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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.

Os episódios de chuva levam ao aumento da vazão do corpo hídrico e ao consequente incremento de poluição por vias difusa devido ao carreamento de particulado pelo escoamento superficial. A forma como os elementos nitrogênio (N) e fósforo (P) se encontram no sistema aquático define o tipo de interações que podem ocorrer com eles ou a partir deles em um corpo d´água. Portanto, o objetivo deste trabalho foi quantificar N e P nas formas dissolvida e particulada, em amostras de um evento de chuva, a fim de verificar em qual fração são predominantes. Foram testados os métodos de separação por filtração e centrifugação. A área de estudo foi a Bacia do Rio Barigui, em dois pontos de monitoramento na porção norte da bacia. Os resultados indicaram que o P está predominante na fração particulada, e que o N está predominante na fração dissolvida, devido às forças de interação e solubilidade desses elementos. Além disso, o método da filtração mostrou-se mais eficiente na separação das frações do que o método da centrifugação. Desta forma, o entendimento desta dinâmica corrobora com o determinado em legislação, contudo medidas de controle de poluição por vias difusas e seus impactos na qualidade da água devem ser refinados para a melhoria dos instrumentos de gestão de recursos hídricos.

Lack of sewage treatment is amongst the main sanitation problems of Brazil, mainly in low income rural communities. Seeking alternative and low cost technologies to treat such effluents is mandatory. This study aimed to verify the efficacy of a sewage treatment system by root zone stations (constructed wetlands) to remove potentially toxic elements (Cu and Zn) in two wastewater treatment stations (WWTS) (school and single family residence) of small communities in the city of Irati (PR). Three campaigns were carried out between May and September 2011, with two samples each (inlet and outlet), all in replicate, and quantified through atomic absorption spectrometry with flame atomization (AAS-flame). The presence of NH3 in the effluent favored the reduction of pH values, which remained within the neutrality and alkalinity range (from 8.0 to 9.1 for the school effluent and from 6.9 to 7.8 for the single family residence). For this pH range, it was possible to obtain Cu (25% to 75%) and Zn (0 to 100%) precipitation. In general, the constructed wetlands systems were efficient to remove Cu and Zn (between 25% to 75% regarding Cu; and between 67% to 100% regarding Zn), revealing advantages of its use in small communities.

Diffuse pollution caused by rainfall events potentially affects water quality in rivers and, therefore, must be investigated in order to improve water quality planning and management recovery strategies. For these, a quali-quantitative approach was used to monitor the water quality parameters in a river located in a semi-urban watershed area based upon automatic sampling. Thirteen water quality parameters were measured during five rainfall events. Events ranged from 2.3 to 56.8 mm and water peak flows from 3.3 to 4.5 m3/s. The pollutographs measured showed a standard pattern for total suspended solids (TSS). However, for the other chemical parameters, as total phosphorous (TP) and dissolved organic carbon (DOC), the dilution effects were more evident. It was possible to observe the rainfall influence mainly for physical parameters indicating a mass transport pattern for diffuse pollutants, which increased, for example, the amount of TSS in the river. Furthermore, hydrological characteristics were relevant considering the pollutant behavior. Antecedent dry periods, ranging from 1.3 days to 21.4 days, and critical time, from 2.0 to 10.4 h, are determinants to evaluate non-traditional water quality impacts in the river. In general, each rainfall episode has its own characteristics, which produces distinct mass contribution and temporal behavior, being challenging in making generalization. Therefore, the results indicate that diffuse pollution has to be considered to establish future decision-making strategies to water resources management.

Due to the difficult access to conventional systems of collection and sewage treatment in low income rural communities, there is the need for low cost alternative technologies to treat such effluents. This study aimed to verify the efficacy of sewage treatment systems by constructed wetlands in the removal of the nutrients: nitrogen (N), phosphorus (P), calcium (Ca) and Magnesium (Mg), in two wastewater treatment stations (WWTS) located in a school and in a family house in small communities in the city of Irati/Brazil. Results revealed a good performance in the removal of the nutrients N and P in both systems, 75% and 37% for the house and 41% and 69% for the school, respective; which is associated to the plant uptake ability. However, the index of Ca and Mg presented significant increase, with 156% and 88% for the house and 165% and 128% for the school effluent, respectively, due to the use of gravel (rich in Ca and Mg) in the filter composition.

Understanding the phosphorus dynamics in the ecosystem and its correct and accurate quantification is fundamental for proper decision making in water resources management. Thus, the aim of this study was to evaluate the best analytical method for quantifying phosphorus using three distinct acid digestion methodologies for total phosphorus extraction. The study areas were the Barigui and Passauna Rivers which have different land use and soil occupation, as well as water uses. The results showed that all proposed methods have good reproducibility with R² greater than 0.98, for low and high concentrations. However, in the samples quantification, method 2 presented the most satisfactory results, in which the smaller sample volume and reagents used, shorter digestion time and good precision and reproducibility of P concentration of the samples stand out. Improper use of an analytical procedure or calibration curve may underestimate the quantification of P in samples with low concentrations by about 70%, highlighting the importance of good experimental design and concern for the quality of the information generated.