Document Details
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Document Type |
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Article In Journal |
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Document Title |
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Atmospheric formation and occurrence of nitrous acid and its role in the formation of ozone in the city centre in Cairo, Egypt. تكون وتواجد حمض النيتروز الجوي ودوره في تكوين الأوزون في وسط مدينة القاهرة |
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Document Language |
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English |
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Abstract |
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NITROUS ACID, nitrogen dioxide and ozone were measured in
the city centre in Cairo during autumn 2001 up to summer 2002
inclusive. Concentrations of nitrogen dioxide (N02) and nitrous acid
(HONO) varied diumally during the four seasons. The highest NO,
concentrations were found during the daytime hours. in contrast.
HONO levels were highest in the nighttime hours. This is probably
due to the rapid nighttime build up of HONO and its daytime
photolysis. The average daytime concentrations of HONO were 3.40,
4.78, 1.83 and l.l7 ppb, whereas the average nighttime levels were
4.64, 5.97, 3.58 and 3.1 ppb during the autumn, winter, spring and
summer seasons, respectively. The highest daily average concentration
of HONO was found in the winter and the lowest level in the summer
season. The ratios of HONO to NO; concentrations (HONO/NO!) also
exhibited a marked diumal cycle, with maximum ratios in the
nighttime hours during the four seasons. The average daytime
HONO/NO; ratios were 0.023, 0.027, 0.0l5 and 0.011, whereas the
average nighttime ratios were 0.054, 0.058, 0.049 and 0.047 during the
autumn, winter, spring and summer seasons, respectively. Significant
positive correlation coefficients were found between daily HONO and
NO; concentrations and between daily HONO concentration and
relative humidity during the four seasons. These correlations suggest
that heterogeneous chemical production of HONO may occur through
reactions of N02 and H20 on surfaces. lhe highest ozone
concentrations were found in the summer and the lowest levels in the
winter. Significant positive correlation coefficients were found
between nighttime concentration of HONO and daytime concentration
of ozone on the following day during the four seasons. These
oorrelations indicate that the accumulated nighttime concentration of
HONO followed by HONO photolysis after sunrise leads to increase
the photochemical fomiation of ozone on the following day. |
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ISSN |
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189 |
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Journal Name |
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Egyptian Journal of Chemistry |
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Volume |
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47 |
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Issue Number |
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2 |
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Publishing Year |
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1425 AH
2004 AD |
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Article Type |
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Article |
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Added Date |
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Monday, August 29, 2011 |
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Researchers
| ممدوح ابراهيم خضير | Khoder, Mamdouh Ibraheim | Investigator | Doctorate | Khoder_55@yahoo.com |
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