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1
Lee, L., P. J. Wooldridge, J. deGouw, S. S. Brown, T. S. Bates, P. K. Quinn und R. C. Cohen. „Particulate organic nitrates observed in an oil and natural gas production region during wintertime“. Atmospheric Chemistry and Physics Discussions 15, Nr. 7 (13.04.2015): 10677–708. http://dx.doi.org/10.5194/acpd-15-10677-2015.
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Abstract. Organic nitrates in both gas and condensed (aerosol) phases were measured during the Uintah Basin Winter Ozone Study from January to February in 2012. A high degree of correlation between total aerosol volume at diameters less than 500 nm and the particulate organic nitrate concentration indicates that organic nitrates are a consistent, if not dominant, fraction of fine aerosol mass. In contrast, a similar correlation with sub 2.5 μm aerosol volume is weaker. The C : N atomic ratio inferred from field measurements of PM2.5 and particulate organic nitrate is 34 : 1. Calculations constrained by the observations indicate that both condensation of gas phase nitrates and heterogeneous reactions of NO3 / N2O5 are responsible for introducing organic nitrate functionality into the aerosol and that the source molecules are alkanes. Extrapolating the results to urban aerosol suggests organic nitrate production from alkanes may be a major secondary organic aerosol source.
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Lee, L., P. J. Wooldridge, J. deGouw, S. S. Brown, T. S. Bates, P. K. Quinn und R. C. Cohen. „Particulate organic nitrates observed in an oil and natural gas production region during wintertime“. Atmospheric Chemistry and Physics 15, Nr. 16 (21.08.2015): 9313–25. http://dx.doi.org/10.5194/acp-15-9313-2015.
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Abstract. Organic nitrates in both gas and condensed (aerosol) phases were measured during the Uintah Basin Winter Ozone Study from January to February in 2012. A high degree of correlation between total aerosol volume at diameters less than 500 nm and the particulate organic nitrate concentration indicates that organic nitrates are a consistent, if not dominant, fraction of fine aerosol mass. In contrast, a similar correlation with sub-2.5 μm aerosol volume is weaker. The C : N atomic ratio inferred from field measurements of PM2.5 and particulate organic nitrate is 34 : 1. Calculations constrained by the observations indicate that both condensation of gas-phase nitrates and heterogeneous reactions of NO3 / N2O5 are responsible for introducing organic nitrate functionality into the aerosol and that the source molecules are alkanes. Extrapolating the results to urban aerosol suggests organic nitrate production from alkanes may be a major secondary organic aerosol source.
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Lean, D. R. S., und R. Knowles. „Nitrogen Transformations in Lake Ontario“. Canadian Journal of Fisheries and Aquatic Sciences 44, Nr. 12 (01.12.1987): 2133–43. http://dx.doi.org/10.1139/f87-262.
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Concentrations of ammonium plus nitrite in Lake Ontario were highly correlated with ammonium regeneration from zooplankton excretion (r = 0.966), inferring that elevated nitrite concentrations result from nitrification. Nitrapyrin-sensitive dark 14C-labeled bicarbonate assays confirmed high rates of nitrification by chemoautotrophic bacteria. 15N-labeled nitrate experiments showed that nitrate, not ammonium, was the principal form of N used for total microbial protein synthesis. Size fractionation experiments also suggested that small cells were responsible for most of the ammonium uptake, while large cells used mostly nitrate. Nitrate depletion in the surface waters during summer stratification resulted from movement to particulate N, nitrite, and ammonium as well as losses in particulate N due to sedimentation. At least one third, however, was unaccounted for (i.e. 30 mg N∙m−2∙d−1) and may have been converted to protein which would move up the food chain to larger organisms (e.g. fish) not sampled during conventional water chemistry. Nitrous oxide profiles showed that nitrate losses through denitrification are unlikely to occur. Consequently, unless nitrate loading to Lake Ontario is reduced, nitrate concentrations should be expected to continue to increase.
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Jacob, Juliane, Tina Sanders und Kirstin Dähnke. „Nitrite consumption and associated isotope changes during a river flood event“. Biogeosciences 13, Nr. 19 (11.10.2016): 5649–59. http://dx.doi.org/10.5194/bg-13-5649-2016.
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Abstract. In oceans, estuaries, and rivers, nitrification is an important nitrate source, and stable isotopes of nitrate are often used to investigate recycling processes (e.g. remineralisation, nitrification) in the water column. Nitrification is a two-step process, where ammonia is oxidised via nitrite to nitrate. Nitrite usually does not accumulate in natural environments, which makes it difficult to study the single isotope effect of ammonia oxidation or nitrite oxidation in natural systems. However, during an exceptional flood in the Elbe River in June 2013, we found a unique co-occurrence of ammonium, nitrite, and nitrate in the water column, returning towards normal summer conditions within 1 week. Over the course of the flood, we analysed the evolution of δ15N–NH4+ and δ15N–NO2− in the Elbe River. In concert with changes in suspended particulate matter (SPM) and δ15N SPM, as well as nitrate concentration, δ15N–NO3− and δ18O–NO3−, we calculated apparent isotope effects during net nitrite and nitrate consumption. During the flood event, > 97 % of total reactive nitrogen was nitrate, which was leached from the catchment area and appeared to be subject to assimilation. Ammonium and nitrite concentrations increased to 3.4 and 4.4 µmol L−1, respectively, likely due to remineralisation, nitrification, and denitrification in the water column. δ15N–NH4+ values increased up to 12 ‰, and δ15N–NO2− ranged from −8.0 to −14.2 ‰. Based on this, we calculated an apparent isotope effect 15ε of −10.0 ± 0.1 ‰ during net nitrite consumption, as well as an isotope effect 15ε of −4.0 ± 0.1 ‰ and 18ε of −5.3 ± 0.1 ‰ during net nitrate consumption. On the basis of the observed nitrite isotope changes, we evaluated different nitrite uptake processes in a simple box model. We found that a regime of combined riparian denitrification and 22 to 36 % nitrification fits best with measured data for the nitrite concentration decrease and isotope increase.
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Karwowska, Małgorzata, und Anna Kononiuk. „Nitrates/Nitrites in Food—Risk for Nitrosative Stress and Benefits“. Antioxidants 9, Nr. 3 (16.03.2020): 241. http://dx.doi.org/10.3390/antiox9030241.
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In the context of impact on human health, nitrite/nitrate and related nitrogen species such as nitric oxide (NO) are a matter of increasing scientific controversy. An increase in the content of reactive nitrogen species may result in nitrosative stress—a deleterious process, which can be an important mediator of damage to cell structures, including lipids, membranes, proteins and DNA. Nitrates and nitrites are widespread in the environment and occur naturally in foods of plant origin as a part of the nitrogen cycle. Additionally, these compounds are used as additives to improve food quality and protect against microbial contamination and chemical changes. Some vegetables such as raw spinach, beets, celery and lettuce are considered to contain high concentrations of nitrates. Due to the high consumption of vegetables, they have been identified as the primary source of nitrates in the human diet. Processed meats are another source of nitrites in our diet because the meat industry uses nitrates/nitrites as additives in the meat curing process. Although the vast majority of consumed nitrates and nitrites come from natural vegetables and fruits rather than food additives, there is currently a great deal of consumer pressure for the production of meat products free of or with reduced quantities of these compounds. This is because, for years, the cancer risks of nitrates/nitrites have been considered, since they potentially convert into the nitrosamines that have carcinogenic effects. This has resulted in the development and rapid expansion of meat products processed with plant-derived nitrates as nitrite alternatives in meat products. On the other hand, recently, these two ions have been discussed as essential nutrients which allow nitric oxide production and thus help cardiovascular health. Thus, this manuscript reviews the main sources of dietary exposure to nitrates and nitrites, metabolism of nitrites/nitrates, and health concerns related to dietary nitrites/nitrates, with particular emphasis on the effect on nitrosative stress, the role of nitrites/nitrates in meat products and alternatives to these additives used in meat products.
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Yu, Kuangyou, Qiao Zhu, Ke Du und Xiao-Feng Huang. „Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China“. Atmospheric Chemistry and Physics 19, Nr. 7 (17.04.2019): 5235–49. http://dx.doi.org/10.5194/acp-19-5235-2019.
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Abstract. Organic nitrates are important atmospheric species that significantly affect the cycling of NOx and ozone production. However, characterization of particulate organic nitrates and their sources in polluted atmosphere is a big challenge and has not been comprehensively studied in Asia. In this study, an aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed at an urban site in China from 2015 to 2016 to characterize particulate organic nitrates in total nitrates with a high time resolution. Based on the cross-validation of two different data processing methods, organic nitrates were effectively quantified to contribute a notable fraction of organic aerosol (OA), namely 9 %–21 % in spring, 11 %–25 % in summer, and 9 %–20 % in autumn, while contributing a very small fraction in winter. The good correlation between organic nitrates and fresh secondary organic aerosol (SOA) at night, as well as the diurnal trend of size distribution of organic nitrates, indicated a key role of nighttime local secondary formation of organic nitrates. Furthermore, theoretical calculations of nighttime SOA production of NO3 reactions with volatile organic compounds (VOCs) measured during the spring campaign were performed, resulting in three biogenic VOCs (α-pinene, limonene, and camphene) and one anthropogenic VOC (styrene) identified as the possible key VOC precursors to particulate organic nitrates. The comparison with similar studies in the literature implied that nighttime particulate organic nitrate formation is highly relevant to NOx levels. This study proposes that unlike the documented cases in the United States and Europe, modeling nighttime particulate organic nitrate formation in China should incorporate not only biogenic VOCs but also anthropogenic VOCs for urban air pollution, which needs the support of relevant smog chamber studies in the future.
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Parks, S. E., D. O. Huett, L. C. Campbell und L. J. Spohr. „Nitrate and nitrite in Australian leafy vegetables“. Australian Journal of Agricultural Research 59, Nr. 7 (2008): 632. http://dx.doi.org/10.1071/ar07198.
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A market survey of Australian leafy vegetables and a winter and spring experiment with Swiss chard were conducted to examine nitrate and nitrite levels in leaves. The relationship between growth response to nitrogen (N) supply and light level and accumulation of N in leaves was of particular interest. The survey that included 7 types of lettuce and endive (Asteraceae), 6 leafy Asian vegetables (Brassicaceae), and Swiss chard and spinach (Amaranthaceae) showed that fresh leafy vegetables available during a 6-month period on the Australian market can range in nitrate-N from 12 to 1400 mg/kg fresh weight and nitrite-N from 0 to 37.5 mg/kg. Some samples exceeded the limits for nitrate and nitrite based on international food safety standards. The response of Swiss chard to N supply and light was investigated. The accumulation of nitrate in Swiss chard was primarily influenced by increasing N supply and not by light level. Light conditions for all treatments in both the winter and spring experiments exceeded the critical level (~200 μmol/m2.s) required to increase leaf nitrate. Growth and leaf nitrate concentration were higher for spring, associated with average minimum to maximum temperatures of 18–39°C, compared with 14–28°C for winter. Treatment effects on nitrite-N in Swiss chard could not be determined because nitrite was only detected in one-third of plants. The importance of N supply in affecting nitrate accumulation in vegetables is highlighted by the Swiss chard experiments. It confirmed that nitrate accumulation occurs at optimal to supra-optimal nitrate supply, emphasising for growers the undesirable effect of excessive fertiliser use.
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González-Sánchez, Juan Miguel, Nicolas Brun, Junteng Wu, Julien Morin, Brice Temime-Roussel, Sylvain Ravier, Camille Mouchel-Vallon, Jean-Louis Clément und Anne Monod. „On the importance of atmospheric loss of organic nitrates by aqueous-phase ●OH oxidation“. Atmospheric Chemistry and Physics 21, Nr. 6 (30.03.2021): 4915–37. http://dx.doi.org/10.5194/acp-21-4915-2021.
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Abstract. Organic nitrates are secondary species in the atmosphere. Their fate is related to the chemical transport of pollutants from polluted areas to more distant zones. While their gas-phase chemistry has been studied, their reactivity in condensed phases is far from being understood. However, these compounds represent an important fraction of organic matter in condensed phases. In particular, their partition to the aqueous phase may be especially important for oxidized organic nitrates for which water solubility increases with functionalization. This work has studied for the first time the aqueous-phase ⚫OH-oxidation kinetics of four alkyl nitrates (isopropyl nitrate, isobutyl nitrate, 1-pentyl nitrate, and isopentyl nitrate) and three functionalized organic nitrates (α-nitrooxyacetone, 1-nitrooxy-2-propanol, and isosorbide 5-mononitrate) by developing a novel and accurate competition kinetic method. Low reactivity was observed, with kOH ranging from 8×107 to 3.1×109 L mol−1 s−1 at 296±2 K. Using these results, a previously developed aqueous-phase structure–activity relationship (SAR) was extended, and the resulting parameters confirmed the extreme deactivating effect of the nitrate group, up to two adjacent carbon atoms. The achieved extended SAR was then used to determine the ⚫OH-oxidation rate constants of 49 organic nitrates, including hydroxy nitrates, ketonitrates, aldehyde nitrates, nitrooxy carboxylic acids, and more functionalized organic nitrates such as isoprene and terpene nitrates. Their multiphase atmospheric lifetimes towards ⚫OH oxidation were calculated using these rate constants, and they were compared to their gas-phase lifetimes. Large differences were observed, especially for polyfunctional organic nitrates: for 50 % of the proposed organic nitrates for which the ⚫OH reaction occurs mainly in the aqueous phase (more than 50 % of the overall removal), their ⚫OH-oxidation lifetimes increased by 20 % to 155 % under cloud/fog conditions (liquid water content LWC = 0.35 g m−3). In particular, for 83 % of the proposed terpene nitrates, the reactivity towards ⚫OH occurred mostly (>98 %) in the aqueous phase, while for 60 % of these terpene nitrates, their lifetimes increased by 25 % to 140 % compared to their gas-phase reactivity. We demonstrate that these effects are of importance under cloud/fog conditions but also under wet aerosol conditions, especially for the terpene nitrates. These results suggest that considering aqueous-phase ⚫OH-oxidation reactivity of biogenic nitrates is necessary to improve the predictions of their atmospheric fate.
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McKnight, G. M., C. W. Duncan, C. Leifert und M. H. Golden. „Dietary nitrate in man: friend or foe?“ British Journal of Nutrition 81, Nr. 5 (Mai 1999): 349–58. http://dx.doi.org/10.1017/s000711459900063x.
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Based on the premise that dietary nitrate is detrimental to human health, increasingly stringent regulations are being instituted to lower nitrate levels in food and water. Not only does this pose a financial challenge to water boards and a threat to vegetable production in Northern Europe, but also may be eliminating an important non-immune mechanism for host defence. Until recently nitrate was perceived as a purely harmful dietary component which causes infantile methaemoglobinaemia, carcinogenesis and possibly even teratogenesis. Epidemiological studies have failed to substantiate this. It has been shown that dietary nitrate undergoes enterosalivary circulation. It is recirculated in the blood, concentrated by the salivary glands, secreted in the saliva and reduced to nitrite by facultative Gram-positive anaerobes (Staphylococcus sciuriandS. intermedius) on the tongue. Salivary nitrite is swallowed into the acidic stomach where it is reduced to large quantities of NO and other oxides of N and, conceivably, also contributes to the formation of systemic S-nitrosothiols. NO and solutions of acidified nitrite, mimicking gastric conditions, have been shown to have antimicrobial activity against a wide range of organisms. In particular, acidified nitrite is bactericidal for a variety of gastrointestinal pathogens such asYersiniaandSalmonella.NO is known to have vasodilator properties and to modulate platelet function, as are S-nitrosothiols. Thus, nitrate in the diet, which determines reactive nitrogen oxide species production in the stomach (McKnightet al.1997), is emerging as an effective host defence against gastrointestinal pathogens, as a modulator of platelet activity and possibly even of gastrointestinal motility and microcirculation. Therefore dietary nitrate may have an important therapeutic role to play, not least in the immunocompromised and in refugees who are at particular risk of contracting gastroenteritides.
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Spryn, K. R., M. V. Sabadashka und N. O. Sybirna. „Effects of agmatine and red wine concentrate, enriched with polyphenolic compounds, on L-arginine / nitrogen oxide system in the brain of rats with experimental diabetes mellitus“. Studia Biologica 15, Nr. 2 (2021): 25–34. http://dx.doi.org/10.30970/sbi.1502.655.
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Background. Diabetes mellitus is a chronic endocrine metabolic disease with absolute or relative insufficiency of insulin, accompanied by impaired metabolism. Endogenous bioamine agmatine may become a basis of new antidiabetic drugs, as it is capable to induce the release of some peptide hormones, in particular insulin, and can regulate NO synthesis. Natural polyphenols are potential multifunctional agents that also can reduce the risk of diabetes and diabetic complications. The aim of the study was to evaluate the effect of agmatine and red wine concentrate, enriched with polyphenolic compounds, on NO-synthase activity and the content of NO stable metabolites under experimental diabetes mellitus. Materials and Methods. The experiments were conducted on white Wistar male rats. Diabetes was induced by intra-abdominal injection of streptozotocin. From the 14th day after the induction of diabetes, agmatine was injected intramuscularly or red wine concentrate, enriched with polyphenolic compounds was administrated orally to animals for 14 days. Rats were decapitated under ether anesthesia on the 28th day of the experiment. In the brain of rats, the activity of constitutive (Ca2+-dependent) and inducible (Ca2+-independent) isoforms of NO-synthase and the content of nitrite and nitrate anions were determined. Results and Discussion. The activities of constitutive and inducible isoforms of NO-synthase were increased in the brain of diabetic rats. The administration of both agmatine and red wine concentrate, enriched with polyphenolic compounds, caused the reduction of the activities of NO-synthase isoforms. In the case of diabetes, the administration of agmatine contributes to the increase of nitrite and nitrate content in brain cells compared to diabetes. The administration of red wine concentrate, enriched with polyphenolic compounds, also promotes nitrite levels but does not affect the nitrate level. Conclusion. We found that the red wine concentrate, enriched with polyphenolic compounds, has a stronger effect on the activity of Ca2+-dependent and Ca2+-independent isoforms of NO-synthase, as well as the content of nitrites and nitrates in brain of rats with experimental diabetes mellitus, compared to the effect of agmatine.
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Luque-Almagro, Víctor M., Andrew J. Gates, Conrado Moreno-Vivián, Stuart J. Ferguson, David J. Richardson und M. Dolores Roldán. „Bacterial nitrate assimilation: gene distribution and regulation“. Biochemical Society Transactions 39, Nr. 6 (21.11.2011): 1838–43. http://dx.doi.org/10.1042/bst20110688.
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In the context of the global nitrogen cycle, the importance of inorganic nitrate for the nutrition and growth of marine and freshwater autotrophic phytoplankton has long been recognized. In contrast, the utilization of nitrate by heterotrophic bacteria has historically received less attention because the primary role of these organisms has classically been considered to be the decomposition and mineralization of dissolved and particulate organic nitrogen. In the pre-genome sequence era, it was known that some, but not all, heterotrophic bacteria were capable of growth on nitrate as a sole nitrogen source. However, examination of currently available prokaryotic genome sequences suggests that assimilatory nitrate reductase (Nas) systems are widespread phylogenetically in bacterial and archaeal heterotrophs. Until now, regulation of nitrate assimilation has been mainly studied in cyanobacteria. In contrast, in heterotrophic bacterial strains, the study of nitrate assimilation regulation has been limited to Rhodobacter capsulatus, Klebsiella oxytoca, Azotobacter vinelandii and Bacillus subtilis. In Gram-negative bacteria, the nas genes are subjected to dual control: ammonia repression by the general nitrogen regulatory (Ntr) system and specific nitrate or nitrite induction. The Ntr system is widely distributed in bacteria, whereas the nitrate/nitrite-specific control is variable depending on the organism.
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Oaks, Ann. „Primary nitrogen assimilation in higher plants and its regulation“. Canadian Journal of Botany 72, Nr. 6 (01.06.1994): 739–50. http://dx.doi.org/10.1139/b94-094.
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Characteristics of the enzymes involved in the assimilation of NO3− and NH4+, in particular the nitrate and nitrite reductases, glutamine synthetase, glutamate synthase, glutamate dehydrogenase, glutamate decarboxylase, and asparagine synthetase, are described. The cellular organization of these enzymes in root and leaf tissues are assessed in view of recent research developments that utilize various tissue blotting techniques. Regulation of nitrate assimilation is analyzed at the physiological, biochemical, and molecular levels. Key words: nitrate, ammonium, assimilation, regulation.
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Mercado, Jesús M., Teodoro Ramírez, Dolores Cortésand und Esperanza Liger. „Isotopic composition of particulate organic nitrogen and its relationship to nitrate assimilation in the Mediterranean Sea“. Scientia Marina 74, Nr. 4 (01.07.2010): 745–53. http://dx.doi.org/10.3989/scimar.2010.74n4745.
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Simon, Poruthoor K., und Purnendu K. Dasgupta. „Continuous Automated Measurement of Gaseous Nitrous and Nitric Acids and Particulate Nitrite and Nitrate“. Environmental Science & Technology 29, Nr. 6 (Juni 1995): 1534–41. http://dx.doi.org/10.1021/es00006a015.
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Zhou, Hong Yi, Si Liang, Si Si Zeng und Shuang Jian Lei. „Chemical Reduction of Nitrate in Aqueous Solution by Iron Powder“. Advanced Materials Research 777 (September 2013): 71–76. http://dx.doi.org/10.4028/www.scientific.net/amr.777.71.
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Nitrate is a common groundwater contaminant and poses health and environmental threats. Reductive denitrification of nitrate by zero-valent iron was investigated in unbuffered solutions at 20 °C. Nitrate was effectively removed at low initial solution pH. The reaction was accompanied by the production and then disappearance of a small quantity of nitrite, suggesting that nitrite was the intermediate and subsequently further reduced. A rapid rise in solution pH was also observed during the reaction. At the initial pH of 4, a reduction of 90% in nitrate concentration from 60 to 7.0 mg/L at 60 min was observed. The extent of nitrate removal decreased with increasing solution pH within the tested range of 3 - 6, suggesting that the reaction was an acid-driven process. The extent of nitrate removal also increased with Fe dosage over the range of 5 - 20 g/L, as higher Fe dosages provided more reactive surfaces. It is proposed that protons participate in the nitrate reduction by Fe0 via an initial reduction of protons to reduced hydrogen species followed by a subsequent reaction with nitrate. The hydrolysis of Fe corrosion products (e.g., ferrous ions) produces protons, in particular, near the surfaces of Fe, which drives the reaction to continue.
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Xu, Weiqi, Masayuki Takeuchi, Chun Chen, Yanmei Qiu, Conghui Xie, Wanyun Xu, Nan Ma, Douglas R. Worsnop, Nga Lee Ng und Yele Sun. „Estimation of particulate organic nitrates from thermodenuder–aerosol mass spectrometer measurements in the North China Plain“. Atmospheric Measurement Techniques 14, Nr. 5 (21.05.2021): 3693–705. http://dx.doi.org/10.5194/amt-14-3693-2021.
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Abstract. Particulate organic nitrates (pON) are an important component of secondary organic aerosol in biogenic-emission-dominant environments and play a critical role in NOx cycles. However, estimation of pON has been a challenge in polluted environments, e.g., North China Plain, with high concentrations of inorganic nitrate and NOx. Here we developed a method for estimation of pON from the measurements of high-resolution aerosol mass spectrometer coupled with a thermodenuder based on the volatility differences between inorganic nitrate and pON. The results generally correlated well with those estimated from positive matrix factorization of combined organic and inorganic mass spectra and from the ratio of NO+ to NO2+ (NOx+ ratio), yet they had improvements in reducing negative values due to the influences of high concentration of inorganic nitrate and constant NOx+ ratio of organic nitrates (RON). By applying this approach to the measurements at an urban (Beijing) and a rural site (Gucheng) in summer and winter in the North China Plain, we estimated that the average mass concentrations of NO3,org (1.8 µg m−3 vs. 1.0 µg m−3) and pON to OA (27.5 % vs. 14.8 %) were higher in summer than in winter in Beijing, indicating more pON formation in biogenically and anthropogenically mixed environments. In addition, the average NO3,org loading in Gucheng was 1.9 µg m−3, and the pON at the rural site also showed higher contribution to OA than that in Beijing during wintertime due to higher primary emissions and gaseous precursors in Gucheng. In addition, RON was determined and showed considerable differences between day–night and clean–polluted periods, highlighting the complexity of pON compounds from different chemical pathways (e.g., OH and NO3 oxidation) and sources.
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Dahab, M. F., Y. W. Lee und Istvan Bogardi. „A rule-based fuzzy-set approach to risk analysis of nitrate-contaminated groundwater“. Water Science and Technology 30, Nr. 7 (01.10.1994): 45–52. http://dx.doi.org/10.2166/wst.1994.0302.
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Groundwater nitrate contamination has been a subject of concern because nitrate salts can induce infant methemoglobinemia and possibly human gastric cancer. In general, nitrates in drinking water may not be the main component of total nitrate intake, but nitrate-contaminated drinking water can make an important contribution to total nitrate intake. In this paper, a nitrate risk-assessment methodology is developed to assist decision makers in estimating human health risks corresponding to a particular nitrate dose to humans and in determining whether regulatory action must be taken to reduce the health risks. The case of a community with a nitrate water quality problem is used to illustrate the nitrate risk assessment methodology. The uncertainty associated with assessing health risks of nitrate and its impact on results are represented by using a fuzzy-set approach and incorporated into the nitrate risk assessment methodology. Therefore, a nitrate risk assessment can be made that is more realistic and appropriate than the one made without taking uncertainty into account.
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Nielsen, Torben, Jesper Platz, Kit Granby, Asger B. Hansen, Henrik Skov und Axel H. Egeløv. „Particulate organic nitrates“. Atmospheric Environment 32, Nr. 14-15 (August 1998): 2601–8. http://dx.doi.org/10.1016/s1352-2310(97)00483-4.
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Duermeyer, Lisza, Ehsan Khodapanahi, Dawei Yan, Anne Krapp, Steven J. Rothstein und Eiji Nambara. „Regulation of seed dormancy and germination by nitrate“. Seed Science Research 28, Nr. 3 (06.06.2018): 150–57. http://dx.doi.org/10.1017/s096025851800020x.
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AbstractNitrate promotes seed germination at low concentrations in many plant species, and functions as both a nutrient and a signal. As a nutrient, it is assimilated via nitrite to ammonium, which is then incorporated into amino acids. Nitrate reductase (NR) catalyses the reduction of nitrate to nitrite, the committed step in the assimilation. Seed sensitivity to nitrate is affected by other environmental factors, such as light and after-ripening, and by genotypes. Mode of nitrate action in seed germination has been well documented in Arabidopsis thaliana and the hedge mustard Sisymbrium officinale. In these species nitrate promotes seed germination independent of its assimilation by NR, suggesting that it acts as a signal to stimulate germination. In Arabidopsis, maternally applied nitrate affects the degree of primary dormancy in both wild-type and mutants defective in NR. This indicates that nitrate acts not only during germination, but also during seed development to negatively regulate primary dormancy. Functional genomics studies in Arabidopsis have revealed that nitrate elicits downstream events similar to other germination stimulators, such as after-ripening, light and stratification, suggesting that these distinct environmental signals share the same target(s). In Arabidopsis, the NIN-like protein 8 (NLP8) transcription factor, which acts downstream of nitrate signalling, induces nitrate-dependent gene expression. In particular, a gene encoding the abscisic acid (ABA) catabolic enzyme CYP707A2 is directly regulated by NLP8. This regulation triggers a nitrate-induced ABA decrease that permits seed germination. This review article summarizes an update of our current understanding of the regulation of seed dormancy and germination by nitrate.
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Zeller, Frederick P., Giselle Rivera und Michelle Depot. „Tolerance to Organic Nitrates in Ischemic Heart Disease“. Drug Intelligence & Clinical Pharmacy 21, Nr. 11 (November 1987): 857–64. http://dx.doi.org/10.1177/106002808702101101.
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The development of tolerance to organic nitrates in patients with ischemic heart disease is reviewed, with particular interest in alterations to both the hemodynamic and antiischemic effects over time. The article primarily focuses on how tolerance is defined, what biochemical mechanisms are involved when this condition occurs, which agents have been associated with the development of tolerance, and what can be done to prevent or reverse the condition in patients taking nitrates for ischemic heart disease. From a historical perspective, tolerance to organic nitrates has been a recognized phenomenon since the last century. The role that blood-level determinations and nitroglycerin pharmacokinetics have in the development of tolerance is discussed, and an extensive overview of currently marketed organic nitrate preparations and a few others available only through approved investigational protocols is presented. The role of cross-tolerance is discussed as is the role that nitrate-free intervals play in partially or completely reversing the effects of tolerance during chronic nitrate therapy. Additionally, a discussion of which specific nitrate formulations are least likely to have tolerance associated with their use is included, such as short-acting nitrate formulations with the exception of the intravenous dosage form. Finally, buccal nitroglycerin is presented as another new formulation that appears to be associated with minimal tolerance in studies already completed. Extracto Se revisa en este artículo el desarrollo de tolerancia a los nitratos orgánicos en pacientes con enfermedad isquémica del corazón, con particular interés en la alteración de los efectos hemodinámicos y anti-isquémicos con el tiempo. El artículo enfoca primeramente como se define tolerancia, qué mecanismos bioquímicos están envueltos cuando esto ocurre, qué agentes se han asociado al desarrollo de tolerancia, y qué se puede hacer para prevenir o revertir la condición en pacientes que toman nitratos para enfermedad isquémica del corazón. La tolerancia a nitratos orgánicos es un fenómeno que se ha descrito desde principios de este siglo. Se discute el rol de la farmacocinética de nitroglicerina y de la determinación de concentraciones sanguíneas en el desarrollo de tolerancia. Además se presentan las diferentes preparaciones de nitratos orgánicos disponibles en el mercado al igual que otros que están en investigación. Se discute el rol de tolerancia cruzada y el de los intérvalos libres de nitrato en revenir parcial ó completamente los efectos de tolerancia durante la terapia crónica con nitratos. En adición, los autores discuten cual formulación de nitrato tiene menor probabilidad de desarrollar tolerancia con su uso, tales como las preparaciones de acción corta exceptuando la forma intravenosa. Finalmente, se presenta la nitroglicerina bucal como una nueva formulación que, en estudios recientes, aparenta estar mínimamente asociada con el desarrollo de tolerancia. Resume Le phénomène de tolérance développé au cours de l'utilisation des dérivés nitrés chez les patients avec ischémie cardiaque est revisé. Cet article de revue met une emphase particulière sur les effets hémodynamiques et anti-ischémiques des dérivés nitrés en usage chronique. Les éléments discutés incluent une définition du terme tolérance, les mécanismes biochimiques impliqués dans ce phénomène, les agents associés au développement de tolérance, et la prévention ou les mesures disponibles pour remédier au développement de tolérance chez les patients traités avec les dérivés nitrés. Le rôle de la détermination des niveaux sanguins et des paramètres pharmacocinétiques de la nitroglycérine dans le développement de tolérance, de même que l'avantage de périodes d'arrêt du médicament dans le rétablissement partiel ou complet du phénomène de tolérance durant un traitement chronique y sont discutés. L'évaluation des composés nitrés présentement sur le marché et ceux en investigation clinique a démontré que les composés nitrés à courte durée d'action sont les moins susceptibles d'être associés à ce phénomène. Finalement, la nitroglycérine orale est présentée comme étant une nouvelle formulation causant le moins de tolérance.
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Kolm, Hedda Elisabeth. „INFLUENCE OF RAINFALL ON PHYSICAL, CHEMICAL AND BIOLOGICAL PARAMETERS IN WASHOUTS ON THE COAST OF PARANÁ STATE, BRAZIL“. Brazilian Journal of Aquatic Science and Technology 20, Nr. 2 (26.09.2016): 1. http://dx.doi.org/10.14210/bjast.v20n2.7843.
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Reduction in precipitation, and consequently fresh water, can affect the food loop and the time necessary for an increase in nutrients and contaminants in coastal and estuarine ecosystems. The combined effect of human development and reduction in river flow can degrade water quality, negatively affecting the fishery and human health. The objective of the present research was the study of the water quality (temperature, salinity, alkalinity, carbon dioxide, dissolved oxygen, phosphate, silicate, nitrate, nitrite, ammonium, humic substances, suspended particulate material, particulate organic matter, chlorophyll-a, total coliforms and Escherichia coli), of two washouts (Barranco and Olho d’Água) located in the municipality of Pontal do Paraná (Pontal do Paraná, Brazil), comparing them in periods of lower and higher rainfall. The results showed that during the rainy period, there was an increase in nitrite, suspended particulate material, particulate organic matter, and a decrease in nitrate and chlorophyll-a in the two washouts. An increase in phosphate, ammonium and humic substances were only observed in Barranco; whereas an increase in dissolved oxygen and E. coli were only observed in Olho d’Água. These results showed that larger quantities of nutrients are exported to the adjacent continental shelf in high rainfall periods.
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Smith, Ralph E. H., W. Glen Harrison, Leslie R. Harris und Alex W. Herman. „Vertical Fine Structure of Particulate Matter and Nutrients in Sea Ice of the High Arctic“. Canadian Journal of Fisheries and Aquatic Sciences 47, Nr. 7 (01.07.1990): 1348–55. http://dx.doi.org/10.1139/f90-154.
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The vertical fine structure of particulate matter and inorganic nutrients through the bottom layers of sea ice was determined at a site in the Canadian high arctic. Intense vertical gradients of chlorophyll a, nitrate, ammonium, nitrite, phosphate, and silicate developed in the lower 6 cm of the ice as ice algae attained standing crops of 250 mg∙m−2 (up to 60 mg∙L−1) of chlorophyll a. Pigment and inorganic nutrient concentrations were closely correlated, and pools of inorganic nutrient were shown to exist in the particulate matter, suggesting that the extremely high dissolved nutrient concentrations in the bottom ice (e.g. up to 400 μmol∙L−1 nitrate) were derived at least in part from leakage of algal intracellular pools. Nitrogen and phosphorus were present in excess of algal needs, but silicon may not have been. The ratios of particulate organic carbon to chlorophyll a and to particulate organic nitrogen increased from the ice–water interface upwards, consistent with a physiological response of the ice algae to the strong corresponding gradient of light availability. Although spatially compact, the assemblage of algae in the bottom ice inhabits a highly stratified environment.
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Gushchin, Ivan, Vladimir A. Aleksenko, Philipp Orekhov, Ivan M. Goncharov, Vera V. Nazarenko, Oleg Semenov, Alina Remeeva und Valentin Gordeliy. „Nitrate- and Nitrite-Sensing Histidine Kinases: Function, Structure, and Natural Diversity“. International Journal of Molecular Sciences 22, Nr. 11 (31.05.2021): 5933. http://dx.doi.org/10.3390/ijms22115933.
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Under anaerobic conditions, bacteria may utilize nitrates and nitrites as electron acceptors. Sensitivity to nitrous compounds is achieved via several mechanisms, some of which rely on sensor histidine kinases (HKs). The best studied nitrate- and nitrite-sensing HKs (NSHKs) are NarQ and NarX from Escherichia coli. Here, we review the function of NSHKs, analyze their natural diversity, and describe the available structural information. In particular, we show that around 6000 different NSHK sequences forming several distinct clusters may now be found in genomic databases, comprising mostly the genes from Beta- and Gammaproteobacteria as well as from Bacteroidetes and Chloroflexi, including those from anaerobic ammonia oxidation (annamox) communities. We show that the architecture of NSHKs is mostly conserved, although proteins from Bacteroidetes lack the HAMP and GAF-like domains yet sometimes have PAS. We reconcile the variation of NSHK sequences with atomistic models and pinpoint the structural elements important for signal transduction from the sensor domain to the catalytic module over the transmembrane and cytoplasmic regions spanning more than 200 Å.
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Ward, Scott M., Arjan F. Bormans und Michael D. Manson. „Mutationally Altered Signal Output in the Nart (NarX-Tar) Hybrid Chemoreceptor“. Journal of Bacteriology 188, Nr. 11 (01.06.2006): 3944–51. http://dx.doi.org/10.1128/jb.00117-06.
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ABSTRACT Signal-transducing proteins that span the cytoplasmic membrane transmit information about the environment to the interior of the cell. In bacteria, these signal transducers include sensor kinases, which typically control gene expression via response regulators, and methyl-accepting chemoreceptor proteins, which control flagellar rotation via the CheA kinase and CheY response regulator. We previously reported that a chimeric protein (Nart) that joins the ligand-binding, transmembrane, and linker regions of the NarX sensor kinase to the signaling and adaptation domains of the Tar chemoreceptor elicits a repellent response to nitrate and nitrite. As with NarX, nitrate evokes a stronger response than nitrite. Here we show that mutations targeting a highly conserved sequence (the P box) in the periplasmic domain alter chemoreception by Nart and signaling by NarX similarly. In particular, the G51R substitution converts Nart from a repellent receptor into an attractant receptor for nitrate. Our results underscore the conclusion that the fundamental mechanism of transmembrane signaling is conserved between homodimeric sensor kinases and chemoreceptors. They also highlight the plasticity of the coupling between ligand binding and signal output in these systems.
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Liu, Lei, Xiuying Zhang, Yan Zhang, Wen Xu, Xuejun Liu, Xiaomin Zhang, Junlan Feng et al. „Dry Particulate Nitrate Deposition in China“. Environmental Science & Technology 51, Nr. 10 (28.04.2017): 5572–81. http://dx.doi.org/10.1021/acs.est.7b00898.
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Yu, Xiao-Ying, Taehyoung Lee, Benjamin Ayres, Sonia M. Kreidenweis, Jeffrey L. Collett und William Malm. „Particulate Nitrate Measurement Using Nylon Filters“. Journal of the Air & Waste Management Association 55, Nr. 8 (August 2005): 1100–1110. http://dx.doi.org/10.1080/10473289.2005.10464721.
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Millstein, Dev E., Robert A. Harley und Susanne V. Hering. „Weekly cycles in fine particulate nitrate“. Atmospheric Environment 42, Nr. 4 (Februar 2008): 632–41. http://dx.doi.org/10.1016/j.atmosenv.2007.10.010.
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Mykaylo, I. I., M. V. Kryvtsova und V. I. Nikolaichuk. „Моніторинг вмісту нітратів в овочевих культурах Ужгородського району“. Visnyk of Dnipropetrovsk University. Biology, medicine 4, Nr. 2 (14.09.2013): 47–51. http://dx.doi.org/10.15421/021308.
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The aim of our research was to conduct a monitoring study of nitrate content in plant products of Uzhgorod district and to accomplish comparative analysis of the survey results in different periods of crop ripening. Selection of vegetable samples was carried out in Uzhgorod district in the early spring and summer periods. Determination of the nitrate content was performed using an ion-selective method at the Chemical and Toxicological Department of the Regional State Veterinary Medicine Laboratory in the Transcarpathian region of Ukraine. Vegetables were tested for nitrate content using the ion-selective method with the laboratory ion meter AI-123. Core investigation samples were crushed and homogenized. A 10.0 g weight of the investigated product, which was prepared according to MIR № 5048-89, was placed in a flat-bottomed or a conical flask, which was then filled with 50 cm3 potassium alumens solution and shaken in a shaking-machine for 5 minutes and then transferred into a measuring glass. The nitrate weight fraction in milligrams per kilogram was obtained together with the weight concentration value of nitrate ions in solution. For our study we selected vegetables grown in both public and private gardens of Uzhgorod district, namely: common onions, radishes, garden parsley, cucumbers, tomatoes, bell peppers, white cabbages, carrots and table beets. 25 samples were selected for each type of vegetable. Nitrate content was determined in the early spring growing period (from February 9 to May 27, 2011) and in the summer growing period (from June 3 to September 28, 2011), because in these particular periods we recorded the most frequent cases of food poisoning from nitrates among the population of the region. A clear trend has been traced towards increasing the nitrate content in food plant production, at levels which exceed the maximum permissible concentration (MPC). The results of our research demonstrate that the nitrate content exceeded the maximum permissible concentration in 9 kinds of vegetables out of the 11 selected for the investigation, which composes 82% of total production. In particular, among the selected vegetables an excess of nitrate content, above MPC was recorded in 100% of cucumbers, 92% of carrots, 40% samples of green onions, 40% of radishes, 40% of tomatoes, 28% bell peppers, and 16% of early white cabbages. However, the most significant nitrate excess, which was more than double the MPC, was observed in 56% of cucumbers, 20% of tomatoes, 8% of radishes in the early spring period and 4% of tomatoes in the summer period. Consequently, it has been established that the consumption of early vegetable production contributes to the ingestion by humans of significant amounts of nitrates. The application of an agrochemical system based upon sound measurement of the nitrate content would allow us to solve the task of increasing soil fertility and to form a deficit-free and positive balance of biogenic elements and humus in the "soil – plant – fertilizer" system and develop a system of crop production which is balanced in its chemical composition and nutritional value. To sum up, detailed determination of the factors that lead to the accumulation of nitrates in vegetable crops and the development of methods to reduce nitrate concentrations in crop production require further investigation.
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Charron, A., C. Degrendele, B. Laongsri und R. M. Harrison. „Receptor modelling of secondary particulate matter at UK sites“. Atmospheric Chemistry and Physics Discussions 12, Nr. 10 (17.10.2012): 27255–95. http://dx.doi.org/10.5194/acpd-12-27255-2012.
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Abstract. Complementary approaches have been taken to better understand the sources and their spatial distribution for secondary inorganic (nitrate and sulphate) and secondary organic aerosol sampled at a rural site (Harwell) in the southern United Kingdom. A concentration field map method was applied to 1581 daily samples of chloride, nitrate and sulphate from 2006 to 2010, and 982 samples for organic carbon and elemental carbon from 2007 to 2010. This revealed a rather similar pattern of sources for nitrate, sulphate and secondary organic carbon within western/central Europe, which in the case of nitrate and sulphate, correlated significantly with EMEP emissions maps of NOx and SO2. A slightly more southerly source emphasis for secondary organic carbon may reflect the contribution of biogenic sources. Trajectory clusters confirm this pattern of behaviour with a major contribution from mainland European sources. Similar behaviours of, on the one hand, sulphate and organic carbon and, on the other hand, EC and nitrate showed that the former are more subject to regional influence than the latter in agreement with the slower atmospheric formation of sulphate and secondary organic aerosol than for nitrate, and the local/mesoscale influences upon primary EC. In a separate study, measurements of sulphate, nitrate, elemental and organic carbon were made in 100 simultaneously collected samples at Harwell and at a suburban site in Birmingham (UK). This showed a significant correlation in concentrations between the two sites for all of the secondary constituents, further indicating secondary organic aerosol to be a regional pollutant behaving similarly to sulphate and nitrate.
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Hao, L. Q., A. Kortelainen, S. Romakkaniemi, H. Portin, A. Jaatinen, A. Leskinen, M. Komppula et al. „Atmospheric submicron aerosol composition and particulate organic nitrate formation in a boreal forestland–urban mixed region“. Atmospheric Chemistry and Physics Discussions 14, Nr. 11 (27.06.2014): 17263–98. http://dx.doi.org/10.5194/acpd-14-17263-2014.
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Abstract. The Puijo aerosol-cloud observation station is a~unique measurement site for its location in the mixed region between the boreal forestland and the municipality of Kuopio, Finland. A measurement campaign was carried out at the station during fall 2010. An Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-Tof-AMS) was deployed to characterize the atmospheric submicron aerosols. Positive Matrix Factorization (PMF) was applied to the unified high resolution mass spectra organic species with NO+ and NO2+ ions to discover the intrinsic relationships between the organic and inorganic species and their daily cycles. On average, the submicron aerosols in this study were dominated by organic and sulfate species, making 76.9% of total observed aerosol mass, with smaller contributions from ammonium (9.3%), nitrate (4.9%), chloride (0.8%) and BC (8.1%). The sources of these species included the primary emissions originating from the city area, secondary formation from both natural and anthropogenic emissions and regional transport. The PMF analysis succeeded in separating the mixed organic and inorganic spectra into three distinct organic and one inorganic factors. For organic factors, the semi-volatile oxygenated organic aerosol (SVOOA) and low-volatile oxygenated OA (LVOOA) accounted for 89.6% of total organic masses, while the hydrocarbon-like organic aerosol (HOA) consisted of 10.4% of total organics with its main source from urban emissions. The inorganic factor is identified as NH4NO3, comprising 7.5% of the fitted aerosol mass by PMF. Based on the PMF results, the nitrate species were separated into organic and inorganic components, with the organic nitrates contributing 1 / 3 of the total nitrate mass. The results highlight both anthropogenic and biogenic emissions as important atmospheric aerosol sources in a~forest-urban mixed region.
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Hao, L. Q., A. Kortelainen, S. Romakkaniemi, H. Portin, A. Jaatinen, A. Leskinen, M. Komppula et al. „Atmospheric submicron aerosol composition and particulate organic nitrate formation in a boreal forestland–urban mixed region“. Atmospheric Chemistry and Physics 14, Nr. 24 (18.12.2014): 13483–95. http://dx.doi.org/10.5194/acp-14-13483-2014.
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Abstract. The Puijo aerosol–cloud observation station is a unique measurement site for its location in the mixed region between the boreal forestland and the municipality of Kuopio, Finland. A measurement campaign was carried out at the station during fall 2010. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-Tof-AMS) was deployed to characterize the atmospheric submicron aerosols. Positive matrix factorization (PMF) was applied to the unified high-resolution mass spectra organic species with NO+ and NO2+ ions to discover the intrinsic relationships between the organic and inorganic species and their daily cycles. On average, the submicron aerosols in this study were dominated by organic and sulfate species, composing 48.2 and 28.7% of total observed aerosol mass, respectively, with smaller contributions from ammonium (9.3%), nitrate (4.9%), chloride (0.8%) and BC (8.1%). The sources of these species included the primary emissions originating from the city area, secondary formation from both natural and anthropogenic emissions and regional transport. The PMF analysis succeeded in separating the mixed organic and inorganic spectra into three distinct organic and one inorganic factors. For organic factors, the semi-volatile oxygenated organic aerosol (SVOOA) and low-volatility oxygenated OA (LVOOA) accounted for 54.8 and 36.3% of total organic masses, respectively, while the hydrocarbon-like organic aerosol (HOA) accounted for 8.9% of total organics, with its main source from urban emissions. The inorganic factor is identified as NH4NO3, comprising 6.9% of the fitted aerosol mass by PMF. Based on the PMF results, the nitrate species were separated into organic and inorganic components, with the organic nitrates contributing one-third of the total nitrate mass. The results highlight both anthropogenic and biogenic emissions as important atmospheric aerosol sources in a forest–urban mixed region.
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Kolisnyk, I. L. „INTENSITY OF NITRIC OXIDE SYNTHESIS IN THE BLOOD OF RATS UNDER THE INFLUENCE OF SODIUM FLUORIDE“. Medical and Ecological Problems 24, Nr. 5-6 (30.12.2020): 25–28. http://dx.doi.org/10.31718/mep.2020.24.5-6.07.
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The influence of fluoride ion as a chemical agent affects the metabolism, the change of which is manifested in functional and structural changes. The final stable metabolites of NO include nitrite and nitrate anions (NO2, NO3), the concentration of which serves as an indirect method for estimating the intensity of NO synthesis. The concentration of NO is a major factor in its numerical biological effects (regulatory, protective). At low NO concentrations, direct effects aimed at maintaining homeostasis, such as the vascular, respiratory, and nervous systems, predominate; at high concentrations of NO, indirect effects prevail, due primarily to the formation of peroxynitrite. It is known that when the rate of free radical reactions in the body increases, NO can react with a superoxide anion radical to form peroxynitrite, a highly reactive compound with destructive properties against proteins and lipids. Oral administration of FN to rats in doses of 1/10 and 1/100 DL50 leads to an increase in the content of nitrite and nitrate anions in the blood plasma during the first 30 days, which indirectly indicates excess production of nitric oxide, which in the initial stages of intoxication may play a compensatory role, but subsequently cause pathological reactions associated with the activation of oxidative stress. The decrease in nitrite and nitrate anions at the end of long-term action of FN indirectly indicates a decrease in nitric oxide generation, which may be associated, in particular, with an increase in peroxynitrite concentration due to the use of nitric oxide in reaction with superoxide anion radical and antioxidant deficiency.
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Yoshie, S., N. Noda, T. Miyano, S. Tsuneda, A. Hirata und Y. Inamori. „Characterization of microbial community in nitrogen removal process of metallurgic wastewater by PCR-DGGE“. Water Science and Technology 46, Nr. 11-12 (01.12.2002): 93–98. http://dx.doi.org/10.2166/wst.2002.0722.
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The metallurgic wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of nitrogen compounds such as ammonia and nitric acid and of salts such as sodium chloride and sodium sulfate. Biological nitrogen removal from this wastewater was attempted by a circulating bioreactor system equipped with an anoxic packed bed and an aerobic fluidized bed. The anoxic packed bed of this system was found to effectively remove nitrite and nitrate from the wastewater by denitrification at a removal ratio of 97%. As a result of denitrification activity tests at various NaCl concentrations, the sludge obtained from the anoxic packed bed exhibited accumulation of nitrite at 5.0 and 8.4% NaCl concentrations, suggesting that the reduction of nitrite is the key step in the denitrification pathway under hypersaline conditions. The microbial community analysis by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments revealed that the community diversity varied in accordance with water temperature, nitrate-loading rate and ionic strength. When particular major DGGE bands were excised, reamplified and directly sequenced, the dominant species in the anoxic packed bed were affiliated with the beta and gamma subclasses of the class Proteobacteria such as Alcaligenes defragrans and Pseudomonas spp., respectively.
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Below, Michael, und Bernd Georgi. „Plant growth — Influenced by particulate nitrate application“. Journal of Aerosol Science 20, Nr. 8 (Januar 1989): 1433–36. http://dx.doi.org/10.1016/0021-8502(89)90855-0.
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Wrona, Paulina, Krystyna Pogoń und Magdalena Dróżdż. „Assessment of Particular Qualities of Carrot Availalbe in Selected Retailers in Krakow“. Agricultural Engineering 21, Nr. 4 (01.12.2017): 93–102. http://dx.doi.org/10.1515/agriceng-2017-0040.
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AbstractThe objective of the paper was assessment of the selected qualities of carrot from retailer's shops, organic and traditional food shops in Krakow. The following quality parameters of the fruit pulp were investigated: content of extract, sugars, polyphenols, nitrite, flavonoids, beta-carotene, colour, and antioxidant activity. The investigation shows that the content of nitrogen (V) in the samples of carrot from traditional cultivations was higher than in case of carrot from organic crops, and in case of a sample from traditional cultivation it exceeds the admissible norms. However, the research which was carried out provides no justification for the statement that the content of nitrate (III) depends on the production system of carrot. The research on the content of polyphenols, flavonoids and antioxidant activity of juice proved the increased antioxidant ability of carrot that was traditionally cultivated with reference to carrot cultivated organically. However, the differences were not statistically confirmed. Beta-carotene content in all samples was comparable regardless the cultivation system. Content of extracts, total carbohydrates and sucrose was significantly higher for carrot from traditional crops than for eco-carrot.
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Peake, Eric, M. A. MacLean und H. S. Sandhu. „Total Inorganic Nitrate (Particulate Nitrate and Nitric Acid) Observations in Calgary, Alberta“. Journal of the Air Pollution Control Association 35, Nr. 3 (März 1985): 250–53. http://dx.doi.org/10.1080/00022470.1985.10465909.
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Santegoeds, Cecilia M., Gerard Muyzer und Dirk de Beer. „Biofilm dynamics studied with microsensors and molecular techniques“. Water Science and Technology 37, Nr. 4-5 (01.02.1998): 125–29. http://dx.doi.org/10.2166/wst.1998.0600.
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Here we present preliminary data on the development of a biofilm from a wastewater treatment plant studied with microsensors and molecular techniques. The development during biofilm growth of oxygen, sulfide and pH profiles was measured with microsensors. Anoxic zones developed within one week and further increased during the following weeks. However, sulfide production was delayed and was first detected in a six-week-old biofilm. With denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments the sequence of the bacterial community was followed showing an increasing complexity of the biofilm community during development. In a mature biofilm the influence of nitrate on sulfide production was studied by measuring oxygen, sulfide, pH, nitrite and nitrate profiles with microsensors. Sulfide production was detected deeper in the biofilm and in lower concentrations, when nitrate was added to the medium. The DGGE pattern of the mature biofilm showed both differences and similarities with the DGGE pattern of the 12-week-old biofilm. In particular the RNA pattern changed when nitrate was added to the medium, indicating a change in activity of certain strains.
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Nóbrega, Mariana Magna Santos da, André Luis Calado Araújo und Jerônimo Pereira dos Santos. „AVALIAÇÃO DAS CONCENTRAÇÕES DE NITRATO NAS ÁGUAS MINERAIS PRODUZIDAS NA REGIÃO DA GRANDE NATAL“. HOLOS 3 (02.03.2009): 4. http://dx.doi.org/10.15628/holos.2008.221.
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RESUMO A Região Metropolitana de Natal, no estado do Rio Grande do Norte, é detentora de grandes reservas de águas subterrâneas pertencentes ao aqüífero Dunas/Barreiras. Essas águas são utilizadas pela população para seu abastecimento e consumo industrial. Além disso, essas reservas possuem características de águas minerais, localizando-se principalmente nos municípios de Parnamirim e Macaíba na região sul e no município de Extremoz, na parte norte. Em contrapartida, o crescimento urbano acelerado da Grande Natal, associado com a falta de esgotamento sanitário e drenagem adequada, resultaram no aporte de carga contaminante originária, principalmente, de fossas e sumidouros domésticos em direção às águas do aqüífero. Este artigo tem como finalidade avaliar as concentrações de nitrato nas fontes de águas minerais, tomando-se como base a proximidade de poços contaminados por esses teores. Para isso, basicamente, se comparou dados que representavam concentrações de NO3- em águas minerais, com teores de nitrato pertencentes à poços de abastecimento público ou particulares da região circunvizinha a essas águas, ambos obtidos através dos projetos de Iniciação Científica desenvolvidos no CEFET-RN. As atividades que fizeram parte da realização do trabalho foram constituídas pela localização da área de estudo, seleção dos poços a serem analisados, análises laboratoriais do íon nitrato, tabulação e tratamento dos dados obtidos, além das considerações a respeito da qualidade das águas subterrâneas. Através dos resultados obtidos foi possível demonstrar a que níveis de concentração de nitrato estão os poços produtores de água mineral, destacando-se dois, dos dez selecionados, que apresentaram valores acima de 10 mg/L. PALAVRAS-CHAVE: água mineral, águas subterrâneas, aqüífero Dunas/Barreiras, contaminação, nitrato e Região Metropolitana de Natal. EVALUATION OF NITRATE CONCENTRATIONS ON MINERAL WATERS PRODUCED IN THE METROPOLITAN REGION OF NATAL ABSTRACT The Metropolitan Region of Natal, located in the state of the Rio Grande do Norte, is detainer of great reserves of groundwater from Dunas/Barreiras aquifer. These waters are used by the population for your supplying and industrial consumption; moreover these reserves possess mineral water characteristics, situated mainly in the cities of Parnamirim and Macaíba, in the south region, and in the city of Extremoz, in the part north. However, the fast urban growth of Natal, associate with the lack of sanitation and drainage, has caused the increase of contamination, mainly by the infiltration of septic tanks effluents in soil. The presented work has as main purpose the evaluation of nitrate concentrations in the mineral water sources, taking in consideration the proximity of wells already contaminated by nitrate. For this, data of nitrate concentrations in mineral waters were compared with those from wells of the public or private supplying from the surrounding region. The work comprised the localization of the study area, selection wells to collect samples, laboratory analyses of the ion nitrate, treatment of data, and the global evaluation of underground waters quality. Through the results was possible to demonstrate the levels of nitrate concentration on mineral water wells, including two with concentration higher than 10 mg/L. KEY WORDS: mineral water, underground waters, aquifer Dunas/Barreiras, contamination, nitrate and Metropolitan Region of Natal.
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Savard, Martine M., Amanda S. Cole, Robert Vet und Anna Smirnoff. „The Δ<sup>17</sup>O and <i>δ</i><sup>18</sup>O values of atmospheric nitrates simultaneously collected downwind of anthropogenic sources – implications for polluted air masses“. Atmospheric Chemistry and Physics 18, Nr. 14 (20.07.2018): 10373–89. http://dx.doi.org/10.5194/acp-18-10373-2018.
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Abstract. There are clear motivations for better understanding the atmospheric processes that transform nitrogen (N) oxides (NOx) emitted from anthropogenic sources into nitrates (NO3-), two of them being that NO3- contributes to acidification and eutrophication of terrestrial and aquatic ecosystems, and particulate nitrate may play a role in climate dynamics. For these reasons, oxygen isotope delta values (δ18O, Δ17O) are frequently applied to infer the chemical pathways leading to the observed mass-independent isotopic anomalies from interaction with 17O-rich ozone (O3). Recent laboratory experiments suggest that the isotopic equilibrium between NO2 (the main precursor of NO3-) and O3 may take long enough under certain field conditions that nitrates may be formed near emission sources with lower isotopic values than those formed further downwind. Indeed, previously published field measurements of oxygen isotopes in NO3- in precipitation (wNO3-) and in particulate (pNO3-) samples suggest that abnormally low isotopic values might characterize polluted air masses. However, none of the air studies have deployed systems allowing collection of samples specific to anthropogenic sources in order to avoid shifts in isotopic signature due to changing wind directions, or separately characterized gaseous HNO3 with Δ17O values. Here we have used a wind-sector-based, multi-stage filter sampling system and precipitation collector to simultaneously sample HNO3 and pNO3-, and co-collect wNO3-. The nitrates are from various distances (<1 to >125 km) downwind of different anthropogenic emitters, and consequently from varying time lapses after emission. The separate collection of nitrates shows that the HNO3 δ18O ranges are distinct from those of w- and pNO3-. Interestingly, the Δ17O differences between pNO3- and HNO3 shift from positive during cold sampling periods to negative during warm periods. The low pNO3-Δ17O values observed during warm periods may partly derive from the involvement of 17O-depleted peroxy radicals (RO2) oxidizing NO during that season. Another possibility is that nitrates derive from NOx that has not yet reached isotopic equilibrium with O3. However, these mechanisms, individually or together, cannot explain the observed pNO3 minus HNO3 isotopic changes. We propose differences in dry depositional rates, faster for HNO3, as a mechanism for the observed shifts. Larger proportions of pNO3- formed via the N2O5 pathway would explain the opposite fall–winter patterns. Our results show that the separate HNO3, wNO3- and pNO3- isotopic signals can be used to further our understanding of NOx oxidation and deposition. Future research should investigate all tropospheric nitrate species as well as NOx to refine our understanding of nitrate distribution worldwide and to develop effective emission reduction strategies.
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Davies, H., und C. Neal. „GIS-based methodologies for assessing nitrate, nitrite and ammonium distributions across a major UK basin, the Humber“. Hydrology and Earth System Sciences 8, Nr. 4 (31.08.2004): 823–33. http://dx.doi.org/10.5194/hess-8-823-2004.
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Abstract. The distributions of nitrate, nitrite and ammonium at various monitoring sites across the Humber basin (area 24 000 km2) were examined within a Geographical Information System (GIS) framework. This basin contains diverse characteristics, from areas of high population and industry to rural and arable regions. The Humber River is a major provider of and nutrient fluxes to the North Sea from the UK. Within the GIS analysis, the distributions of mean and mean flow weighted concentrations, flux and flux per unit area, were investigated. Empirical relationships between land characteristics and water quality for the whole catchment draining to each water quality monitoring site were established. Thirty-eight catchments were chosen for this analysis, with areas ranging from 46 km2 to 8225 km2. These catchments are distributed across the Humber, encompassing the different conditions across the basin, thus allowing relationships between water quality and catchment characteristics to be used to estimate the nitrogen concentrations and flux throughout the basin river network. The main water quality data source was the Land Ocean Interaction Study (LOIS) dataset. The Environment Agency of England and Wales water quality datasets were used to infill areas of sparse LOIS monitoring network density within the Humber. The work shows the feasibility of estimating nitrate and, to a lesser extent, nitrite and ammonium concentrations and fluxes across the river network based on land characteristics, using a GIS methodology. The estimations work particularly well for the main river channels. However, there are local anomalies which are more difficult to predict. Maps showing concentration variations at 500 m intervals along the Humber basin river networks are presented; these are of particular value for environmental managers and socio-economists. Keywords: GIS, nitrate, nitrite, ammonium, catchment characteristics
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Bian, Huisheng, Mian Chin, Didier A. Hauglustaine, Michael Schulz, Gunnar Myhre, Susanne E. Bauer, Marianne T. Lund et al. „Investigation of global particulate nitrate from the AeroCom phase III experiment“. Atmospheric Chemistry and Physics 17, Nr. 21 (03.11.2017): 12911–40. http://dx.doi.org/10.5194/acp-17-12911-2017.
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Abstract. An assessment of global particulate nitrate and ammonium aerosol based on simulations from nine models participating in the Aerosol Comparisons between Observations and Models (AeroCom) phase III study is presented. A budget analysis was conducted to understand the typical magnitude, distribution, and diversity of the aerosols and their precursors among the models. To gain confidence regarding model performance, the model results were evaluated with various observations globally, including ground station measurements over North America, Europe, and east Asia for tracer concentrations and dry and wet depositions, as well as with aircraft measurements in the Northern Hemisphere mid-to-high latitudes for tracer vertical distributions. Given the unique chemical and physical features of the nitrate occurrence, we further investigated the similarity and differentiation among the models by examining (1) the pH-dependent NH3 wet deposition; (2) the nitrate formation via heterogeneous chemistry on the surface of dust and sea salt particles or thermodynamic equilibrium calculation including dust and sea salt ions; and (3) the nitrate coarse-mode fraction (i.e., coarse/total). It is found that HNO3, which is simulated explicitly based on full O3-HOx-NOx-aerosol chemistry by all models, differs by up to a factor of 9 among the models in its global tropospheric burden. This partially contributes to a large difference in NO3−, whose atmospheric burden differs by up to a factor of 13. The atmospheric burdens of NH3 and NH4+ differ by 17 and 4, respectively. Analyses at the process level show that the large diversity in atmospheric burdens of NO3−, NH3, and NH4+ is also related to deposition processes. Wet deposition seems to be the dominant process in determining the diversity in NH3 and NH4+ lifetimes. It is critical to correctly account for contributions of heterogeneous chemical production of nitrate on dust and sea salt, because this process overwhelmingly controls atmospheric nitrate production (typically > 80 %) and determines the coarse- and fine-mode distribution of nitrate aerosol.
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Xu, Z., J. Zhang, G. Yang und M. Hu. „Acyl peroxy nitrate measurements during the photochemical smog season in Beijing, China“. Atmospheric Chemistry and Physics Discussions 11, Nr. 3 (30.03.2011): 10265–303. http://dx.doi.org/10.5194/acpd-11-10265-2011.
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Abstract. In situ measurements of acyl peroxy nitrates (PANs), including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN), were conducted using a gas chromatography-electron capture detector (GC-ECD) system during the photochemical smog season in Beijing, China. The maximum mixing ratios were 17.81, 2.48, and 0.27 ppbv for PAN, PPN, and MPAN, respectively. During the measurement period, PAN levels twice exceeded the maximum recommended mixing ratio established by the World Health Organization (WHO). Average ratios of PAN/PPN, PAN/MPAN, and PPN/MPAN were 7.41, 47.65, and 6.91, respectively. The average ratio of PAN/O3 (0.15) in Beijing was significantly higher than those in other areas studied. The frequencies of PANs showed both Gaussian and Weibull modes of distribution. Wind direction was closely related to PAN variation. Anthropogenic sources played an important role in PAN formation, as estimated from PPN and MPAN levels. Relative humidity (RH) and total particle surface area were related with the heterogeneous reactions of PANs with surface concentrations of particulate matter ≤10 μm in diameter.
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Dong, Liang F., Cindy J. Smith, Sokratis Papaspyrou, Andrew Stott, A. Mark Osborn und David B. Nedwell. „Changes in Benthic Denitrification, Nitrate Ammonification, and Anammox Process Rates and Nitrate and Nitrite Reductase Gene Abundances along an Estuarine Nutrient Gradient (the Colne Estuary, United Kingdom)“. Applied and Environmental Microbiology 75, Nr. 10 (20.03.2009): 3171–79. http://dx.doi.org/10.1128/aem.02511-08.
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ABSTRACT Estuarine sediments are the location for significant bacterial removal of anthropogenically derived inorganic nitrogen, in particular nitrate, from the aquatic environment. In this study, rates of benthic denitrification (DN), dissimilatory nitrate reduction to ammonium (DNRA), and anammox (AN) at three sites along a nitrate concentration gradient in the Colne estuary, United Kingdom, were determined, and the numbers of functional genes (narG, napA, nirS, and nrfA) and corresponding transcripts encoding enzymes mediating nitrate reduction were determined by reverse transcription-quantitative PCR. In situ rates of DN and DNRA decreased toward the estuary mouth, with the findings from slurry experiments suggesting that the potential for DNRA increased while the DN potential decreased as nitrate concentrations declined. AN was detected only at the estuary head, accounting for ∼30% of N2 formation, with 16S rRNA genes from anammox-related bacteria also detected only at this site. Numbers of narG genes declined along the estuary, while napA gene numbers were stable, suggesting that NAP-mediated nitrate reduction remained important at low nitrate concentrations. nirS gene numbers (as indicators of DN) also decreased along the estuary, whereas nrfA (an indicator for DNRA) was detected only at the two uppermost sites. Similarly, nitrate and nitrite reductase gene transcripts were detected only at the top two sites. A regression analysis of log(n + 1) process rate data and log(n + 1) mean gene abundances showed significant relationships between DN and nirS and between DNRA and nrfA. Although these log-log relationships indicate an underlying relationship between the genetic potential for nitrate reduction and the corresponding process activity, fine-scale environmentally induced changes in rates of nitrate reduction are likely to be controlled at cellular and protein levels.
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Pitchford, Marc L., Richard L. Poirot, Bret A. Schichtel und William C. Malm. „Characterization of the Winter Midwestern Particulate Nitrate Bulge“. Journal of the Air & Waste Management Association 59, Nr. 9 (September 2009): 1061–69. http://dx.doi.org/10.3155/1047-3289.59.9.1061.
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Zhai, Shixian, Daniel J. Jacob, Xuan Wang, Zirui Liu, Tianxue Wen, Viral Shah, Ke Li et al. „Control of particulate nitrate air pollution in China“. Nature Geoscience 14, Nr. 6 (26.04.2021): 389–95. http://dx.doi.org/10.1038/s41561-021-00726-z.
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Charron, A., C. Degrendele, B. Laongsri und R. M. Harrison. „Receptor modelling of secondary and carbonaceous particulate matter at a southern UK site“. Atmospheric Chemistry and Physics 13, Nr. 4 (19.02.2013): 1879–94. http://dx.doi.org/10.5194/acp-13-1879-2013.
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Abstract. Complementary approaches have been taken to better understand the sources and their spatial distribution for secondary inorganic (nitrate and sulphate) and secondary organic aerosol sampled at a rural site (Harwell) in the southern United Kingdom. A concentration field map method was applied to 1581 daily samples of chloride, nitrate and sulphate from 2006 to 2010, and 982 samples for organic carbon and elemental carbon from 2007 to 2010. This revealed a rather similar pattern of sources for nitrate, sulphate and secondary organic carbon within western/central Europe, which in the case of nitrate, sulphate, organic carbon and secondary organic carbon, correlated significantly with EMEP emissions maps of NOx, SO2, and VOC respectively. A slightly more southerly source emphasis for secondary organic carbon may reflect the contribution of biogenic sources. Trajectory clusters confirm this pattern of behaviour with a major contribution from mainland European sources. Similar behaviours of, on the one hand, sulphate and organic carbon and, on the other hand, EC and nitrate showed that the former are more subject to regional influence than the latter in agreement with the slower atmospheric formation of sulphate and secondary organic aerosol than for nitrate, and the local/mesoscale influences upon primary EC. However, careful analysis of back trajectories and Concentration Field Maps indicates a strong contribution of mainland European sites to EC concentrations at Harwell. In a separate study, measurements of sulphate, nitrate, elemental and organic carbon were made in 100 simultaneously collected samples at Harwell and at a suburban site in Birmingham (UK). This showed a significant correlation in concentrations between the two sites for all of the secondary constituents, further indicating secondary organic aerosol to be a regional pollutant behaving similarly to sulphate and nitrate.
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Regnier, G., N. Smith, R. Gonzalez und B. Dixon. „Cytodex dextran beads as a substrate for observing the effects of selenium on bacterial morphology“. Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 330–31. http://dx.doi.org/10.1017/s0424820100085952.
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Selenium, through the process of bioconcentration, can accumulate to reach toxic levels in the tissues of birds, fish and other wildlife. To date, little research has focused on the effect os selenium on bacteria and in particular, on the nitrifying bacteria which provide a considerable beneficial impact on the environment. Preliminary studies in our laboratory, have indicated that selenium can disrupt the nitrogen cycle by inhibiting the conversion of nitrite to nitrate by Nitrobacter spp. The effect of selenium on Nitrobacter is as of yet unknown. This break in the normal cycle allows nitrite, which is highly toxic in low levels to aquatic animals, to accumulate in the environment. This study was undertaken to investigate the effects of selenium assimilation, by nitrifying bacteria, on the nitrogen cycle and any resultant morphological changes in cell structure.
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Jones, A. E., E. W. Wolff, D. Ames, S. J. B. Bauguitte, K. C. Clemitshaw, Z. Fleming, G. P. Mills et al. „The multi-seasonal NO<sub>y</sub> budget in coastal Antarctica and its link with surface snow and ice core nitrate: results from the CHABLIS campaign“. Atmospheric Chemistry and Physics 11, Nr. 17 (08.09.2011): 9271–85. http://dx.doi.org/10.5194/acp-11-9271-2011.
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Abstract. Measurements of a suite of individual NOy components were carried out at Halley station in coastal Antarctica as part of the CHABLIS campaign (Chemistry of the Antarctic Boundary Layer and the Interface with Snow). Conincident measurements cover over half a year, from austral winter 2004 through to austral summer 2005. Results show clear dominance of organic NOy compounds (PAN and MeONO2) during the winter months, with low concentrations of inorganic NOy. During summer, concentrations of inorganic NOy compounds are considerably greater, while those of organic compounds, although lower than in winter, are nonetheless significant. The relative concentrations of the alkyl nitrates, as well as their seasonality, are consistent with an oceanic source. Multi-seasonal measurements of surface snow nitrate correlate strongly with inorganic NOy species (especially HNO3) rather than organic. One case study in August suggested that, on that occasion, particulate nitrate was the dominant source of nitrate to the snowpack, but this was not the consistent picture throughout the measurement period. An analysis of NOx production rates showed that emissions of NOx from the snowpack overwhelmingly dominate over gas-phase sources. This result suggests that, for certain periods in the past, the flux of NOx into the Antarctic boundary layer can be calculated from ice core nitrate data.
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Fesefeldt, Andreas, Niels C. Holm und Christian G. Gliesche. „Genetic diversity and population dynamics of hyphomicrobium spp. in a sewage treatment plant and its receiving lake“. Water Science and Technology 37, Nr. 4-5 (01.02.1998): 113–16. http://dx.doi.org/10.2166/wst.1998.0597.
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Hyphomicrobium spp. were counted and isolated for 12 months in a sewage treatment plant with a combination of simultaneous and intermittent nitrification and denitrification using Most-Probable-Number methods. Genomic DNA of these hyphomicrobia was investigated by Southern or dot blot hybridizations with gene probes specific for genes of dissimilatory nitrate reduction (nitrate reductase, narG; cytochrome c,d-containing nitrite reductase, nirS; Cu-containing nitrite reductase, nirK; nitrous oxide reductase, nosZ), nitrification (ammonia monooxygenase, amoA) and N2-fixation (nitrogenase, nifH). In particular, the Hyphomicrobium DNA/DNA-hybridization group HG 27 constituted one of the dominant denitrifying Hyphomicrobium populations in the activated sludge of this sewage treatment plant. A species-specific gene probe (Hvu-1) for HG 27 was generated from a transposon Tn5-132 insertion mutant defective in methanol oxidation using the inverse polymerase chain reaction. With this probe the abundance of this group in activated sludge of the sewage treatment plant and its receiving lake was determined as a subfraction of the total cultivable hyphomicrobia. Fragments of the mxaF gene encoding for the α-subunit of the methanol dehydrogenase of Hyphomicrobium spp. were amplified by PCR and analysed by denaturing gradient gel electrophoresis (DGGE). The DGGE analysis pattern showed a substantial separation of these fragments according to their nucleic acid sequences.
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Wen, Liang, Likun Xue, Xinfeng Wang, Caihong Xu, Tianshu Chen, Lingxiao Yang, Tao Wang, Qingzhu Zhang und Wenxing Wang. „Summertime fine particulate nitrate pollution in the North China Plain: increasing trends, formation mechanisms and implications for control policy“. Atmospheric Chemistry and Physics 18, Nr. 15 (13.08.2018): 11261–75. http://dx.doi.org/10.5194/acp-18-11261-2018.
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Abstract. Nitrate aerosol makes up a significant fraction of fine particles and plays a key role in regional air quality and climate. The North China Plain (NCP) is one of the most industrialized and polluted regions in China. To obtain a holistic understanding of the nitrate pollution and its formation mechanisms over the NCP region, intensive field observations were conducted at three sites during summertime in 2014–2015. The measurement sites include an urban site in downtown Jinan – the capital city of Shandong Province –, a rural site downwind of Jinan city, and a remote mountain site at Mt. Tai (1534 m a.s.l.). Elevated nitrate concentrations were observed at all three sites despite distinct temporal and spatial variations. Using historical observations, the nitrate ∕ PM2.5 and nitrate ∕ sulfate ratios have statistically significantly increased in Jinan (2005–2015) and at Mt. Tai (from 2007 to 2014), indicating the worsening situation of regional nitrate pollution. A multiphase chemical box model (RACM–CAPRAM) was deployed and constrained by observations to elucidate the nitrate formation mechanisms. The principal formation route is the partitioning of gaseous HNO3 to the aerosol phase during the day, whilst the nocturnal nitrate formation is dominated by the heterogeneous hydrolysis of N2O5. The daytime nitrate production in the NCP region is mainly limited by the availability of NO2 and to a lesser extent by O3 and NH3. In comparison, the nighttime formation is controlled by both NO2 and O3. The presence of NH3 contributes to the formation of nitrate aerosol during the day, while there is slightly decreasing nitrate formation at night. Our analyses suggest that controlling NOx and O3 is an efficient way, at the moment, to mitigate nitrate pollution in the NCP region, where NH3 is usually in excess in summer. This study provides observational evidence of a rising trend of nitrate aerosol as well as scientific support for formulating effective control strategies for regional haze in China.