Estimativa da variabilidade nos níveis de NO2 utilizando amostragem passiva em vias comerciais de Fortaleza-CE, considerando efeitos da sazonalidade temporal

Abstract

The increase of the motor vehicles fleet which circulate through urban areas are one of the main causes of harmful polluting gases on the environment. These gases provoke the reduction of the human breathing activity, causing the deterioration of monuments, civil patrimony and the increase of the morbity and mortality of people by respiratory deseases. The monitoring of these polluting gases can be done economically and efficiently through a passive sampling methodology. By these means, this present study aims to estimate the levels of NO2 using the passive sample method around the commercial area in Fortaleza – Ceará. To do so, some streets with the same characteristics in different commercial regions of the city were selected, where a set of tube samplers containing a filter paper soaked in an NO2 absorber sollution were attached on lampposts located on these streets. This process was held in 12 campaigns, 21 days each, covering the rainy season (March-June) and the dry season (July-November) of the city of Fortaleza. Total of 360 samples of NO2. Simultaneously, an estimate of the quantification of vehicles was performed, the measurement of the constructions height, the width of the roads and the tracking of the meteorological situation of the city. The results obtained show that the levels of NO2 were below the patterns stablished by the resolution CONAMA nº 491 and by the international environment entities, EPA, EEA and WHO. They present a rate between 1,5 to 55,7 µg.m-3 , the areas around Montese were the ones which presented high levels to this rate. The seasonal measures of NO2 obtained during the rainy season were superior to the dry season, where Almirante Rubim street presented the biggest rate difference, of 26,6 µg.m-3 on the rainy season and 19,3 µg.m-3 on the dry season. The other streets obtained a rate on the rainy and dry season respectively of de 26,6 µg.m-3 and 25,5 µg.m-3 on Antônio Fiúza; 20,0 µg.m-3 and 18,5 µg.m-3 on 24 de maio; and 25,3 µg.m-3 and 23,6 µg.m-3 on General Sampaio. Pearson’s correlation matrix of the results showed that the relative humidity and precipitation obtained a positive correlation with NO2 concentration in all analyzed subjects, the correlation coefficient r > 0,7 on Almirante Rubim, temperature and speed of the wind presented a negative Pearson’s correlation with a concentration of NO2 in all streets. The analysis of the main components applied to the rates of NO2 concentration on the rainy season, dry season, at the traffic of the vehicles and H/W has pointed that the components CP1, CP2 and CP3 explain 94,4% of the cases studied and that each point of the streets have a unique characteristic, even when compared to another points of the same sector on the same circulation track. Therefore, there was no separation of the points when CP1 and CP2 were applied, although they have presented a clear variation when applied to CP1 and CP3. In conclusion, this present study demonstrated in a satisfying way that the use of passive samplers can assist on the estimation of the NO2 levels in a simultaneous matter in commercial areas in Fortaleza – Ceará, as an alternative low cost method , easy handling of instalation and gathering, and spacial covering.