Urban atmosphere organic compounds

Hundreds of chemical species are present in urban atmospheres. The gaseous air pollutants most commonly monitored are CO, O3, NO2, SO2, and nonmethane volatile organic compounds (NMVOCs), Measurement of specific hydrocarbon compounds is becoming routine in the United States for two reasons (1) their potential role as air toxics and (2) the need for detailed hydrocarbon data for control of urban ozone concentrations. Hydrochloric acid (HCl), ammonia (NH3), and hydrogen fluoride (HF) are occasionally measured. Calibration standards and procedures are available for all of these analytic techniques, ensuring the quality of the analytical results... 

All these contaminants enter into the environment through human activities (urban waste, deposits of the waste cleaning plants and agricultural cultivations) [45] and various other pathways (atmospheric and fluvial transport) [46]. Environmental pollution by these groups of organic compounds has received considerable attention as a result of public awareness towards environmental problems and expectations for good quality of life [13]. 

The first three aspects are related to the release of volatile substances into the gas phase of the sewer and from there into the urban atmosphere. These volatile compounds are H2S and organic odorous compounds produced under anaerobic conditions in the wastewater or associated biofilm and sediment. 

Total volatile organic compounds (TVOCs) in Indoor and Outdoor Urban Atmospheres at a Terai Region Of Northern India... 

Artificial Pollutants Organic compounds (chlorinated pesticides, phosphorus-based pesticides, freons) industriai and municipai wastewaters runoff from urban areas and iandfiii erosion of contaminated soiis and sediments atmospheric deposition Toxic effects inciuding birth defects, reproductive faiiure, cancer, and systemic poisoning. 

Grob, K., and G. Grob. Gas-liquid chromatographic-mass spectrometric investigation of Cf-Cto organic compounds in an urban atmosphere. An application of ultra trace analysb on capillary columns. J. Chromatogr. 62 1-13, 1972. 

Particulate carbon in the atmosphere exists predominantly in three forms elemental carbon (soot) with attached hydrocarbons organic compounds and carbonates. Carbonaceous urban fine particles are composed mainly of elemental and organic carbon. These particles can be emitted into the air directly in the particulate state or condense rapidly after Introduction into the atmosphere from an emission source (primary aerosol). Alternatively, they can be formed in the atmosphere by chemical reactions involving gaseous pollutant precursors (secondary aerosol). The rates of formation of secondary carbonaceous aerosol and the details of the formation mechanisms are not well understood. However, an even more fundamental controversy exists regarding... 

Samburova, V., Zenobi, R., and Kalberer, M. (2005). Characterization of high molecular weight compounds in urban atmospheric particles. Atmos. Chem. Phys. 5, 2163-2170. Sannigrahi, P., Sullivan, A. P, Weber, R. I, and Ingall, E. D. (2006). Characterization of water-soluble organic carbon in urban atmospheric aerosols using solid-state 13C NMR spectroscopy. Environ. Sci. Technol. 40, 666-672. 

Figure 15.12. XH NMR spectra of aqueous soluble species from (A) coarse air particles with diameters of 33-4.7mm (pH 6.55) (B) fine air particles with diameters of 0.65-1.1 mm (pH 3.92). Compounds identified in the spectra include 1, acetic acid 2, monomethylamine 3, succinic acid 4, dimethylamine 5, methanesulfonic acid 6, methanol 7, monomethyl hydrogen sulfate 8, hydroxymethanesulfonic acid 9, phthalic acid 10, terephthalic acid. Reprinted from Suzuki, Y., Kawakami, M., and Akasaka, K. (2001). JH NMR application for characterizing water-soluble organic compounds in urban atmospheric particles. Environ. Sci. Technol. 35, 2656-2664, with permission from the American Chemical Society.

Suzuki, Y., Kawakami, M., and Akasaka, K. (2001). H NMR application for characterizing water-soluble organic compounds in urban atmospheric particles. Environ. Sci. Technol. 35,2656-2664. 

So what are nitrogen oxides Where does they come from And why is there a concern about the amount that enters the atmosphere Nitrogen dioxide (NO2) is a brownish, highly reactive gas that is present in all urban atmospheres. N02 can irritate the lungs, cause bronchitis and pneumonia, and lower resistance to respiratory infections. Nitrogen oxides are an important precursor both to ozone (Oj) and acid rain, and may affect both terrestrial and aquatic ecosystems. The major mechanism for the formation of NO2 in the atmosphere is the oxidation of the primary air pollutant, nitric oxide (NO). NOx plays a major role, together with VOCs (Volatile Organic Compounds), in the atmospheric... 

Although only 10% of atmospheric ozone resides in the troposphere (0-15 km altitude) it has a profound impact on tropospheric chemistry. Ozone concentrations in the troposphere vary from typically 20-40 ppb for a remote pristine site to 100-200 ppb in a highly polluted urban environment. Ozone is a reactive molecule, which readily adds to carbon-carbon double bonds [8]. Reaction with ozone provides an important removal mechanism for many unsaturated reactive organic compounds. 

The basic chemistry responsible for urban photochemistry is essentially the same as that takes place in the unpolluted atmosphere (see Section 2.5). It is the range and concentrations of NMHC fuels and the concentrations of NO coupled to the addition of some photochemical accelerants that can lead to the excesses of urban chemistry. For example, in the Los Angeles basin it is estimated that 3333 ton day of organic compounds are emitted as well as 890 ton day of NO - In addition, to the reactions forming OH in the background troposphere, i.e. via the reaction of 0( D) with H2O, viz... 

There also are major sources of organic compounds from nature. Methane is a major emission from the natural environment and in non-urban atmospheres concentrations generally range between 1-1.5 ppm (6). The major source of atmospheric methane is the decomposition of organic material in swamps, marshes, and other bodies of water. Natural gas seepage possibly significantly contributes methane to the atmosphere in certain petroleum areas. It is estimated that natural sources of methane are about 1600 X 10 tons annually (7). 

These reactions may be important for several reasons. It may be possible to use the chemiluminescent reaction of ozone with organic sulfides to monitor the low concentrations of sulfur compounds in urban atmospheres. Also, excited species are being formed, and these reactive intermediates may be important in high altitude atmospheric reactions. Finally, identifying these emitting species should give information about the mechanisms of gas phase ozone reactions. Current progress on these reactions by the authors is reviewed here. 

Water-soluble organic compounds in urban atmospheric particles can also contain organosulfur compounds. Methanesulfonic acid and hydroxymethanesulfonic acid have been found as the major organosulfur compounds in urban aerosols, most particularly in particles with the diameter range of 0.43-1.1 p.m. Monomethyl hydrogen sulfate has also been detected on urban particles from localities where no oil or coal power plant exist (Suzuki et al., 2001). 

The importance in urban atmospheres of absorbers such as nitrous acid and organic compounds other than those considered here. 

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