The Determination Of Tropospheric Nitrogen Oxides By Colorimetric Method And Chemiluminescence Method

Nitrogen oxides (NO_x=NO+NO₂) are very important in view of airpollution, it has an important effect on nature and human being. Nitrogen dioxide (NO₂)plays a key role in the troposphere. It participates in the control of the strong oxidant,O₃, and the strongest atmosphere oxidizing agent, OH, which determine the oxidizingcapacity of the atmosphere. Recently, it has been recognized that radiative forcing ofclimate. In addition, NO₂ is known to cause respiratory problems for humans in theurban atmosphere. Nitrogen oxides have natural sources and anthropogenic sources,especially fossil fuel combustion and biomass burning. Therefore, the accuratedetermination of nitrogen oxides is the vital significance, regarding the understandingair pollution mechanism, the judgment air pollution degree, and the urban planningconstruction.In this paper, we established Hydrochloride Naphthodiamide method to determinetropospheric nitrogen oxides and improved this method, changed absorption reagentinto sodium hydroxide solution, which is based on the traditional colorimetric method.NO₃^- is converted to NO₂^- by Zinc-cadmium reducer, determined NO₂^- by colorimetricmethod. NO is determined by oxidizing NO to NO₂. Saltzman coefficient is0.96±0.03(σ), approaching to 1, however, reported Saltzman coefficients werebetween 0.72 and 0.88. This method didn't need to determine the Saltzman coefficient,it simplified the process of operation, enhanced the accuracy of the method. Themethod allows to determine 0.5～800ppbv NO₂. with the detection limits of 0.4ppbv,The relative standard deviations is 4.9ï¼…(C=50ppbv, n=5), resolving power is 15min.Inthis method, carbon dioxide and sulfur dioxide have no interference. It was applied todetermine tropospheric NO₂.In addition, we established Chemiluminescence method to determine troposphericnitrogen oxides, NO is determined by oxidizing NO to NO₂. In this paper, Weoptimized the conditions for the determination of NO₂, analyzed some impact on Luminol-NO₂ CL method, such as temperature, pressure, and additive and so on. Thisresearch discovered CL intensity gradually reduced along with the temperature,increased along with pressure ascension. CL intensity gradually increased when methanol,pyrogallic acid, formaldehyde, benzyl alcohol is added to luminol reagent. Iiodocyclohexane andacetone hadn't an effect on CL intensity. Phenol may reduce CL intensity. The methodallows to determine 0.5～400ppbv NO₂, with the detection limits of 0.2ppbv, Therelative standard deviations is1.2ï¼…(C=56ppbv, n=5), resolving power is 0.01s.Weobtained kinetics equation based on experiment, it is r=k[NO₂][OH^-]^0.2. In thismethod, carbon dioxide and sulfur dioxide have no interference. NO interferenegatively and O₃ interfere positively. It was applied to determine tropospheric NO₂.