EVALUATION OF NOy AND NITRIC ACID MEASUREMENT METHODS AND COLLECTION OF AMBIENT DATA
California has an ambient air quality standard for nitrogen dioxide (NO2), and oxides of nitrogen are also critical participants in atmospheric photochemistry to form ozone. Ambient air quality monitoring networks use chemiluminescent analyzers that alternately measure NO and all nitrogenous species that are converted to NO by a heated catalyst. The difference is defined as NO2. In the atmosphere these nitrogenous species (NOy) consist of, in addition to NO and NO2, nitrogenous acids (nitric and nitrous), ammonia (NH3), and organic nitrates. Dual converter NOx analyzers were used during SCOS97-NARSTO to measure NOy and nitric acid. These instruments were refurbished by replacing or reactivating their reduction converters and thoroughly evaluating their efficiency to convert nitrogen-containing species. These instruments are equipped with dual converters with one channel fitted with a NaCl-coated fabric denuder to selectively remove nitric acid (NOy*). Since the instrument automatically cycles between the two channels, the difference is a measure of nitric acid. A pair of collocated analyzers was set up at the CE-CERT laboratory in Riverside and a single analyzer was installed in Azusa at the monitoring site operated by the South Coast Air Quality Management District (SCAQMD). Data collection started April and October 2000, respectively, for the Riverside and Azusa measurement sites. Data were compiled and validated until April 2001. NOy values at Riverside ranged up to 300 ppb, and values at Azusa reached up to 500 ppb. The Azusa NOy and NOx reported by the SCAQMD compared quite closely. Since it was not possible to have both analyzers sample the same span gas, the significance of differences between the two approaches could not be evaluated. The diurnal pattern of nitric acid was observable nearly every day during the smog season. The concentrations at Riverside ranged up to 6 ppb in the summer. Despite the measurement period at Azusa not including the summer smog season, nitric acid concentrations as high as 8 ppb were observed. A thermoevolution denuder (TED) to measure nitric acid was evaluated under laboratory conditions. This device uses a special ceramic fabric denuder coated with sodium chloride to selectively remove nitric acid. Since this fabric strongly adsorbs microwave radiation at the same wavelength as that for cooking, the fabric can be heated rapidly and controllably to high iv temperatures using a standard microwave oven. This heating will decompose the collected sodium nitrate to NOx. While this design allowed the denuder to adsorb nitric acid, the amount recovered was low and variable. We found that the denuder was not evenly heated, and the amount recovered when drops of dilute nitric acid were placed on the denuder depended on the location on the denuder that was used. It was likely that the microwave oven, which was a consumer product, was not designed to produce a uniform microwave field. We concluded that additional research was needed before the system was ready to evaluate with other methods of measuring nitric acid. This report included the initial year of NOy and nitric acid data. We continued to maintain the NOy analyzers and added NO2/PAN gas chromatographs at both sites. These chromatographs separate NO2 and quantify the amount using luminol detection. This selective method of measuring NO2 will be used to quantify the amount of NO2 contained in the NOy. Under additional funding these instruments will be maintained until October 2002. The results from this period will be the subject of a final report for the second period of funding.
A Fabric Denuder for Sampling Semi-Volatile Species
ABSTRACT A new style of diffusion denuder has been evaluated specifically for sampling HNO3. A coated fabric is used as the denuder substrate, which can be loaded directly into a standard filter holder. This approach allows direct denuder sampling with no additional capital costs over filter sampling and simplifies the coating and extraction process. Potential denuder materials and coatings were evaluated in the laboratory to test the removal efficiency. NaCl coatings were used to assess more than 20 materials for HNO3 collection efficiency. Particle retention, which would cause a denuder to have a positive bias for gas concentration measurements, was evaluated by ambient air sampling using particulate sulfate as the reference aerosol. Particle retention varied from 0 to 15%, depending on the denuder material tested. The best performing material showed an average particle retention of less than 3%. Denuder efficiency of four fabric materials was tested under ambient conditions to determine removal efficiency. The fabric denuder method was compared with a long path-length Fourier transform infrared (FTIR) spectrometer, a tunable diode laser absorption spectrometer (TDLAS), and a denuder difference sampler to independently measure HNO3. HNO3 collection efficiency was typically 90% for the denuders, whether coated with NaCl or not. For 10-L/min sampling rates with the fabric denuder, the square of the correlation coefficient with the FTIR spectrometer was 0.73, compared to 0.24 with the TDLAS.
Development of Science and Technology in the Iranian Electric Power Industry: Challenges and Future Progress
This chapter examines four key segments of the electric power industry in Iran: generation, transportation, distribution and consumption. It reviews the method, development, and evolution of electric power generation in the country. Specifically, the chapter reviews the structure of the electric industry, the main players, institutions, standards as well as laws, human resources, technology, the export and import markets, and engineering management of the industry in the country. Finally, the challenges facing the industry will be identified and policy suggestions to remedy the problems will be provided.