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NOx
About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.
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TL;DR: The EMEP MSC-W model has been used to estimate the effects of 50% reductions in man-made NOx (nitrogen oxides = NO + NO2) and volatile organic compounds (VOCs) on rural ozone concentrations in different parts of Europe, under four different assumptions concerning biogenic emissions: (1) medium isoprene emissions, (2) high isoprenes, (3) zero isoprane emissions, and (4) zero soil NOx emissions as discussed by the authors.
Abstract: As shown in a companion paper, uncertainties in the emissions of isoprene in Europe are significant, quite possibly of the order of 500%, and this uncertainty must be taken into account when assessing the effects of emission control measures in reducing ozone. The EMEP MSC-W model has been used to estimate the effects of 50% reductions in man-made NOx (nitrogen oxides = NO + NO2) and volatile organic compounds (VOCs) on rural ozone concentrations in different parts of Europe, under four different assumptions concerning biogenic emissions: (1) medium isoprene emissions, (2) high isoprene emissions, (3) zero isoprene emissions, and (4) zero soil NOx emissions. The model results suggest that uncertainties in isoprene emissions are not very important for the evaluation of long-term (6 monthly) ozone scenarios in Europe, especially with regard to the relative merit of NOx versus VOC control. To explain these results, we have analyzed the sources and sinks of important radical species under different isoprene emission levels. It is shown that isoprene emissions are not sufficient to affect production or loss rates of key-radical species significantly. The main effect of isoprene is to depress OH levels in isoprene-rich areas, thereby reducing somewhat the share of ozone production possible from anthropogenic VOC. However, in such areas it is NOx emissions which are limiting as far as ozone production is concerned, so the policy advice from the model is quite robust against the isoprene uncertainties. The results obtained with respect to the effects of control measures on maximum ozone proved more sensitive to the assumed isoprene level. It is also shown that changes in isoprene emission level can alter the dates upon which ozone maxima occur, so predictions of the effects of man-made control cannot rely upon a consideration of the chemistry occurring at the time of the base case maxima but rather require modeling over the summer period.
162 citations
TL;DR: Simulations with a regional chemical transport model show that anthropogenic emissions of volatile organic compounds and nitrogen oxides lead to a dramatic diurnal variation of surface ozone in Houston, Texas, and suggest that consideration of regulatory control of O(3) precursor emissions from the industrial sources is essential to formulate ozone abatement strategies in this region.
Abstract: Simulations with a regional chemical transport model show that anthropogenic emissions of volatile organic compounds and nitrogen oxides (NOx = NO + NO2) lead to a dramatic diurnal variation of surface ozone (O3) in Houston, Texas. During the daytime, photochemical oxidation of volatile organic compounds catalyzed by NOx results in episodes of elevated ambient O3 levels significantly exceeding the National Ambient Air Quality Standard. The O3 production rate in Houston is significantly higher than those found in other cities over the United States. At night, a surface NOx maximum occurs because of continuous NO emission from industrial sources, and, consequently, an extensive urban-scale “hole” of surface ozone (<10 parts per billion by volume in the entire Houston area) is formed as a result of O3 removal by NO. The results suggest that consideration of regulatory control of O3 precursor emissions from the industrial sources is essential to formulate ozone abatement strategies in this region.
162 citations
TL;DR: In this article, the results of a yearlong continuous measurements of gaseous pollutants, NO, NO2, NOx and O3 in the ambient air at Kathmandu valley were summarized.
162 citations
TL;DR: In this article, the effects of fuel properties on combustion characteristics and emissions such as NOx, smoke, and particulate in a direct-injection diesel engine were investigated and the results showed that reducing cetane number resulted in the increase of NOx and the decrease of particulate at high load.
Abstract: This study investigated the effects of fuel properties on combustion characteristics and emissions such as NOx. THC, smoke and particulate in a direct-injection diesel engine. Cetane number and aromatic content of fuels were varied independently. The results showed that reducing cetane number resulted in the increase of NOx and the decrease of particulate at high load. The aromatic content had little effect on combustion characteristics. However, increasing aromatic content for high cetane number fuel resulted in high NOx and particulate emissions. For low cetane number fuel, increasing aromatic content produced high THC emission at retarded injection timing. In the case of high injection pressure, fuel properties showed little effect on particulate emissions.
162 citations
TL;DR: In this article, the basic combustion parameters including start of the ignition timing, burn duration, cycle-to-cycle variation, and carbon monoxide (CO), unburned hydrocarbon (UHC), and nitric oxide (NOx) emissions of homogeneous charge compression ignition (HCCI) engines fueled with primary reference fuels (PRFs) and their mixtures were evaluated.
162 citations