N2O removal in N2 or air by ArF excimer laser photolysis at atmospheric pressure.

A photochemical process is proposed as a new efficient N(2)O removal technique in N(2) or air at atmospheric pressure and room temperature without using any catalysts. N(2)O diluted in N(2) or air was decomposed into N(2), O(2), and NO by using a 193 nm ArF excimer laser. The maximum conversion of N(2)O in N(2)O/N(2) or N(2)O/N(2)/O(2) mixtures was 93% at a laser power of 136 mJ, a repetition frequency of 5 Hz, and an irradiation time of 30 min. The formation ratios of N(2):O(2):NO in N(2)O/N(2) and N(2)O/N(2)/O(2) mixtures were 64:31:5.1% and 60:27:13%, respectively. The decomposition mechanism of N(2)O under 193 nm photolysis was discussed by comparing experimental data with calculated model using known photochemical and gas kinetic data.

Inhibition of denitrification by ultraviolet radiation.

It has been shown that UV-A (lambda=320-400 nm) and UV-B (lambda=280-320 nm) inhibit photosynthesis, nitrogen fixation and nitrification. The purpose of this study was to determine the effects, if any, on denitrification in a microbial community inhabiting the intertidal. The community studied is the microbial mat consisting primarily of Lyngbya that inhabits the Pacific marine intertidal, Baja California, Mexico. Rates of denitrification were determined using the acetylene blockage technique. Pseudomonas fluorescens (ATCC #17400) was used as a control organism, and treated similarly to the mat samples. Samples were incubated either beneath a PAR transparent, UV opaque screen (OP3), or a mylar screen to block UV-B, or a UV transparent screen (UVT) for 2 to 3 hours. Sets of samples were also treated with nitrapyrin to inhibit nitrification, or DCMU to inhibit photosynthesis and treated similarly. Denitrification rates were greater in the UV protected samples than in the UV exposed samples the mat samples as well as for the Ps fluorescens cultures. Killed controls exhibited no activity. In the DCMU and nitrapyrin treated samples denitrification rates were the same as in the untreated samples. These data indicate that denitrification is directly inhibited by UV radiation.

Exposure of nitrous oxide to X-rays. Production of nitric oxide and nitrogen dioxide.

X-radiation has been shown to produce nitric oxide (NO) and nitrogen dioxide (NO2) in the presence of nitrous oxide (N2O). The purpose of the present study was to confirm how much NO and NO2 was produced when constant amounts of nitrous oxide were exposed to constant X-radiation. Twenty polyethylene bottles (capacity 10 litres) were filled with nitrous oxide alone. Another 20 bottles were filled with nitrous oxide and 30% oxygen. Each bottle was placed at a distance of 30 cm from the X-ray tube and they were directly in the line of the X-ray beam at a setting of 90 kV at 0.5 mA, a standard setting for chest fluoroscopy. The range of duration of X-ray exposure was from 0 (control), to 2, 3, and 5 minutes in five bottles each, respectively. A colorimetric recording method (Saltzman) and a chemiluminescent monitor were used for measurement of NO and NO2. In the bottles filled with nitrous oxide alone, the production of NO was not affected by the duration of X-ray exposure, but the longer duration of X-ray exposure produced a larger amount of NO2. In the bottles filled with nitrous oxide and 30% oxygen, the longer duration of X-ray exposure produced larger amounts of both NO and NO2. These finding confirmed a previous investigation in which nitrous oxide was not inert under X-ray exposure. As the presence of oxygen plays an important role in the oxidation of nitrous oxide under X-ray, this study suggests another potentially hazardous interaction that may occur secondary to the administration of an anaesthetic in the presence of X-irradiation such as pulmonary angiography, cardiac catheterisation, and fluoroscopic bronchoscopy or biopsy.