Determinação de material particulado, íons metálicos e dióxido de nitrogênio no ar atmosférico de carvoaria

Abstract

An emerging global concern is heavy metal poisoning, whose bioaccumulation can cause severe toxic effects. This chemical group is persistent in the environment and has high carcinogenic potential. Heavy metals are generally adsorbed onto particulate matter, a group of atmospheric pollutants that includes dust, smoke, and solid and liquid materials suspended in the air. Considering that nitrogen dioxide is a precursor of particulate matter and both pollutants originate from combustion processes, it is important to quantify them in environments using these processes, such as charcoal kilns. Given the risks posed by these pollutants, this study aimed to determine the concentrations of particulate matter, associated metal ions, and nitrogen dioxide in the air near conventional circular kilns at a charcoal production unit in the Campos Gerais region of Paraná. Samples were collected in triplicate using cassettes and cellulose ester filters, with a portable pump at 2 L min-1 for sampling times of 210 minutes. Charcoal fines from the pyrolysis process were converted into briquettes at another production unit, where additional samples were taken. For NO2 samples, impregnated filters were used for analysis during the wood roasting and carbonization stages. After collection, the filters were analyzed using the Griess-Saltzman colorimetric reaction in a UV-Vis spectrophotometer at 540 nm. Characterization was carried out at the Multiuser Center of the Federal University of Technology – Paraná, using Scanning Electron Microscopy to obtain high-definition images of the materials’ morphology. Energy Dispersive Spectroscopy was also used to qualitatively analyze the elemental composition, with results showing no trace elements. For quantitative trace element characterization, Inductively Coupled Plasma Atomic Emission Spectroscopy detected the presence of nickel and chromium. NO2 analysis showed that the concentrations found in the three main stages of wood pyrolysis were within the limits set by environmental authorities, with the highest concentration of approximately 3 μg m-3 during the roasting phase. Gravimetric analysis revealed higher particulate matter emissions during the roasting and carbonization stages due to greater release of volatile organic compounds, with values of approximately 35 mg m-3.