Cristóvão Fernandes

Copper and zinc accumulation and fractionation in a clayey Hapludox soil subject to long-term pig slurry application

Pig slurry (PS) recycling as fertilizer is commonly practiced as an option for minimizing livestock waste. Successive PS applications on the soil can lead to crop toxicity and environmental risk. Despite extensive investigation of macronutrient behavior, the fate of trace metals remains uncertain and only a few long-term field studies have been reported to date. This study was designed to assess the impact of 11-year continuous PS spreading on Cu and Zn accumulation and fractionation in a Brazilian clayey Hapludox soil. Three different PS application rates--50, 100 and 200m3 ha(-1)year(-1)--were monitored at six soil depths in comparison to a non-amended control soil. The modified Geological Survey of Canada sequential extraction protocol was applied. A statistically significant increase in Cu and Zn total concentration (assessed by the sum of fractions) was noted only within the 0-5 cm soil layer for the 50 and 100 m3 ha(-1) year(-1) (PS50 and PS100) treatments, and up to 10-15 cm for the 200 m3 ha(-1)year(-1) (PS200) treatment. The mass balance, determined for the 22 PS amendments over the period, confirmed the overall exogenous Cu and Zn accumulation within the surface layers. More than 70% of the natural heavy metal content was originally in the residual fraction. However, this was the only fraction not influenced by the PS amendments. After PS input, the exogenous Cu was mainly detected in the fraction bound to organic matter (66.4%) within the PS200 0-5 cm soil layer. Exogenous Zn was mainly distributed between the adsorbed fraction (36.7%) and the organic matter fraction (32.0%) within the PS200 0-5 cm layer.

Estimating P loss potencial by P Index

Phosphorus (P) is the limiting element of eutrophication. The P losses by runoff can affect water quality. The objective of this study was to estimate the P loss from soil to water through the P Index method with Brazilian experimental data and to compare this estimated data with the analytically determined soluble P, particulate P and total P. The P Index was developed in the United States of America, in 1993, and has been widely used in several versions. In this study, four P Index versions were analysed using experiments from southern Brazil. The estimated P Indices were compared with the P concentration and loss in runoff. Besides the correlation analysis, the stepwise regression was used to analyze the influence of different components of the PI in P concentration and loss in the water. The Original P Index version was more significant with P concentration in runoff. The regression analyses indicated that the soil erosion factor did not influence P loss from soil to water.

Runoff from soils under different management and simulated rainfall regimes in southern Brazil

Abstract Surface runoff and drainage were evaluated for southern Brazilian soils subjected to different rainfall intensities and management practices. Soils received up to four applications of simulated rainfall in sequences with one application per day. Seven lysimeters, each of 1 m3 volume, were used to measure drainage volume, with measurement of initial and final water content, times at which surface runoff and lysimeter drainage began, and the volume rates of flow. At the end of the second test, soils were subjected to two levels of disturbance (denoted by low and high soil movement) by opening furrows. These cultivation treatments altered the times at which lysimeter surface runoff and drainage were initiated, the rates of surface runoff, the final infiltration and internal drainage, and the components of the water balance throughout the series of trials. Mean times at which surface runoff was initiated in lysimeters subjected to greater soil disturbance were longer than those with little soil disturbance. Final infiltration rates were greater in lysimeters with little soil disturbance. It was also found that lysimeter surface runoff generation was influenced by the state of development of maize grown in the lysimeter. Editor D. Koutsoyiannis; Associate editor G. Mahé

Radical change of Zn speciation in pig slurry amended soil: Key role of nano-sized sulfide particles

Spreading livestock manure as fertilizer on farmlands is a widespread practice. It represents the major source of heavy metal(loid)s (HM) input in agricultural soils. Since zinc (Zn) is present at high concentrations in manure, it poses special environmental concerns related to phytotoxicity, groundwater contamination, and introduction in the food chain. Therefore, investigations on the fate and behavior of manure-borne Zn, when it enters the soil environment, are necessary to predict the environmental effects. Nevertheless, long-term field studies assessing Zn speciation in the organic waste matrix, as well as within the soil after manure application, are lacking. This study was designed to fill this gap. Using SEM-EDS and XAS analysis, we reported the following new results: (i) ZnS made up 100% of the Zn speciation in the pig slurry (the highest proportion of ZnS ever observed in organic waste); and (ii) ZnS aggregates were about 1-μm diameter (the smallest particle size ever reported in pig slurry). Moreover, the pig slurry containing ZnS was spread on the soil over an 11-year period, totaling 22 applications, and the resulting Zn speciation within the amended soil was analyzed. Surprisingly, ZnS, i.e. the only species responsible for a nearly 2-fold increase in the Zn concentration within the amended soil, was not detected in this soil. Based on SEM-EDS and XAS observations, we put forward the hypothesis that Zn in the pig slurry consisted of nano-sized ZnS crystallites that further aggregated. The low stability of ZnS nanoparticles within oxic and complex environments such as the studied soil was the key explanation for the radical change in pig slurry-borne Zn speciation after long-term amendments.

Nonstationarity in determining flow-duration curves aiming water resources permits

Anthropogenic activities in the watersheds are responsible for land use changes, thus interfering in its rivers flows regimes. Consequently, changes occur in the hydrological series statistical moments, a condition known as nonstationarity. The use of a nonstationary time series can cause relevant errors, misleading and biasing the ongoing analyses. In this manner, this paper evaluates the possible effects of nonstationarity over water availability for water resources permits in six Brazilian gauges, considering the Q95% as reference. Median and seasonal flow-duration curves are employed in two distinct periods, before and after 1969, for all the series. Results suggested that Q95% increased in four gauges and reduced in the remainder two. Moreover, important changes were observed in intermediate flow-durations, suggesting that the variations are not limited to the series extreme values

Não Estacionariedade na Construção de Curvas de Permanência com Vistas à Outorga de Recursos Hídricos

Anthropogenic activities in the watersheds are responsible for land use changes, thus interfering in its rivers flows regimes. Consequently, changes occur in the hydrological series statistical moments, a condition known as nonstationarity. The use of a nonstationary time series can cause relevant errors, misleading and biasing the ongoing analyses. In this manner, this paper evaluates the possible effects of nonstationarity over water availability for water resources permits in six Brazilian gauges, considering the Q95% as reference. Median and seasonal flow-duration curves are employed in two distinct periods, before and after 1969, for all the series. Results suggested that Q95% increased in four gauges and reduced in the remainder two. Moreover, important changes were observed in intermediate flow-durations, suggesting that the variations are not limited to the series extreme values

Curvas de permanência de qualidade da água como subsídio para o enquadramento de corpos d'água a partir de modelagem matemática em regime não permanente

Modelos matematicos de qualidade de agua tem sido utilizados como ferramentas para o planejamento e a gestao de recursos hidricos em diversos paises. Em geral, em rios, as analises sao baseadas em simulacoes considerando condicoes de escoamento de regime permanente. Entretanto, bacias urbanas apresentam uma intensa dinâmica, consequente de mecanismos de uso e ocupacao do solo, capaz de induzir processos de poluicao que requerem uma analise que contemple aspectos fisicos, quimicos e biologicos. A abordagem em estado nao-permanente permite descrever de forma mais realista estas caracteristicas, e associar de maneira consistente as interacoes de qualidade e quantidade de agua, em funcao da representacao hidrodinâmica de um sistema. Esta pesquisa contribui para esse entendimento usando como estudo de caso o rio Iguacu, localizado na regiao metropolitana de Curitiba, ao analisar potenciais impactos de avaliacoes de qualidade baseadas em uma comparacao de condicoes de estado permanente e nao-permanente como forma de subsidiar elementos para a gestao do uso da agua. O modelo aqui proposto (SIHQUAL), desenvolvido em modulos tradicionais, utiliza metodos de diferencas finitas explicitas para solucao das equacoes de Saint-Venant integradas com a equacao de transporte de massa, para demanda bioquimica de oxigenio (DBO) e oxigenio dissolvido (OD). Para a analise de qualidade da agua utilizou-se do conceito de curva de permanencia de qualidade da agua. Observou-se principalmente que modelos em estado transiente oferecem maior flexibilidade e uma distinta perspectiva para o gerenciamento, em especial quanto a aplicacao dos instrumentos de gestao de recursos hidricos, como o enquadramento.

Redistribution of methane emission hot spots under drawdown conditions

In the context of reservoirs, sediment trapping, and aquatic greenhouse gas (GHG) production, knowledge about the distribution of hot and low spots is essential for improved measurement strategies. It is also a key to a precise assessment of the GHG emissions of each reservoir. Large numbers of reservoirs are used mainly for hydroelectric power generation and, hence, affected by strong changes in water level. Drawdown events may lead to significant changes in spatial sediment and organic carbon distribution and, consequently, strongly alter the GHG emission patterns of the water body. We combined hydroacoustic sediment classification, sediment magnitude detection, and ebullition flux assessment with in-situ pore water investigations and sediment coring to detect ebullition distribution patterns after strong reservoir drawdown. The research was conducted in the Capivari Reservoir in the southeast of Brazil, which was affected by up to 15 m of drawdown within the last 10 years. Results show severe changes in sediment accumulation and composition. The focusing of sediment divides the reservoir in extreme hot and low spots. Methane pore water concentrations are highly correlated with acoustic backscatter values (r2 = 0.97) as well as with the organic carbon content (r2 = 0.55) and allow for a precise detection of the newly created emission patterns. Highly productive sediment could be acoustically distinguished from non-productive areas. Only 23.6% of the reservoir surface produced 64% of the detected bubbles. An organic carbon content in the sediment of 2.4% was found to be a prerequisite for the formation of GHG emission hot spots. These findings may help to complement the still insufficient knowledge of methane ebullition fluxes from reservoirs with changing water levels.

Statistical validity of water quality time series in urban watersheds

The water resources quality continuous monitoring is a complex activity. It generates extensive databases with time series of many variables and monitoring points that require the application of statistical methods for the information extraction. The application of statistical methods for frequency analysis of time series is linked to attending of the basic assumptions of randomness, homogeneity, independence, and stationarity. However, despite its importance, the verification of these assumptions in water quality literature is unusual. Therefore, the present study tests the Upper Iguaçu basin water quality time series against the mentioned hypotheses. Rejection was observed in 15%, 26%, 51% e 31% for randomness, homogeneity, independence, and stationarity, respectively. The results evidenced the strong relation between monitoring strategy, data assessment and meeting of basic statistical assumptions for the analysis of water quality time series. Even with the existence of possible solutions for addressing those issues, the standard monitoring strategies, with irregular frequencies and lack of representativeness in relation to other periods, beyond commercial, act as an obstacle to their implementation.

Verification of Saint-Venant equations solution based on the lax diffusive method for flow routing in natural channels

Hydrodynamic models, based on the Saint-Venant equations, represent the transient flow in water systems, and simulate flow routing over time and space. Several numerical solutions have been applied to these expressions, but often differences are found in results among distinct procedures, considering that all numerical approaches have limitations. Natural channels are characterized by a dynamic flow behavior, with multiple uses of water and changes in morphology, which occur naturally and by human influence. In this context, this study seeks to complement the understanding of different assumptions and approximations for solution of the Saint-Venant equations, verifying results of the Lax diffusive scheme and comparing with HEC-RAS model. The case study consists of a river that covers an urban area (River Iguaçu, located in Curitiba, Paraná). Comparing the observed and simulated hydrographs, it was possible to assess that how the equations are solved, which determines the type of boundary conditions to be used, that may contribute to differences in simulated flows. Additionally, the calibration strategy and the hypothesis of trapezoidal cross-sections produced positive results. The development of this research should also encourage the progress in solving the hydrodynamic model trough the Lax diffusive scheme, particularly concerning computational efficiency. Explicit schemes, although more sensitive to the time step, have the advantage of simplicity to implement, which could be beneficial in the study of complex systems such as urban rivers.