Ozone sampling


The sample is burned in oxygen at 1000°C. Nitrogen oxide, NO, is formed and transformed into NO2 by ozone, the NO2 thus formed being in an excited state NO. The return to the normal state of the molecule is accompanied by the emission of photons which are detected by photometry. This type of apparatus is very common today and is capable of reaching detectable limits of about 0.5 ppm.  [c.29]

How would you obtain a sample of pure ozone Account for the conditions used in your method of preparation. What is the arrangement of oxygen atoms in an ozonide and what evidence would you cite in support of the structure you suggest  [c.308]

Sample Collection The simplest approach for collecting a gas sample is to fill a container, such as a stainless steel canister or a Tedlar/Teflon bag, with a portion of the gas. A pump is used to pull the gas into the container, and, after flushing the container for a predetermined time, the container is sealed. This method has the advantage of collecting a more representative sample of the gas than other collection techniques. Disadvantages include the tendency for some gases to adsorb to the container s walls, the presence of analytes at concentrations too low to detect with accuracy and precision, and the presence of reactive gases, such as ozone and nitrogen oxides, that may change the sample s chemical composition with time, or react with the container. When using a stainless steel canister many of these disadvantages can be overcome with cryogenic cooling, which changes the sample from a gaseous to a liquid state.  [c.195]

Suppose you have been asked to monitor the daily fluctuations in atmospheric ozone levels in the downtown area of a city to determine the relationship between daily traffic patterns and ozone levels, (a) Describe the sampling plan you would choose (random, systematic, judgmental, systematic-judgmental, or stratified), (b) Would you choose to collect and analyze a series of grab samples or form a single composite sample (c) How would your answers to these questions change if the purpose of your work is to determine if the average daily ozone level exceeds a threshold value  [c.227]

When and loir are widely separated the effect of background aerosol scattering can be taken account of more effectively by employing a third wavelength, X2, between and in a three wavelength DIAL technique. With this technique, two wavelengths sample the absorption within the Hartley band and the third wavelength lies in a region just outside the band where there is little ozone absorption. For ozone detection in the troposphere the third wavelength employed, I2 in Figure 9.35, is provided by Raman shifting of the 266 nm radiation using a cell containing high pressure deuterium gas to produce radiation of wavelength 289 nm.  [c.381]

In situations where sufficient thermal radiation is available the spectral band can be narrowed (by filters or spectrometer) with only a proportional reduction in sensitivity. When the spectral band is narrowed to a particular absorption band of a given chemical substance the spatial distribution and temporal variation of that substance maybe measured as was done in the visible by astronomers (scanning sHt spectrographs) for many years. Infrared focal plane array technology is making possible spectrographic imaging in the infrared portion of the electromagnetic spectmm which is rich in molecular absorption lines. This will have a major impact on industrial processing where control of the chemistry is essential for cost reduction and safety. The potential appHcations are detection and source location of toxic gases, monitoring chemical manufacturing processes on a real-time basis, remote temperature profile sensing, automobile exhaust gas monitoring and measuring the location and degree of chemical leaks in production or storage. Spectral thermography will help detect and control toxic atmospheric gases such as CO, N O, SO, NH and ozone. A thermographic sensor with an integral gas sampling tube is a spot sensor and that with a remote heat source or retro-mirrors performs remote sensing.  [c.290]

Since antiozonants are affected by most compounding ingredients, each new mbber compound requires the development of a cost-effective antiozonant system. Outdoor as weU as accelerated ozone-chamber tests are available (39—45). Laboratory tests involve exposing a statically or dynamically elongated test sample to ozone and measuring the time to crack formation, the severity of cracking, or the decay of 100% modulus with time. Cracking is affected by ozone concentration and flow rate, temperature, humidity, sample shape, and type of strain (static, dynamic, or both). Cracking is accelerated by increasing ozone concentration. Normal test concentrations are 10—25 pphm, but they can be as high as 50 pphm in accelerated tests. Above 70°C ozone decomposes, and therefore testing is usually carried out at 30 —50°C. Humidity can accelerate ozone cracking, and the maximum recommended value is e 65%.  [c.238]

Sample Collection The simplest approach for collecting a gas sample is to fill a container, such as a stainless steel canister or a Tedlar/Teflon bag, with a portion of the gas. A pump is used to pull the gas into the container, and, after flushing the container for a predetermined time, the container is sealed. This method has the advantage of collecting a more representative sample of the gas than other collection techniques. Disadvantages include the tendency for some gases to adsorb to the container s walls, the presence of analytes at concentrations too low to detect with accuracy and precision, and the presence of reactive gases, such as ozone and nitrogen oxides, that may change the sample s chemical composition with time, or react with the container. When using a stainless steel canister many of these disadvantages can be overcome with cryogenic cooling, which changes the sample from a gaseous to a liquid state.  [c.195]

Suppose you have been asked to monitor the daily fluctuations in atmospheric ozone levels in the downtown area of a city to determine the relationship between daily traffic patterns and ozone levels, (a) Describe the sampling plan you would choose (random, systematic, judgmental, systematic-judgmental, or stratified), (b) Would you choose to collect and analyze a series of grab samples or form a single composite sample (c) How would your answers to these questions change if the purpose of your work is to determine if the average daily ozone level exceeds a threshold value  [c.227]

The Montreal Protocol of July 1987 resulted in an international treaty in which the industrialized nations agreed to halt the production of most ozone-destroying chlorofluorocarbons by the year 2000. This deadline was hastily changed to 1996, in February 1992, after a U.S. National Aeronautics and Space Administration (NASA) satellite and high-altitude sampling aircraft found levels of chlorine monoxide over North America that were 5i % greater than that measured over Antarctica.  [c.16]

Sample until color appears probably 10 ml of air 94-99 Reacts with absorbing solution Ozone in fivefold excess peroxyacyl nitrate  [c.183]

Helium is also being used to advertise on blimps for various companies, including Goodyear. Other lifting gas applications are being developed by the Navy and Air Force to detect low-flying cruise missiles. Additionally, the Drug Enforcement Agency is using radar-equipped blimps to detect drug smugglers along the United States boarders. In addition, NASA is currently using helium-filled balloons to sample the atmosphere in Antarctica to determine what is depleting the ozone layer.  [c.8]

The principal method used for measuring ozone is based on chemiluminescence (3). When ozone and ethylene react chemically, products are formed which are in an excited electronic state. These products fluoresce, releasing light. The principal components are a constant source of ethylene, an inlet sample line for ambient air, a reaction chamber, a photomultiplier tube, and signal-processing circuitry. The rate at which light is received by the photomultiplier tube is dependent on the concentrations of O3 and ethylene. If the concentration of ethylene is made much higher than the ozone concentration to be measured, the light enutted is proportional only to the ozone concentration.  [c.197]

FIGURE 13.49 Sdietnatic diagram of an instrument for the measurement of rjitrpgen oxides based on chemiluminescence. I. ozone generator 2. pressure gauge 3. oxygen control 4. air. S. pfiotomultipiier tube 6. reaction chamber 7. NO, converter 8. sample gas.  [c.1302]


See pages that mention the term Ozone sampling : [c.1696]    [c.31]    [c.7]    [c.31]   
Fundamentals of air pollution (1994) -- [ c.181 , c.182 , c.183 , c.184 , c.185 , c.197 , c.224 ]