Thomas Vincent Gloaguen

Sistema de extração seqüencial da solução na macro e microporosidade do solo

Various methodologies for soil solution sampling are available, but the proportion between gravitational and capilar water is usually unknown. In this study, a sequential extraction system of soil water for determining its chemical composition as a function of the soil porosity is presented. Soil columns were filled by air-dried clay-loam Ultisol. The columns were saturated with distilled water for 24 h, and then the soil solution was sampled at the base of the column by applying the suction equivalent to 0, 13.3, 26.7, 40.0, 53.3 and 66.6 kPa. Volume, pH, electrical conductivity, Na+, K+ and NO3- were measured in the solution. The high correlation (non linear; r2 = 0.998) between applied suction and soil matrix potencial, which was assessed by a tensiometer within the soil column, validated the proposed method for sequential soil solution extraction. Ionic concentrations were highly variable in different soil pore sizes, with low concentrations in the soil macroporosity, except for K+, which demonstrated the necessity of standardizing the sampling methodology to avoid incorrect estimation of concentration of solute in soil.

Metal accumulation in soils derived from volcano-sedimentary rocks, Rio Itapicuru Greenstone Belt, northeastern Brazil

Many countries and some Brazilian regions have defined the guideline values for metals in soils. However, the local geological features may be so heterogeneous that global or even regional guideline values cannot be applied. The Greenstone Belts are worldwide geological formations of vast extension, containing mineralization of various metals (e.g., Au, Cr, Ni, and Ag). Natural concentrations of soils must be known to correctly assess the impact of mining. We studied the soils of the Rio Itapicuru Greenstone Belt (RIGB), of Paleoproterozoic age, sampling at 24 sites (0-0.20m) in the areas not or minimally human impacted, equally distributed in the three units of the RIGB: Volcanic Mafic Unit (VMU), Volcanic Felsic Unit (VFU), and Volcano-clastic Sedimentary Unit (SU). The natural pseudo-total concentrations of Cr, Ni, Cu, Zn, Pb, Fe, and Mn were obtained by acid digestion (EPA3050b) both in the soil and the particle-size fractions (sand and clay+silt). The concentrations of metals in RIGB soils, especially Cr and Ni, are generally higher than those reported for other regions of Brazil or other countries. Even the sedimentary soils have relatively high metal values, naturally contaminated by the VMU of the RIGB; a potential impact on Mesozoic and Cenozoic sedimentary rocks located near the study region is highly expected. Metals are concentrated (80%) in the fine particle-size fraction, implying an easy availability through surface transport (wind and runoff). We introduced a new index, called the Fe-independent accumulation factor - AF-Fe, which reveals that 90-98% of the dynamics of the trace metals is associated with the iron geochemical cycle. We primarily conclude that determining the guideline values for different soil classes in variable geological/geochemical environment and under semiarid climate is meaningless: the concentration of metals in soils is clearly more related to the source material than to the pedogenesis processes.

Crescimento e estado nutricional de helicônia irrigada com água residuária tratada em casa de vegetação

In this study the growth and nutritional status of heliconias irrigated with treated wastewater of domestic origin associated with chemical fertilizers (NPK) was studied. The experiment was conducted in a greenhouse utilizing plants of heliconia Golden Adrian. The experiment was installed in 5 x 3 + 1 factorial scheme consisting of five depths of irrigation water (equivalent to 60, 80, 100, 120 and 140% of class A pan evaporation - ECA), three types of water (wastewater (AR), rainwater (AP) and a mixture of 50% AR + 50% AP) and control (soil without fertilizer and receiving rainwater corresponding to 100% ECA). The experimental design was in randomized blocks with five repetitions. The use of AR and larger depths of irrigation provided increases in evaluated parameters of growth. The levels of macronutrients in the leaves of plants irrigated with AR were similar to plants that received AP. The use of AR and AP resulted in increases in the content of micronutrients in leaves, especially Fe and Mn, above the levels recommended for the crop.

Composição química da solução do solo nas diferentes classes de poro do solo

A composicao quimica da solucao do solo pode ser considerada indicadora da presenca de nutrientes ou contaminantes no solo. Para analisar a variacao dessa composicao nos poros do solo, utilizou-se um sistema de extracao sequencial da solucao do solo em diferentes classes de diâmetro de poro. Colunas de PVC foram construidas e preenchidas com terra fina seca ao ar de um Cambissolo Haplico distrofico, e irrigadas com agua destilada (T1), efluente de estacao de tratamento de esgoto sanitario EETE (T2) e EETE + 1,2 g L-1 CaSO4 (T3), aplicando lâminas de 150 e 300 mm. Antes da irrigacao e apos cada lâmina, aplicaram-se na base de cada coluna os seguintes potenciais: 0, 13,3, 26,7, 40,0 e 53,3 kPa para extracao e coleta da solucao do solo nas faixas de poros: O > 76,2 µm, 44,6 44,6 m). Todos os dados foram ajustados significativamente ao modelo linear Y = a - b.log(X), onde Y e o atributo avaliado e X o diâmetro de poro do solo. Embora a concentracao de NO3-na microporosidade supere o valor limite [NO3-]lim para agua doce potavel (Classe 1), a baixa concentracao na macroporosidade (sempre inferior a [NO3-]lim/4) limita o risco de contaminacao por lixiviacao. Constatou-se tambem que a adicao de gesso promove a reducao da concentracao de NO3-e de Na+ no solo.