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There has been an increasing number of global model studies that relate water quality to the watershed land use. The strategy of considering a model that is comparable to the Soil Conservation Service Curve-Number method that employs land use maps to estimate the effects of land use on the water quality, has considerable potential for application. In this context, this paper presents the LUPC (Land Use Pollutant Contribution) Model that relates pollutant loads originated by several types of coverage and a weight function which determines the load decay through water basin. It makes an estimate of the watershed features that are produced by conducting an analysis of the river profile, which is shown here in terms of the labile and refractory organic matter (OM), differentiated by its percentage of aromaticity. The initial results which were obtained by applying the model in a river basin located in the south of Brazil, suggest that the model can estimate the load of OM at a point of interest in the river and has proved to be a valuable tool for enabling managers to make decisions about the use planning land use and its impacts for water resources planning and management.

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.

O acompanhamento do avanço antrópico em bacias hidrográficas a partir da avaliação da cobertura do solo tem grande utilidade na gestão de recursos hídricos, como no caso do modelo chuva-vazão CN-SCS que utiliza o conceito de curva-número (CN) para estimar qual o potencial da precipitação tornar-se escoamento superficial com base na cobertura e tipo do solo em uma bacia hidrográfica. Nesta pesquisa foi avaliada a evolução da cobertura do solo na bacia do Rio Barigüi entre os anos de 1999 e 2019 e seu impacto sobre as características hidrológicas com base na variação da CN. Para tanto, imagens Landsat foram classificadas para os anos em estudo e os tipos hidrológicos de solo na bacia definidos. Os resultados indicaram que houve relevante avanço antrópico na região, com aumento de urbanização (~21 km2) e redução de áreas florestadas (~22 km2). No entanto, tal avanço não afetou de forma expressiva o valor de CN total da bacia, devido ao tipo do solo predominante, mais impermeável, e à forma em que ocorreram as alterações na cobertura do solo, com aterro de áreas alagadiças e consequente acréscimo de permeabilidade em algumas regiões.

The challenge imposed by law no. 9433/97 to establish mechanisms for the recovery of bodies of water led to a dynamic of research that could guarantee not only an adequate understanding of the management instruments but also the technical basis for their application. In this research, emphasis was placed on understanding the dynamics of organic matter (OM) in a drainage basin heavily influenced by anthropogenic activities, through the analysis and interpretation of qualitative and quantitative information. The case study was the Iguaçu River basin, from its headwaters in the Metropolitan Region of Curitiba (MRC) to the municipality of União da Vitória. The results obtained showed a large deposition of labile OM in the MRC coming probably from domestic effluents, with consequent DO depletion and water quality degradation. However, after the more urbanized region, there is a reduction in the concentration of OM and the indication of the predominance of pedogenic material, suggesting that in addition to the dilution effect, there is less input of anthropogenic effluents in this region, which results in an improvement in water quality, represented mainly by the recovery of the DO concentration. The combined use of quantitative data and UV-visible spectroscopy was fundamental to comprehend the variation in the characteristics of OM and its sources along the studied section. RESUMO O desafio imposto pela lei n. 9433/97 de estabelecer mecanismos de recuperação de corpos hídricos induziu a uma dinâmica de pesquisas que pudessem garantir, não só o adequado entendimento dos instrumentos de gestão, mas a fundamentação técnica necessária à sua aplicação. Nesta pesquisa, ênfase foi dada na compreensão da dinâmica da MO em bacia hidrográfica fortemente influenciada pelas atividades antrópicas, através da análise e interpretação conjunta de informações qualitativas e quantitativas. O estudo de caso abordado foi a bacia do rio Rio Iguaçu e os resultados obtidos demonstraram grande aporte de MO lábil na RMC proveniente provavelmente de efluentes domésticos, com consequente depleção do OD e degradação da qualidade das águas. No entanto, após a região mais urbanizada há redução da concentração de MO e a indicação da predominância de material pedogênico, sugerindo que além do efeito de diluição, há menor aporte de efluentes antrópicos nesta região, o que resulta numa melhoria da qualidade das águas, representada principalmente pela recuperação da concentração do OD. A utilização conjunta dos dados quantitativos e da espectroscopia de UV-visível foi fundamental para compreender a variação nas características da MO e de suas fontes ao longo do trecho estudado.

We studied the transesterification of two vegetable oils: soybean and waste frying oil. The main problem of transesterification is related to the measurement of the ethyl ester content. In this work we used a quick analytical method for assessing the ethyl ester fraction of the purified fuel-grade transesterification products by applying a simple correlation with density. If the ester content is higher than 85% by weight the correlation allows the determination by a single density measurement. This method is suitable for control and determines the ethyl ester quickly and simply.