ERW against a subset of data from ERW field trials in the US Corn Belt. Using the new scheme, we provide a specific example of the effect of large-scale ERW deployment with croplands on soil nitrogen fluxes across five key regions with high potential for CDR with ERW (North America, Brazil, Europe, India, and China). Across these regions, ERW implementation led to marked reductions in N2O and NO (both 18 %), with moderate increases in NH3 (2 %). While further developments are still required in our implementations when additional ERW data become available, our improved N cycle scheme within CLM5 has utility for investigating the potential of ERW point-source and regional effects of soil N2O, NO, and NH3 fluxes in response to current and future climates. This framework also provides the basis for assessing the implications of ERW for air quality given the role of NO in tropospheric ozone formation, as well as both NO and NH3 in inorganic aerosol formation.