RESUMEN
Rainfall events induce water quality transformation in river systems influenced by the watershed land use and hydrology dynamics. In this context, an adaptive monitoring approach (AMA) is used to assess non-point sources (NPS) of pollution events, through dissolved organic matter (DOM) contribution. The case study is a monitoring site in a semi-urban watershed characterized by NPS contribution. An integrated quali-quantitative method for DOM based on dissolved organic carbon (DOC) content, spectroscopic techniques of excitation-emission fluorescence (EEF), and UV-visible absorbance is proposed. The results indicate a mix of allochthonous and autochthonous DOM characteristics from NPS sources associated to vegetation area influence (A285/DOC of 15.43 L (g cm)-1 and SUVA254 of 2.11 L (mg m)-1). The EEF signals showed more humic-like than protein-like characteristics with peaks A and C (approximately 5.72 r.u.) more intense than peaks B, T1, and T2 (approximately 4.33 r.u.), indicating NPS from the soil leachate. The absorbance ratio values indicate a mix of organic compounds with greater proportion of refractory characteristics with high aromaticity and molecular weight (approximately A300/A400 of 4.15 and A250/A365 of 4.48), associated with the surface wash-off of accumulated residual and subsurface soil erosion, which contribute to complex organic matter structures. The fluorescence indexes, overall, indicated allochthonous sources with intermediate humic characteristics (FI ≈ 1.43, BIX ≈ 0.65, and HIX ≈ 7.98). The proposed integrated optical property strategy represents an opportunity for better understanding of DOM dynamic assessment for identifying potential mitigation techniques for organic pollution control and improving water quality conditions.
Asunto(s)
Monitoreo del Ambiente , Ríos , Compuestos Orgánicos , Suelo , Espectrometría de Fluorescencia , Calidad del AguaRESUMEN
RESUMO Previsto na Lei nº 9.433/97 e em legislações estaduais de recursos hídricos, o enquadramento de corpos de água segundo seus usos preponderantes tem sido aplicado em diversas bacias hidrográficas brasileiras. Por ser de uso relativamente recente, pairam muitas dúvidas em detalhes de sua efetiva aplicação. Isso posto, o presente trabalho apresenta uma sugestão de metodologia que vem sendo aplicada pelos autores, compreendendo os diversos passos citados na Resolução CNRH nº 91/08. A metodologia não se pretende definitiva e visa contribuir para a aplicação da importante ferramenta do enquadramento.
ABSTRACT The classification of water bodies according to designated uses is a tool present in the 9.433/97 federal law and has being applied in several Brazilian hydrographic basins. Due to its relatively recent application, there are many doubts about the details of its implementation. The paper suggests a methodology that is being used by the authors, comprising the steps foreseen in Conselho Nacional de Recursos Hídrico's (CNRH) Resolution nº 91/08. Although it is not a definitive methodology, it aims to contribute to the debate about the use of this relevant management tool of water resources.
RESUMEN
This article explores the applicability of fluorescence and absorbance spectroscopy for estimating organic pollution in polluted rivers. The relationship between absorbance, fluorescence intensity, dissolved organic carbon, biochemical oxygen demand (BOD), chemical oxygen demand (COD), and other water quality parameters were used to characterize and identify the origin and the spatial variability of the organic pollution in a highly polluted watershed. Analyses were performed for the Iguassu River, located in southern Brazil, with area about 2,700 km2 and â¼3 million inhabitants. Samples were collect at six monitoring sites covering 107 km of the main river. BOD, COD, nitrogen, and phosphorus concentration indicates a high input of sewage to the river. Specific absorbance at 254 and 285 nm (SUVA254 and A285/COD) did not show significant variation between sites monitored, indicating the presence of both dissolved compounds found in domestic effluents and humic and fulvic compounds derived from allochthonous organic matter. Correlations between BOD and tryptophan-like fluorescence peak (peak T2, r=0.7560, and peak T1, r=0.6949) and tyrosine-like fluorescence peak (peak B, r=0.7321) indicated the presence of labile organic matter and thus confirmed the presence of sewage in the river. Results showed that fluorescence and absorbance spectroscopy provide useful information on pollution in rivers from critical watersheds and together are a robust method that is simpler and more rapid than traditional methods employed by regulatory agencies.