Atmospheric Ammonia Research Articles

Crystal Structure and Predominant Defects in CdS Quantum Dots Fabricated by the Langmuir-Blodgett Method.

The crystal structure and shape of the CdS quantum dots (QDs) obtained by the Langmuir-Blodgett method were studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy (EXAFS), and ultraviolet spectroscopy. X-ray photoelectron spectroscopy (XPS) and stationary photoluminescence spectroscopy (PL) methods were used to determine the dominant surface defects. Initially synthesized QDs within the Langmuir-Blodgett film of fatty behenic acid have a cubic structure and oblate spheroid shape, while free-standing QDs obtained after the matrix evaporation have a wurtzite structure and sphere-like shape. QDs within the matrix demonstrate a wide PL band centered at 2.3 eV corresponding to defect-assisted radiative recombination; after the matrix annealing and passivation of the QD surface in an ammonia atmosphere, the PL spectrum demonstrates a high-intensity band-edge peak together with a low-intensity defect-assisted shoulder. It was established that sulfur (VS) vacancies are the dominating defects. A model of simultaneous band-edge and defect-assisted recombination through the VS level was proposed.

Chemiresistive sensing of volatile ammonia over zinc oxide encapsulated polypyrrole based nanocomposite

The present research manuscript demonstrates the chemiresistive sensing of volatile ammonia from the soil over zinc oxide encapsulated polypyrrole (ZnO-en-PPy) composite prepared by in-situ chemical polymerization technique using ferric chloride as a polymerizing agent. The observed analytical result revealed the formation of nanocomposite with optimized crystallinity, improved thermal stability, and responsive electrical conductivity against ammonia concentration. Further, a thin film of the composite was casted on a glass rod to prepare a portable resistive type ammonia sensor for atmospheric and volatile ammonia from the soil with observed sensing parameters i.e. sensitivity range of 1 ppm–100 ppm, sensitivity 0.4947 kΩ-ppm−1, response time 45 s, recovery time 55 s, and stability for 90 days.

Analysis of atmospheric ammonia over South and East Asia based on the MOZART-4 model and its comparison with satellite and surface observations

Abstract. Limited availability of atmospheric ammonia (NH3) observations limits our understanding of controls on its spatial and temporal variability and its interactions with the ecosystem. Here we used the Model for Ozone and Related chemical Tracers version 4 (MOZART-4) global chemistry transport model and the Hemispheric Transport of Air Pollution version 2 (HTAP-v2) emission inventory to simulate global NH3 distribution for the year 2010. We presented a first comparison of the model with monthly averaged satellite distributions and limited ground-based observations available across South Asia. The MOZART-4 simulations over South Asia and East Asia were evaluated with the NH3 retrievals obtained from the Infrared Atmospheric Sounding Interferometer (IASI) satellite and 69 ground-based monitoring stations for air quality across South Asia and 32 ground-based monitoring stations from the Nationwide Nitrogen Deposition Monitoring Network (NNDMN) of China. We identified the northern region of India (Indo-Gangetic Plain, IGP) as a hotspot for NH3 in Asia, both using the model and satellite observations. In general, a close agreement was found between yearly averaged NH3 total columns simulated by the model and IASI satellite measurements over the IGP, South Asia (r=0.81), and the North China Plain (NCP), East Asia (r=0.90). However, the MOZART-4-simulated NH3 column was substantially higher over South Asia than East Asia, as compared with the IASI retrievals, which show smaller differences. Model-simulated surface NH3 concentrations indicated smaller concentrations in all seasons than surface NH3 measured by the ground-based observations over South and East Asia, although uncertainties remain in the available surface NH3 measurements. Overall, the comparison of East Asia and South Asia using both MOZART-4 model and satellite observations showed smaller NH3 columns in East Asia compared with South Asia for comparable emissions, indicating rapid dissipation of NH3 due to secondary aerosol formation, which can be explained by larger emissions of acidic precursor gases in East Asia.

WN Coupled with Bi Nanoparticles to Enhance the Localized Surface Plasmon Resonance Effect for Photocatalytic Hydrogen Evolution.

Conversion of light energy and chemical energy in a wide spectrum region, especially in the near-infrared (NIR) light region, is still a challenge in the field of photocatalysis. In this work, a layered Bi-WN photocatalyst with a heterojunction was prepared by reducing flake-shaped WN and flower-shaped Bi2O3 in an ammonia atmosphere. Under the process of NIR light (λ > 700 nm)-driven water splitting, the optimal hydrogen (H2) generation rates based on the Bi-WN photocatalyst can reach to 7.49 μmol g-1 h-1, which is 2.47 times higher than that of WN of 3.03 μmol g-1 h-1. The result indicates that the Bi-WN photocatalyst can be effective under NIR light. Through ultraviolet-visible-NIR diffuse reflectance spectrum analysis, it can be seen that the light absorption edge of Bi-WN is obviously redshifted. Combining the results of electrochemical characterizations, we have found that the addition of the Bi metal plays an important role in NIR light-driven water splitting. Under irradiation of NIR light, the electrons on the Bi-WN substrate are stronger due to local surface plasmon resonance, which reduces the possibility of recombination of photogenerated electrons and holes on WN. In addition, after the Bi metal absorbs the photon energy, the electron-hole pairs are separated, and the H2 production rate increases significantly under the combined action of the charge transfer mechanism and the local electric field enhancement mechanism.

Isothermal and kinetic evaluation of adsorption of organic pollutants from fish farm effluents (Aq Qala, Golestan province, Iran) by Nano composites (chitosan and activated carbon)

The purpose of present study was to study absorbent ability of organic pollutants from warm water fish farms by synthesized nano-composite adsorbent. study was performed at different physicochemical condition of pH (5-8), effluent concentration (25-100 mg/L), contact time (15-90) minutes. Adsorption isotherm studies were analyzed using Freundlich, Langmuir models and adsorption kinetics studies using pseudo-first-order and pseudo-second-order kinetic models. The Langmuir and Freundlich isotherms, first and second order adsorption kinetics were investigated. The Langmuir and Freundlich isotherms for nitrite (R2 = 0.9076, R2 = 0.5911), phosphate (R2= 0.9307, R2= 0.5755) and ammonia (R2 = 0.7288 and R2 = 0.7549), respectively obtained. According to the results, the data of nitrite and phosphate pollutants were more consistent with the Langmuir model, but the data of ammonia pollutants were more consistent with the Freundlich model. According to the results, the adsorption of phosphate pollutants was more consistent with pseudo-first order kinetic model and the adsorption of nitrite and ammonia pollutants was more consistent with the pseudo-second order kinetic model.

Isothermal and Kinetic Evaluation of Adsorption Fish Farm Effluents by Nanocomposites (Chitosan and Activated Carbon)

Background: In wastewater treatment, removal of phosphate and ammonia is of great importance. Chitosan is a copolymer, which can be applied in low-cost adsorption. Thus, in this study, chitosan and activated carbon nanocomposite adsorbents were prepared to remove organic pollutants from the fish farm effluents. Methods: This study was performed at different physicochemical conditions of pH (5-8), effluent dose (25-100 mg/L), and contact time (15-90 min) minutes. Adsorption isotherm studies were analyzed using Freundlich, Langmuir models, and adsorption kinetics studies. Results: The Langmuir and Freundlich isotherms for nitrite (R2=0.9076, R2=0.5911), phosphate (R2=0.9307, R2=0.5755), and ammonia (R2=0.7288 and R2=0.7549) were respectively obtained. According to the results, the data of nitrite and phosphate pollutants were more consistent with the Langmuir model, but the data of ammonia pollutants were more consistent with the Freundlich. The best optimal adsorption occurred at a pH=7. Elevation of the initial concentration of the pollutant led to the depletion of the removal functions. With increasing the contact time, adsorption efficiency increased. Conclusion: Finally, with respect to the obtained elimination percentage (R=99.98%), chitosan and activated carbon nanocomposites have a high ability to remove organic pollutants.

Atmospheric ammonia point source detection technique at regional scale using high resolution satellite imagery and deep learning

Ammonia (NH3) is a precursor of atmospheric aerosols. The lack of real-time updated and high spatial resolution atmospheric NH3 point source information is one of the critical problems in the study of atmospheric pollution. Satellite-based NH3 observation data provide a new approach to NH3 point source detection. However current spatial resolution of NH3 concentration satellite data is still not sufficient to extract NH3 point sources at regional scale with high accuracy. Based on the traditional oversampling method to improve the spatial resolution of NH3 satellite data, this paper used high-resolution satellite image data with the geometric morphological features of NH3 point sources to detect the NH3 point sources at regional scale under deep learning techniques. The high-precision NH3 point source location and category information at regional scale is extracted concurrently, solving the current problem that multiple point sources cannot be detected in a single satellite NH3 concentration hotspot. After analyzing a priori knowledge, the industrial sources were further subdivided. The atmospheric ammonia point source detection technique in this paper were used in Northeast China, where the number and types of NH3 emission sources are abundant. The detection results significantly increased the number of NH3 potential point sources detected in Northeast China compared with the traditional oversampling method. The deep learning-based technology combines NH3 concentration remote sensing products with high resolution satellite image data to effectively detect the spatial distribution and types of NH3 point sources at regional scale, providing powerful technical support for NH3 emission regulation and control.

High-performance CrN tight ultrafiltration membranes prepared by in situ gas–solid catalytic reaction

To expand the industrial application of membranes, high-performance CrN tight ultrafiltration membranes (UF) were prepared by in situ gas–solid reaction using Cr2O3 as a nanoprecursor and TiO2 as a nitriding catalyst in ammonia atmosphere. The phase composition and microstructure of CrN UF membranes were characterized by X-ray diffraction and field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy. The effects of TiO2 and sintering parameters on the crystalline phase and pore size of CrN UF membranes were investigated. The results identified Ti4+ as a key factor influencing the transformation of the Cr2O3 phase into the CrN phase. The as-prepared CrN membranes exhibited enhanced hydrophilicity, no cracks or pinholes, water flux of 121 L·m−2h−1 bar−1, and a molecular weight cut-off of 1500 Da. The membranes also had retention rates of 100% for methyl blue (50 ppm) and 90% for methylene blue (50 ppm), which almost remained constant under repeated use.

A Multiyear Constraint on Ammonia Emissions and Deposition Within the US Corn Belt

AbstractThe US Corn Belt is a global hotspot of atmospheric ammonia (NH3), a gas known to adversely impact the environment and human health. We combine hourly tall tower (100 m) measurements and bi‐weekly, spatially distributed, ground‐based observations from the Ammonia Monitoring Network with the US National Emissions Inventory (NEI) and WRF‐Chem simulations to constrain NH3 emissions from April to September 2017–2019. We show that: (1) NH3 emissions peaked from May to July and were 1.6–1.7 times the annual NEI average; (2) average growing season NH3 emissions from agricultural lands were remarkably similar across years (3.27–3.64 nmol m−2 s−1), yet showed substantial episodic variability driven by meteorology and land management; (3) dry deposition was 40% of gross emissions from agricultural lands and exceeded 100% of gross emissions in natural lands. Our findings provide an important benchmark for evaluating future NH3 emissions and mitigation efforts.

Water quality criteria and ecological risk assessment for ammonia in the Shaying River Basin, China

Current Chinese surface water environmental quality standard GB3838-2002 for ammonia fails to take water quality factors and native organism distributions in different basins into consideration. In this study, ammonia toxicity tests were performed using three aquatic organisms native to the Shaying River Basin (China). Published ammonia toxicity data with pH and temperature, and toxicity data acquired in this study were used to establish water quality criteria. The final criterion maximum concentration (CMC) and criterion continuous concentration (CCC) for the Shaying River Basin were 5.09 and 1.36 (mg total ammonia nitrogen (TAN))/L (pH 7 and 20 °C), respectively. In addition, based on the corresponding relationship between ammonia toxicity and temperature and pH, the ecological risk assessment of ammonia was conducted in different seasons for the Shaying River using a tiered approach of both hazard quotient (HQ) and the joint probability (JPC) methods. Two methods gave consistent results: the ecological risks of ammonia to aquatic species in the Shaying River Basin were severe and the risk could be ranked as wet season > flat season > dry season. It is therefore indicating that monitoring, evaluation, and early warning of ammonia pollution need to be taken to prevent and control the risks posed by ammonia pollution, especially for wet season (because of high temperatures and pH) or flat season (because of high pH values). We hope the present work could provide valuable information to manage and control ammonia pollution in the Shaying River Basin.

New horizons in the application of a neglected biomass pyrolysis byproduct: A marked simultaneous decrease in ammonia and carbon dioxide emissions

During the process of biochar production, large amounts of wood vinegar (WV) are obtained as a byproduct, and the objective of this study was to investigate the efficiency of this byproduct in reducing the ammonia (NH3) pollution and greenhouse gas emissions that are associated with animal husbandry. Special attention was given to the potential of WV in bringing about NH3 and carbon dioxide (CO2) emission reductions, and the dynamic mean of the concentrations of NH3 and CO2 as well as the effect of WV on several environmental indicators were investigated. For the first time, a positive correlation was observed between the removal efficiencies of NH3 and CO2 and WV concentration. Specifically, when the concentration of WV was 7%, the highest removal efficiencies for NH3 and CO2 were obtained (79.1 ± 1.8 and 54.3 ± 4.9%, respectively). These results confirmed that acidification using WV could be a promising approach for the synergistic mitigation of NH3 and CO2 emission in swine houses. The results of this study also clarify the connection between the products of biomass pyrolysis, livestock sector pollution, and gas emission reduction. Therefore, it is expected that the results of this study will generate a global discussion regarding the removal of the pollutants that are associated with animal housing facilities and these three fields to the end of promoting green development and cleaner production globally.

Broiler performance and litter ammonia levels as affected by sulfur added to the bird's diet

Ammonia buildup in poultry houses is a concern for the poultry industry as it can lead to potential losses because of reduced bird performance, damage to the birds' skin and respiratory tract, and loss of customers owing to animal welfare issues. Current methods for ammonia control are useful, but there is considerable variation in ammonia levels from farm to farm. A potential strategy for eliminating this variation would be to approach ammonia management by using a feed additive, thereby increasing uniformity of application among farms and houses. This study tested the effects of using elemental sulfur as a feed additive (feedthrough sulfur) on ammonia levels, live performance, and paw quality of broilers raised on fresh bedding for 3 consecutive experiments. Feedthrough sulfur had no negative or positive effects on bird performance in terms of average BW and feed conversion ratio, and this treatment as well as sodium bisulfate appeared to perform at least in controlling atmospheric ammonia levels. However, no significant difference in ammonia levels was detected between any of the treatments and the control. Final litter pH was lower for feedthrough sulfur–treated birds than that of the control, and the percentage of birds with footpad lesions was lower in 2 of 3 experiments than that of the control. These results indicate that feedthrough sulfur may be a useful litter treatment compared with existing alternatives, though more research is needed to confirm this.

Kinetic Study of Ammonia Removal using Activated Rice Husk

Ammonia pollution causes eutrophication and algal bloom, which eventually disrupts the marine ecosystem’s equilibrium. Efforts have been made to either recover or remove ammoniacal nitrogen from water resources. Electrochemical, precipitation, adsorption, biological and membrane technology have been developed with varying degrees of complexity and arrangement to overcome this problem. To date, adsorption is widely used to remedy water resources as it is cost and energy effective while being simple to operate and maintain. Adsorption kinetic models are important in evaluating the performance of adsorbent and reveals the adsorption mass transfer mechanism. Nevertheless, the kinetic studies reported in the literature was not complete as only a few models were considered. Meanwhile, the statistical parameter to validate the model was commonly depended on R2 value alone. The objective of this study is to provide a comprehensive kinetic study of ammonia adsorption using activated rice husk, to the readers by investigating the validity of 9 kinetic models in fitting the experimental data. All the models are validated by using R2, R2, residual sum of square (SSE) and (mean square error) MSE. Result showed > 0.99 R2 values and low R2, SSE, MSE were found for Mixed order, Ritchie’s and Elovich models. This indicates that the ammonia adsorption process was governed by the adsorption at the active sites of the adsorbent and it was mainly driven by the chemisorption.

Experimental investigation of formation and decomposition of roaldite in ammonia atmosphere at 300–700 °C and associated nitrogen isotope fractionations

Roaldite (Fe4N) is one of the few nitride minerals found in meteorites. Their nitrogen (N) isotopic signatures carry important information for understanding the early N cycle in the proto-solar nebula. However, the lack of knowledge on the N isotopic effects from nitride formation to its survival from frictional heating during landing impedes the interpretation and application of N isotope compositions of nitride minerals in meteorites. Here, we carried out laboratory experiments under a recently proposed roaldite forming condition, i.e., NH3 (as starting N source) reacting with metallic Fe at medium temperatures. We observed Fe4N formation over a large range of temperatures from 300 °C to 700 °C. The formation of Fe4N was associated with equilibrium N isotope fractionations with αFe4N-NH3 values of 0.9907 (±0.0004) at 300 °C and 0.9936 (±0.0004) at 500 °C, respectively. In the experimental pressure conditions (initial PNH3 = 3.9–6.4 bar, PTotal < 8.3 bar), the formed Fe4N remained stable at 300 °C, but was unstable and quickly decomposed to Fe and N2 at 500 °C and 700 °C. The decomposition of Fe4N was associated with large kinetic isotope fractionations with αN2-Fe4N values of 0.9811 (±0.0009) at 500 °C and 0.9839 (±0.0011) at 700 °C, respectively. Our experimental results suggest that roaldite formed from NH3 can carry an isotopic signature very close to that of its source, but partial decomposition (if there is any) can easily shift its N isotope composition for several tens of per mil, and in extreme cases, to >300‰. Thus, great caution is needed when using N isotope composition of roaldite (and probably other nitride minerals as well) to trace source information.

Green conversion of bamboo chips into high-performance phenol adsorbent and supercapacitor electrodes by simultaneous activation and nitrogen doping

Nitrogen doping is one of the most promising approaches for improving the properties of carbon materials. Here, we reported a simple and effective method for the preparation of nanoporous nitrogen-doped carbonaceous material for liquid phase adsorbents and supercapacitor electrodes. In this method, the target carbonaceous material (biochar) was produced by one-step pyrolysis and activation of bamboo chips under the ammonia atmosphere. Two green activation reagents (K2C2O4 and KHCO3) were introduced into the preparation process simultaneously. The physicochemical properties of biochar were studied by means of SEM, BET, XRD, XPS and so on. The characterization results confirmed that the vascular bundle structure of bamboo can be well preserved by pyrolysis under ammonia atmosphere combined with green activation, and the nitrogen atoms were successfully introduced into the biochar’s skeleton uniformly. The physicochemical properties of biochar can be adjusted suitable for high phenol adsorption and supercapacitor electrodes at different temperatures. Optimum nitrogen-doped biochar showed a high phenol adsorption capacity of 169.5 mg/g at 25 ℃ and exhibited exceptional specific capacitance of 208 F/g at the current density of 1 A/g due to its unique nanoporous structures and surface functional groups. This novel nanoporous nitrogen-doped bamboo chips have great application potential in pollutant removal and energy storage.

Impact of selective thermal etching in mixed H2/NH3 atmosphere on crystal quality of AlGaN/GaN heterostructures

We investigated the impact of selective thermal etching in a mixed hydrogen and ammonia atmosphere on the crystal quality and electrical characteristics of Ga- and N-polar AlGaN/GaN heterostructures. It was revealed that the etching rate of N-polar GaN is lower than that of Ga-polar GaN under our experimental conditions, and they showed a similar dependence on process temperature with almost the same activation energies. We demonstrated the use of a thin AlGaN layer as a selective etching stopper for both Ga- and N-polarity. The AlGaN stoppers exhibited a smooth surface after etching the GaN layer above them. As for the electrical characteristics, there was no significant degradation in the mobility of the two-dimensional electron gas. The results indicate that selective thermal etching is a promising technique for device fabrication and is especially suitable for precise GaN layer removal when GaN-based devices are fabricated with an epitaxial layer transfer technique.

Insight into the Mechanism of Glycerol Dehydration and Subsequent Pyridine Synthesis

In the present study, glycerol was exploited as the feedstock to synthesize pyridine with ammonia gas as a carrier and reactant through thermal conversion. A density functional theory (DFT) at the M06-2X method was applied to understand the mechanism of glycerol dehydration, the ammonization of oxygenated compounds, and the condensation of imines. The results confirmed that glycerol could be directly converted into pyridine in ammonia atmosphere at 550 °C. The overall view of the thermal conversion mechanism of glycerol was compared with the previous experimental data and the proposed mechanisms, which indicated that the neutral glycerol dehydration process should mainly produce acrolein, acetaldehyde, formaldehyde, and acetol. The produced oxygenated compounds (acrolein and acetaldehyde) can react with ammonia to form imine, which would further undergo Michael addition, a Diels-Alder reaction, deammonization, and dehydrogenation to form pyridine. In a catalytic condition, ZSM-5 not only plays a shape-selective effect on the conversion of glycerol to pyridine but also changes the path of the reaction. The structure of ZSM-5 limits the formation of multisubstituted pyridine products, which is beneficial to the formation of pyridine and monosubstituted pyridine. Protonated vinylamine intermediates may be a critical step limiting pyridine yield and selectivity. The kinetic analysis that is based on transition state theory was consistent with product contribution in experiments. The present study confirmed the selectivity and the conversion route of glycerol to pyridine.

An efficient WN catalyst nitrogenized from morphology-controllable WO3 for oxygen reduction reaction

Tungsten oxide (WO3) as precursor was prepared by one-step hydrothermal method and then nitrogenized under ammonia atmosphere to obtain tungsten nitride (WN) electrocatalyst for oxygen reduction reaction (ORR). Different morphological structures such as rod-like, needle-like and urchin-like of WO3 were carried out by adding morphology control agents and adjusting hydrothermal time. WN catalyst from needle-like WO3 with minimum section diameter emerged outstanding ORR performance (rapid kinetics of oxygen reduction and approach to four-electron reaction) for its nanoscale particles, low agglomeration and nitrogen doping. The low-cost WN possessed fine durability and better methanol resistance compared to commercial Pt/C, which were also crucial issues in fuel cells.

Nanostructures Composed of Dual Plasmonic Materials Exhibiting High Thermal Stability and SERS Enhancement

AbstractAs one kind of alternative to conventional metals, titanium nitride offers many advantages in the rapidly growing fields of plasmonics and metamaterials. However, the development of TiNx‐based plasmonics is severally limited by the difficulty in the preparation. Herein, a facial approach is developed for the preparation of Au@TiNx core‐shell nanostructures. The synthesis starts with colloidal Au nanospheres, followed by the growth of amorphous TiO2 shells. The obtained Au@a‐TiO2 nanostructures convert into Au@TiNx through nitridation at high temperature in ammonia atmosphere. The prepared Au@TiNx nanostructures have strong plasmonic scatting in the visible region and strong field enhancement at the surface of nanostructures. Au@TiNx nanostructures also exhibit a relatively large enhancement for Raman scattering. The developed preparation method can produce TiNx nanostructures with relatively uniform size and thus will be very helpful to the development of TiNx‐base plasmonics.

Predicting atmospheric ammonia dispersion and potential ecological effects using monitored emission rates from an intensive laying hen facility in Ireland

Agriculture is responsible for 98% of atmospheric ammonia (NH3) in Ireland, of which pigs and poultry produce 7%; with laying hens specifically contributing 0.6%. Though a small proportion of the national NH3 total emissions, the ecological impacts on sensitive sites attributed to laying hen farms can be substantial. NH3 emission monitoring was conducted in Spring (February to March) and Summer (July to August) 2016 to account for seasonal variation. The total average emission and ventilation rate was 0.25 g bird−1 day−1 and 931 cm3 s−1 bird−1. This is lower than the previously used emission factor for the Irish national inventory of 0.5 g bird−1 day−1, but broadly similar to factors reported in the United Kingdom (UK) and the European Union (EU). Dispersion modelling using monitored data indicated potentially acute effects within 84 m, critical level exceedance within 312 m and exceedance of 0.3 kg N ha−1 year−1 deposition within 2.9–5.2 km. The sensitivity of the model was tested using SCAIL-Agriculture emission and ventilation rates which showed P-values for one tailed critical level below 0.01 for all models, indicating that when normalised the maximum extents modelled by AERMOD were significantly different. This analysis showed emission rate having more influence than ventilation rate. Both parameters combined had the greatest increase in dispersion extent, on average 55.8% greater than the use of monitored rates. A deposition rate of 0.3 kg N ha−1 year−1 was modelled to occur within 5.1–7.7 km when using SCAIL-Agriculture rates. Indicating that the use of SCAIL-Agriculture recommended emission and ventilation rates would have been sufficiently precautionary to assess negative ecological effects on a Natura 2000 site under the Habitats Directive (92/43/EEC). In relation to Appropriate Assessment (AA) screening, the use of any contribution from a source within a set distance may be an appropriate full AA trigger.