Avaliação da presença de poluentes orgânicos semivoláteis nas águas do Rio Macaé, Macaé – RJ

Abstract

The scarcity of data on the presence of organic pollutants in the Macaé River prompted an investigation of these compounds. Understanding the chemical composition of organic substances present in the river's water is essential for assessing environmental impacts and public health risks, especially given the importance of the Macaé River to the region. The study area is characterized by a combination of agricultural, industrial, and urban activities, which can significantly impact the health of the aquatic ecosystem and human health. Conventional analytical techniques do not allow for the separation of more than a few hundred peaks in a chromatogram. For this reason, conducting a diagnostic study of unknown compounds requires the use of advanced analytical techniques, such as comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC/TOFMS). The research was conducted by collecting five water samples from four sampling points along the Macaé River, considering criteria such as local characteristics and ease of access. The analytes were concentrated by Solid Phase Extraction (SPE), and the GC×GC/TOFMS technique was used to tentatively identify the compounds present in the water. The spectral similarity of the compounds was evaluated against the NIST library standards in the ChromaTOF software, allowing for a detailed analysis of the mass spectra of the compounds in each sample. The number of peaks detected per sample ranged from 207 to 505, and the number of tentatively identified compounds exceeded 500, with spectral similarity to the NIST Library spectra greater than 80% and the retention index was calculated. The results revealed a significant diversity of tentatively identified chemical substances in the water samples, highlighting the presence of hydrocarbons, pharmaceuticals, solvents, and pesticides. It would not have been possible to identify such a large number of substances, as observed in the studied samples, using conventional chromatographic techniques. Sampling points near rural areas showed contamination by pesticides and agricultural byproducts, while the urban point revealed the presence of compounds such as solvents, hydrocarbons, and phthalates, indicating the influence of industrial and commercial activities with possible improper waste disposal into the river. This study demonstrated that conducting a qualitative analysis of organic substances present in the water of the Macaé River was a strategy to identify the main compounds that can be monitored in future quantitative studies.