Biogenic nitric oxide emissions from soils: impact on NOx and ozone over West Africa during AMMA (African Monsoon Multidisciplinary Analysis) - observational study

Chemical and meteorological parameters measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the African Monsoon Multidisciplinary Analysis (AMMA) campaign are presented to show the impact of NOx emissions from recently wetted soils in West Africa. NO emissions from soils have been previously observed in many geographical areas with different types of soil/vegetation cover during small scale studies and have been inferred at large scales from satellite measurements of NOx. This study is the first dedicated to showing the emissions of NOx at an intermediate scale between local surface sites and continental satellite measurements. The measurements reveal pronounced mesoscale variations in NOx concentrations closely linked to spatial patterns of antecedent rainfall. Fluxes required to maintain the NOx concentrations observed by the BAe-146 in a number of cases studies and for a range of assumed OH concentrations (1��106 to 1��107 molecules cm���3) are calculated to be in the range 8.4 to 36.1 ng N m���2 s���1. These values are comparable to the range of fluxes from 0.5 to 28 ng N m���2 s���1 reported from small scale field studies in a variety of non-nutrient rich tropical and sub-tropical locations reported in the review of Davidson and Kingerlee (1997). The fluxes calculated in the present study have been scaled up to cover the area of the Sahel bounded by 10 to 20 N and 10 E to 20 W giving an estimated emission of 0.03 to 0.30 Tg N from this area for July and August 2006. The observed chemical data also suggest that the NOx emitted from soils is taking part in ozone formation as ozone concentrations exhibit similar fine scale structure to the NOx, with enhancements over the wet soils. Such variability can not be explained on the basis of transport from other areas. Delon et al. (2008) is a companion paper to this one which models the impact of soil NOx emissions on the NOx and ozone concentration over West Africa during AMMA. It employs an artificial neural network to define the emissions of NOx from soils, integrated into a coupled chemistry-dynamics model. The results are compared to the observed data presented in this paper. Here we compare fluxes deduced from the observed data with the model-derived values from Delon et al. (2008).

Biogenic nitric oxide emissions from soils: impact on NOx and ozone over West Africa during AMMA (African Monsoon Multidisciplinary Analysis) - Modelling study

Nitrogen oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions linked to precipitations in the Sahel on the 6 August 2006 during the AMMA campaign. This algorithm has been coupled in the surface scheme of a coupled chemistry dynamics model (MesoNH Chemistry) to estimate the impact of the NO emissions on NOx and O3 formation in the lower troposphere for this particular episode. Four different simulations on the same domain and at the same period are compared: one with anthropogenic emissions only, one with soil NO emissions from a static inventory, at low time and space resolution, one with NO emissions from neural network, and one with NO from neural network plus lightning NOx. The influence of NOx from lightning is limited to the upper troposphere. The NO emission from soils calculated with neural network responds to changes in soil moisture giving enhanced emissions over the wetted soil, as observed by aircraft measurements after the passing of a convective system. The subsequent enhancement of NOx and ozone is limited to the lowest layers of the atmosphere in modelling, whereas measurements show higher concentrations above 1000 m. The neural network algorithm, applied in the Sahel region for one particular day of the wet season, allows an immediate response of fluxes to environmental parameters, unlike static emission inventories. Stewart et al (2008) is a companion paper to this one which looks at NOx and ozone concentrations in the boundary layer as measured on a research aircraft, examines how they vary with respect to the soil moisture, as indicated by surface temperature anomalies, and deduces NOx fluxes. In this current paper the model-derived results are compared to the observations and calculated fluxes presented by Stewart et al (2008).

HOx observations over West Africa during AMMA: impact of isoprene and NOx

Aircraft OH and HO2 measurements made over West Africa during the AMMA field campaign in summer 2006 have been investigated using a box model constrained to observations of long-lived species and physical parameters. "Good" agreement was found for HO2 (modelled to observed gradient of 1.23 �� 0.11). However, the model significantly overpredicts OH concentrations. The reasons for this are not clear, but may reflect instrumental instabilities affecting the OH measurements. Within the model, HOx concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O(1D) with water vapour, and loss processes dominated by HO2 + HO2 and HO2 + RO2. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NOx and high isoprene environments, we do not observe any dependence of model success for HO2 on isoprene and attribute this to efficient recycling of HOx through RO2 + NO reactions under the moderate NOx concentrations (5���300 ppt NO in the boundary layer, median 76 ppt) encountered during AMMA. This suggests that some of the problems with understanding the impact of isoprene on atmospheric composition may be limited to the extreme low range of NOx concentrations.

NOx and O3 above a tropical rainforest: an analysis with a global and box model

A cross-platform field campaign, OP3, was conducted in the state of Sabah in Malaysian Borneo between April and July of 2008. Among the suite of observations recorded, the campaign included measurements of NOx and O3 ��� crucial outputs of any model chemistry mechanism. We describe the measurements of these species made from both the ground site and aircraft. We then use the output from two resolutions of the chemistry transport model p-TOMCAT to illustrate the ability of a global model chemical mechanism to capture the chemistry at the rainforest site. The basic model performance is good for NOx and poor for ozone. A box model containing the same chemical mechanism is used to explore the results of the global model in more depth and make comparisons between the two. Without some parameterization of the nighttime boundary layer ��� free troposphere mixing (i.e. the use of a dilution parameter), the box model does not reproduce the observations, pointing to the importance of adequately representing physical processes for comparisons with surface measurements. We conclude with a discussion of box model budget calculations of chemical reaction fluxes, deposition and mixing, and compare these results to output from p-TOMCAT. These show the same chemical mechanism behaves similarly in both models, but that emissions and advection play particularly strong roles in influencing the comparison to surface measurements.

Design and development of a low NOx Coanda ejector burner

Small gaseous combustion systems are being targeted by strict pollution legislation which will provide challenges to reduce the NOx being emitted. A novel type of gas burner has been successfully designed and developed which incorporates a Coanda ejector to promote recirculation of flue gas from the burner exit. This provides a combustion system which gives very low emissions of NOx and CO, whilst maintaining a high degree of flame stability over a range of air/fuel ratios and fuel flow rates. Recirculation of flue gas was obtained by manipulating the aerodynamics of the system, without the aid of external duct work or moving parts. The design of the burner allowed very low pollutant emissions near stoichiometric conditions, resulting in high temperatures of the exit gas. Potential applications of this type of burner are in small and intermediate furnaces where low NOx emissions are required. Moreover, very high-temperature applications, such as glass furnaces could benefit in both cost and pollutant emissions from such a burner.

Latitudinal variation of the effect of aviation NOx emissions on atmospheric ozone and methane and related climate metrics

We evaluate the response to regional and latitudinal changes in aircraft NOx emissions using several climate metrics (radiative forcing (RF), Global Warming Potential (GWP), Global Temperature change Potential (GTP)). Global chemistry transport model integrations were performed with sustained perturbations in regional aircraft and aircraft-like NOx emissions. The RF due to the resulting ozone and methane changes is then calculated. We investigate the impact of emission changes for specific geographical regions (approximating to USA, Europe, India and China) and cruise altitude emission changes in discrete latitude bands covering both hemispheres. We find that lower latitude emission changes (per Tg N) cause ozone and methane RFs that are about a factor of 6 larger than those from higher latitude emission changes. The net RF is positive for all experiments. The meridional extent of the RF is larger for low latitude emissions. GWPs for all emission changes are positive, with tropical emissions having the largest values; the sign of the GTP depends on the choice of time horizon.

Potencialidade do uso de solu����o alcalina do ��on ferrato (VI) na oxida����o de ��xidos de nitrog��nio (NOx) presentes em emiss��es gasosas

O ferrato(VI) de pot��ssio, composto fortemente oxidante, foi testado em uma coluna de absor����o de gases a fim de remover o NO presente em gases oriundos de fontes fixas de queima de combust��veis f��sseis. O poder oxidativo do ferrato(VI) e seu comportamento atrav��s da cin��tica de decaimento do NO foram avaliados com o prop��sito de melhor entender a rea����o de oxida����o. O sistema lavador de gases foi constitu��do por tr��s subsistemas: o primeiro, um cilindro contendo uma mistura de NO/N2 com concentra����es de NO de 50 e 98 ppm; o segundo, os lavadores de gases, constitu��do por dois reatores/lavadores com capacidade de 1.000 mL que foram completados com 600 mL de solu����o lavadora e com 400 mL de an��is de Rasching de vidro e um terceiro, reator/lavador que continha 400 mL da mesma solu����o dos demais, sem os an��is; o terceiro subsistema, constitu��do por equipamentos analisadores de NO e NO2. Os equipamentos de medi����o foram os da marca Oldham, modelo TX 2000, para NO, com escala de medida de 0-100 ppm NO e TX 2000, para NO2, com escala de medida de 0-30 ppm NO2. O ferrato(VI) de pot��ssio foi obtido via ��mida e analisado por volumetria de oxida����oredu����o. Os testes de oxida����o foram realizados �� temperatura de 25oC �� 0,5oC e press��o de uma atmosfera. Inicialmente, testou-se t��cnicas padr��es de remo����o de NO de gases a frio. Hidr��xido de s��dio e hidr��xido de pot��ssio tem sido empregados comercialmente na remo����o de NOx. As solu����es de hidr��xido de pot��ssio e de s��dio apresentaram a mesma remo����o de NO quando a concentra����o inicial do NO no g��s foi de 50 ppm. A maior efici��ncia de remo����o de NO deu-se para a raz��o molar de 5 OH�� / 1 NO em cinco minutos de tempo de deten����o, utilizando solu����o de ferrato(VI): 86% para a concentra����o inicial de 50 ppm e 85% para a concentra����o inicial de 98 ppm. Os resultados experimentais mostram que a solu����o de ferrato(VI) de pot��ssio apresentou efici��ncia de remo����o 25% superior �� das outras solu����es testadas. Apesar das rea����es de oxida����o do NO serem bastante complexas, em fun����o dos resultados anal��ticos realizados em termos de nitritos e nitratos, pode -se concluir que o NO �� oxidado a NO2 e este passa a NO2 - e NO3 2- em solu����o, confirmando o mecanismo proposto por diversos autores. A abordagem cin��tica mostrou que a rea����o de oxida����o pelo ��on ferrato(VI) �� de primeira ordem em rela����o ao NO e a constante m��dia de velocidade de rea����o resultante dos dados experimentais foi de 9,80 x 10-4 s-1. A viabilidade t��cnica do uso do ferrato(VI) de pot��ssio como oxidante do NOx em torres absorvedoras de gases foi comprovada, pois o composto mostrou-se um eficiente oxidante para o NO nas condi����es testadas.

Tratamento termoqu��mico do tit��nio auxiliado por plasma de ar - N2 - O2

Discs were grade II cp Ti oxynitride by plasma of Ar - N2 - O2 using different proportions of individual gases. These ratios were established from analysis of optical emission spectroscopy (OES) of plasma species. The proportions that resulted in species whose spectra showed an abrupt change of light intensity were chosen for this study. Nanohardness tests revealed that there was a correlation between the intensity of N2 + species with the hardness, because the treatments where they had a higher intensity, obtained a higher value nanohardness, although the crystalline phases have remained unchanged. With respect to topography, it was observed that in general, the surface roughness is related to the intensities of plasma species, because they may have different values depending on the behavior of the species. Images obtained by optical microscopy revealed a surface with grains of different colors to optical reflectance showed a peak of reflection in the red area. Measures the contact angle and surface tension showed hydrophilic properties and hydrophilic with little variation of polar and dispersive components of surface tension

Influ��ncia das esp��cies do plasma de N2 + O2 nas propriedades f��sicoqu��micas das superf��cies do pet

This work reports the influence of the poly (ethylene terephthalate) textile and films surface modification by plasmas of O2 and mixtures (N2 + O2), on their physical and chemical properties. The plasma surface polymeric modification has been used for many researchs, because it does not affect the environment with toxic agents, the alterations remains only at nanometric layers and this technique shows expressive results. Then, due to its good acceptance, the treatment was carried out in a vacuum chamber. Some parameters remained constant during all treatment, such as: Voltage 470 V; Pressure 1,250 Mbar; Current: 0, 10 A and gas flow: 10 cm3/min, using oxygen plasma alternating the treatment time 10 to 60 min with an increase of 10 min to each subsequent treatment. Also, the samples were treated with a gas mixture (nitrogen + oxygen) which was varied only the gas composition from 0 to 100% leaving the treatment time remaining constant to all treatment (10 min). The plasma treatment was characterized in-situ with Optics Emission Spectroscopy (OES), and the samples was characterized by contact angle, surface tension, Through Capillary tests, Raman spectroscopy, Infrared attenuated total reflection (IR-ATR) and atomic force microscopy, scanning electronic Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The results showed that oxygen treated fabrics presented high wettability, due to the hydrophilic groups incorporation onto the surface formed through spputering of carbon atoms. For the nitrogen atmosphere, there is the a film deposition of amine groups. Treatment with small oxygen concentration in the mixture with nitrogen has a higher spputered species of the samples

Estudo da molhabilidade de tecidos 100% poli��ster tratados em plasma N2/O2 em fun����o do seu envelhecimento natural

This work reports the influence of the poly (ethylene terephthalate) textile surface modification by plasmas of O2 and mixtures (N2 + O2), on their physical and chemical properties. The treatment was carried out in a vacuum chamber. Some parameters remained constant during all treatment, such as: Voltage 470 V; Pressure 1,250 Mbar; Current: 0, 10 A and gas flow: 10 cm3/min. Other parameters, such as working gas composition and treatment time, were modified as the following: to the O2 plasma modified samples only the treatment time was changed (10, 20, 30, 40, 50 and 60 minutes). To the plasma with O2 and N2 only the chemical concentrations were changed. Through Capillary tests (vertical) an increase in textile wettability was observed as well as its influence on aging time and its consequence on wettability. The surface functional groups created after plasma treatments were investigated using X-ray Photoelectron Spectroscopy (XPS). The surface topography was examined by scanning electron microscope (SEM)

Experimental measurements of the NOx and CO concentrations operating in oscillatory and non-oscillatory burning conditions

The effects of combustion driven acoustic oscillations in carbon monoxide and nitrogen oxides emission rates of a combustor operated with liquefied petroleum gas (LPG) were investigated. Because the fuel does not contain nitrogen, tests were also conducted with ammonia injected in the fuel, in order to study the formation of fuel NOx. The main conclusions were: (a) the pulsating combustion process is more efficient than the non-pulsating one and (b) the pulsating combustion process generates higher rates of NOx, with and without ammonia injection, as shown by CO and NO concentrations as function of the O-2 concentration. An increase in the LPG flow rate, keeping constant the air to fuel ratio, increased the acoustic pressure amplitude and the frequency of oscillation. The injection of ammonia had no influence on either pressure amplitude or frequency. (c) 2005 Elsevier Ltd. All rights reserved.

Efeitos da fisioterapia respirat��ria convencional versus aumento do fluxo expirat��rio na satura����o de O2, freq����ncia card��aca e freq����ncia respirat��ria, em prematuros no per��odo p��s-extuba����o

INTRODU����O: Rec��m-nascidos (RN) prematuros apresentam elevada morbidade respirat��ria e necessidade de ventila����o mec��nica, assim, a fisioterapia respirat��ria �� parte integrante da assist��ncia neonatal. Objetivo: Comparar os efeitos da fisioterapia respirat��ria convencional (FRC) versus aumento do fluxo expirat��rio (AFE), na satura����o de O2 (SpO2), freq����ncia card��aca (FC) e na freq����ncia respirat��ria (FR) em prematuros no per��odo p��s-extuba����o. M��todo: Ensaio cl��nico randomizado realizado na UTI Neonatal do Hospital das Cl��nicas de BotucatuUNESP, comparando duas t��cnicas fisioterap��uticas, aplicadas em rec��m-nascidos prematuros, nas primeiras 48 horas p��s-extuba����o. Para a an��lise estat��stica foram utilizados o teste t Student, Mann-Whitney, Qui-quadrado e o teste exato de Fisher, com n��vel de signific��ncia em 5%. Resultados: Os dois grupos de estudo: Grupo FRC (n= 20) e grupo AFE (n= 20), n��o diferiram quanto �� idade gestacional (m��dia de 28 semanas) e peso de nascimento (m��dia de 1100 gramas). em ambos os grupos a s��ndrome do desconforto respirat��rio (SDR) foi o principal diagn��stico. A mediana da idade no in��cio da fisioterapia foi de sete dias no grupo AFE e 11 dias na FRC. Ambas as t��cnicas produziram aumento significativo da SpO2 aos 10 e 30 minutos, sem altera����es na FR. A FC aumentou significativamente ap��s a FRC e n��o se alterou ap��s o AFE. Conclus��o: Os resultados sugerem que o AFE �� menos estressante que a FRC e pode ser aplicado em prematuros no per��odo p��s-extuba����o. Nestes rec��m-nascidos o AFE parece ser seguro e ben��fico a curto prazo.

Altera����es do pH, da P O2 e da P CO2 arteriais e da concentra����o de lactato sang����neo de cavalos da ra��a ��rabe durante exerc��cio em esteira de alta velocidade

Avaliaram-se as altera����es do pH, da P O2 e da P CO2 do sangue arterial e da concentra����o de lactato sang����neo de 11 cavalos adultos da ra��a ��rabe, submetidos a exerc��cio progressivo em esteira de alta velocidade. Antes do exerc��cio, no intervalo dos 15 segundos finais de cada mudan��a de velocidade e aos 1, 3 e 5 minutos ap��s o t��rmino do exerc��cio foram coletadas amostras de sangue arterial e venoso para a mensura����o dos gases sang����neos e da concentra����o de lactato. O exerc��cio resultou em diminui����o do pH, da press��o parcial de O2 (P O2) e da press��o parcial de CO2 (P CO2). A concentra����o de lactato sang����neo elevou-se exponencialmente a partir da velocidade de 8,0m/s at�� os momentos ap��s t��rmino do exerc��cio.