Levels Of Nitrogen Oxides Research Articles

Projected changes in particulate matter concentrations in the South Coast Air Basin due to basin-wide reductions in nitrogen oxides, volatile organic compounds, and ammonia emissions

ABSTRACTAn ozone abatement strategy for the South Coast Air Basin (SoCAB) has been proposed by the South Coast Air Quality Management District (SCAQMD) and the California Air Resources Board (ARB). The proposed emissions reduction strategy is focused on the reduction of nitrogen oxide (NOx) emissions by the year 2030. Two high PM2.5 concentration episodes with high ammonium nitrate compositions occurring during September and November 2008 were simulated with the Community Multi-scale Air Quality model (CMAQ). All simulations were made with same meteorological files provided by the SCAQMD to allow them to be more directly compared with their previous modeling studies. Although there was an overall under-prediction bias, the CMAQ simulations were within an overall normalized mean error of 50%; a range that is considered acceptable performance for PM modeling. A range of simulations of these episodes were made to evaluate sensitivity to NOx and ammonia emissions inputs for the future year 2030. It was found that the current ozone control strategy will reduce daily average PM2.5 concentrations. However, the targeted NOx reductions for ozone were not found to be optimal for reducing PM2.5 concentrations. Ammonia emission reductions reduced PM2.5 and this might be considered as part of a PM2.5 control strategy.Implications: The SCAQMD and the ARB have proposed an ozone abatement strategy for the SoCAB that focuses on NOx emission reductions. Their strategy will affect both ozone and PM2.5. Two episodes that occurred during September and November 2008 with high PM2.5 concentrations and high ammonium nitrate composition were selected for simulation with different levels of nitrogen oxide and ammonia emissions for the future year 2030. It was found that the ozone control strategy will reduce maximum daily average PM2.5 concentrations but its effect on PM2.5 concentrations is not optimal.

Effect of air and fuel supercharging on emissions from an agricultural engine

Pollutant gases emitted by engines depend mainly on the applied load and engine speed. This study quantifies the emissions of pollutant gases from a diesel-cycle engine, while changing the configuration of the air and fuel supply system. We analyzed the variables particulate matter (g kWh -1 ), carbon monoxide (g kWh -1 ), nitrogen oxides (g kWh -1 ), oxygen (%vol.) and hydrocarbons (g kWh -1 ), in different engine configurations (aspirated; aspirated + service; turbocharged + service; and turbocharged). Dynamometric experiments were carried out by means of the power take-off of an agricultural tractor. The experimental design was completely randomized, in a two-factorial scheme with three replicates. The results indicate that engine supercharging, compared to the original configuration, significantly reduces the particulate matter of gases and carbon monoxide, but increases the levels of nitrogen oxides emitted. The load applied to the engine was directly related to the emissions, except for oxygen.

Nonparametric estimation of the marginal effect in fixed-effect panel data models

This paper considers multivariate local linear least squares estimation of panel data models when fixed effects are present. One-step estimation of the local marginal effect is of prime interest. A within-group nonparametric estimator is developed, where the fixed effects are eliminated by subtracting individual-specific locally weighted time average, i.e., the local-within-transformation. It is shown that the local-within-transformation-based estimator satisfies the standard properties of the local linear estimator. In comparison, nonparametric estimators based on the conventional (global) within-transformation or first difference result in estimators which are biased, even in large samples. The new estimator is used to examine the nonlinear relationship between income and nitrogen-oxide level (i.e., the environmental Kuznets curve) based on US state-level panel data.

Understanding mercury oxidation and air–snow exchange on the East Antarctic Plateau: a modeling study

Abstract. Distinct diurnal and seasonal variations of mercury (Hg) have been observed in near-surface air at Concordia Station on the East Antarctic Plateau, but the processes controlling these characteristics are not well understood. Here, we use a box model to interpret the Hg0 (gaseous elemental mercury) measurements in thes year 2013. The model includes atmospheric Hg0 oxidation (by OH, O3, or bromine), surface snow HgII (oxidized mercury) reduction, and air–snow exchange, and is driven by meteorological fields from a regional climate model. The simulations suggest that a photochemically driven mercury diurnal cycle occurs at the air–snow interface in austral summer. The fast oxidation of Hg0 in summer may be provided by a two-step bromine-initiated scheme, which is favored by low temperature and high nitrogen oxides at Concordia. The summertime diurnal variations of Hg0 (peaking during daytime) may be confined within several tens of meters above the snow surface and affected by changing mixed layer depths. Snow re-emission of Hg0 is mainly driven by photoreduction of snow HgII in summer. Intermittent warming events and a hypothesized reduction of HgII occurring in snow in the dark may be important processes controlling the mercury variations in the non-summer period, although their relative importance is uncertain. The Br-initiated oxidation of Hg0 is expected to be slower at Summit Station in Greenland than at Concordia (due to their difference in temperature and levels of nitrogen oxides and ozone), which may contribute to the observed differences in the summertime diurnal variations of Hg0 between these two polar inland stations.

Application of overfire air technology on an example of a steam boiler PK-39 of the Aksu TPP (Kazakhstan)

When burning any fossil fuels, one of the most harmful combustion products are nitrogen oxides NOx, which damage both the environment and human health in particular. Reduction of NOx emissions from fuel combustion at TPPs plays an important role in reducing the total level of nitrogen oxides NOx emitted into the atmosphere. One way to reduce the concentration of nitrogen oxides NOx is the stepwise combustion of the pulverized coal mixture, in particular the «Overfire Air» technology. The essence of this method is that the main volume of air is fed into the pulverized burners, and the rest of the air is further along the height of the torch through special nozzles. Structurally, the method of stepwise combustion of fuel can be carried out in boilers with a two-tier arrangement of burners along the height of the combustion chamber. In this case, practically no significant reconstruction of the boiler is required, which is associated with additional costs. In the present work, computational experiments on the use of modern overfire air technology (OFA) in the combustion chamber of the PK-39 boiler of the Aksu TPP were carried out and the fields of the main characteristics of heat and mass transfer, as well as the influence of the mass flow of the oxidant through the OFA injectors on the combustion process were obtained.

Effect of water injection into the intake manifold on combustion and NOx emissions of CHP engine fuelled with natural gas

The impact of variable water injection by mass on nitrogen oxide emission and performance characteristics of combined heat and power single-cylinder spark ignition engine fuelled by natural gas under constant power was investigated. For each water/fuel ratio, the combustion phasing was varied by adjusting spark timing and mass of fuel injection to maintain the indicated mean effect pressure at 6.35 bar. It was reported that the nitrogen oxide emissions decreased with the same centre of combustion when the amount of injected water increases. The nitrogen oxide emission averagely decreased by 20–25%, depending on combustion phasing with water/fuel ratio 0.3 compared to 0. Furthermore, the centre of combustion between 15 and 19 °CA after top dead centre represents lower nitrogen oxide emissions. It was recorded that the spark timing had to be advanced with water injection to maintain the indicated mean effect pressure at 6.35 bar. Also, the results of the effects of intake manifold water injection system on performance, combustion and emissions at the lowest level of the nitrogen oxides have been presented. The thermal efficiency and indicated specific fuel consumption were improved with water injection at an operation point compared with a reference point. The maximum nitrogen oxide reduction depends on the maximum water injection rate which is limited by intake air characteristics. NOx emission for various WI rates over the centre of combustion CA50

Effects of Air Pollution and Land Use Characteristics on Development and Respiratory Health among Children in the Greater Taipei Area

Indoor and outdoor air pollution poses an important health threat to children. Exposure to air pollution may cause various acute and chronic respiratory diseases, and affect neurodevelopment and cognitive functions in children. To evaluate the impact of air pollution on children's health, we conduct a study to examine the effect of prenatal and early childhood exposure to air pollution on development and respiratory health in the first 3 years of life among a birth cohort in the Greater Taipei area. We will recruit 500 cohort children, and evaluate their development and respiratory diseases using standardized questionnaires and Bayley Scales of Infant and Toddler Development. One hundred children will be selected to conduct indoor and outdoor environmental samplings of their residences. Four hundred and fifty-six cohort children have been recruited so far, and environmental measurements have been implemented in 40 homes. According to our analyses, most ambient pollutant concentrations near participants' homes were lower than Taiwan National Ambient Air Quality Standard, expect PM2.5, which exceeded the annual average level (15µg/m3). A few households had elevated indoor pollution levels due to a low ventilation rate or recent remodeling. Several children's bed dust samples contained dust mite allergen levels > 2 µg/g, which may increase the risk of child sensitization to dust mites. According to multiple regression analyses, a high level of nitrogen oxides during first trimester near residence as well as living near gas stations, social welfare facilities, or high ways had adverse effects on children's health; living near green parks was beneficial to children's neurodevelopment. Overall, residential environments, such as air quality and land use type nearby, may significantly influence children's health and neurodevelopment.

Two months sodium nitrate supplementation alleviates testicular injury in streptozotocin-induced diabetic male rats.

What is the central question of this study? Can low-dose inorganic nitrate supplementation prevent testicular structural and functional alterations in streptozotocin-induced type 1 diabetic male rats? What is the main finding and it's important? Treatment with a low dose of inorganic nitrate for 2 months had protective effects on the male reproductive system in diabetic rats including improved body weight loss, sperm and testis parameters, spermatogenesis index and testicular histology as well as increased serum testosterone levels. These favourable effects may be associated with increased serum insulin and decreased serum glucose, and with modulation of apoptosis in testis. Inorganic nitrate supplementation is a possible therapeutic agent in diabetes. The aim of this study was to evaluate the effect of nitrate on the reproductive system in streptozotocin-induced diabetic male rats. Fifty male Wistar rats were allocated randomly to five groups: control (C), control plus nitrate (CN), diabetic (D), diabetic plus insulin (DI) and diabetic plus nitrate (DN). Sodium nitrate was administered for 2months in the drinking water (100mgl-1 ) of the CN and DN groups. Insulin was injected at 2-4U daily in the DI group. Serum glucose level and body weight were measured at the beginning of the study and at regular intervals. At the end of the study, serum levels of glucose, insulin, nitrogen oxides (NOx), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone were assessed as well as sperm parameters, testis morphometry and histology, and testicular miR-34b and p53 mRNA expression. Nitrate treatment in diabetic rats significantly improved sperm parameters, epididymal weight, spermatogenesis and testicular histology as well as decreasing serum glucose and testicular p53 gene and miR-34b expression, although it had no effect on serum LH and FSH levels. In diabetic rats, serum insulin and NOx, body weight, testicular and epididymal weight, sperm count and motility, testis morphology, spermatogenesis indices, Johnsen's score, and testosterone were significantly lower than in controls. Nitrate administration increased serum insulin, NOx and testosterone levels in the DN group. Consuming water supplemented with sodium nitrate could improve diabetes-induced testicular functional and structural disorders; these favourable effects may be related to increased serum insulin and decreased serum glucose, as well as modulation of apoptosis in testis.

Influence of different complexity levels of road traffic models on air quality modelling at street scale

Urban mobility accounts for 38 and 19% of nitrogen oxide (NOx) and particulate matter (PM) emissions at European urban areas, respectively. Despite of all the technological development around automobile industry, urban areas are still facing problems related to exposure to high levels of air pollutants. Increasing the accuracy of both emissions and air quality modelling from road traffic is a key-issue for the management of air pollution in road transport sector. This study assessed the influence of using different road traffic emission models on the accuracy of air quality modelling with street-level resolution, having as a case study an urban area located on the centre region of Portugal. Two emission models, with different complexity levels regarding the ability to characterise the traffic dynamics were analysed, namely, transport emission model for line sources (TREM) and vehicle-specific power (VSP), based on data obtained in an experimental campaign. To perform the air quality simulations, the pollutant dispersion in the atmosphere under variable wind conditions (VADIS) model was used and two pollutants were analysed: NOx and PM10. The results showed that the magnitude of PM10 and NOx concentrations were result of a conjoint influence of traffic dynamics and meteorological conditions. Comparison between measured and modelled data showed that the VADIS model could track the evolution of NOx levels, for both emission models considered, displaying a high correlation (> 0.8) between traffic-related NOx emissions and NOx concentrations. For PM10, VADIS model is more sensitive to the differences in the emissions calculation; however, it was observed that the traffic-related PM10 emissions accounts 1.3–8.4% to the PM10 concentration levels at the study area.

Long- and short-term air pollution exposure and measures of arterial stiffness in the Framingham Heart Study

BackgroundStudies of air pollution exposure and arterial stiffness have reported inconsistent results and large studies employing the reference standard of arterial stiffness, carotid-femoral pulse-wave velocity (CFPWV), have not been conducted. AimTo study long-term exposure to ambient fine particles (PM2.5), proximity to roadway, and short-term air pollution exposures in relation to multiple measures of arterial stiffness in the Framingham Heart Study. MethodsWe assessed central arterial stiffness using CFPWV, forward pressure wave amplitude, mean arterial pressure and augmentation index. We investigated long-and short-term air pollution exposure associations with arterial stiffness with linear regressions using long-term residential PM2.5 (2003 average from a spatiotemporal model using satellite data) and proximity to roadway in addition to short-term averages of PM2.5, black carbon, particle number, sulfate, nitrogen oxides, and ozone from stationary monitors. ResultsWe examined 5842 participants (mean age 51 ± 16, 54% women). Living closer to a major roadway was associated with higher arterial stiffness (0.11 m/s higher CFPWV [95% CI: 0.01, 0.22] living <50 m vs 400 ≤ 1000 m). We did not observe association between arterial stiffness measures and long-term PM2.5 or short-term levels of PM2.5, particle number, sulfate or ozone. Higher levels of black carbon and nitrogen oxides in the previous days were unexpectedly associated with lower arterial stiffness. ConclusionsLong-term exposure to PM2.5 was not associated with arterial stiffness but positive associations with living close to a major road may suggest that pollutant mixtures very nearby major roads, rather than PM2.5, may affect arterial stiffness. Furthermore, short-term air pollution exposures were not associated with higher arterial stiffness.

광주 지역에서 2015년 10월에 발생한 PM2.5 고농도 사례 특성 분석

A severe haze event occurred in October 2015 in Gwangju, Korea. In this study, the driving chemical species and the formation mechanisms of PM2.5 pollution were investigated to better understand the haze event. Hourly concentrations of PM2.5, organic and elemental carbon, water-soluble ions, and elemental constituents were measured at the air quality intensive monitoring station in Gwangju. The haze event occurred was attributed to a significant contribution (72.3%) of secondary inorganic species concentration to the PM2.5, along with the contribution of organic aerosols that were strongly attributed to traffic emissions over the study site. MODIS images, weather charts, and air mass backward trajectories supported the significant impact of long-range transportation (LTP) of aerosol particles from northeastern China on haze formation over Gwangju in October 2015. The driving factor for the haze formation was stagnant atmospheric flows around the Korean peninsula, and high relative humidity (RH) promoted the haze formation at the site. Under the high RH conditions, SO₄2- and NO₃- were mainly produced through the heterogenous aqueous-phase reactions of SO₂ and NO₂, respectively. Moreover, hourly O₃ concentration during the study period was highly elevated, with hourly peaks ranging from 79 to 95 ppb, suggesting that photochemical reaction was a possible formation process of secondary aerosols. Over the PM2.5 pollution, behavior and formation of secondary ionic species varied with the difference in the impact of LTP. Prior to October 19 when the influence of LTP was low, increasing rate in NO3- was greater than that in NO₂, but both SO₂ and SO₄2- had similar increasing rates. While, after October 20 when the impact of haze by LTP was significant, SO₄2- and NO₃- concentrations increased significantly more than their gaseous precursors, but with greater increasing rate of NO₃-. These results suggest the enhanced secondary transformation of SO₂ and NO₂ during the haze event. Overall, the result from the study suggests that control of anthropogenic combustion sources including vehicle emissions is needed to reduce the high levels of nitrogen oxide and NO₃- and the high PM2.5 pollution occurred over fall season in Gwangju.

Revisiting the Veterans Cohort Mortality Study: New results and synthesis

ABSTRACTThe Veterans Cohort Mortality Study began in 1999 in collaboration with Washington University in St. Louis, comprising ~70,000 male military veterans. We published six research papers on this cohort, considering the dynamics of all-cause mortality as the subjects aged and environmental parameters changed. This paper summarizes those results and presents new results by age group. Pollutants included monitored and modeled criteria pollutants, vehicular traffic density (annual km driven per unit of county land area), and modeled nationwide levels of hazardous species. In addition to spatial relationships, we examined the effects of exposure timing through separate analyses of sequential follow-up and exposure periods from 1976 to 2001. Risks associated with peak ozone decreased with lag between exposure and response, suggesting acute effects. Risks associated with traffic were invariant over time and consistent across five exposure databases. Associations with ozone were also coherent across databases; we found no consistent associations with particulate matter. Epidemiology considers both spatial and temporal relationships; most long-term studies focus on spatial gradients at a given time, thus masking effects of cohort aging and other trends during follow-up. Our new analyses distinguished between these temporal effects by analyzing age deciles for which separate mortality risks had been estimated for nationwide levels of nitrogen oxides (NOx), benzene, and traffic density during four sequential follow-up subperiods, thus providing 40 sets of mortality risk coefficients. We used ordinary least squares regression to define relationships with subject age and follow-up year for the data set of 40 coefficients. We found strong nonlinear relationships between subject age and mortality coefficients for smoking, climate, poverty status, and air pollution; only smoking and climate coefficients changed over time as well. We concluded that these pollutant-mortality relationships reflected differences among the veterans’ residential locations rather than changes in their pollution exposures during follow-up. We saw no evidence that cleaner air reduced mortality.Implications: Recent air pollution mortality studies emphasize PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm); we show associations with many other pollutants and a measure of traffic intensity. Control policies should thus be based on multipollutant analyses. We found no reduced risks with improved air quality after distinguishing cohort aging from purely temporal effects; longitudinal studies of accountability must thus account for changes in demography and exposures. Our studies of exposure timing indicate mainly coincident responses and no evidence for cumulative effects typical of smoking; we had no information on personal exposures. We found the strongest risks were associated with high-traffic locations rather than outdoor air quality per se.

Ferulic acid protects against heat stress-induced intestinal epithelial barrier dysfunction in IEC-6 cells via the PI3K/Akt-mediated Nrf2/HO-1 signaling pathway

Purpose: Intestinal epithelial barrier dysfunction is crucial in the pathogenesis of intestinal and systemic diseases. Ferulic acid (FA) possesses promising antioxidant activities. In a previous study, we demonstrated potentially protective effects of FA against heat stress-induced intestinal epithelial barrier dysfunction in IEC-6 cells. However, the underlying mechanisms are unclear. The present study aimed to elucidate whether FA protects IEC-6 cells from heat stress-induced intestinal epithelial barrier dysfunction via antioxidative mechanisms.Materials and methods: IEC-6 cells were pretreated with FA prior to hyperthermia exposure at 42 °C for 6 h, and the levels of intracellular reactive oxygen species (ROS), malondialdehyde (MDA), nitrogen oxide (NO), and superoxide dismutase (SOD) activity were analyzed. The intestinal epithelial barrier function was determined by transepithelial electrical resistance (TER) values and 4-kDa fluorescein isothiocyanate-dextran (FD4) flux in IEC-6 cell monolayers. Expression of related proteins was detected by Western blotting.Results: FA suppressed heat stress-induced intestinal oxidative stress damage by reducing ROS, MDA and NO production, while enhancing SOD activity. Furthermore, FA treatment strengthened intestinal barrier function via increasing the phosphorylation levels of Akt, nuclear factor-erythroid 2-related factor 2 (Nrf2) and hemeoxygenase-1 (HO-1) protein expression, which was reversed by zinc protoporphyrin (an HO-1 inhibitor). Additionally, LY294002, a specific PI3K/Akt inhibitor, significantly suppressed FA-induced Nrf2 nuclear translocation and HO-1 protein expression and inhibited FA-induced occludin and ZO-1 protein expression.Conclusions: FA protected against heat stress-induced intestinal epithelial barrier dysfunction via activating the PI3K/Akt-mediated Nrf2/HO-1 signaling pathway in IEC-6 cells.

Road traffic noise, air pollution, and risk of dementia – results from the Betula project

BackgroundThere is growing evidence for a negative impact of traffic-related air pollution on risk of dementia. However, the contribution of noise exposure to this association has been rarely examined. ObjectiveWe aimed to investigate the individual and combined effect of noise and air pollution on risk of dementia. MethodsData on dementia incidence over a 15 year period was obtained from the Betula project, a longitudinal study on health and ageing. Estimates of annual mean levels of nitrogen oxides (NOx) at the participants’ residential address were obtained using a land-use regression model. Modelled data provided road traffic noise levels (Leq. 24 h) at the participants’ residential address at baseline. Cox proportional hazard regression was used to calculate hazard ratios (HR). ResultsOf 1721 participants at baseline, 302 developed dementia during the follow up period. Exposure to noise levels (Leq. 24 h) > 55 dB had no significant effect on dementia risk (HR 0.95; CI: 0.57, 1.57). Residing in the two highest quartiles of NOx exposure was associated with an increased risk of dementia. The risk associated with NOx was not modified by adjusting for noise. Moreover, we found no significant interaction effects between NOx and road traffic noise on dementia risk. ConclusionWe found no evidence that exposure to road traffic noise, either independently or in combination with traffic air pollution, was associated with risk of dementia in our study area. Our results suggest that pollution should be considered the main component in the association between traffic related exposures and dementia.

Wintertime characteristic of peroxyacetyl nitrate in the Chengyu district of southwestern China.

Atmospheric concentrations of peroxyacetyl nitrate (PAN) were measured in Ziyang in December 2012 to provide basic knowledge of PAN in the Chengyu district and offer recommendations for air pollution management. The PAN pollution was relatively severe in Ziyang in winter, with the maximum and average PAN concentrations of 1.61 and 0.55ppbv, respectively, and a typical single-peak diurnal trend in PAN and theoretical PAN lost by thermal decomposition (TPAN) were observed. PAN and O3 concentrations were correlated (R2 = 0.52) and the ratios of daily maximum PAN to O3 ([PAN]/[O3] ratio) ranged from 0.013 to 0.108, with an average of 0.038. Both acetone and methyl ethyl ketone (MEK) were essential for producing the acetylperoxy radicals (PA) and subsequently PAN in Ziyang in winter, and PAN concentrations at the sampling site exhibited more sensitivity to volatile organic compound (VOC) concentrations than nitrogen oxide (NOx) levels. Therefore, management should focus on reducing VOCs emissions, in particular those that produce acetone and MEK through photolysis and oxidizing reactions. In addition, the influence of relative humidity (RH) on the heterogeneous reactions between PAN and PM2.5 in the atmospheric environment may have led to the strong correlation between observed PM2.5 and PAN in Ziyang in winter. Furthermore, a typical air pollution event was observed on 17-18 December 2012, which Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and PSCF simulations suggest that it was caused by the local formation and the regional transport of polluted air masses from Hanzhong, Nanchong, and Chengdu.

Heparin promotes recanalization of venous thrombotic occlusions.

Thrombosis is a consequence of disbalance between the procoagulant and fibrinolytic activity of blood and is frequently associated with chronic sequelae, which are the consequence of chronic occlusion of affected veins. Treatment of venous thrombosis should not be oriented in the prevention of thrombus progression and associated thromboembolic events, but also in stimulation of thrombolysis and recanalization of occluded veins, which are one of the most important preventive mechanisms of late sequelae, including post-thrombotic syndrome. The treatment of acute venous thrombosis (superficial and deep) is based on drugs with anticoagulant activity, like antagonists of vitamin K, heparins, and new oral anticoagulants. One of the most frequently used anticoagulant drugs is heparin, particularly the low molecular weight heparin (LMWH). It was shown that besides strong anticoagulant activity heparin has pro-fibrinolytic effects, which promote thrombolysis and recanalization of occluded veins. LMWH markedly increases tissue factor pathway inhibitor levels and a release of tissue plasminogen activator from vascular endothelium. Heparins are also capable of increasing the nitrogen oxide level, which is responsible for circulatory homeostasis.

Experimental study on the effects of co-firing coal mine waste residues with coal in PF swirl burners

Co-firing coal mine discards with coal in pulverized fuel burners of the current power plants would be a promising way both to reduce the environmental impact of coal production and to energy valorize such residues, with an acceptable economic investment. Changes in fuel blends bring along alterations in flame dynamics and structure which must be considered for successful operation. The paper addresses the challenge of co-firing coal mine waste residues of low rank, high ash content and rich in sulfur with bituminous South African coal in a 500 kWth pulverized fuel pilot plant. The effect of fuel blend composition on combustion performance is investigated by means of image processing and through some relevant operation parameters recordered during the tests. Lower brightness, fluctuations and flicker frequency are registered in the flame videos as coal mine waste residues are added. Nonetheless, the experimental tests confirmed the viability of the process with acceptable levels of carbon monoxide and nitrogen oxides, very stable chamber pressure and gases temperature. The present work also shows the usefulness of visualization systems for detecting and characterizing dynamical instabilities associated with changes in flame structure and certain flame features could be used as inputs in monitoring systems or predictive control.

Traffic-related Air Pollution, Lung Function, and Host Vulnerability. New Insights from the PARIS Birth Cohort.

Although the effects of traffic-related air pollution on respiratory exacerbations have been well documented, its impact on lung function in childhood remains unclear. Our aim was to investigate the associations of prenatal, early, and lifetime traffic-related air pollution exposure with lung function at 8-9 years studying possible effect modification by sex, sensitization at 8-9 years, and early lower respiratory tract infections. We conducted this study among 788 children from the PARIS (Pollution and Asthma Risk: an Infant Study) birth cohort. Lung function tests were performed during the medical examination at 8-9 years. Traffic-related air pollution exposure during each trimester of pregnancy was estimated using nitrogen oxides background measurements. Postnatal traffic-related air pollution exposure was assessed by a nitrogen oxides air dispersion model at both residential and daycare/school addresses. Associations between lung function and traffic-related air pollution exposure were analyzed by multiple linear regression models. Higher prenatal nitrogen oxides levels, especially during the second trimester of pregnancy, were associated with a lower forced expiratory flow at 25-75% of the forced vital capacity, but there were no significant associations between prenatal nitrogen oxide levels and forced vital capacity, forced expiratory volume during 1 second, or the forced expiratory volume during 1 second/forced vital capacity ratio overall. Postnatal traffic-related air pollution exposure was associated with lower lung function among children with early lower respiratory tract infections or sensitization at 8-9 years, but not in the full cohort. In children with early repeated lower respiratory tract infections, an interquartile increase in lifetime nitrogen oxides exposure was associated with both a lower forced expiratory volume during 1 second (-62.6 ml; 95% confidence interval = -107.0 to -18.1) and forced vital capacity (-55.7 ml; 95% confidence interval = -109.5 to -1.8), but was not associated with the forced expiratory volume during 1 second/forced vital capacity ratio. There was an association between greater early postnatal nitrogen oxide exposure and a lower forced expiratory volume during 1 second/forced vital capacity ratio among sensitized children (-0.65%; 95% confidence interval = -1.25 to -0.05). This study sheds new light, suggesting associations between postnatal traffic-related air pollution exposure and reduced lung function may be enhanced by early, repeated lower respiratory tract infections or allergic sensitization.

Which processes drive observed variations of HCHO columns over India?

Abstract. We interpret HCHO column variations observed by the Ozone Monitoring Instrument (OMI), aboard the NASA Aura satellite, over India during 2014 using the GEOS-Chem atmospheric chemistry and transport model. We use a nested version of the model with a horizontal resolution of approximately 25 km. HCHO columns are related to local emissions of volatile organic compounds (VOCs) with a spatial smearing that increases with the VOC lifetime. Over India, HCHO has biogenic, pyrogenic, and anthropogenic VOC sources. Using a 0-D photochemistry model, we find that isoprene has the largest molar yield of HCHO which is typically realized within a few hours. We also find that forested regions that neighbour major urban conurbations are exposed to high levels of nitrogen oxides. This results in depleted hydroxyl radical concentrations and a delay in the production of HCHO from isoprene oxidation. We find that propene is the only anthropogenic VOC emitted in major Indian cities that produces HCHO at a comparable (but slower) rate to isoprene. The GEOS-Chem model reproduces the broad-scale annual mean HCHO column distribution observed by OMI (r = 0.6), which is dominated by a distinctive meridional gradient in the northern half of the country, and by localized regions of high columns that coincide with forests. Major discrepancies are noted over the Indo-Gangetic Plain (IGP) and Delhi. We find that the model has more skill at reproducing observations during winter (JF) and pre-monsoon (MAM) months with Pearson correlations r &gt; 0.5 but with a positive model bias of ≃ 1×1015 molec cm−2. During the monsoon season (JJAS) we reproduce only a diffuse version of the observed meridional gradient (r = 0.4). We find that on a continental scale most of the HCHO column seasonal cycle is explained by monthly variations in surface temperature (r = 0.9), suggesting a role for biogenic VOCs, in agreement with the 0-D and GEOS-Chem model calculations. We also find that the seasonal cycle during 2014 is not significantly different from the 2008 to 2015 mean seasonal variation. There are two main loci for biomass burning (the states of Punjab and Haryana, and northeastern India), which we find makes a significant contribution (up to 1×1015 molec cm−2) to observed HCHO columns only during March and April over northeastern India. The slow production of HCHO from propene oxidation results in a smeared hotspot over Delhi that we resolve only on an annual mean timescale by using a temporal oversampling method. Using a linear regression model to relate GEOS-Chem isoprene emissions to HCHO columns we infer seasonal isoprene emissions over two key forest regions from the OMI HCHO column data. We find that the a posteriori emissions are typically lower than the a priori emissions, with a much stronger reduction of emissions during the monsoon season. We find that this reduction in emissions during monsoon months coincides with a large drop in satellite observations of leaf phenology that recovers in post monsoon months. This may signal a forest-scale response to monsoon conditions.

Characterization of the ozone zero phenomenon by infrared spectroscopy

ABSTRACTThe presence of a small amount of nitrogen in the feed gas is necessary to generate ozone efficiently out of oxygen. Operating an ozone generator with ultra-pure oxygen for extended periods results in highly deteriorated ozone generation efficiency. In extreme cases, when the nitrogen levels in the feed gas are in the lower ppm range, the efficiency of the ozone generation process even drops to zero. In this article, we present our results concerning the correlation between the N2O5 concentration in the off-gas and the ozone generation efficiency. After the ozone generator is run for a well-defined amount of time with an oxygen–nitrogen mixture, the N2 supply is shut off, and the behavior of the system is monitored by near-infrared spectroscopy. Different surface materials lead to different temporal behavior of both the nitrogen oxide levels and the ozone concentration after shutting down the nitrogen supply. The measurements show a good correlation between the evolution of ozone generation efficiency and the changes of the N2O5 concentration in the off-gas.