انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 10 4 2017 01 11 Estimation of ground level ozone and photochemical smog production using concentrations of NOx and O3 in Isfahan برآورد تولید اُزون سطح زمین و دودمِه نورشیمیایی با استفاده از غلظت NOx وO3 در اصفهان 75 84 41735 FA فریده کنعانی دپارتمان شیمی، دانشگاه سمنان مصطفی فضلی دپارتمان شیمی، دانشگاه سمنان ویکتوریا عزتیان سازمان هواشناسی شهر اصفهان Journal Article 2015 06 22 The concentration of ground-level ozone is the result of thousands of complex chemical reactions. Basically, an increase of ozone concentration occurs in the presence of NO_x, VOCs, and the sun’s radiation. This study deals with analyzing the ground-level ozone in Isfahan city from November 22 to December 21 (a full solar month) in 2009. According to the observations made by the Isfahan Meteorological Organization, photochemical smog was visible over the city during this month. The data used in this study include NO₂, NO and O₃ concentrations and the meteorological variables of temperature, relative humidity and wind speed which have been measured in Isfahan in 2009. The analyses were carried out for the sunshine hours in two time periods of 9 to 12 am and 6 am to 15 pm whose main characteristics are: <br />A) During 6–15 period: the sun rises from 6 am and by becoming closer to the dusk, i.e. about 15 pm, both the radiation intensity, and temperature decrease; <br />B) During 9–12 period: the higher temperature, radiation intensity, and traffic are the effective factors in the emission of pollutants when compared to the other hours of the day. <br />The days under study are classified based on maximum, minimum and average ozone concentration. In order to analyze the tropospheric ozone and smog creation, in this study, the photochemical and semi-empirical models were used.  The kinetic and mechanism of a number of photochemical reactions effective in ozone formation were taken into account in order to analyze the changes in ozone concentration. Calculations were carried out by using the Excel and Matlab software programs. Making use of the steady-state approximation method and considering oxygen atom in the steady state, the reaction rates have been computed. The differential relation obtained (d[O₃]/dt = k₂k₁[NO₂]- k₃[O₃][NO]) is a function of three variables of NO, NO₂ and O₃concentrations. The amounts of reaction rate (d[O₃]/dt) and also the rate constants k₂k₁ and k₃ were also calculated. Analysis of the experimental relation between the activation energy and the results obtained from calculations indicate that the reactions that take place in the troposphere can be considered rank 3 reactions. In the troposphere, the quantum of energy (hν), which is released in some reactions, is very strong. The activation energies obtained for all days of this study include negative values, and this confirms the fact that the energy of the photons of the sun is needed to change NO₂ and O₂ to O₃ in the troposphere. Based on the negative activation energies obtained, we can consider the reaction NO₂+O₂+ hν→NO+O₃ as the mechanism for the tropospheric ozone production in Isfahan. <br />The creation of photochemical smog, SP(<em>t</em>) with <em>t</em> denoting the time, during the mentioned days was studied based on the Jonson’s semi-empirical model. The relations obtained based on the changes in NO and O₃ concentrations with respect to time show that smog creation follows a quadratic nonlinear relation. <br />In general, the increase of the concentration of pollutants on the ground as a result of photolysis reactions has led to the production of ozone concentrations. The results achieved from the analysis of reaction rate, smog creation, and the resulting curves indicate that ozone concentration has not been uniformly increasing or decreasing during the studied days, but there were both the increasing and decreasing trends. In general, the photochemical reactions taken place in the atmosphere of Isfahan city have caused both production and loss of ozone. Consequently, the investigation showed that the changes of the ozone concentrations under the effects of the solar radiation followed the same pattern in autumn 2009. On the other hand, the changes in the ozone concentration on the ground level caused changes in smog creation during the studied time. With regard to the above-mentioned arguments and on the basis of the effect of nearly the same conditions, a constant process prevailed. It could be predicted that this pattern will be the same in the future years. <br /><strong> </strong> <br />  اُزون سطح زمین در طی فرایندهای نورشیمیایی اکسیژن هوا در حضور نور خورشید و NO_x به‌عنوان یکی از مهم‌ترین عوامل موثر، تولید می‌شود. در این پژوهش به بررسی اُزون در شهر اصفهان در آذرماه سال 1388 پرداخته شده، که بنابر مشاهدات سازمان هواشناسی، در طی این بازه دودمِه‌ نورشیمیایی بر فراز اصفهان قابل مشاهده بود. همه بررسی‌ها در ساعت‌های تابش آفتاب (15-6 محلی) انجام گرفته است. در این پژوهش با استفاده از روش تقریب حالت پایا رابطه سرعت دیفرانسیل تابعی از سه متغیر NO،NO₂ و O₃ برای بررسی تغییرات غلظت اُزون به‌دست آمده است. انرژی فعال‌سازی، مرتبه واکنش و سازوکار تشکیل واکنش اُزون در وردسپهر مطالعه و محاسبه شده‌اند .   NOو O₃ سطح زمین به‌عنوان شاخصی برای تشکیل دودمه نورشیمیایی درنظر گرفته می‌شوند، لذا تولید دودمِه بر مبنای تغییرات غلظت NO وO3  مورد توجه قرار گرفت. بررسی روابط تولید دودمِه برمبنای غلظت‌ها و بررسی براساس زمان، نشان‌دهنده پیروی تولید دودمه از روابط غیرخطی و درجه دوم است. بنا به معادله آهنگ تغییر زمانی اُزون،  d[O₃]/dt و نتایج انرژی فعال‌سازی می‌توان تولید اُزون را در شهر اصفهان از واکنش‌هایی که دارای سینتیک کلی مرتبه سوم هستند، در نظر گرفت. از طرف دیگر افزایش غلظت NO_x در سطح زمین در اثر واکنش‌های نورکافتی (فوتولیز) افزایش غلظت اُزون را سبب گردیده است. https://www.ijgeophysics.ir/article_41735_f253583b1a624623e5ef92e6c6f0f7d9.pdf