A erosão hídrica é uma das maiores causas de degradação dos solos no mundo, sendo responsável por perdas de solo superiores às taxas naturais de reposição. Objetivou-se estimar a distribuição espacial do potencial anual médio de perda de solo na bacia hidrográfica do Rio das Mortes (MG), com a finalidade de identificar as áreas mais susceptíveis à erosão hídrica e fornecer subsídio para a gestão dos recursos naturais na região. Para isso, foi aplicado o modelo RUSLE (Revised Universal Soil Loss Equation) implementado em ambiente SIG. O fator erosividade da chuva foi obtido com base em um modelo geográfico multivariado desenvolvido para o Brasil; o fator cobertura e manejo do solo foi derivado do mapa de uso do solo do Brasil; o fator erodibilidade do solo foi obtido pelo mapa de solos de Minas Gerais; e o fator topográfico foi obtido pelo modelo digital de elevação. Os mapas dos fatores foram combinados por meio de álgebra de mapas, originando o mapa de vulnerabilidade dos solos à erosão hídrica. Observou-se que 45,20% dos solos da bacia hidrográfica estudada apresentaram “Ligeira” vulnerabilidade à erosão hídrica. No entanto, 50,28% da área da bacia apresentaram perda de solo superior a 10 t ha-1 ano-1, o que indica a existência de áreas altamente susceptíveis à erosão hídrica e evidencia a necessidade de implementação de melhorias no manejo e práticas conservacionistas do solo.

Este estudo teve como objetivo avaliar o efeito da aplicação de diferentes taxas de efluente proveniente da Estação de Tratamento de Esgoto da Universidade Federal de Lavras nas características químicas do solo, na produtividade e na composição química da grama Esmeralda (Zoysia japonica). Avaliou-se o pH, condutividade elétrica (CE), matéria orgânica (MO), nitrogênio (N), fósforo (P), potássio (K), sódio (Na), cálcio (Ca) e magnésio (Mg) do solo e a produtividade de matéria seca e os teores foliares de N, P, K, Na, Ca e Mg da grama Esmeralda. O esquema experimental adotado foi o delineamento em blocos casualizados, com cinco tratamentos e quatro repetições. Os resultados obtidos foram submetidos à análise de variância, empregando-se o teste F, e as médias foram comparadas pelo teste de Tukey, ambos a 5% de probabilidade. Após análise, verificou-se que a aplicação do efluente nas diferentes taxas proporcionou aumento significativo nos valores de pH, K, Ca, Mg, e Na do solo e na produtividade de matéria seca e nos teores foliares de N, P, K e Na da grama Esmeralda. No entanto, recomenda-se que a aplicação do efluente seja avaliada por períodos de monitoramento superiores aos deste trabalho, visto que é importante observar as variações climáticas, as condições do solo e o efeito da aplicação do efluente em longo prazo.

Abstract In drip-irrigated systems, the understanding of the soil wetting pattern is essential in defining the area effectively irrigated, the spacing between the emitters and their installation depth, and the irrigation rate. Thus, this study aims to estimate soil hydraulic characteristics through inverse modeling of an analytical equation used in wetting bulb simulation based on soil moisture measurements obtained in the field. The parameters of the Gardner model, which describes the unsaturated soil hydraulic conductivity, and the van Genuchten model that describes the soil moisture retention curve, were estimated by inverse modeling techniques. The following options were considered: (A) estimating parameter β while considering the other parameters, Ko, θr, θs, α, n, and m, as known and obtained experimentally; (B) estimating parameters Ko and β while considering the experimental retention curve as known; (C) estimating parameters Ko, β, α, n, and m while considering the values of the θr and θs volumetric moisture as known; (D) estimating all the parameters of Gardner and van Genuchten models (Ko, θr, θs, α, n, and m). The results indicate that option D showed better concordance between the estimated and observed moisture values. Thus, the inverse modeling of the analytical equation is an important tool for irrigation design and management.

This study evaluated the efficiency of a constructed wetland system (CWS) in removing total coliforms (TC) and thermotolerant coliforms (ThC) of swine wastewater, as a complementary treatment to an anaerobic system. At Stage 1, the experimental system was combined using a vertical flow constructed wetland system (VFCWS) cultivated with Tifton 85 grass in series with a horizontal subsurface flow constructed wetland system (HFCWS1) cultivated with Taboa. In HFCWS1, the hydraulic detention times (HDT) were 4.7, 3.1 and 2.3 days and the surface application rates (SAR) were 294, 319 and 397 kg ha-1 d-1 of COD, in Phases I, II and III, respectively. At Stage 2, the experimental system was combined using a horizontal subsurface flow constructed wetland system (HFCWS2) cultivated with Tifton 85 grass, HDT were 6.1, 2.0 and 0.5 days and the SAR were 850, 656 and 6.34 kg ha-1 d-1 of COD, in Phases I, II and III, respectively. In Stage 1, it was verified that the VFCWS was more efficient in coliform removal when compared to HFCWS1. When only HFCWS were compared, coliform removal in Stage 1 was between 1 and 2 log units in HFCWS1. In the stage 2, the HFCWS2 was more limited, with the highest removal efficiencies during Phase I of 1.6 and 0.8 log units for TC and ThC, respectively. In general, the association resulted in efficiencies that ranged from 96.4 to 99.0% for TC, 94.2 and 97.6% for ThC, equivalent to the average removal of 1.2 to 2 log units, considered satisfactory.

This study investigated the adsorption capacity of the elements Chromium (Cr), Manganese (Mn) and Zinc (Zn) to marine algae Lithothamnium calcareum by means of adsorption kinetics and batch adsorption tests, with a view to the development of a simple technique for the treatment of effluents that have a high concentration of metal ions. The algae was sieved, washed and subjected to treatment. In the adsorption kinetics, 0.2 g of algae was weighed, an amount transferred to 125 mL Erlenmeyer flasks, to which was added 15 mL of solution with a concentration of 5 mg L-1 of the metal ion. The flasks were stirred at 60 rpm for 240 minutes. In batch adsorption, 0.2 g of algae was weighed, amount transferred to 125 mL Erlenmeyer flasks, to which was added 15 mL of solution with concentrations of 5, 10, 20, 50, 100, 250 e 500 mg L-1 of the metal ion. The flasks were stirred at 60 rpm for 24 hours. In the two tests, the supernatant solutions collected were centrifuged at 2000 rpm for 5 minutes and the equilibrium concentrations of metal ions were determined by atomic absorption spectrometry. It was found that, in 240 minutes of contact, the Lithothamnium calcareum removed 15.5% of Cr, 33.0% of Mn and 8.0% of Zn in solution; and that in 24 hours of contact, at a concentration of 5 mg L-1, it removed 0.4% of Cr, 52.5% of Mn and 92.6% of Zn; and, at a concentration of 500 mg L-1, it removed 20.0% of Cr, 22.6% of Mn and 40.8% of Zn.  The results showed that the Lithothamnium calcareum submitted to thermochemical treatment presented potential for use in the adsorption of Cr, Mn and Zn.