Estudo preliminar de NO2 na atmosfera da cidade de João Pessoa, PB, Brasil

Abstract

NO2 is a gas found in trace amounts in the atmosphere. Its main natural source of emissions is the rapid oxidation of NO by O3 in the upper troposphere. For this reaction to occur, first it is necessary for stable N2 molecule to be broken by natural or man-made phenomena that requires high energy. These phenomena consist of rays, lightning, combustion processes such as fires, the industrial combustions and those by vehicles. In metropolitan areas it has been observed an increase in the concentrations of NO2 relating them to diseases of the respiratory and cardiovascular causes of death. NO2 is a precursor to other strong oxidants such as tropospheric ozone, nitric acid and peroxyacetyl nitrate (PAN) therefore it is an indicator of a mixture of pollutants. This work aims to analyze the NO2 in the city of João Pessoa, get the time profile of their concentration and to identify pollution peaks. The method used was modified Griess-Saltzman with active sampling and pre-concentration of the sample in SPE cartridge, silica C-18. The determination of NO2 was made by molecular absorption spectrophotometer, UV-Vis. There were two sampling sites in the two seasons, in downtown during summer (January and February 2011) and in UFPB during autumn (April and May 2011). From the results, the samples from downtown had the highest concentrations of NO2, as 15 μg/m³, after 17h and 8 μg/m³, between 12/14 h, probably due to heavy traffic of diesel vehicles. The air collected in the UFPB showed lowest concentrations, ranged from 7 μg/m³ (at night) to 0.9 μg/m³, at 12 to 14 h. The data from PCA showed that the moisture influences the NO2 concentration in the morning while solar radiation and the radiation and the temperature affect NO2 concentrations in the afternoon.