Célia Regina Montes

Reclaimed wastewater: Impact on soil-plant system under tropical conditions

This study investigated the ionic speciation of reclaimed urban wastewater (RWW), and the impact of increasing RWW irrigation rates on soil properties and plant nutrition under field conditions. Most RWW elements (>66%) are readily available as NH(4)(+), Ca(2+), Mg(2+), K(+), SO(4)(2-), Cl(-), H(3)BO(3), Mn(2+) and Zn(2+), but in imbalanced proportion for plant nutrition. Lead, Cd, Cr and Al in RWW are mostly bounded with DOM or OH(-).(.)Irrigation with RWW decreased soil acidity, which is beneficial to the acidic tropical soil. Although RWW irrigation builds exchangeable Na(+) up, the excessive Na(+) was leached out of the soil profile after a rainy summer season (>400 mm). Benefits of the disposal of RWW to the soil under tropical conditions were discussed, however, the over irrigation with RWW (>100% of crop evapotranspiration) led to a nutritional imbalance, accumulating S and leading to a plant deficiency of P and K.

Soil exchangeable cations, sugarcane production and nutrient uptake after wastewater irrigation

A irrigacao com aguas residuarias pode beneficiar as culturas agricolas com agua e nutrientes essenciais (especialmente nitrogenio), afetando tambem a quimica do solo. Os efeitos da irrigacao por 16 meses com efluente de esgoto na produtividade, extracao de nutrientes pelo colmo, e nos atributos quimicos do solo, foram estudados em um Latossolo cultivado com cana-de-acucar (Saccharum spp.), situado em Lins, Sao Paulo. As parcelas irrigadas receberam 50% do N mineral recomendado e 100, 125, 150 ou 200% da demanda hidrica da cultura, enquanto o controle nao recebeu N mineral e nem agua. As elevadas concentracoes de sodio do efluente ocasionaram um aporte de Na de ate 6,2 t ha-1, juntamente com ate 1497 kg N ha-1 e 628 kg K ha-1. Todas as parcelas irrigadas, com excecao do T125, apresentaram maior produtividade (ate 247 t ha-1) do que o controle (153 t ha-1). Quantidades expressivas de N (ate 597 kg ha-1) e de K (ate 546 kg ha-1) foram exportadas atraves da colheita da cultura. As adicoes de nutrientes e de Na via irrigacao nao foram compensadas pelo crescimento da planta, ocasionando uma baixa recuperacao de N, P, Ca e Na, evidenciando uma excessiva fertilizacao da planta (N). Alteracoes no solo de pH, H + Al, Ca, Mg e K, foram de pequena magnitude, enquanto houve acumulo de Na trocavel ao longo do tempo nos tratamentos irrigados. A irrigacao com aguas residuarias devera adquirir importância crescente, exigindo atencao detalhada ao balanco entre o aporte de nutrientes via irrigacao e as quantidades requeridas para a otimizacao da produtividade da cultura.A irrigacao com aguas residuarias pode beneficiar as culturas agricolas com agua e nutrientes essenciais (especialmente nitrogenio), afetando tambem a quimica do solo. Os efeitos da irrigacao por 16 meses com efluente de esgoto na produtividade, extracao de nutrientes pelo colmo, e nos atributos quimicos do solo, foram estudados em um Latossolo cultivado com cana-de-acucar (Saccharum spp.), situado em Lins, Sao Paulo. As parcelas irrigadas receberam 50% do N mineral recomendado e 100, 125, 150 ou 200% da demanda hidrica da cultura, enquanto o controle nao recebeu N mineral e nem agua. As elevadas concentracoes de sodio do efluente ocasionaram um aporte de Na de ate 6,2 t ha-1, juntamente com ate 1497 kg N ha-1 e 628 kg K ha-1. Todas as parcelas irrigadas, com excecao do T125, apresentaram maior produtividade (ate 247 t ha-1) do que o controle (153 t ha-1). Quantidades expressivas de N (ate 597 kg ha-1) e de K (ate 546 kg ha-1) foram exportadas atraves da colheita da cultura. As adicoes de nutrientes e de Na via irrigacao nao foram compensadas pelo crescimento da planta, ocasionando uma baixa recuperacao de N, P, Ca e Na, evidenciando uma excessiva fertilizacao da planta (N). Alteracoes no solo de pH, H + Al, Ca, Mg e K, foram de pequena magnitude, enquanto houve acumulo de Na trocavel ao longo do tempo nos tratamentos irrigados. A irrigacao com aguas residuarias devera adquirir importância crescente, exigindo atencao detalhada ao balanco entre o aporte de nutrientes via irrigacao e as quantidades requeridas para a otimizacao da produtividade da cultura.

GENESIS, MINERALOGY AND GEOCHEMISTRY OF KAOLIN DEPOSITS OF THE JARI RIVER, AMAPÁ STATE, BRAZIL

Kaolin samples from the Jari deposit (Amazon region) were studied using various techniques to characterize its structural and crystallochemical aspects, and to establish its origin and evolution. A profile 60 m thick was selected in a kaolin mine (Morro do Felipe) located at the banks of the Jari river. Despite the great thickness of the deposit and the variety of kaolin types, the mineralogical composition is rather homogeneous and is mainly kaolinite associated with gibbsite and small amounts of quartz, anatase, goethite and hematite. The field observations and the morphological analysis indicate the existence of sedimentary features throughout the whole profile except for the upper aluminous clayey layer (Belterra Clay). This is evidence that the Rio Jari kaolin deposit originated from sedimentary material, the Alter do Chão Formation. The presence of alternating clay and sandy layers is explained by sedimentation processes with great depositional energy variation. Thus, the accumulation of thick clay layers was related to a low-energy phase, and during the high-energy phases, the deposition process led to the accumulation of sandy materials, constituted essentially of quartz and showing strong textural and structural variation. Later on, periods of hydromorphy were responsible for iron removal and consequently for the bleaching of the sedimentary formation. The crystallinity data show an increase of the structural disorder toward the surface associated with an increase in the amount of structural Fe in the kaolinite. The Rio Jari kaolin deposits should be considered as having originated from kaolinitic clay sediments of the Alter do Chão formation (protore) that was submitted to intensive lateritic weathering processes.

Quantification of total carbon in soil using laser-induced breakdown spectroscopy: a method to correct interference lines

The C cycle in the Brazilian forests is very important, mainly for issues addressed to climate changes and soil management. Assessing and understanding C dynamics in Amazonian soils can help scientists to improve models and anticipate scenarios. New methods that allow soil C measurements in situ are a crucial approach for this kind of region, due to the costs for collecting and sending soil samples from the rainforest to the laboratory. Laser-induced breakdown spectroscopy (LIBS) is a multielemental atomic emission spectroscopy technique that employs a highly energetic laser pulse for plasma production and requires neither sample preparation nor the use of reagents. As LIBS takes less than 10 s per sample measurement, it is considered a promising technique for in situ soil analyses. One of the limitations of portable LIBS systems, however, is the common overlap of the emission lines that cannot be spectrally resolved. In this study a method was developed capable of separating the Al interference from the C emission line in LIBS measurements. Two typical forest Brazilian soils rich in Al were investigated: a spodosol (Amazon Forest) and an oxisol (Atlantic Forest). Fifty-three samples were collected and analyzed using a low-resolution LIBS apparatus to measure the intensities of C lines. In particular, two C lines were evaluated, at 193.03 and 247.86 nm. The line at 247.86 nm showed very strong interference with Fe and Si lines, which made quantitative analysis difficult. The line at 193.03 nm showed interference with atomic and ionic Al emission lines, but this problem could be solved by applying a correction method that was proposed and tested in this work. The line at 247.86 was used to assess the proposed model. The strong correlation (Pearsons coefficient R=0.91) found between the LIBS values and those obtained by a reference technique (dry combustion by an elemental analyzer) supported the validity of the proposed method.

Use of pedological maps in the identification of sensitivity of soils to acidic deposition: application to Brazilian soils

The pedogeochemical maps present the spatial distribution of soils according to crystalochemical parameters (clay fraction) and physic-chemical aspects of the sorting complex (CEC and BS). These maps are adequate tool for environmental studies and particularly, for the analysis of the terrestrial ecosystem sensibility to acidic deposition. The pedogeochemical maps of the Brazilian soils, elaborated using FAO Soil World Map, allowed establishing the soil distribution according to 5 classes of vulnerability to acidic deposition, as defined by Stockholm Environmental Institute (SEI). From these maps, it is observed that about 50% of the Brazilian soils are high vulnerable to acidic deposition and can be included within the most sensitive class. This group is formed by well-developed and mature soils, constituted by clay minerals of kaolinite type associated with variable amount of gibbsite. About 8% of the soils can be considered as the least sensitive class. They correspond to Topomorphic Vertisols (Vertissolo, Embrapa 1999), Planosols (Planossolo, Embrapa 1999) and saline soils. Finally, the remaining soils represent the balanced media that dominate the northeastern semiarid zones and the south and northeastern subtropical zones.

Nutrients and nonessential elements in soil after 11 years of wastewater irrigation.

Irrigation of citrus (Citrus aurantium L. × Citrus paradise Macf.) with urban reclaimed wastewater (RWW) can be economical and conserve fresh water. However, concerns remain regarding its deleterious effects on soil quality. We investigated the ionic speciation (ISP) of RWW and potential impacts of 11 yr of irrigation with RWW on soil quality, compared with well-water (WW) irrigation. Most of nutrients (∼53-99%) in RWW are free ionic species and readily available for plant uptake, such as: NH(4+), NO(3-), K(+), Ca(2+), Mg(2+), SO(4)(2-), H(3)BO(3), Cl(-), Fe(2+), Mn(2+), Zn(2+), Co(2+), and Ni(2+), whereas more than about 80% of Cu, Cr, Pb, and Al are complexed with CO(3-), OH(-), and/or organic matter. The RWW irrigation increased the availability and total concentrations of nutrients and nonessential elements, and soil salinity and sodicity by two to three times compared with WW-irrigated soils. Although RWW irrigation changed many soil parameters, no difference in citrus yield was observed. The risk of negative impacts from RWW irrigation on soil quality appears to be minimal because of: (i) adequate quality of RWW, according to USEPA limits; (ii) low concentrations of metals in soil after 11 yr of irrigation with RWW; and (iii) rapid leaching of salts in RWW-irrigated soil during the rainy season.

Synthesis and Characterization of Boehmites Obtained from Gibbsite in Presence of Different Environments

In this study, results related to boehmite synthesis by hydrothermal processes starting from a Bayer commercial gibbsite are reported. The processes have been conducted from aqueous suspensions with initial acidic or alkaline pH, without or with acetate ion, at 160oC for 72h to 168h. The final materials were characterized by X-ray diffraction (XRD), thermal methods (DTA and TGA) and scanning electron microscopy (SEM). The influence of the synthesis conditions on the morphology of the boehmite crystals obtained from the gibbsite at different hydrothermal processes are discussed.

Structure of Humic Substances from Some Regions of the Amazon Assessed Coupling 3D Fluorescence Spectroscopy and CP/PARAFAC

The Amazon rainforest presents one of the greater biodiversity in the world and a huge and dynamic carbon reservoir, both in the vegetation and in the soil pools, so it is an attractive subject of study. In the present paper, humic acids from a toposequence of an Oxisol-Spodosol system associated with kaolin was studied using fluorescence emission-excitation matrix combined with parallel factor analysis. The combined techniques allowed to assess the intensities of the two different fluorophores associated with humic acid with core consistency diagnoses of 84.2%. The results for the Humiluvic Spodosol seem to corroborate the model of the supramolecular structure of humic acid, because the intensity ratio of fluorophores does not remain in the profile. Therefore, the use of these combined techniques can provide information about the transformation processes of humic substances in soils, becoming an interesting analytical tool for studying these substances of different soils.

Parasitological risk assessment from wastewater reuse for disposal in soil in developing countries

The purpose of this work is to analyze the parasitological risks of treated wastewater reuse from a stabilization pond in the city of Piracicaba, in the State of São Paulo (Brazil), and the level of treatment required to protect public health. Samples were taken from raw and treated wastewater in stabilization ponds and submitted to a parasitological, microbiological and physicochemical analysis. The study revealed on treated wastewater the presence of Ascaris sp. and Entamoeba coli with an average density of 1 cysts L(-1) and 6 eggs L(-1), respectively. For Ascaris, the annual risks of infection due to the accidental ingestion of wastewater irrigation were 7.5 × 10(-2) in 208 days and 8.7 × 10(-2) in 240 days. For Total Coliforms and Escherichia coli in treated wastewater, the average density was 1.0 × 10(5) MPN/100 ml and 2.7 × 10(4) MPN/100 ml respectively, representing 99% and 94% removal efficiency, respectively. For BOD, COD, TS and TSS removal efficiency was 69, 80, 50 and 71%, respectively. The removal efficiency for nitrogen; ammonia nitrogen and total phosphate was 24, 19 and 68%, respectively. The average density of helminths eggs in treated wastewater is higher compared to the density of the limit value of ≤1 egg L(-1) and tolerable risk is above the level recommended by the World Health Organization. Multiple barriers are necessary for the reduction of organic matter, chemical contaminants and parasites from treated wastewater. Standards for the sanitary control of treated wastewater to be reused in agricultural irrigation areas should be compiled for developing countries in order to minimize public health risks.

Cation exchange capacity of an oxisol amended with an effluent from domestic sewage treatment

The addition of Na-rich anthropogenic residues to tropical soils has stimulated the scientific community to study the role of sodium in both the soil solution and the exchange complex. In this study, several different methods were used to calculate the concentration of exchangeable and soluble cations and this data was then used to establish correlations between the level of these cations and both the accumulation of various elements and the dry weight of maize grown in a greenhouse under different conditions. In the closed environments of the pots, the most suitable method for calculating the effective cation exchange capacity (ECEC) was the cation exchange capacity calculated by cations removed with barium chloride solution (CECS). Then again, the actual cation exchange capacity (CECA) should be measured by using Mg adsorption to prevent ionic force from influencing electric charges. A strong positive correlation was obtained between the concentrations of Na in the 1:2 soil:water extracts and the accumulation of Na in the maize plants, indicating saline or double acid extractors are not needed when monitoring the Na concentration only.