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The requirements of the Texas State Implementation Plan of the U.S. Clean Air Act for the Houston-Galveston Ozone Nonattainment Area stipulate large reductions in oxides of nitrogen (NO(x)) emissions. A large number of sources at Dow Chemical Co. sites within the nonattainment area may require the addition of continuous emission monitoring systems...
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... Comparing the FTIR analyzer with the CLA at the tailpipe, the former recorded, on average, 8 mg/km higher values. CLAs have some uncertainties due to the use of NO2-to-NO converters with conversion efficiencies >95% (which need to be checked every month according to EU regulation), possible NO2 losses in their chiller, and influence exerted by quenching with water and CO2 [115]. FTIR instruments' NO2 measurement is affected by water vapor interference. ...
Light-duty vehicle emission regulations worldwide set limits for the following gaseous pollutants: carbon monoxide (CO), nitric oxides (NOX), hydrocarbons (HCs), and/or non-methane hydrocarbons (NMHCs). Carbon dioxide (CO2) is indirectly limited by fleet CO2 or fuel consumption targets. Measurements are carried out at the dilution tunnel with “standard” laboratory-grade instruments following well-defined principles of operation: non-dispersive infrared (NDIR) analyzers for CO and CO2, flame ionization detectors (FIDs) for hydrocarbons, and chemiluminescence analyzers (CLAs) or non-dispersive ultraviolet detectors (NDUVs) for NOX. In the United States in 2012 and in China in 2020, with Stage 6, nitrous oxide (N2O) was also included. Brazil is phasing in NH3 in its regulation. Alternative instruments that can measure some or all these pollutants include Fourier transform infrared (FTIR)- and laser absorption spectroscopy (LAS)-based instruments. In the second category, quantum cascade laser (QCL) spectroscopy in the mid-infrared area or laser diode spectroscopy (LDS) in the near-infrared area, such as tunable diode laser absorption spectroscopy (TDLAS), are included. According to current regulations and technical specifications, NH3 is the only component that has to be measured at the tailpipe to avoid ammonia losses due to its hydrophilic properties and adsorption on the transfer lines. There are not many studies that have evaluated such instruments, in particular those for “non-regulated” worldwide pollutants. For this reason, we compared laboratory-grade “standard” analyzers with FTIR- and TDLAS-based instruments measuring NH3. One diesel and two gasoline vehicles at different ambient temperatures and with different test cycles produced emissions in a wide range. In general, the agreement among the instruments was very good (in most cases, within ±10%), confirming their suitability for the measurement of pollutants.
... There is uncertainty in each stage of our modeling and data, including uncertainty regarding emissions, the resulting PM 2.5 concentrations as determined by InMAP, and the health impacts determined from the dose-response function. Uncertainty in the emissions is present in two forms: first, from measurement errors in the underlying data source, which has been estimated to be <5% [25], and second in variability in emissions and electricity transfers between years. To address the latter uncertainty, we perform the same baseline analysis for another year (2016), with different generation and consumption patterns (see SI section 4.2). ...
The electric grid is evolving rapidly in response to climate change. As renewables are incorporated, more interconnection of the grid is expected. Exposure to fine particulate matter (PM2.5) from fossil-fuel generation causes adverse health impacts, including thousands of premature deaths each year in the United States. It is well understood that PM2.5 exposure can occur at great distances from pollutant sources, but insufficient work has been done to understand the role of grid interconnection and trade in causing pollution-related mortality. Regions with clean generation can import electricity from regions with highly polluting generation sources, allowing them to benefit from the electricity consumption while people in other regions suffer the associated health damages. We use flow tracing and consumption-based accounting to characterize the health damages from exposure to PM 2.5 from electricity imports. We find that 8% of our estimated premature deaths from electricity consumption in the United States are due to electricity imports. There is large geographic heterogeneity, with the most impacts occurring in the Midwest. While the West Coast has much cleaner generation and lower impacts overall, in many West Coast Balancing Areas, more than 50% of the estimated premature mortality associated with electricity consumption is caused by electricity imports, with some groups experiencing larger impacts than others.
... Satellite NO 2 observations have proven useful for constraining NO x emissions, for instance, through fitting downwind line densities (e.g., Lin et al., 2012;de Foy et al., 2015;Liu et al., 2016) and chemical transport modeling (e.g., Stavrakou et al., 2013;Ding et al., 2015;Miyazaki et al., 2017). Using TROPOMI NO 2 , surface NO x emissions have been estimated at high spatial and temporal resolutions, but studies are mostly limited to specific areas at point source to urban scales Goldberg et al., 2019;Lorente et al., 2019;van der A et al., 2020;Huber et al., 2020;Lange et al., 2021). In recent studies, TROPOMI NO 2 retrievals have also been used to provide a detailed understanding of regional and global emission reductions during the COVID-19 lockdowns (Ding et al., 2020;Miyazaki et al., 2020bMiyazaki et al., , 2021Kim et al., 2021;Zhang et al., 2021). ...
... For Japan, we excluded measurement sites for automobile exhaust gases. More than 97 % of the observed NO 2 concentrations used in this study were measured by commercial chemiluminescence analyzers, with typical measurement errors of 1 %-5 % (Gluck et al., 2003). These analyzers overestimate the ambient NO 2 concentrations, because the measurements contain interference from reactive nitrogen compounds other than NO 2 (e.g., Dickerson et al., 2019). ...
... The NO x emissions derived from TROPOMI DA were compared with previous estimates over large urban areas based on statistical fits of NO 2 line density data with the exponentially modified Gaussian (EMG) function using TROPOMI NO 2 Lorente et al., 2019;Goldberg et al., 2019;Lange et al., 2021). We focused on large urban areas where at least two estimates were avail-able. ...
This study gives a systematic comparison of the Tropospheric Monitoring Instrument (TROPOMI) version 1.2 and Ozone Monitoring Instrument (OMI) QA4ECV tropospheric NO2 column through global chemical data assimilation (DA) integration for the period April–May 2018. DA performance is controlled by measurement sensitivities, retrieval errors, and coverage. The smaller mean relative observation errors by 16 % in TROPOMI than OMI over 60∘ N–60∘ S during April–May 2018 led to larger reductions in the global root-mean-square error (RMSE) against the assimilated NO2 measurements in TROPOMI DA (by 54 %) than in OMI DA (by 38 %). Agreements against the independent surface, aircraft-campaign, and ozonesonde observation data were also improved by TROPOMI DA compared to the control model simulation (by 12 %–84 % for NO2 and by 7 %–40 % for ozone), which were more obvious than those by OMI DA for many cases (by 2 %–70 % for NO2 and by 1 %–22 % for ozone) due to better capturing spatial and temporal variability by TROPOMI DA. The estimated global total NOx emissions were 15 % lower in TROPOMI DA, with 2 %–23 % smaller regional total emissions, in line with the observed negative bias of the TROPOMI version 1.2 product compared to the OMI QA4ECV product. TROPOMI DA can provide city-scale emission estimates, which were within 10 % differences with other high-resolution analyses for several limited areas, while providing a globally consistent analysis. These results demonstrate that TROPOMI DA improves global analyses of NO2 and ozone, which would also benefit studies on detailed spatial and temporal variations in ozone and nitrate aerosols and the evaluation of bottom-up NOx emission inventories.
... Linearity of the models was evaluated using mean absolute error (percent) with respect to the maximum NO x in the dataset. As can be seen from Table 4, the percent MAE with respect maximum NO x for all the models are well within 1-2%, which is comparable to the NO x measurement accuracy of NO x emissions analyzers which have linearity of 1% of full-scale NO x (Gluck et al., 2003). Figure 3 presents the training and validation MSE (loss) and R 2 curves for each model. ...
As emissions regulations for transportation become stricter, it is increasingly important to develop accurate nitrogen oxide (NOx) emissions models for heavy-duty vehicles. However, estimation of transient NOx emissions using physics-based models is challenging due to its highly dynamic nature, which arises from the complex interactions between power demand, engine operation, and exhaust aftertreatment efficiency. As an alternative to physics-based models, a multi-dimensional data-driven approach is proposed as a framework to estimate NOx emissions across an extensive set of representative engine and exhaust aftertreatment system operating conditions. This paper employs Deep Neural Networks (DNN) to develop two models, an engine-out NOx and a tailpipe NOx model, to predict heavy-duty vehicle NOx emissions. The DNN models were developed using variables that are available from On-board Diagnostics from two datasets, an engine dynamometer and a chassis dynamometer dataset. Results from trained DNN models using the engine dynamometer dataset showed that the proposed approach can predict NOx emissions with high accuracy, where R2 scores are higher than 0.99 for both engine-out and tailpipe NOx models on cold/hot Federal Test Procedure (FTP) and Ramped Mode Cycle (RMC) data. Similarly, the engine-out and tailpipe NOx models using the chassis dynamometer dataset achieved R2 scores of 0.97 and 0.93, respectively. All models developed in this study have a mean absolute error percentage of approximately 1% relative to maximum NOx in the datasets, which is comparable to that of physical NOx emissions measurement analyzers. The input feature importance studies conducted in this work indicate that high accuracy DNN models (R2 = 0.92–0.95) could be developed by utilizing minimal significant engine and aftertreatment inputs. This study also demonstrates that DNN NOx emissions models can be very effective tools for fault detection in Selective Catalytic Reduction (SCR) systems.
... TiO 2 , particularly in its nano form, is a very good photo-catalyst and has been used extensively in the construction industry due to its excellent compatibility and inertness with cementitious materials . Recently many countries around the world have started incorporating nano TiO 2 in cementitious materials and the use of nanocoatings for the protection of buildings and cultural heritage (Gluck et al., 2003). The photocatalytic activity of TiO 2 has also been studied through application in asphalt pavements for the degradation of air pollutants. ...
... Maggos et al. (2007) gave the difference between the initial and final concentration of NO x (Combination of NO and NO 2 ). (Gluck et al., 2003). ...
With increasing urbanization and industrialization there is an upsurge in air pollution that demands immediate attention. The use of nanomaterials to alleviate air pollution is gaining importance. Certain nanomaterials can photocatalytically act on air pollutants such as oxides of nitrogen (NOx), sulfur (SOx), and carbon (CO2), thereby bringing down their concentration locally. Titanium Dioxide (TiO2), its composites, and TiO2 based Z/S scheme heterojunction photocatalysts are a few such nanomaterials. The band-gap of TiO2 in solid-state (3.2 eV) makes it a good photocatalyst in the ultraviolet region and its composites in the visible light region of the spectrum. Metropolitan cities are densely filled with high-rise buildings and the exteriors of these buildings, which are largely exposed to the atmosphere, can be utilized to coat these nano materials to enable photocatalytic reduction of air pollutants in the surrounding atmosphere. The nano photocatalysts can either be applied as coatings on the existing buildings or incorporated into the construction materials during construction. In this review article, an attempt is made to cover the application of photocatalysts in the construction industry starting from the working principle (mechanism) of heterogeneous and heterojunction photocatalysts, their advantages and disadvantages, methods of synthesis, pollution control applications, with emphasis on the methods of incorporating the photocatalysts into construction materials and also as a coating on existing buildings, the set up required to evaluate NOx reduction and the factors that affect the NOx reduction. The current status of pollution control applications in the construction industry and the authors perspective on the application of heterojunction photocatalysts in construction industry are highlighted.
... For Japan, we excluded measurement sites for automobile exhaust gases. More than 97% of the observed NO 2 concentrations used in this study were measured by commercial chemiluminescence analyzers, with typical measurement errors of 1-5% (Gluck et al., 2003). These analyzers overestimate the ambient NO 2 concentrations, because the measurements contain interference from reactive nitrogen compounds other than NO 2 (e.g., Dickerson et al., 2019). ...
This study gives a systematic comparison of the Tropospheric Monitoring Instrument (TROPOMI) version 1.2 and Ozone Monitoring Instrument (OMI) QA4ECV tropospheric NO2 column through global chemical data assimilation (DA) integration for the period April−May 2018. DA performance is controlled by measurement sensitivities, retrieval errors, and coverage. The smaller mean relative observation errors by 16 % in TROPOMI than OMI over 60° N−60° S during April−May 2018 led to larger reductions in the global root mean square error (RMSE) against the assimilated NO2 measurements in TROPOMI DA (by 54 %) than in OMI DA (by 38 %). Agreements against the independent surface, aircraft-campaign, and ozonesonde observation data were also improved by TROPOMI DA compared to the control model simulation (by 12−84 % for NO2 and by 7−40 % for ozone), which were more obvious than those by OMI DA for many cases (by 2−70 % for NO2 and by 1−22 % for ozone). The estimated global total NOx emissions were 15 % lower in TROPOMI DA, with 2−23 % smaller regional total emissions, in line with the observed negative bias of the TROPOMI version 1.2 product compared to the OMI QA4ECV product. TROPOMI DA can provide city scale emission estimates, which were within 10 % differences with other high-resolution analyses for several limited areas, while providing a globally consistent analysis. These results demonstrate that TROPOMI DA improves global analyses of NO2 and ozone, which would also benefit studies on detailed spatial and temporal variations in ozone and nitrate aerosols and the evaluation of bottom-up NOx emission inventories.
... For the analysis of NO x , NO 2 is reduced to NO, and its mixing ratios are quantified by difference. Many analyzers deployed in routine monitoring stations use molybdenum (Mo) heated to 300 °C -350 °C ( Gluck et al., 2003 ). However, heated Mo converters also reduce other components of odd nitrogen (NO y ) to NO, such as peroxyacetyl nitrate (CH 3 C(O)O 2 NO 2 ; PAN), alkyl nitrates (RONO 2 ), nitrous acid (HONO), HNO 3 , and particulate nitrate ( Dunlea et al., 2007 ;Fehsenfeld et al., 1987 ), which are by-products of some of the same photochemistry that produces O 3 in the troposphere. ...
The reference method to quantify mixing ratios of the criteria air pollutant nitrogen dioxide (NO2) is NO-O3 chemiluminescence (CL), in which mixing ratios of nitric oxide (NO) are measured by sampling ambient air directly, and mixing ratios of NOx (= sum of NO and NO2) are measured by converting NO2 to NO using, for example, heated molybdenum catalyst or, more selectively, photolytic conversion (P-CL). In this work, the nitrous acid (HONO) interference in the measurement of NO2 by P-CL was investigated. Results with two photolytic NO2 converters are presented. The first used radiation centered at 395 nm, a wavelength region commonly utilized in P-CL. The second used light at 415 nm, where the overlap with the HONO absorption spectrum and hence its photolysis rate are less. Mixing ratios of NO2, NOx and HONO entering and exiting the converters were quantified by Thermal Dissociation Cavity Ring-down Spectroscopy (TD-CRDS). Both converters exhibited high NO2 conversion efficiency (CFNO2; > 90%) and partial conversion of HONO. Plots of CF against flow rate were consistent with photolysis frequencies of 4.2 s⁻¹ and 2.9 s⁻¹ for NO2 and 0.25 s⁻¹ and 0.10 s⁻¹ for HONO at 395 nm and 415 nm, respectively. CFHONO was larger than predicted from the overlap of the emission and HONO absorption spectra. The results imply that measurements of NO2 by P-CL marginally but systematically overestimate true NO2 concentrations, and that this interference should be considered in environments with high HONO:NO2 ratios such as the marine boundary layer or in biomass burning plumes.
... NO and NO x (sum of NO and NO 2 ) are typically measured with chemiluminescence analyzers (CLA) developed in early 1970s [120]. NO reacts with O 3 and the excited NO 2 molecules spontaneously return to normal state emitting light (chemiluminescence) [136]. The sensitivity for NO is influenced by the existence of CO 2 or H 2 O in the sample gas, because the excited NO 2 can react with CO 2 and H 2 O (quenching effect) [128]. ...
... The CLA can be used to measure NO x . In this case, a carbon or active metal-based furnace converts NO 2 into NO (NO x converter) [120,136]. Regulations require a conversion efficiency of >95%. However, NH 3 can also be converted to NO in the converter. ...
... Ammonia scrubbers can be used to avoid this problem with CLA [138]. The disadvantages over FTIR are the extra expenses required for an ozonizer, NO 2 to NO converter with converter efficiencies >95% (which need to be checked every month according to EU Regulation), possible NO 2 losses in the chiller, influence due to quenching from water and CO 2 [136,139]. FTIR was also found to provide accurate measurements of NO x in the presence of NH 3 [120]. Table A3 summarizes the studies that the FTIR NO x reading was compared to calibration cylinders or CLA. ...
Pollution from vehicles is a serious concern for the environment and human health. Vehicle emission regulations worldwide have limits for pollutants such as hydrocarbons, CO, and NOx. The measurements are typically conducted at engine dynamometers (heavy-duty engines) sampling from the tailpipe or at chassis dynamometers (light-duty vehicles) sampling from the dilution tunnel. The latest regulations focused on the actual emissions of the vehicles on the road. Greenhouse gases (GHG) (such as CO2, CH4, N2O), and NH3 have also been the subject of some regulations. One instrument that can measure many gaseous compounds simultaneously is the Fourier transform infrared (FTIR) spectrometer. In this review the studies that assessed FTIRs since the 1980s are summarized. Studies with calibration gases or vehicle exhaust gas in comparison with well-established techniques were included. The main conclusion is that FTIRs, even when used at the tailpipe and not at the dilution tunnel, provide comparable results with other well-established techniques for CO2, CO, NOx, while for hydrocarbons, higher deviations were noticed. The introduction of FTIRs in the regulation needs a careful description of the technical requirements, especially interference tests. Although the limited results of prototype portable FTIRs for on-road measurement are promising, their performance at the wide range of environmental conditions (temperature, pressure, vibrations) needs further studies.
... In this study, the correction factor computed from concentrations in the data assimilation was used. The typical measurement error is 1%-5% (Gluck et al., 2003), while the correction factor should add uncertainties originating from reactive nitrogen compounds. In our approach, it is difficult to quantify the additional uncertainties from reactive nitrogen compounds. ...
We present the results from a global 0.56°‐resolution chemical data assimilation that integrates satellite observations of ozone, NO2, CO, HNO3, and SO2 from OMI, GOME‐2, SCIAMACHY, TES, MOPITT, and MLS. The assimilation is based on an ensemble Kalman filter technique and simultaneously optimizes ozone precursor emissions and concentrations of various species. The data assimilation at 0.56° resolution reduced model errors against independent surface, aircraft, and ozonesonde observations, which was larger than at coarser resolutions for many cases. By the data assimilation, surface model errors over major polluted regions were reduced by 33%–75% for NO2 and by 15%–18% for ozone. Agreements against assimilated observations for NO2 were improved using the data assimilation at 0.56° resolution by a factor of 1.5–3 compared to 2.8° resolution over major polluted regions. The estimated global total NOx emission over medium and strong source areas were smaller by 15% at 0.56° resolution than at 2.8° resolution associated with resolving small‐scale transport and chemistry processes, while 2%–26% smaller emissions were found for regional total emissions over Europe, the United States, China, India, and South Africa, with larger differences over megacities such as Los Angeles (−41%). The estimated ship emissions were 5%–7% smaller at 0.56° resolution over the Pacific and Atlantic. The 0.56°‐resolution data assimilation provides globally consistent analyses of the emissions and concentrations on a megacity scale, which benefit studies on air quality and its impact on human health at various spatial scales over different regions of the world.
... The basic idea of a virtual sensor is to take advantage of existing, reliable measurements such as pressure drops and damper openings and to combine them with a physical model of the air distribution system to compute the air flow rates in all ducts. The physical relevance of the model allows for a robust process control with high dynamic capabilities that are essential during 200 load variations.The EUSoft Air system already described in [25,26,20,21] better accuracy [27]. ...
As they deliver dispatchable renewable energy, biomass power plants are expected to play a key role in the stability of the future electricity grids dominated by intermittent renewables. Large-scale, biomass-fired power plants are often retrofitted from coal-fired plants. Such a fuel modification combined with decreasing pollutant emission limits and higher requirements in terms of load flexibility can lead to a decrease of the maximum power delivered by the unit. The limiting factors are partly related to the control systems of those plants. In this paper, we present the results of the upgrading of a 80 MWe, retrofitted biomass power plant that was achieved by improving the dynamic control of the combustion process. Thanks to the addition of virtual air flow sensors in the control system and the re-design of the combustion control loops, the undesired effects of a recent 10% power increase on NOx emissions were more than compensated. The accurate control of the local NOx production in the furnace resulted in a decrease of these emissions by 15% with an increased stability. This study will help increasing the cost-effectiveness of such conversions, and facilitate the development of dispatchable, renewable power units able to contribute to the grid stability.
