Avaliação das concentrações de amônia atmosférica na região Sul de Minas Gerais

Abstract

Throughout the 21st century, atmospheric ammonia has been characterized, as the only precursor source of aerosol particles, with a growth prediction. Ammoniac emissions have shown a growth trend in the last decade, on a global scale, accompanying the increase on agricultural activities, as a consequence of the growth in the demand for food production. The objective of the present study is to verify the concentration levels of atmospheric ammonia present in Lavras, Southern Region of Minas Gerais, using different methods of quantification and sampling. Specifically, based on this initiative, results are presented regarding the calibration, and chemical analysis of ammonia background concentrations Two equipment were used for the sample campaigns: (i) the gas sampler - APV TRIGAS (referenced as "impinger"); and (ii) the automatic weather station - WatchDog model. Data of solar radiation, relative air humidity, ambient temperature, atmospheric pressure, and dew temperature were used for the calibration of the sampling method, as well as the different analytical procedures used. As absorption solutions, sulfuric, oxalic and citric acids were evaluated, quantified by liquid chromatography and Kjeldahl method. After calibration, the following flows were obtained in the critical holes: OC 350 - 1.91 L.min -1 ; OC 483 - 0.17 L.min -1 ; OC 482 - 0.14 L.min -1 . With analysis of variance - ANOVA, was verified that the concentrations of ammonia obtained by the critical orifice OC 350, and with the citric acid, can be considered as outliers, being excluded from the final estimate of NH3. The Pearson correlation coefficients observed between the results, and the variables: relative humidity and sampling time, were considered significant for the present study. The mean atmospheric ammonia concentration was 33.16 μg.m -3 ; for the municipality of Lavras / Minas Gerais.