Ozone trace analysis

Bromate has been classified as a human carcinogen by both the I/VRC (International Agency for the Research on Cancer) and the USEPA (United States Environmental Protection Agency) and is known to be toxic to fish and other aquatic life [11, 12]. Bromate could be produced in aquatic systems upon the oxidation of aqueous bromide. Controlled ozonation has been considered as an effective disinfectant tool in aquatic systems [13] but when sea water is subjected to ozonation, oxy-bromide ozonation by-products (OBP) are produced and these are important both in terms of their disinfection ability and also in relation to their potential toxicity. When seawater is oxidized, aqueous bromide (Br-) is initially converted to hypobro-mite (OBr ) which can then either be reduced back to bromide or oxidized further to bromate (Br03-) which is known to be toxic to fish and other aquatic life and classified as a human carcinogen. There has been thus a considerable interest in bromate analysis so that trace analysis of bromate in water has received considerable attention in recent years. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

Further studies are needed to give better dose-response information and to provide a frequency distribution of the population response to oxidants alone and in combination with other pollutants at various concentrations. Such studies should include the effects of mixed pollutants over ranges corresponding to the ambient atmosphere. With combinations of ozone and sulfur dioxide, the mixture should be carefully characterized to be sure of the effects of trace pollutants on sulfate aerosol formation. The design of such studies should consider the need to use the information for cost-benefit analysis and for extrapolation from animals to humans and from small groups of humans to populations. Recent research has indicated the possibility of human a ptation to chronic exposure to oxidants. Further study is desirable. 

Kim, J.-H., R.D. Hudson and A.M. Thompson (1996) A new method for deriving time averaged tropospheric column ozone over die tropics using total ozone monitoring spectrometer (TOMS) radiances intercomparison and analysis using TRACE A data. Journal of Geophysical Research 101 24317-24330. 

In the early part of2004 there was a problem in the UK caused by low levels ofbromate in a branded bottled water. This arose from the presence of low levels of bromide in the water that was then disinfected by treatment with ozone. The bromate ions formed were at levels above the EU and EPA limit of lOpg/l for drinking water. The analysis of this anion at trace levels is demanding and should be left to a specialist laboratory. However, Dionex have published four methods that can be used for the analysis of bromate ions in water and the application notes (81, 101, 136 149) are available from the Dionex website (http /www. dionex. com/)... 

The relation between ambient levels and precursor emissions is somewhat easier to identify for particulates than for ozone, because the chemical composition of individual particulates provides evidence for their origin sulfate particulates are associated with sulfur dioxide emissions organic particulates with specific VOCs, and so on. A variety of statistical methods have been used to identify source types for particulates based on chemical composition, especially in terms of trace metal components (e.g., Henry, 1992 Seinfeld and Pandis, 1998). This type of analysis requires sophisticated measurements of the chemical composition of individual particulates, rather than the more common measurement of summed concentrations. Statistical methods have also been used to gain information about ozone and ozone precursors (e.g., Buhr et al., 1995 Stehr et al., 2000). 

G.T. Coyle, et al, Broad Spectrum Analysis of the Removal of Trace Organics in an Ozone Granular Activated Carbon Potable Water Pilot Plant Study , in Water Chlorination Environmental Impact and Health Effects, Volume 4, ed. R. L. Jolley, Ann Arbor Science, Ann Arbor, MI, 1983, p. 421. 

Pathway 1 (eq 6a) shows no oxygen-atom transfer and the production of r, as discussed for the H202 reaction (eq 3). The I+ can form a variety of products, in particular I2 from excess T as discussed for the H202 reaction. The [I-03] intermediate should break down to oxygen and hydroxide on H20 and anion attack. The reaction of ozone with iodide to form I2 is quantitative in the presence of excess T and can be used for the analysis of ozone (43). In seawater this process seems less likely to occur because I" is a trace constituent. 

Bromate is a disinfection by-product that is produced from the ozonation of source water that contains naturally occurring bromide, whereas chlorite and chlorate are produced as a result of using chlorine dioxide as a disinfectant. Recently, bromate has become the most important inorganic oxyhalide by-product, and its concentration in drinking water has to be controUed. Another chaUenge is seawater, which represents a vay difficult matrix for the analysis of trace ionic constituents, because chloride, sulfate, and sodium are the primary ions and they are presort at extremely high concentrations. " ... 

Trace gas analysis in air Greenhouse gases such as methane, CO2 and N2O are causing the temperature of the planet to increase, or they are interfering with ozone chemistry in the stratosphere. Isotope analysis of these gases may help to understand their cycling in the atmosphere or between global pools. For CH4... 

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