Tratamento de dados censurados em estudos ambientais

Due to the inherent limitations of the analytical methods of measurement, environmental exposure data often present observations described as below a certain detection limit, also called left-censored data. Censored data directly interferes in almost all types of statistical analyzes, including descriptive parameters, hypothesis testing, confidence intervals, correlations and regressions. In this work, we investigated the performance of the main classes of methods from major publications available in the literature, considering their advantages and limitations. Some criteria for selecting the best method of dealing with censored data are presented

Caracterização temporal do arsênio nos cursos d'água da bacia hidrográfica do Rio das Velhas, MG, Brasil, ao longo de uma década (1998 - 2007)

Arsenic, a metalloid with wide distribution in nature, can be found in natural environments in the forms of high toxicity. Monitoring conducted in the Basin of the das Velhas River, MG, demonstrates the occurrence of this metal in all sampling stations distributed over the water course and main tributaries. Thus, this study aims to evaluate the time trends of concentration of arsenic in water courses of the basin of das Velhas River, considering the data of twenty-nine monitoring stations from 1998 to 2007. The tests included the verification of seasonality, autocorrelation and temporal trend with the non-parametric tests of Mann-Kendall and Mann-Kendall seasonal. Eight sampling stations showed seasonality, with higher concentrations observed in rainy season. The autocorrelation was virtually nonexistent, which may be associated with low sample found in a monitoring program (three to six months). Only seven monitoring stations showed significant negative trend, indicating a reduction in the concentration of arsenic over the period studied. The results showed that the time trend studies have great relevance for the management of pollution of water resources from tracking data, providing subsidies for preventive and corrective measures differentiated between the stations and sampling periods of the year and also be used in evaluation of the effectiveness of these measures

Temporal characterization of Arsenic in das Velhas River hydrographic basin waters, MG, Brazil for one decade (1998 - 2007)

Arsenic, a metalloid with wide distribution in nature, can be found in natural environments in the forms of high toxicity. Monitoring conducted in the Basin of the das Velhas River, MG, demonstrates the occurrence of this metal in all sampling stations distributed over the water course and main tributaries. Thus, this study aims to evaluate the time trends of concentration of arsenic in water courses of the basin of das Velhas River, considering the data of twenty-nine monitoring stations from 1998 to 2007. The tests included the verification of seasonality, autocorrelation and temporal trend with the non-parametric tests of Mann-Kendall and Mann-Kendall seasonal. Eight sampling stations showed seasonality, with higher concentrations observed in rainy season. The autocorrelation was virtually nonexistent, which may be associated with low sample found in a monitoring program (three to six months). Only seven monitoring stations showed significant negative trend, indicating a reduction in the concentration of arsenic over the period studied. The results showed that the time trend studies have great relevance for the management of pollution of water resources from tracking data, providing subsidies for preventive and corrective measures differentiated between the stations and sampling periods of the year and also be used in evaluation of the effectiveness of these measures

Avaliação de risco ecológico na prevenção da poluição de produtos auxiliares do setor têxtil

O estudo teve como objetivo verificar a aplicabilidade da avaliação de risco ecológico na Prevenção da Poluição (P2) industrial. Treze produtos auxiliares utilizados pelas indústrias têxteis foram selecionados a partir das Fichas de Informação de Produtos Químicos â FISPQs. Os produtos auxiliares tiveram sua exposição e seu comportamento no meio aquático caracterizados nos programas E-FAST e EPIWin, considerando: potencial de bioconcentração (Kow e Fator de Bioconcentração), potencial de adsorção ao solo (Koc), biodegradabilidade e percentual de remoção após o tratamento de efluentes. O perigo à biota aquática foi quantificado a partir dos efeitos tóxicos agudos e crônicos a algas, invertebrados e peixes, considerando a relação quantitativa de estrutura e atividade (QSAR). O risco ecológico foi caracterizado pela interação entre a exposição e o perigo. Dos trezes compostos avaliados, três umectantes e um dispersante apresentaram risco ecológico suficiente para que seu uso fosse desaconselhado. Os compostos avaliados apresentaram baixo potencial de acumulação na biota (baixo Kow e fator de bioacumulação) e nos sedimentos (baixo Koc), porém baixo potencial de remoção via tratamento convencional de efluentes. A avaliação de risco ecológico permitiu a seleção, de forma rápida, barata e relativamente segura, de produtos menos poluentes, demonstrando potencial de aplicação em qualquer segmento industrial. Palavras-chave: ecotoxicologia, QSAR, poluição aquática, poluição industrial. ABSTRACT The purpose of this study is to demonstrate the application of ecological risk assessment for Pollution Prevention (P2). Thirteen textile industry auxiliary products were selected by their Material Safety Data Sheets â MSDS. The exposure and environmental behavior of substances were estimated by the softwares E-FAST and EPIWin, respectively, considering the following properties: bio-concentration potential (Kow and Bioconcentration Factor), soil absorption potential (Koc), biodegradability, and removal percentage after effluent treatment. The hazards to aquatic biota identified were the acute and chronic toxic effects to algae, aquatic invertebrates and fish, estimated through Quantitative Structure-Activity Relationship (QSAR), using the ECOSAR software. The ecological risk was determined considering the hazards and exposure of each substance, and demonstrated that three wetting agents and one dispersant have ecological risks in sufficient degree to justify their exclusion. The products evaluated presented low potentials for biota distribution (low Kow and bio-accumulation factor) and soil absorption (low Koc). The study demonstrates that ecological risk assessment is a low-cost, fast, and relatively reliable method for selecting products with lower pollution potentials that can be used by any industrial sector. Keywords: ecotoxicology, QSAR, aquatic pollution, industrial pollution. </div

Comparação entre parâmetros morfométricos de bacias hidrográficas gerados por dados SRTM e ASTER GDEM: estudo de caso para bacias do Vale do Jequitinhonha-MG

This study compared the influence of image resolution SRTM and ASTER in morphometric analysis of five sub-basins of the river Jequitinhonha: Ribeirão Caraíbas, Ribeirão Ilha do Pão, Ribeirão Prates, Ribeirão Pasmado e Ribeirão Santo Antônio. The hydrography of the sub-basins was extracted from both types of images. Morphometric variables were calculated from the sub-basins, including: perimeter, area, coefficient of compactness, total length of canals, slope and drainage density. It was possible to visualize the areas and perimeters of the sub-basins were observed did not differ significantly. Compactness all coefficient values obtained were higher for unit 1, indicating that the sub-basins are elongated shape. Comparing the lengths of channels between the SRTM and ASTER images, we can see a considerable difference. The values obtained in ASTER images tend to be higher, ie, due to a better resolution of the image resulting in a more detailed delineation of the basins. The results of the drainage density calculations show that the sub-watersheds have low density. It is notable that generate high resolution images in more detail in the definition of basins, however, in some cases, these details large, difficult to visualize and understand the basin generated.Pages: 5443-545

Artificial neural networks for performance prediction of full-scale wastewater treatment plants: a systematic review

Wastewater treatment plants (WWTPs) are complex systems that must maintain high levels of performance to achieve adequate effluent quality to protect the environment and public health. Artificial intelligence and machine learning methods have gained attention in recent years for modeling complex problems, such as wastewater treatment. Although artificial neural networks (ANNs) have been identified as the most common of these methods, no study has investigated the development and configuration of these models. We conducted a systematic literature review on the use of ANNs to predict the effluent quality and removal efficiencies of full-scale WWTPs. Three databases were searched, and 44 records of the 667 identified were selected based on the eligibility criteria. The data extracted from the papers showed that the majority of studies used the feedforward neural network model with a backpropagation training algorithm to predict the effluent quality of plants, particularly in terms of organic matter indicators. The findings of this research may help in the search for an optimum design modeling process for future studies of similar prediction problems. HIGHLIGHTS Machine learning approaches are effective for modeling wastewater treatment plants (WWTPs).; Artificial neural networks (ANNs) are the most employed in the wastewater treatment sector.; The various ANN structures used in the sector have not been adequately studied.; The systematic review focused on the use of ANN for performance prediction of WWTPs.; The findings are beneficial for future studies with similar prediction problems.

CHARACTERIZATION OF HEADWATERS PEATS OF THE RIO ARAÇUAÍ, MINAS GERAIS STATE, BRAZIL

Peatlands are soil environments that accumulate water and organic carbon and function as records of paleo-environmental changes. The variability in the composition of organic matter is reflected in their morphological, physical, and chemical properties. The aim of this study was to characterize these properties in peatlands from the headwaters of the Rio Ara&#231;ua&#237; (Ara&#231;ua&#237; River) in different stages of preservation. Two cores from peatlands with different vegetation types (moist grassland and semideciduous seasonal forest) from the Rio Preto [Preto River] headwaters (conservation area) and the C&#243;rrego Cachoeira dos Borges [Cachoeira dos Borges stream] (disturbed area) were sampled. Both are tributaries of the Rio Ara&#231;ua&#237;. Samples were taken from layers of 15 cm, and morphological, physical, and chemical analyses were performed. The 14C age and &#948;13C values were determined in three samples from each core and the vertical growth and organic carbon accumulation rates were estimated. Dendrograms were constructed for each peatland by hierarchical clustering of similar layers with data from 34 parameters. The headwater peatlands of the Rio Ara&#231;ua&#237; have a predominance of organic material in an advanced stage of decomposition and their soils are classified as Typic Haplosaprists. The organic matter in the Histosols of the peatlands of the headwaters of the Rio Ara&#231;ua&#237; shows marked differences with respect to its morphological, physical, and chemical composition, as it is influenced by the type of vegetation that colonizes it. The peat from the headwaters of the C&#243;rrego Cachoeira dos Borges is in a more advanced stage of degradation than the peat from the Rio Preto, which highlights the urgent need for protection of these ecosystems/soil environments

CHARACTERIZATION OF HEADWATERS PEATS OF THE RIO ARAÇUAÍ, MINAS GERAIS STATE, BRAZIL

Peatlands are soil environments that accumulate water and organic carbon and function as records of paleo-environmental changes. The variability in the composition of organic matter is reflected in their morphological, physical, and chemical properties. The aim of this study was to characterize these properties in peatlands from the headwaters of the Rio Araçuaí (Araçuaí River) in different stages of preservation. Two cores from peatlands with different vegetation types (moist grassland and semideciduous seasonal forest) from the Rio Preto [Preto River] headwaters (conservation area) and the Córrego Cachoeira dos Borges [Cachoeira dos Borges stream] (disturbed area) were sampled. Both are tributaries of the Rio Araçuaí. Samples were taken from layers of 15 cm, and morphological, physical, and chemical analyses were performed. The 14C age and δ13C values were determined in three samples from each core and the vertical growth and organic carbon accumulation rates were estimated. Dendrograms were constructed for each peatland by hierarchical clustering of similar layers with data from 34 parameters. The headwater peatlands of the Rio Araçuaí have a predominance of organic material in an advanced stage of decomposition and their soils are classified as Typic Haplosaprists. The organic matter in the Histosols of the peatlands of the headwaters of the Rio Araçuaí shows marked differences with respect to its morphological, physical, and chemical composition, as it is influenced by the type of vegetation that colonizes it. The peat from the headwaters of the Córrego Cachoeira dos Borges is in a more advanced stage of degradation than the peat from the Rio Preto, which highlights the urgent need for protection of these ecosystems/soil environments