Measurements Of NO2 Concentrations Research Articles

Application of Effective Conversion Rates between NO and NO2 in a Standard Airport Dispersion Model System

The NO/NO2/O3 reaction mechanism of the standard VDI 3783 Part 19 was coupled to the Lagrangian particle model LASAT and quasi-stationary, individual plumes were calculated for a point source under various conditions. First-order conversion rates between NO and NO2 were derived by fitting to these plumes and further simplified to sets of categorized conversion rates which depend on background NO2 concentration, atmospheric stability and time of the day. The rates were applied in the standard airport dispersion model system LASPORT and compared to measured NO2 concentrations at Los Angeles International Airport. The agreement between modelled and measured NO2 concentrations (weekly averages) and ratios NO2 over NOx at monitor stations dominated by airport emissions was in most cases better than a factor of 2 with a Pearson correlation coefficient of about 0.9 or above.

Simultaneous decreases in NO2 levels and disparities in California during the COVID-19 pandemic

This study investigated the changes in nitrogen dioxide (NO2) air pollution levels and their disparities in California, U.S. during the pandemic of coronavirus disease 2019 (COVID-19). From pre-COVID (February 11–March 10, 2020) to peri-COVID (March 22–April 21, 2020) periods, ground-level measured NO2 concentrations decreased by 6.9 ppb (54.2%) on average across California. Our novel statistical approach showed that the meteorology-adjusted NO2 concentrations declined to a smaller extent (4.3 ppb, 34.4%), implying that the meteorological parameters helped reduce NO2 concentrations along with lockdown-related NOx emission reductions. In addition, satellite TROPOspheric Monitoring Instrument (TROPOMI) tropospheric NO2 data demonstrated substantial decreases in NO2 levels in urban (49.7% versus 16.5% in rural areas) and high-traffic (50.1%) areas. On average, 32.8%, 62.8%, and 14.9% higher TROPOMI NO2 levels were identified for socially vulnerable populations, as defined by the CalEnviroScreen 3.0, race/ethnicity, and educational attainment, respectively. The NO2 exposure differences generally decreased as average TROPOMI NO2 levels decreased during the pandemic (Pearson correlations = 0.61–0.95). From pre- to peri-COVID periods, the decreasing NO2 disparities were pronounced in relation to race/ethnicity [from 39.0 (78.6%) to 10.4 (36.7%) μmol/m2]. Despite the remaining NO2 disparities during the pandemic, our findings indicated that the mitigation of NO2 disparities (particularly racial inequity) would be achievable by the continued regulatory actions emphasizing the reduction of traffic-related NOx emissions such as electrification of passenger cars and diesel trucks.

A miniaturized photodiode-based chemiluminescence sensor for measurement of fractional exhaled nitric oxide

Fractional exhaled nitric oxide (FENO) measurement is a valuable tool in diagnosing and monitoring certain respiratory diseases, low cost and miniaturized NO sensor is highly demanded for FENO home healthcare self-monitoring. In this work, a miniature photodiode-based chemiluminescence sensor is presented for the sensitive measurement of NO concentration. Effects of various reflective film materials including stainless-steel, aluminum and silver for coating the inner surface of the optical cell were investigated for higher photon collection efficiency, and the silver reflective film displayed the best sensitivity. As the oxidation and pollution of silver film led to dramatical decay of signal, a quartz inner chamber with reflectance film layer coated on its outer surface was developed to achieve high stability and sensitivity simultaneously. The limit of detection for FENO was 6.6 ppb, the linear range of 10–100 ppb with a response time of 6.8 s was reached, which was satisfied the requirements for FENO measurement. The weight of the sensor is 96 g with a size of only 6.5 × 3 × 2 cm3, and the cost is estimated less than $1 K, which is suit for on-site monitoring of FENO. FENO50 was obtained the response difference of room air and breath air measured successively with a switching valve, the beath air was sampled into a bag at flow rate of 50 ml/s by offline sampling device, and multiple measurements were executed for better accuracy. The potential usage of the sensor was further illustrated by studying the FENO50 levels of individuals before and after consuming nitrate-rich sports drinks.

Bakuchiol reduces the severity of Mycoplasma pneumoniae-induced pneumonia in mice by attenuating inflammatory responses

BackgroundPneumonia has become a leading cause of death due to its high morbidity rates worldwide. Pneumonia is caused by the bacterium Mycoplasma pneumoniae (MP), which is a prominent airway pathogen. MP infection is usually self-limiting, but an alarming increase in cases has recently developed into refractory, severe, and even fatal pneumonia. ObjectiveThe objective of the current work was to study the anti-inflammatory and antioxidant properties of bakuchiol in ameliorating MP-induced pneumonia in mice. MethodologyBALB/c mice were challenged with MP (100 µl) via nasal drops for 2 days to induce pneumonia, and bakuchiol (25 mg/kg) was given concurrently to the mice for 3 days. Thereafter, measurements of lung weight, MPO, and NO concentrations were done. The corresponding kits were used to analyze the GSH, SOD, and MDA concentrations. The DNA contents of MP were assessed by PCR, and the total cells in BALF were counted. The corresponding kits were used to measure NF-κB levels and examine the inflammatory cytokine levels in the BALF samples. The lung histopathology was assessed to identify the histological changes. ResultsIn pneumonia-induced mice, the lung weight was significantly reduced after treatment with 25 mg/kg of bakuchiol. The bakuchiol treatment exhibited an effective antioxidant and anti-inflammatory properties on the pneumonia mice. Bakuchiol also lowered the NF-κB level and attenuated histological alterations in the lungs of pneumonia-induced mice. Conclusion: In summary, our findings exhibited that bakuchiol significantly reduced inflammation induced by MP in a mouse model of pneumonia. As a result, it has potential as a future salutary agent for the pneumonia treatment.

Data fusion in a two-stage spatio-temporal model using the INLA-SPDE approach

This paper proposes a two-stage estimation approach for a spatial misalignment scenario that is motivated by the epidemiological problem of linking pollutant exposures and health outcomes. We use the integrated nested Laplace approximation method to estimate the parameters of a two-stage spatio-temporal model — the first stage models the exposures using data fusion while the second stage links the health outcomes to exposures. The first stage is based on the Bayesian melding model, which assumes a common latent field for the different data sources for the pollutants. The second stage fits a generalized linear mixed model using the spatial averages of the estimated latent field, and additional spatial and temporal random effects. Uncertainty from the first stage is accounted for by simulating repeatedly from the posterior predictive distribution of the latent field. A simulation study was carried out to assess the impact of the sparsity of the data on the monitors, number of time points, and the specification of the priors in terms of the biases, RMSEs, and coverage probabilities of the parameters and the block-level exposure estimates. The results show that the parameters are generally estimated correctly but there is difficulty in estimating the Matèrn field parameters. The effect of exposures on the health outcomes is the primary parameter of interest for spatial epidemiologists and health policy makers, and our results show that the proposed method estimates these very well. The proposed method is applied to measurements of NO2 concentration and respiratory hospitalizations for year 2007 in England. The results show that an increase in NO2 levels is significantly associated with an increase in the relative risks of the health outcome. Also, there is a strong spatial structure in the risks, a strong temporal autocorrelation, and a significant spatio-temporal interaction effect.

Effects of Acute Red Spinach Extract Ingestion on Repeated Sprint Performance in Division I NCAA Female Soccer Athletes

Red spinach extract is high in inorganic nitrate/nitrite (NO3/NO2) which has been shown to enhance vascular function, cognition, and physical performance. To date, there have been no investigations as to whether red spinach extract serves as an effective strategy to improve repeated exercise performance, which is applicable to many sports and activities. The purpose of this study was to investigate the effect of acute red spinach extract ingestion on repeated sprint ability in female athletes. Eleven Division I NCAA female athletes (ages 18–24) were recruited. In a double-blinded, randomized, counterbalanced design, participants completed two separate visits each with a different treatment: placebo (placebo; tomato juice) or red spinach extract (~400 mg nitrate). For each trial, participants consumed their respective treatment two hours before exercise. Following a warm-up, participants completed 3 × 15 s Wingate Anaerobic Tests (WAnTs) separated by 2 min of recovery. A capillary blood sample was obtained pre-exercise to measure NO2 concentrations. Performance outcomes, heart rate (heart rate), and rate of perceived exertion were measured following each WAnT. Blood lactate (La-) was obtained prior to exercise (PRE) and after the completion of the repeated sprints (POST). Each visit was separated by a minimal recovery period of 72 h. Mean power (p = 0.204), peak power (p = 0.067), heart rate (p = 0.151), and rate of perceived exertion (p = 0.379) were not significantly different between treatments. POST La- concentration was significantly higher with red spinach extract when compared to the placebo (p = 0.030). Furthermore, the fatigue index (p = 0.018) was significantly lower with red spinach extract. The results do not support the use of red spinach extract for the enhancement of power output during repeated anaerobic exercise. However, it may result in improved La-/H+ removal from the muscle, thereby combating physical fatigue.

Assessing the Spatial Distribution of NO2 and Influencing Factors in Urban Areas—Passive Sampling in a Citizen Science Project in Berlin, Germany

Nitrogen dioxide (NO2) is a major air pollutant with diverse impacts on human health and the environment. In urban areas, road traffic is the main emission source for NO2. In Berlin, Germany, a network of measurement stations is operated by the state, fulfilling the monitoring requirements set by the European Union. To get a more detailed overview of the spatial distribution of NO2 concentrations in Berlin, a citizen science project allowed for collection of additional data and an increase in the number of sampling sites. Passive samplers (modified Palmes tubes) were distributed to participants to collect NO2 at a site of their choice. When returned, the samplers were analyzed based on the Griess–Ilosvay reaction and spectrophotometric detection. The results confirmed a seasonal trend of higher NO2 concentrations in winter and lower concentrations during the summer period. Furthermore, the spatially and monthly averaged NO2 concentrations observed in the study period from March 2019 to October 2020 were in good agreement with the average urban background concentration. At small spatial scales, a tendency of decreasing NO2 concentrations with increasing distance from roads was observed. Overall, this study shows the added benefit of extensive low-cost measurements of NO2 concentrations across urban environments in a citizen science project to complement stationary air pollution monitoring networks.

The risk of hidden “hot spots” with high levels of air pollution in Madrid (Spain)

All urban areas at risk of breathing polluted air should be identified. In the outskirts of Madrid (Spain), there are roads with high traffic (highway A5) that are <5 meters away from nearby residential homes and schools with children and adolescents. The objective of this study is to ascertain the levels of NO2 in these populated areas. Several NO2 diffusion tubes were installed at a height of 3-m to measure NO2 concentrations in various locations of the A5 during the month of May 2022 (30 days). The four tubes located near the A5 measured a NO2 concentration of 49.7; 88.2; 56.8; and 60 μg/m³. The standard deviation and variation coefficient of the measurements were 0.5 and 2.7%, respectively. According to the WHO (2021), the admissible average annual limit is 10 μg/m³ and the daily limit is 25 μg/m³. This study aimed at measuring the concentration of NO2 near homes and primary and secondary schools located in a “toxic microenvironment” (close to the A5 in Madrid) found high and dangerous levels of NO2 impacting the health of the population. This is an area with a population of low socioeconomic level, which increases the impact on health.

Case study on The Assessment of Air Quality and Pollution in a Sensitive Area of Bucharest

Monitoring air quality in urban areas is essential due to increased pollution and health hazards. In this study, the air quality in the busiest area of Bucharest’s central was assessed, and the main car-related pollutants, NO2 and PM10, have been examined in relation to the influence of meteorological parameters. During the measurement campaign, the monitored NO2 pollutant concentration values did not exceed the limit value (LV), and the measured NO2 exceeded this limit on day 1. Although the monitored NO2 concentrations had the same pattern as the measured NO2 concentrations; however, there is a delay in the amplitude of the values, which can be explained by the location of each measurement point in relation to the main source of pollution. The particulate matter PM10 showed exceedances of the daily limit values (DLV) in conditions of intense traffic, and the decrease in concentrations was related to the conditions of increased precipitation and humidity. In order to adopt the most effective measurements to reduce pollution in metropolitan areas, it is crucial to evaluate the air quality and identify the primary sources of pollutants.

Experimental and modeling study of NO formation in methyl acetate + air flames

Premixed laminar flat non-stretched flames of methyl acetate + air have been studied at atmospheric pressure. The heat flux method was employed to stabilize the flames over equivalence ratios ɸ = 0.7–1.5 at initial gas temperatures from 298 to 348 K. The laminar burning velocities of methyl acetate + air mixtures have been measured at these conditions and compared with the literature data. Laser-induced fluorescence was used to measure NO concentrations in the post-combustion region of the flames at 298 K. The detailed kinetic mechanism of the authors was extended by the reactions of methyl acetate, mostly relying on the model developed by Ahmed et al. (2019). The mechanism was tested against selected literature data from measurements in a shock tube and jet-stirred reactor. Moreover, it was compared with new measurements of the laminar burning velocity and NO concentrations in methyl acetate flames. In all cases, good agreement between the experimental and modeling results was observed. A comparison with LIF measurements obtained for methane + air flames at the same conditions shows that NO concentrations in methyl acetate flames are lower than those in methane + air flames both in stoichiometric and rich mixtures. These differences were interpreted using sensitivity and rate-of-production analyses of NO formation via different routes.

Intervention of an Upgraded Ventilation System and Effects of the COVID-19 Lockdown on Air Quality at Birmingham New Street Railway Station.

High NO2 concentrations (long term average of 383 µg/m3 in 2016/2017) recorded at Birmingham New Street railway station have resulted in the upgrade of the bi-directional fan system to aid wind dispersion within the enclosed platform environment. This paper attempts to examine how successful this intervention has been in improving air quality for both passengers and workers within the station. New air pollution data in 2020 has enabled comparisons to the 2016/2017 monitoring campaign revealing a 23–42% decrease in measured NO2 concentrations. The new levels of NO2 are below the Occupational Health standards but still well above the EU Public Health Standards. This reduction, together with a substantial decrease (up to 81%) in measured Particulate Matter (PM) concentrations, can most likely be attributed to the new fan system effectiveness. Carbon Monoxide levels were well below Occupational and Public Health Standards at all times. The COVID-19 pandemic “initial lockdown” period has also allowed an insight into the resultant air quality at lower rail-traffic intensities, which produced a further reduction in air pollutants, to roughly half the pre-lockdown concentrations. This study shows the scope of improvement that can be achieved through an engineering solution implemented to improve the ventilation system of an enclosed railway station. Further reduction in air pollution would require additional approaches, such as the removal of diesel engine exhaust emissions via the adoption of electric or diesel-electric hybrid powered services.

Experimental and numerical investigation of NO oxidation on Pt/Al2O3- and NOxstorage on Pt/BaO/Al2O3-catalysts

Effects of temperature and inlet conditions on NO oxidation and NOxstorage, as well as reduced NOxstorage capacity over time – reflected by changes of measured NO concentration, which are reproduced by CFD using detailed reaction mechanisms.

Variability of ozone and oxides of nitrogen in the tropical city, Bengaluru, India

Bengaluru, also considered India's Silicon Valley, has seen steady growth in population over the years. Bengaluru's rapid development has resulted in dwindling reservoirs, increased traffic congestion, high levels of air pollution, and, to some measure, a rise in summer temperatures. As a result of these changes in urban form over the last decade, anthropogenic heat fluxes for ozone production have increased. However, an observational study on the effects of growing urbanisation on trace gases in Bengaluru for various seasons and periods of the day is missing. Hence, in situ measurements of O3, NO, NO2, and NOX concentrations were carried out at Bengaluru, India, from January 2015 to December 2018. The data were examined for diurnal and interannual variations in trace gas mixing concentrations. The diurnal trend in O3 exhibits unimodal behaviour. Changes in photochemistry, local meteorology, and the planetary boundary layer's distinctive features cause a rise in the value of concentrations and lead to a peak. In contrast, the diurnal trend in NO, NO2, and NOX displayed a bimodal peak due to the combined effect of vehicular emissions and the planetary boundary layer. The link involving the oxidant OX (O3 + NO2) and NOx levels were investigated to determine the NOx-independent regional and NOx-dependent local contributions to OX in the atmosphere. Daytime contributions are higher than night-time contributions, according to the present study. The observed anomalies could be the consequence of photochemical processes that produce OX.

Oxygen-depletion by rapid ammonia oxidation regulates kinetics of N2O, NO and N2 production in an ammonium fertilised agricultural soil

Oxygen (O2) is a key factor driving the expression of N-cycle-related functional genes and regulating nitrogenous gas production in the soil. However, how and to what extent the associated gene transcription and corresponding gas kinetics interact with the transition of soil O2 status caused by N fertilisation, remains poorly understood. In this context, we conducted a robotized incubation experiment using a He/O2 atmosphere with different amounts of ammonium-based fertiliser (0 (control), 60 (AS60) and 200 mg N kg−1 (NH4)2SO4 (AS200)) applied to an agricultural soil with a strong nitrification potential under three different initial O2 levels (oxic 21%, sub-oxic 3%, and anoxic 0%) over 14 days. Through repeated measurements of N2O, NO, and N2 concentrations and kinetics of mineral N following the decline of O2 concentrations, we found that higher ammonium addition (200 vs. 60 mg N kg−1) caused faster O2 consumption in the headspace and induced up to 238 times higher net accumulation of N2O under initially oxic headspace condition. We speculate that this was due to: 1) the rapid transition of O2 status from oxic to anoxic due to vigorous ammonia oxidation; and 2) the increased N2O/(N2O + NO + N2) ratio of denitrification with higher N addition. The amoA and nosZ gene transcript numbers changed significantly in response to ammonium addition and decreasing O2 concentration, whereas high-throughput sequencing revealed a significant structural alteration of the soil microbiota along with the transition of O2 status. Our results highlight that the vigorousness of oxygen depletion in the soil matrix driven by rapid ammonia oxidation is the proximal factor that regulates gas kinetics in high nitrification-potential soil when O2 diffusion is limited. This implies that practices which reduce hotspots of ammonia oxidation have the potential to mitigate N2O emissions from nitrifier denitrification and denitrification in agricultural soil.

Nitrogen Dioxide Concentrations in the Air in Increasing Superoxide Dismutase Enzyme and Malondialdehyde Serum Levels in Bus Terminal Officers

Introduction: Free radicals in the air such as NO2 , O3 , PM2,5 induce the production of reactive oxygen species (ROS) in the body and stimulates the production of superoxide dismutase (SOD) enzyme. Imbalanced levels of free radicals and antioxidants will trigger the production of malondialdehyde (MDA). This study aimed to analyze the correlation between NO2 concentrations in the air with SOD and MDA levels in bus terminal officers. Methods: This study was an analytical observational and used a cross-sectional design. The population included terminal operational officers and desk administrative officers in the bus terminal. A number of 12 people was chosen as a sample calculated with averaging formula between case and control. The measurement of NO2 concentrations in the ambient air was performed using the Griess Saltzman method. The ELISA method was utilized to analyze the levels of the SOD enzyme, and the TBARS method was used to analyze the level of MDA serum. A statistical test was conducted using a Mann-Whitney test and Independent-2 Sample T-test. Results and Discussion: The average of NO2 concentrations in the ambient air showed 106.5 µg/Nm3 and in the administration room at 17.8 µg/Nm3 . There was a very significantly higher exposure to NO2 in the air towards the level of SOD enzyme (p < 0.01) and to the level of MDA serum (p < 0.01). Conclusion: The high level of exposure to NO2 in the ambient air will increase SOD enzyme and MDA serum production in the body. It is recommended that the officers consume more fruit and vegetables containing vitamins C and E to fulfill the daily nutritional intake for antioxidants, and for the operational officers, always use a mask

Towards an Optical Gas Standard for Traceable Calibration-Free and Direct NO2 Concentration Measurements

We report a direct tunable diode laser absorption spectroscopy (dTDLAS) instrument developed for NO2 concentration measurements without chemical pre-conversion, operated as an Optical Gas Standard (OGS). An OGS is a dTDLAS instrument that can deliver gas species amount fractions (concentrations), without any previous or routine calibration, which are directly traceable to the international system of units (SI). Here, we report NO2 amount fraction quantification in the range of 100–1000 µmol/mol to demonstrate the current capability of the instrument as an OGS for car exhaust gas application. Nitrogen dioxide amount fraction results delivered by the instrument are in good agreement with certified values of reference gas mixtures, validating the capability of the dTDLAS-OGS for calibration-free NO2 measurements. As opposed to the standard reference method (SRM) based on chemiluminescence detection (CLD) where NO2 is indirectly measured after conversion to NO, titration with O3 and the detection of the resulting fluorescence, a dTDLAS-OGS instrument has the benefit of directly measuring NO2 without distorting or delaying conversion processes. Therefore, it complements the SRM and can perform fast and traceable measurements, and side-by-side calibrations of other NO2 gas analyzers operating in the field. The relative standard uncertainty of the NO2 results reported in this paper is 5.1% (k = 1, which is dominated (98%) by the NO2 line strength), the repeatability of the results at 982.6 µmol/mol is 0.1%, the response time of the instrument is 0.5 s, and the detection limit is 825 nmol/mol at a time resolution of 86 s.

High NO2 Concentrations Measured by Passive Samplers in Czech Cities: Unresolved Aftermath of Dieselgate?

This work examines the effects of two problematic trends in diesel passenger car emissions—increasing NO2/NOx ratio by conversion of NO into NO2 in catalysts and a disparity between the emission limit and the actual emissions in everyday driving—on ambient air quality in Prague. NO2 concentrations were measured by 104 membrane-closed Palmes passive samplers at 65 locations in Prague in March–April and September–October of 2019. NO2 concentrations measured by city stations during those periods were comparable with the average values during 2016–2019. The average measured NO2 concentrations at the selected locations, after correcting for the 18.5% positive bias of samplers co-located with a monitoring station, were 36 µg/m3 (range 16–69 µg/m3, median 35 µg/m3), with the EU annual limit of 40 µg/m3 exceeded at 32% of locations. The NO2 concentrations have correlated well (R2 = 0.76) with the 2019 average daily vehicle counts, corrected for additional emissions due to uphill travel and intersections. In addition to expected “hot-spots” at busy intersections in the city center, new ones were identified, i.e., along a six-lane road V Holešovičkách. Comparison of data from six monitoring stations during 15 March–30 April 2020 travel restrictions with the same period in 2016–2019 revealed an overall reduction of NO2 and even a larger reduction of NO. The spatial analysis of data from passive samplers and time analysis of data during the travel restrictions both demonstrate a consistent positive correlation between traffic intensity and NO2 concentrations along/near the travel path. The slow pace of NO2 reductions in Prague suggests that stricter vehicle NOx emission limits, introduced in the last decade or two, have so far failed to sufficiently reduce the ambient NO2 concentrations, and there is no clear sign of remedy of Dieselgate NOx excess emissions.

Understanding Spatial Variability of NO2 in Urban Areas Using Spatial Modelling and Data Fusion Approaches

Small-scale spatial variability in NO2 concentrations is analysed with the help of pollution maps. Maps of NO2 estimated by the Airviro dispersion model and land use regression (LUR) model are fused with measured NO2 concentrations from low-cost sensors (LCS), reference sensors and diffusion tubes. In this study, geostatistical universal kriging was employed for fusing (integrating) model estimations with measured NO2 concentrations. The results showed that the data fusion approach was capable of estimating realistic NO2 concentration maps that inherited spatial patterns of the pollutant from the model estimations and adjusted the modelled values using the measured concentrations. Maps produced by the fusion of NO2-LCS with NO2-LUR produced better results, with r-value 0.96 and RMSE 9.09. Data fusion adds value to both measured and estimated concentrations: the measured data are improved by predicting spatiotemporal gaps, whereas the modelled data are improved by constraining them with observed data. Hotspots of NO2 were shown in the city centre, eastern parts of the city towards the motorway (M1) and on some major roads. Air quality standards were exceeded at several locations in Sheffield, where annual mean NO2 levels were higher than 40 µg/m3. Road traffic was considered to be the dominant emission source of NO2 in Sheffield.

Anthropogenic deposition increases nitrogen-phosphorus imbalances in tree vegetation, litter and soil of Atlantic Forest remnants

Increased N deposition may cause nutritional imbalances in tropical ecosystems, by shifting N:P stoichiometry (as they are typically P-limited) and NH4-N:NO3-N ratios throughout their compartments. Based on this assumption, we aimed at verifying if the anthropogenic N deposition are inducing nutritional imbalances in trees, litter and soil in the remaining Atlantic Forest in SE Brazil. Three forest remnants were selected, one of them supposedly exposed to lower levels anthropogenic N deposition (peri-urban forest) than the other two (urban and agricultural-urban forests). We measured NO2 concentrations, wet and dry deposition of NH4-N, NO3-N and PO4-P and determined total/soluble N and P contents in samples of pioneer and non-pioneer trees, litter and soil. NH4-N:NO3-N and N:P ratios were calculated in all compartments. Multivariate analysis indicated associations between NH4-N, PO4-P and NH4:NO3 ratios in atmospheric deposition or NO2 concentrations and N and P contents in trees, litter and soil of all forest remnants. The comparison of N:P ratios in tree species and litter with those from studies conducted in the 1980–2000 indicated a tendency of N enrichment and increasing P scarcity in the Atlantic Forest remnants studied. Confirming the hypothesis, anthropogenic N deposition increases nutritional imbalances in the ecosystem compartments of forest remnants studied. The peri-urban forest showed to be more vulnerable to nutritional imbalances than the other forests, based on the comparisons with data from 30 to 40 years ago.

Development of a 443 nm diode laser-based differential photoacoustic spectrometer for simultaneous measurements of aerosol absorption and NO2

Measurement of ambient aerosol and nitrogen dioxide (NO2) is important as they are major pollutants from the burning of fossil fuel and biomass. In the present work, a differential photoacoustic spectrometer (D-PAS) was developed for simultaneous, online measurements of aerosol optical absorption and NO2 concentration. A novel photoacoustic resonator was designed and employed in the D-PAS for controlling a large flow rate, improving response time, and keeping the flow noise at a low level. The detection limits of 1.0 Mm−1 and 0.87 ppb for aerosol absorption and NO2 concentration measurements were achieved with a lock-in amplifier time constant of 1 s. The D-PAS accuracy was demonstrated by performing a long-time, continuous measurement of aerosol, and NO2 in ambient air. The measured results of NO2 are consistent with the NOx analyzer and environmental monitoring station results.