Các oxit nitơ là một trong các loại dai dẳng nhất của chất gây ô nhiễm không khí phát ra trên toàn cầu bởi vì họ là những sản phẩm cháy của cả hai nguồn văn phòng phẩm và điện thoại di động. Bởi đến nay nồng độ cao nhất của các oxit được hình thành trong quá trình đốt cháy là NO và NO2. Với thời gian, và trong sự hiện diện của O2 hoặc trong khí thải trong bầu khí quyển của NO được chuyển thành NO2. Có sáu oxit thường gặp của nitơ: (1) nitric oxide (NO),. | NITROGEN OXIDES REDUCTION INTRODUCTION Nitrogen oxides are one of the most persistent categories of globally emitted air pollutants because they are combustion products of both stationary and mobile sources. By far the highest concentration of the oxides formed during combustion are NO and NO2. Given time and in the presence of O2 either in the flue gases or in the atmosphere most of the NO is converted to NO2. There are six commonly encountered oxides of nitrogen 1 nitric oxide NO 2 nitrous oxide N2O 3 nitrogen dioxide NO2 4 nitrogen trioxide N2O3 5 nitrogen tetroxide N2O4 6 nitrogen pentoxide N2O5 . Typically nitrogen oxides or NOX refers to a collective name for nitric oxide NO and nitrogen dioxide NO2 both of which are formed as a by-product during combustion. Nitric oxide is a colorless odorless toxic nonflammable gas which is slightly soluble in water. Nitrogen dioxide however is a reddish-brown gas that is toxic and highly corrosive with a pungent odor. This gas can contribute to highly visible plumes. Emissions of nitrogen oxides are of concern due to their potential role in ozone formation acid rain deposition health effects and formation of toxic air pollutants. EFFECTS OF O Human and Animal Health Effects Of the two compounds nitrogen dioxide is the most toxic and dangerous to humans. A variety of studies has been performed to observe the effects of NO2 on humans and animals. Most of these studies have been performed using pure NO2. Effects of acute NO2 exposure have been reported as nose and eye irritation obliterative bronchiolitis pulmonary congestion and edema pneumonitis and death. Most of these reactions such as pulmonary edema and obliterative bronchiolitis can occur at extremely high concentrations 150-500 ppm for short periods of time minutes to an hour. It appears however that mixtures of oxides tend to lessen the discomfort and the potential to contract severe disorders. It has also been shown that chronic intermittent exposure to NO2 10-40 .
