Tropical Soil Samples Research Articles

Characterization, Hydraulic Conductivity and Compatibility of Mixtures of Tropical Soil and Bentonite for Barrier Usage Purpose

Compacted tropical soils have great potential to be used in barriers, once some technical issues are correctly addressed, including low hydraulic conductivity and compatibility to the disposed fluids. This paper involves a laboratorial study of the hydraulic conductivity of mixtures of a tropical soil sample and bentonite and also their compatibility to different chemical solutions. The experimental program consisted of (1) sample characterization, (2) hydraulic conductivity determination using a triaxial cell, and (3) compatibility assessment with different chemical solutions (HNO3 , NaOH, NaCl, and ethanol) using the modified Atterberg Limits. The characterization results revealed important changes in the index properties of the tropical soil sample as the result of the bentonite addition, especially in the plasticity, cation exchange capacity and free swelling. The hydraulic conductivity, in turn, experimented significant decreasing as the proportions of bentonite and confining pressure increased. The compatibility results showed a significant reduction in the plasticity of the samples when subjected to the chemical solutions, especially for the salt solution. In general terms, the addition of bentonite reduced the compatibility of the samples.

Factorial Designs Application to Study Enhanced Bioremediation of Soil Artificially Contaminated with Weathered Bonny Light Crude Oil through Biostimulation and Bioaugmentation Strategy

The objective of this study was designed to evaluate the effects of biostimulation and bioaugmentation amendment agents (NPK fertilizer, Tween 80 and mixed culture) on the bioremediation of tropical soil samples artificially contaminated with Weathered Bonny Light Crude Oil (WBLCO). Response Surface Methodology (RSM) with Box Behnken Design (BBD) was used with three levels and three factors of NPK fertilizer (2 - 6 g), Tween 80 (5 - 15 mg/l) and mixed culture (0.5 - 1.5 g/l) as independent variables and WBLCO removal as dependent variable (response) in a six weeks remediation period. The results showed that the rate of WBLCO removal generally increased with increase in the amount of NPK fertilizer, Tween 80 and mixed culture (biomass), respectively. A statistically significant (P < 0.0001) second-order quadratic regression model for WBLCO removal (using design-expert statistical program (v. 6.0.8)) with a coefficient of determination, R (=0.9996) was obtained. Numerical optimization technique based on desirability function was carried out to optimize the bioremediation process. The optimum values for biostimulation and bioaugmentation amendment agents to achieve a predicted maximum WBLCO removal of 84.88 percent were found to be: NPK fertilizer, 4.25 g; Tween 80, 10.22 mg/l and mixed culture, 0.46 g/l. At this optimum point, the observed WBLCO removal was found to be 83.79 percent. The statistical analyses and the closeness of the experimental results and model predictions show the reliability of the regression model and thus, biostimulation and bioaugmentation of indigenous microbial density and activity can reduce remediation period of petroleum hydrocarbon contaminated environment and subsequently the cost of remediation.

A Flexible Wall Permeameter for the Determination of the Water Permeability Function in Unsaturated Soils

Abstract This paper describes the development of a suction controlled flexible wall permeameter for the direct determination of the water permeability function in unsaturated soils. The new permeameter works with applied constant head or constant rate of flow, i.e., the common steady-state techniques. Total volume change of soil specimens during the test are monitored using a high resolution electronic scale. Numerical simulations were performed to evaluate the influence of factors such as flow velocity and matric suction distribution within the specimen and effects of sample height on such factors. Analyses of tests conducted on two tropical soil samples are used to evaluate conventional proposals for the determination of the water permeability function. It is shown that such proposals do not apply in the case of the materials tested and solutions to that are put forwards.

Purification and partial characterization of a detergent and oxidizing agent stable alkaline protease from a newly isolated Bacillus subtilis VSG-4 of tropical soil

An extracellular detergent tolerant protease producing strain VSG-4 was isolated from tropical soil sample and identified as Bacillus subtilis based on morphological, biochemical characteristics as well as 16S-rRNA gene sequencing. The VSG-4 protease was purified to homogeneity using ammonium sulphate precipitation, dialysis and sephadex G-200 gel permeation chromatography with a 17.4 purification fold. The purified enzyme was active and stable over a broad range of pH (8.0-11.0, optimum at 9.0) and temperature (40°C to 60°C, optimum at 50°C). The thermostability of the enzyme was significantly increased by the addition CaCl(2). This enzyme was strongly inhibited by PMSF and DFP, suggesting that it belongs to the serine protease superfamily. The purified VSG-4 alkaline protease showed remarkable stability in anionic (5 mM SDS) and ionic (1% Trion X-100 and 1% Tween 80) detergents. It retained 97±2% and 83.6±1.1% of its initial activity after 1 h preincubation in the presence of 1 % H(2)O(2) and 1 % sodium perborate, respectively. Furthermore, the purified enzyme showed excellent stability and compatibility with some commercial laundry detergents besides its stain removal capacity. Considering these promising properties, VSG-4 protease may find tremendous application in laundry detergent formulations.

Uso de ICP OES e titrimetria para a determinação de cálcio, magnésio e alumínio em amostras de solos

O crescente interesse dos laboratórios brasileiros de análise de fertilidade de solos pela espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) em detrimento da técnica de titrimetria deve-se à possibilidade da determinação simultânea de diferentes metais em uma ampla faixa de concentrações em extratos de interesse agronômico. Este estudo compara a precisão, reprodutibilidade e exatidão das duas técnicas de determinação de Ca, Mg e Al trocáveis extraídos com KCl 1 mol L-1 em amostras de solos. Foram analisadas 15 amostras de solos de referência, sendo três deles selecionados para avaliar a precisão e a reprodutibilidade das técnicas de determinação. A titrimetria e o ICP OES forneceram resultados mais reprodutíveis e precisos para a determinação de Ca, Mg e Al quando o extrato foi analisado sem diluição. As técnicas de determinação diferiram estatisticamente (p &lt; 0,05) pelo teste de identidade aplicado para comparação dos resultados de Ca, Mg e Al. Nas condições testadas, não se recomenda o uso de ICP OES para as determinações de Ca, Mg e Al trocáveis em amostras de solos.

PENURUNAN AKTIVITAS FOSFATASE ASAM Dl DAERAH PERAKARAN BEBERAPA JENIS TANAMAN AKIBAT PERLAKUAN KAPUR DAN LIMBAH INDUSTRI BERTIMAH HITAM

Heavy metals are potentially toxic to soil microorganims and are suggested to decrease soil enzymatic activities. Changes in activity of acid phosphatase in root-zones of some tropical plants treated with a lead-containing industrial waste were studied in a glasshouse experiment. Tropical soil sample (from Gedongmeneng and Banjaragung, Lampung) thoroughly treated with an electronics industrial waste at 0 to 40 ton ha·1 and lime at 0 or 5 ton CaC03 ha·1 were cultured with corn (Zea mays L.), amaranth (Amaranthus tricolor L), and green kyllinga (Cyperus kyllinga). Changes in acid phosphatase activity, soil Pb concentration, and soil pH were measured after a 4-week growing period. Soil analysis showed that the activity of acid phosphatase was higher in Banjaragung soil than that in Gedongmeneng soil except in those cultured with green kyllinga. The activity of acid· phosphatase was in general higher in the root-zone of corn than those in the root-zone of amaranth and green kyllinga.The activity of acid phosphatase in both soils decreased with waste addition regardless of plant grown. This was in a good correlation with the increase in soil available Pb as waste was added. However, the decrease in the activity of acid phosphate as the soil pH increased by lime or waste addition suggested that the decrease in the phosphatase activity with waste addition was driven by the increase in soil pH rather than by the increase in the soil available Pb With waste 3dclitton.

Relationship between chemical and mineralogical properties and the rapid response to acid load of soils in humid Asia: Japan, Thailand and Indonesia

It is essential to determine the relationship between soil chemical and mineralogical properties and soil response to acid load to understand the acid-neutralizing capacity and cation behavior of different ecosystems. For 46 soil samples from a subsurface horizon in humid Asia, that is, Japan, Thailand and Indonesia, exchangeable cations, total bases and oxalate-extractable Al (Alo) were determined, and acid titration was conducted to investigate the rapid soil response to acid load. The acid titration experiment indicated three types of soil response: (1) the release of base cations (particularly Ca and Mg) strongly correlated with exchangeable bases, which dominated the tropical soil samples, (2) the release of Al correlated with Alo content, which dominated the Japanese soil samples, (3) acid and anion adsorption in soil samples with low acid-neutralizing capacity. To gain further information on the source of soil alkalinity, a column experiment with HCl was conducted using eight selected soil samples in which first-order kinetics were assumed to simulate the time-courses of cation release. In the column experiment, the amounts of Ca and Mg released were close to the exchangeable amounts, and Alo dissolved more rapidly than Al in crystalline minerals. The rate constants of cation release were large for Ca and Mg, and small for Al, clearly indicating a difference between the exchange and dissolution reactions. Thus, rapid soil response to acid load differed among the soils. A cation exchange reaction was dominant in the tropical soils. In some tropical soils, Ca and Mg were present in exchangeable forms at a higher ratio in the total amounts and they were considered to be easily utilized by plants, but leached out from the soils. In the Japanese soils, including the Andisols, secondary mineral dissolution was conspicuous, resulting in a large acid-neutralizing capacity. In both the tropical and Japanese soils with low acid-neutralizing capacity, anion adsorption mainly contributed to acid neutralization.

Total carbon measurement in whole tropical soil sample

Soils are an important component in the biogeochemical cycle of carbon, storing about four times more carbon than biomass plants and nearly three times more than the atmosphere. Moreover, the carbon content is directly related on the capacity of water retention, fertility, among other properties. Thus, soil carbon quantification in field conditions is an important challenge related to carbon cycle and global climatic changes. Nowadays, Laser Induced Breakdown Spectroscopy (LIBS) can be used for qualitative elemental analyses without previous treatment of samples and the results are obtained quickly. New optical technologies made possible the portable LIBS systems and now, the great expectation is the development of methods that make possible quantitative measurements with LIBS. The goal of this work is to calibrate a portable LIBS system to carry out quantitative measures of carbon in whole tropical soil sample. For this, six samples from the Brazilian Cerrado region (Argisoil) were used. Tropical soils have large amounts of iron in their compositions, so the carbon line at 247.86 nm presents strong interference of this element (iron lines at 247.86 and 247.95). For this reason, in this work the carbon line at 193.03 nm was used. Using methods of statistical analysis as a simple linear regression, multivariate linear regression and cross-validation were possible to obtain correlation coefficients higher than 0.91. These results show the great potential of using portable LIBS systems for quantitative carbon measurements in tropical soils.

Tropical Soils and Landmine Detection—An Approach for a Classification System

Electromagnetic induction is the most common technique used in landmine detection. In soils exhibiting high magnetic susceptibility, metal detectors based on this method may become useless for landmine detection. Currently, no soil classification system exists that allows a prediction of negative effects on metal detectors. A total of 511 tropical soil samples from 15 different countries were investigated with regard to their susceptibility and some basic chemical parameters. Samples were separated into six classes based on their chemistry and their parent material. Soils derived from ultrabasic to basic parent material, on average, exhibited the highest susceptibilities because both rock types often contain a large amount of weathering‐resistant magnetite. Independent of the origin, the variance of the susceptibilities is large. Even in soils derived from rocks initially low in magnetite, high susceptibilities may develop with pedogenesis. This may be due to either the enrichment of residual magnetite or the formation of maghemite. In addition to a soil's parent material, its degree of weathering should also be considered in a proper classification scheme. We used a coefficient based on soil chemistry that correlates with the degree of weathering. Based on this coefficient and the soil parent material, we determined the median and the 90th percentile of the corresponding distribution of soil susceptibilities for each combination of the classification factors. The resulting classification scheme has the form of a matrix and may serve as a first approximation of expected susceptibilities when only parent material and degree of weathering are known.

Thermal analysis of brazilian tropical soils originating from different sources

Brazilian tropical Latosol soil samples were thermally analyzed associating thermogravimetric (TG) and differential scanning calorimetric (DSC) techniques under synthetic air or argon atmospheres. Rhodic eutrudox soils with forest vegetation, from unburnt and burnt cane plantations and that of a sandy phase having cerrado vegetation were investigated. From the organic soil fraction humic acids were extracted that decompose similarly to the commercial product, following the steps: i) adsorbed water, dehydrations, decarboxylations and release of organic molecules, ii) thermolabile decomposition fraction, iii) macromolecular organic matter and iv) residues. The DSC curves gave the corresponding peak for water release near 100 ºC and exothermic peaks at temperatures higher than 300 ºC, attributed to the combustion of thermolabile organic matter. The TG curves for all soil samples are more complex than those of the humic acids due to the inorganic components, being characterized by stages i) dehydration process, ii) thermolabile organic matter, iii) macromolecular organic domain and iv) oxide residues. These steps of decomposition correspond to three endothermic DSC peaks and one exothermic peak clearly shown under a synthetic air atmosphere, being attributed to the combustion of the macromolecular organic fraction near 300 ºC. The DSC curves from burnt and unburnt red Latosol soils from sugar cane cultivation showed more intense endothermic peaks than those of the forest. These thermal results show the influence of both the type and the organic matter contents on curve profiles, which are highly influenced by the soil mineral compositions and land-use activities, as well as the burning processes.

Using perlite as a substrate carrier for measuring microbial available phosphorus by respiration kinetics in soils

The release of CO2 by soil microorganisms after the addition of nitrogen and glucose in excess and calibration additions of phosphorus has successfully been used to assess microbial available P, assuming the native soil P pool is then limiting respiration. However, in P-fixing soils and soils with high P content, carbon can be exhausted before the available soil P pool. It is not possible to simply increase the amount of glucose as then the glucose concentration would be lethal for microorganisms. A modified method was tested where soil is mixed with perlite. It was hypothesised that perlite, having a high water holding capacity, would dilute the concentration of glucose, while maintaining the bioavailability of added nutrients, thus avoiding carbon limitation. Factorial combinations of amount of soil and perlite (both adjusted to −25 kPa water potential) were tested to examine if perlite as such had any effect on the respiration. Five tropical soil samples with a sharp gradient in P availability and one N-limited compost material were used. The method successfully reduced the risk of carbon limitation. Microbial indices, such as basal respiration, substrate-induced respiration and maximum P-limited respiration, were directly proportional to the amount of soil in the experiments but unrelated to the amount of perlite, showing that perlite did not affect microbial measurements.

Application of sequential injection–square wave voltammetry (SI–SWV) to study the adsorption of atrazine onto a tropical soil sample

Square wave voltammetry automated by sequential injection analysis was applied to determine the Freundlich adsorption coefficients for the adsorption of atrazine onto a clay rich soil. The detection limit in soil extracts was between 0.18 and 0.48 μmol L −1, depending on the medium used to prepare the extracts (0.010 mol L −1 KCl, CaCl 2 or HNO 3 and 0.0050 mol L −1 H 2SO 4), all of them conditioned in 40 mmol L −1 Britton–Robinson buffer at pH 2.0 in presence of 0.25 mol L −1 NaNO 3. Also in soil extracts the linear dynamic range was between 1.16 and 18.5 μmol L −1 (0.25–4.0 μg mL −1), with a sampling frequency of 190 h −1. The K f Freundlich adsorption coefficient was 3.8 ± 0.2 μmol 1−1/ n L n kg −1 in medium of 0.010 mol L −1 KCl or CaCl 2, but increased to 7.7 ± 0.1 and 9.0 ± 0.3 μmol 1−1/ n L n kg −1 in 0.010 mol L −1 HNO 3 and 0.0050 mol L −1 H 2SO 4, respectively. The increase of K f was related to the decrease of pH from 6.4–6.7 in KCl and CaCl 2 to 3.7–4.0 in presence of HNO 3 or H 2SO 4, which favors protonation of atrazine, facilitating electrostatic attractions with negative charges of the clay components of the soil. The 1/ n parameters were between 0.76 and 0.86, indicating that the isotherms are not linear, suggesting the occurrence of chemisorption at specific adsorption sites. No statistically significant differences were observed in comparison to the adsorption coefficients obtained by HPLC. The advantage of the proposed SI–SWV method is the great saving of reagent because it does not use organic solvent as in the case of HPLC (50% (v/v) acetonitrile in the mobile phase). Additionally the start up of SI–SWV is immediate (no column conditioning necessary) and the analysis time is only 19 s.

Compressibilidade de agregados de um Latossolo Amarelo da Amazônia em resposta ao potencial da água do solo

Normalmente a utilização agrícola dos solos é realizada com máquinas e implementos pesados que lhes causam compactação, responsável por afetar a disponibilidade de ar e de água para as plantas. O objetivo deste trabalho foi estudar o comportamento de agregados de Latossolo Amarelo da Amazônia sob compressão mecânica, submetidos a quatro níveis de umidade. Amostras de solo, úmidas e indeformadas, coletadas sob floresta, no horizonte A, a 10 cm de profundidade, e no horizonte B, a 150 cm de profundidade, foram utilizadas neste trabalho. No laboratório, essas amostras foram fragmentadas e peneiradas para obtenção de agregados de 2 a 3 mm de diâmetro, os quais foram colocados em equilíbrio com umidade de quatro potenciais matriciais para, após essa etapa, sofrerem uma compressão uniaxial com pressões de 32 a 1.000 kPa. Os resultados mostraram que a maior compressibilidade dos agregados, tanto para o horizonte A como para o B, ocorreu para o potencial matricial -32 kPa (umidade de 0,38 kg kg-1), enquanto a menor ocorreu para os potenciais -1 kPa e -1.000 kPa (umidade de 0,32 e 0,30 kg kg-1, respectivamente), indicando que esse solo não deve ser trabalhado com umidades próximas a 0,38 kg kg-1. A maior redução de volume dos agregados, tanto para o horizonte A como para o horizonte B, foi obtida para pressões mecânicas inferiores a 400 kPa, indicando que esses solos são bastante sensíveis à compactação, principalmente os agregados do horizonte A, possivelmente por terem melhores condições estruturais decorrentes do maior teor de matéria orgânica.

A novel actinomycete strain de-replication approach based on the diversity of polyketide synthase and nonribosomal peptide synthetase biosynthetic pathways

The actinomycetes traditionally represent one of the most important sources for the discovery of new metabolites with biological activity; and many of these are described as being produced by polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS). We present a strain characterization system based on the metabolic potential of microbial strains by targeting these biosynthetic genes. After an initial evaluation of the existing bias derived from the PCR detection in a well defined biosynthetic systems, we developed a new fingerprinting approach based on the restriction analysis of these PKS and NRPS amplified sequences. This method was applied to study the distribution of PKS and NRPS biosynthetic systems in a collection of wild-type actinomycetes isolated from tropical soil samples that were evaluated for the production of antimicrobial activities. We discuss the application of this tool as an alternative characterization approach for actinomycetes and we comment on the relationship observed between the presence of PKS-I, PKS-II and NRPS sequences and the antimicrobial activities observed in some of the microbial groups tested.

Cupric oxide oxidation products of tropical peat soils

Cupric oxide oxidation was used in order to examine the composition of lignin-derived phe nolic compounds and to estimate the degree of lignin alteration of tropical peat soils. KVila's pyrophosphate index (PPI) was used to assess the degree of decomposition of peat soils. Tropical peat soil samples were collected from soil profiles in three areas of Indone sia including of 11 sites, located in reclaimed / cultivated areas and under forest stands. Ox idation of these samples produced vanillyl and syringyl phenols as major components while cinnamyl phenol as a minor component. Phenolic aldehydes almost always predominated, followed by phenolic acids, ugh correlations between the yield of the oxidation products and PPI suggested that lignin-derived oxidation products could be used to describe the alteration of lignin in tropical peat soils, Based on the samples studied, two groups of lignin alteration with depth were recognized, which could be best described by acid to aldehyde ratios. The first group was observed in inland peat soils associated with a relatively more anaerobic history of alteration in the lower layers and the second group in marginal peat soils. The pattern of lignin alteration with depth also revealed that reclamation/cultivation mostly affected the surface layers to a depth of about 40 cm.

Microbial biomass and microcalorimetric methods in tropical soils

The type of organic matter (OM) plays an essential role in nutrient cycling in agricultural soil systems. Microbial activity in tropical soils was calorimetrically followed as a useful tool in this investigation. Tropical soil samples with different textures: Rhodic eutrudox (R), Typic eutrudox (V) and a Quartzipsamment (Q) from Brazil were amended with 25% cattle manure (E), municipal refuse compost (L), earthworm casts (H), the agrochemical trifluralin (T); (23 μg, equivalent dose of 1.25 kg ha −1) were explored. The microbial activity was determined by calorimetry and simultaneously by fumigation–extraction (microbial biomass carbon, C) to compare both methods. The results for R, Q, and V soils were: (212.04 A, 195.99 B, 204.47 A) for microbial biomass C and (0.692 B, 0.714 B, 0.784 A) for thermal effect with P<0.05, respectively, over a period of incubation of 91 days. The microbial activity of the modified soils decreases in the order: E, H, L and T. Both methods showed a coefficient of correlation r=0.7443 and the statistical probability of occurrence of the event, P<0.0001. From this correlation the utility of both methods for measuring the microbial activity in soils could be deduced.

The porosity of tropical soils and implications for geomorphological and pedogenetic processes and the movement of solutions within the weathering cover

As there is a lack of research carried into the relationship between soil porosity, pedogenesis and geomorphological processes, this study contains an overview of research results on this topic from the ‘soil and relief in the tropics’ project at the University of Cologne. The macroporosity (volume, poretypes, porefillings, etc.) of 641 tropical soil samples was examined using thin sections. The samples form part of a database project, which allows correlation of field and laboratory parameters. Analyses show a high macropore content even in fine-grained soils and subsoil and saprolite horizons. Pore fillings are mainly found in relic soils on old landscapes, yet the complete filling of pores seems to be the exception. Thus, the passage of solutions and suspensions within a soil cover has, in most cases, only minor restrictions. This suggests that the lateral transport of solutions, which may be crucial for the nutrient supply in areas with depleted soils, may be possible in tropical regions. Pore fillings may also be used to reconstruct polygenetic soil development. They allow a relative dating of soil-forming processes either by establishing a ‘pore stratigraphy’ or by identifying precipitates that are incompatible with each other in the same horizon.

Atributos de solos tropicais e a sorção de imazaquin

O imazaquin é um herbicida com caráter ácido, de uso intensivo no Brasil para controlar plantas daninhas associadas à cultura da soja. Estudou-se a sorção do imazaquin e a sua relação com a CTC, o pH e os teores de carbono orgânico (Corg) e argila de onze amostras de solos tropicais. Para a obtenção das isotermas de sorção, soluções de imazaquin nas concentrações de 0,53; 0,88; 1,45; 2,71 e 5,20 mg mL-1 foram preparadas em CaCl2 0,005 mol L-1 com a adição de um traçador radioativo (14C-imazaquin). O coeficiente de sorção (Kf) foi calculado a partir da equação linearizada de Freundlich. A sorção do imazaquin variou de baixa a moderada (Kf &lt;3,0), exceto no Gleissolo. O teor de Corg e o pH da solução foram os principais atributos do solo correlacionados com a sorção do imazaquin. A inclusão do teor de argila na análise de regressão aumentou em 20% a precisão do modelo. O imazaquin apresenta maior disponibilidade e, portanto, maior potencial de lixiviação em solos com valores de pH acima de 6 e com baixos teores de Corg e argila.

New thermal inducible Streptomyces phages isolated from tropical soils

Two new Streptomyces phages, øBP1 and øBP2, were isolated from tropical soil samples. These phages presented a large host range and developed both lytic and lysogenic responses in different Streptomyces species tested. Variations in the incubation temperature showed to be important in the development of the replication cycle. Increasing incubation temperature from 30oC to 42oC induced the lytic response of øBP2 and lysogenic of øBP1 in the host strain Streptomyces sp. WL6. øBP1 and øBP2 have icosahedral heads with long tails and were characterized in relation to morphology, G + C content, genome size and adsorption curve

First Co‐Operative Study on Four Tropical Soil Samples and One Lateritic Bauxite (Suriname) Proposed as Geochemical Reference Samples

Five samples from Suriname have been analysed for their chemical composition by 18 laboratories. The proposed reference samples are four soil samples and one lateritic bauxite. The samples were analyzed for major and minor elements as well as for 36 trace elements. More data are needed for better characterization of these samples, particularly for trace elements.