Análise da qualidade da água e identificação de contaminantes emergentes no estuário do Rio Paraíba-PB

Abstract

Water is an essential resource with significant economic, social, and environmental value. The global increase in freshwater consumption, driven by population growth and economic development, negatively impacts its quality. The discharge of wastewater into rivers is a global practice that threatens the health of aquatic ecosystems and the communities that depend on these waters. In Brazil, despite laws and regulations that govern water quality and effluent treatment, only a portion of the population has access to wastewater treatment. In the state of Paraíba, the situation is concerning due to insufficient coverage in sewage collection and treatment, resulting in significant pollution of water bodies. The Paraíba River, essential for water supply, agriculture, and recreation, faces severe challenges caused by pollution and anthropogenic activities. This study evaluated water quality in the lower course of the Paraíba River using physical, chemical, and microbiological analyses, as well as techniques such as Direct Infusion Mass Spectrometry (DIMS) and Ultra-fast liquid chromatography (UFLC). The developed methodology advanced the detection and characterization of contaminants, emphasizing the importance of analytical techniques in monitoring and protecting aquatic ecosystems. The results revealed that low dissolved oxygen concentrations and high levels of thermotolerant coliforms indicate critical conditions, posing risks to public health and the aquatic environment. The analysis of upstream and downstream points of the Sewage Treatment Plant (STP) demonstrated significant variations in water quality parameters, with low oxygen levels and high coliform loads in the downstream area. For the samples collected from the Paraíba River, the DIMS and UFLC methodologies, combined with Solid-Phase Extraction (SPE), identified emerging contaminants such as bisphenol A, lidocaine, ractopamine, venlafaxine, paracetamol, ibuprofen, diazinon, caffeine, histamine, and pyocyanin. Analyzing the Logarithm of the Octanol-Water Partition Coefficient (LogP) and Total Polar Surface Area (tPSA) properties revealed the bioaccumulation potential of the compounds. Additionally, statistically significant results obtained in the quantification of caffeine in the waters of the Paraíba River, using UFLC-UV-Vis chromatography, highlighted the precision of the analysis. As evidenced by the Analysis of Variance (ANOVA), the model showed high regression significance, with a calculated F-value (7353.60 x 10³) exceeding the critical F-value (4.24), demonstrating the adequacy of the model. Furthermore, the absence of lack-of-fit, confirmed by a calculated F-value (0.4444) lower than the critical F-value (2.58), reinforces the robustness of the constructed model, resulting in the precise quantification of caffeine in environmental samples. The predictive results were highly satisfactory, achieving Root Mean Square Error of Prediction (RMSEP) values of 0.14 mg L-1 and Relative Error of Prediction (REP) of 9.49%, respectively, demonstrating the method's efficacy, even in the presence of interferents in the water samples from the Paraíba River. This study directly contributes to the Sustainable Development Goals (SDGs), particularly SDG 14, which aims to ensure life below water, by identifying contaminants that are toxic to aquatic ecosystems and the population that relies on the ecosystem services provided by the Paraíba River.