Brazilian Soils Research Articles

Environmental and agronomic assessment of soil conditioners produced from bauxite residue and oil palm wastes

Soil conditioner is class of products used to enhance physics, physicochemical or soil biological activities, being able to recover disturbed or nutritional unbalanced soils. The formulation of a soil conditioner composed by bauxite residue (BR), and organic oil palm wastes, as raw materials, was recently proposed as an innovative strategy for the Brazilian acid soils amendment. Here we show the results of soil conditioner amended soil leaching tests and agronomical performance. The soil conditioners were formulated by BR mixed with decomposed POC (palm oil compost) and non-decomposed POMW (palm oil mill waste) oil palm wastes, in the proportion of 25% BR + 75% POC (T1) and 50% BR + 50% POMW (T2), in addition to the treatment with 100% POMW without BR (T3) and limestone at a dose calculated to raise soil pH to 6.0 (T4). Except for T4, all conditioners were applied to the soil at doses of 40, 80, and 120 t ha−1 for leaching tests. The experimental plots were composed of polyvinyl chloride columns, filled with 5 kg of soil, with bottles adapted with hoses at the bottom to facilitate drainage of the leachate. After leaching tests, the respective columns were used as pots for the cultivation of Brachiaria grass, stage with addition of a control composed by undisturbed soil (T5). The pH of the leachates had changes, but the use of BR associated with POMW was similar to the use of limestone. Of the 65 chemical elements evaluated, only nine were identified in the leachate, being most of them considered as plant nutrients. As for soil pH, limestone was slightly higher (6.6) than treatments that had BR (5.5). Brachiaria grass cultivated in the soil amended with conditioners showed similar results of limestone treated soil for the parameters of plant development and showed fertility improvement.

Soil enzymatic activity in Brazilian biomes under native vegetation and contrasting cropping and management

Enzymatic activity is a useful indicator for the evaluation of soil biological components. However, a detailed analysis of such indicators in Brazilian soils is lacking. In this study, the activity of soil enzymes was evaluated using data from 73 publications covering 57 locations across all six biomes and eight soil orders out of the 13 that occur in Brazil. The results indicated a wide variation of enzymatic activity in soils, where the means in μg p-nitrophenol g−1 soil h−1 were 569, 116, 112, and 80 for acid phosphatase, alkaline phosphatase, β-glucosidase, and arylsulfatase, respectively. Likewise, values of 148 μg reducing sugars g−1 soil day−1 for cellulase, 57 μg triphenyl tetrazolium formazan g−1 soil day−1 for dehydrogenase, and 38 μg N-NH4+ g−1 soil h−1 for urease were recorded. Soil organic matter and microbial biomass were the best attributes correlated with enzymatic activity, followed by clay content and pH. A more detailed analysis of the acid phosphatase, arylsulfatase, and β-glucosidase activities showed that land-use effects were more pronounced in the Atlantic Forest and Cerrado than in the Caatinga biome. Soils under non-tillage and integrated crop-livestock systems showed higher enzymatic activity than soils under conventional tillage. Soils housing higher biodiversity and delivering higher crop yields also presented higher enzymatic activity, especially in terms of arylsulfatase and β-glucosidase. Enzymatic activity has been shown to be a versatile indicator of soil quality, as it can elucidate how to achieve high-quality standards in tropical and subtropical soils.

Lateritic soil deformability regarding the variation of compaction energy in the construction of pavement subgrade

The performance of the subgrade towards the main deterioration mechanisms must be considered in the pavement structure design. Thus, this paper discusses the resilient modulus and permanent deformation evaluation of a pedological horizon of a Brazilian lateritic soil deposit, comparing samples compacted in the laboratory at the three compaction energies (standard, intermediate and modified) and undisturbed samples. Physical, chemical, and mechanical characterization tests were conducted. The cyclic tests were performed in repeated load triaxial tests and according to the current Brazilian standards. Five mathematical models widely used were employed to verify the resilient modulus behavior of the sample conditions, in which the Compound and Universal models showed the best correlations. For permanent deformation, the model was used, which well-expressed the plastic behavior of the analyzed conditions. Although all cases appeared to attend the shakedown criteria, some samples did not reach the deformation rate required by the standard. As the compaction energy was increased, the resilient modulus increased, and the permanent deformation decreased. Therefore, there is a substantial modification of the material behavior by increasing the compaction.

Controle biológico do fungus gnats (Bradysia matogrossensis) em mudas de tabaco

ABSTRACT Tobacco production in Brazil is an essential source of income for many families, especially in the southern region. However, it is subject to attack by pests and diseases, such as the fungus gnats insect. To control this pest, the mite Stratiolaelaps scimitus is found in Brazilian soil, which has a predatory potential to fungus gnats. This study aimed to evaluate the use of S. scimitus as an insect control agent, compared to chemical control, in the production of tobacco seedlings in the floating system. The experiment was carried out on a farm in Crissiumal-RS, in a randomized block design, with four replications: T1= control, T2= chemical control based on Imidacloprid and Azadirachtin, and T3= S. scimitus. To analyze the control efficiency, adult insects were captured at different times, and the biological control did not differ from the chemical control. The biological treatment made it possible to reduce the use of chemical products. Concomitantly, questionnaires verified that producers are well accepting the new control model. Therefore, using S. scimitus could reduce the proliferation of fungus gnats in the production of tobacco seedlings in the floating system, but more studies need to be carried out for a better evaluation.

Soil potentially toxic element contents in an area under different land uses in the Brazilian Amazon

Soil pollution with potentially toxic elements (PTE) from incipient basic sanitation, dumps and industrial activities developed in the Amazon has been of international interest due to health and environmental issues. This study aimed to evaluate the concentration of PTE in five adjacent land occupations (a dump, a alumina refinery area and three residential centers) in the municipality of Barcarena, Amazon Region, Brazil. In a total area of 912 ha, 274 soil samples were collected at a depth of 0–0.2 m. Afterwards, the concentrations of As, Ba, Pb, Co, Cu, Cr, Hg, Ni and Zn were determined. The results were explored using descriptive and multivariate statistics, as well as geostatistical. Considering the data by location, maximum concentrations exceeding the prevention values of Brazilian soils were found for Cu, Ni and Zn in Dump (148; 42.8 and 356 mg kg−1), for Cu and Hg in Bom Futuro (333 and 1.99 mg kg−1) and for Cu in Itupanema (91.2 mg kg−1). Cu, Hg, Pb and Zn were grouped in the same principal component and showed the highest similarity measure in the cluster analysis. The interpolation point maps of the two principal components and of the individual concentrations of the PTEs showed the area of influence of the dump as the main reason for the increase in soil contamination. These results show the need for public policies aimed at the proper disposal of solid waste, in order to promote the reduction of pollutants in the soil, health and well-being for the local population, and also the environmental quality of the study area.

Corn Cropping System and Nitrogen Fertilizers Technologies Affect Ammonia Volatilization in Brazilian Tropical Soils

The adoption of technologies for N fertilization has become essential for increasing the N use efficiency in no-till (NT) systems in Brazil. Thus, this study aimed to quantify ammonia losses, N removal in grains, and second crop season yield in no-till and conventional (T) areas that received the application of different N fertilizers and their technologies. Ammonia volatilization, N extraction in grains, and corn yield in response to the application of conventional fertilizers were compared to urea treated with urease inhibitors in NT and conventional systems. The treatments were: no-N (Control); Prilled urea (PU); urea + N-(n-Butyl) thiophosphoric triamide (UNBPT); urea + Cu + B (UCuB); ammonium nitrate (AN), and ammonium sulfate (AS). In the NT system, the N-NH3 losses were 49% higher than in the conventional; without differences in corn yield. The fertilizers AN and AS had the lowest N-NH3 losses, regardless of the tillage system. UNBPT reduced the mean N-NH3 loss by 33% compared to PU. UNBPT (1200 mg kg−1) and UNBPT (180 mg kg−1) reduced the N-NH3 losses by 72% and 22%, respectively, compared to PU in the NT system. We noticed that the NBPT concentration to be used in soils under NT should be adjusted, and a reduction of N-NH3 losses does not directly reflect an increase in yield and N extraction by corn.

Sensor-based field methods for pedology and soil surveys: Protocol suggestions for Brazilian tropical soils

Although limited alternatives have been proposed to describe soils by using proximal sensors under natural conditions, efforts must be made to apply the newest technologies to assist in soil characterization and mapping. Our main objective was: to create a protocol incorporating technology that assists pedologists: (i) to compare soil horizonation by using visible, near, and shortwave infrared (Vis-NIR-SWIR) spectroscopy, mid-infrared spectroscopy (MIR), portable X-ray fluorescence (pXRF) indices, and conventional field observations; (ii) to identify mineralogical and physico-chemical variations between soil horizons by using proximal sensors, with inferences about pedogenic processes; and (iii) to expand punctual information to spatial dimensions with RGB images and terrain attributes. Seven soil profiles located through a toposequence evaluation were analyzed on a farm in the São Paulo State, Brazil. First, when the area consisted of exposed soils, images were obtained by Landsat and an unmanned aerial vehicle (UAV), and a digital surface model (DSM) was then built by stereoscopy, which was subsequently used to calculate thirteen terrain attributes. Each soil profile was evaluated with devices directly in the field (except for the MIR analyses, for which soil samples were brought to the laboratory and dried). Several indices were calculated from the pXRF data during the profile analysis, while principal component analyses (PCA) were performed to reduce the dimensions of the spectral data. Four datasets for each soil profile (VIS-NIR-SWIR, pXRF, MIR, and a combination of all the data) were submitted for k-means clustering analysis and the similarities among the layers were evaluated. Following the profile evaluation, spatialization was performed based on single bands from the RGB image and PCA using terrain attributes. The data were sampled to a punctual view of 370 points, classified, and then interpolated with the spline method. The Vis-NIR-SWIR spectral range, together with soil color, provided better correspondence with conventional field observations. We observed that the combined use of Vis-NIR-SWIR, MIR, and pXRF helped to identify and describe the soil profiles appropriately. Proximal sensors also allowed us to make more robust inferences regarding pedogenesis. We delineated soil information profiles in soil units by using the spatial dimension's terrain attributes and, RGB images from a UAV.

A Brief Snapshot of Aspergillus Section Nigri Isolated from Brazilian Peanuts and Soil

The occurrence of mycotoxigenic species in peanuts is a major concern, and has been investigated in depth for many years. However, most studies focus on the occurrence of aflatoxigenic fungi, such as Aspergillus section Flavi. The present study aimed to clarify the occurrence of Aspergillus section Nigri, a group that harbors species capable of producing ochratoxin A (OTA), which has scarcely been investigated in peanuts. A total of 52 peanut samples, collected in the field and from storage, were analyzed. Aspergillus section Nigri was isolated from 64% and 100% of field and storage samples, respectively, and 218 strains were obtained. Based on the multiloci phylogeny of the CaM and BenA loci, six species of Aspergillus section Nigri were identified: A. brasiliensis, A. niger, A. neoniger, A. welwitschiae, A. costaricaensis, and A. japonicus. The incidence of ochratoxigenic strains was 5.0% (11/218), and only A. niger and A. welwitschiae were able to produce OTA. The presence of OTA in peanuts was found in 6 field and 8 storage samples, with levels ranging from 0.106 to 0.387 and 0.090 to 0.160 µg/kg, respectively.

Seasonal variation of the shaft resistance of CFA piles in unsaturated soil: a case study

Excessive settlements or failure of piles observed in some Brazilian unsaturated soil sites indicates that the shaft resistance can vary with the seasonal variability of top soil water content, especially in the case of foundations of transmission towers or installed at the periphery of buildings, situations in which the soil is more susceptible to suction fluctuation due to the higher exposure to rainfall action. The objective of the research described in this paper was to provide field evidence with the purpose of alerting practising engineers and to help researchers to better understand the contribution of matric suction on pile capacity. For this aim, the seasonal variability of the shaft resistance of Continuous Flight Auger (CFA) piles in a typical Brazilian unsaturated tropical soil was evaluated by performing axial tensile load tests on eight instrumented CFA piles in different periods of the year. Soil suction was monitored throughout the period of tests, and the results indicate that the shaft resistance of the pile upper part varies considerably during the year and tends to decrease with decreasing soil suction. This work provides valuable insights into the application of unsaturated soil mechanics, which is usually disconnected to classical geotechnical practice.

Obtention and Selection of Experimental Strawberry Genotypes (Fragaria x ananassa) Adapted to Brazilian Soil and Climatic Conditions

Obtention and Selection of Experimental Strawberry Genotypes (Fragaria x ananassa) Adapted to Brazilian Soil and Climatic Conditions

Pseudomonas aeruginosa and Bacillus cereus Isolated from Brazilian Cerrado Soil Act as Phosphate-Solubilizing Bacteria

The phosphate-solubilizing microorganism is essential for soil quality and plant development and can serve as an alternative to reduce such Brazilian needs for importing phosphate overseas. Here, we isolated and selected bacteria from Brazilian Cerrado soils capable of solubilize phosphate. We obtained 53 bacteria isolates, of which 23 could solubilize phosphate at a pH of 7.0, 17 could solubilize phosphate at a pH of 6.0, and 8 could solubilize at a pH of 5.5. Using 16S rRNA gene sequences, we identified nine bacteria species clustered in four groups: Bacillus sp., Pseudomonas sp., Priestia sp., and Klebsiella sp. Our results revealed that the UFT01 (P. aeruginosa) and UFT42 (B. cereus) isolates exhibited the best phosphate solubilization performance at all tested pH values. We further recorded higher levels of solubilization and phosphate availability six days after the soil inoculation with P. aeruginosa, and enzymatic analysis of the soil samples revealed that the P. aeruginosa-inoculated samples resulted in four-fold higher enzymatic activities when compared to non-inoculated soils. The B. cereus soil inoculation increased β-glucosidase activities and resulted in reduced the activities of arylsulfatase. Altogether, our findings demonstrated that P. aeruginosa and B. cereus isolated from Cerrado soils showed high phosphate solubilization potential.

Passive of CRFS Technology in Soil-Cement Application

In Brazil, with the ban on the production, sale, and use of chrysotile asbestos, the sector’s industry opted to replace asbestos with CRFS Technology—Cement Reinforced with Synthetic Wire (fiber cement); that is, another product to be disposed of in landfills. This work aimed to determine a composite based on clay, fiber cement powder, and cement that meets the technical specifications of Brazilian soil–cement application standards to contribute to a more sustainable treatment of the future disposal of fiber cement products. With the characterization analysis of the materials, we identified that the clay granulometry is heterogeneous and distributed from 0.1 µm to 25 µm. In comparison, 75% of the fiber cement powder has grains greater than 10 µm. For clay, the liquidity limit is 39.67%, the plasticity limit is 25.01%, and the plasticity index is 14.66%. In the semiquantitative chemical analysis, silicon oxide (SiO2) and calcium oxide (CaO) stood out as the main oxides found, reflected in the mineralogy as quartz and calcium silicate. Therefore, we identified the percentage of organic matter in clay at 2%, using the result of the thermogravimetric analysis. The results described met the normative parameters foreseen for soil–cement applications. That said, the technological characterization was carried out by tests of linear retraction, water absorption, and simple mechanical compression on the specimens made under an axial pressure of 31.2 Mpa in the formulations defined in this work. The formulations with 10% cement and 20% and 30% fiber cement powder are suitable for use in soil–cement bricks, as they have volumetric shrinkage percentages from 2% to 2.5%, water absorption ranging from 18.66% to 19.39%, and simple compressions from 4.25 Mpa to 6.88 Mpa, meeting the requirements of Brazilian standards for soil–cement applications. It is concluded that the results showed that it is possible to produce soil–cement bricks with passive fiber cement products converted into powder, avoiding improper disposal and unwanted environmental impacts.

Soil contamination by copper: Sources, ecological risks, and mitigation strategies in Brazil

BackgroundSeveral activities can build up soil copper (Cu) concentrations leading to incorporation into the food chain and adversely affect natural and managed ecosystems. This study provides a synthesis of Cu sources, ecological risks, and mitigation strategies of Cu-contaminated soils in Brazil. MethodsA systematic data search was conducted based on publications from three databases. Data on Cu contamination in Brazilian soils were collected from selected publications; descriptive statistics, regressions, and geo-accumulation indices were obtained. Ecological risks and remediation methods were identified. ResultsBased on total soil Cu concentrations and the geo-accumulation index (Igeo), it was evident that some Cu sources are more problematic for soils. These sources include antifouling paint particles (Igeo = 9.5), tailings from Cu mining (Igeo = 2.8), and Cu-based fungicides applied to vineyards/orchards (Igeo = 1.8). Other Cu sources such as organic waste, solid waste, dust fallout, and metal scraps have generally resulted in moderate to low levels of soil contamination. Soils contaminated by Cu can also impact water since soil erosion carries elements into water bodies. Contaminated environments may lead to increased Cu absorption by organisms, which pose ecological risks. Reference values of total Cu concentrations used for assessing soil quality have been proposed for almost half of Brazilian states. The most prescribed Cu mitigation actions for soil amelioration are phytomanagement with non-accumulator cover crops or native plant species that can accumulate up to 1000 mg Cu kg−1 in roots/stems combined with liming/fertilization and microbial inoculation. ConclusionThe most Cu contaminated sites in Brazil occur on soils affected by Cu mine tailings and vineyards where Cu-based fungicides have been applied for several decades, which results in environmental, social, economic, and health issues. Strategies have been proposed for the mitigation of Cu contaminated soils, mainly phytomanagement options. However, there is still a strong need for joint efforts by public and private sectors to implement remediation practices on contaminated soils and to prevent Cu contamination of new areas.

Confirming sulfluramid (EtFOSA) application as a precursor of perfluorooctanesulfonic acid (PFOS) in Brazilian agricultural soils

Perfluorooctanesulfonic acid (PFOS) is a manmade chemical with several industrial applications and also a potential byproduct of many other per- and polyfluorinated substances (PFAS) in the environment. Due to the gathered evidence on its environmental persistence, long-range transport, toxicity, and bioaccumulative and biomagnifying properties, PFOS, its salts and perfluorooctane sulfonyl fluoride (PFOSF), were listed for global restriction under the Stockholm Convention on Persistent Organic Pollutants in 2009. Nevertheless, Brazil has granted an acceptable purpose exemption for using PFOSF to produce sulfluramid (EtFOSA) and to apply it as insecticide to control leaf-cutting ants of the genus Atta and Acromyrmex. Previous studies have pointed out EtFOSA as a precursor of PFOS in the environment, including in soils. Therefore, we aimed to confirm the role of EtFOSA in PFOS formation in soils representing areas where sulfluramid-based ant baits are used. A biodegradation assay was carried out by applying technical EtFOSA in triplicate samples of ultisol (PV) and oxisol (LVd) and measuring the contents of EtFOSA, perfluorooctane sulfonamide acetic acid (FOSAA), perfluorooctane sulfonamide (FOSA), and PFOS at seven moments (0, 3, 7, 15, 30, 60, and 120 days). The monitored byproducts started being noticed on the 15th day. After 120 days, PFOS yields were 30% for both soils, whereas FOSA yields were 46% (PV soil) and 42% (LVd soil) and FOSAA yields were 6% (PV soil) and 3% (LVd soil). It can be expected that FOSAA and FOSA contents will eventually be converted into PFOS in the environment and that the presence of plants could boost PFOS formation. Therefore, the ongoing extensive and intensive use of sulfluramid-based ant baits pose a considerable source of PFOS to the environment.

Mapping Brazilian soil mineralogy using proximal and remote sensing data

Minerals control many soil functions and play a crucial role in addressing global existential issues. Measuring the abundance of soil minerals is a laborious, costly, and time-consuming task; however, soil spectroscopy can be a useful tool to overcome this issue. This work aimed to map the abundance of major mineralogical components of soils in Brazil from surface to 1 m deep and at a spatial resolution of 30 m. Spectral data of the Brazilian Soil Spectral Library with Vis-NIR-SWIR was used to estimate the abundance of haematite, goethite, kaolinite, and gibbsite. These minerals were spatialized using digital soil mapping techniques. We also developed a novel framework to obtain bare soil reflectance for areas without natural or anthropic soil exposure (continuous image) and used it as covariate. Soil minerals and their abundances were successfully estimated by Vis-NIR-SWIR reflectance. Haematite predictions presented the most accurate results with Random Forest models, followed by gibbsite, kaolinite, and goethite. The spatial validation with reference mineralogical data found R2 of 0.64 (haematite), 0.40 (goethite), 0.20 (kaolinite/Kt), 0.29 (gibbsite/Gbs), and 0.40 (Kt/Kt + Gbs). The resulting maps of soil minerals were in accordance with the geology, pedology, climate, and relief of Brazil and revealed the spatial distribution of mineral abundances at a finer resolution than existing geological and pedological maps, reaching a farm level detail.

Maximum shear modulus estimative from SPT for some Brazilian tropical soils

Maximum shear modulus (G0) has been used in various geotechnical jobs (e.g., seismic site assessment, machine vibration and pile driven). Laboratory and in situ determination of G0 is not a current practice in Brazil. G0 can be estimated from empirical correlations based on in situ tests like Standard Penetration Test (SPT) and Cone Penetration Test (CPT) in the preliminary design phase. Several empirical correlations to estimate G0 from SPT N value have been developed and are available in the literature. However, most of these correlations were established based on experience with well-behaved soils formed in temperate and glacial zones, which may not always be used for tropical soils. This paper assessed and discussed the applicability of some correlations for G0 estimative from SPT data in lateritic and saprolitic soils. The classical correlations for sedimentary soils underestimated G0 of tropical soils. After updating the database, the tropical soils correlations reasonably estimated G0 for the lateritic ones, which was not the case for the saprolitic soils. It was observed that differentiating the soils only as lateritic or saprolitic was not adequate for a good G0 estimate for the saprolitic sandy soils. It was found that only the lateritic soils correlation can be used with caution as a preliminary attempt to estimate G0 from SPT N value in soils with similar characteristics to the ones presented in this paper.

Development of a soil exposure assessment for plant protection products in Brazil: Requirements, options, and recommendations.

The Brazilian Environmental Authority (IBAMA) has recently identified soil organisms as a priority area for risk assessment development for plant protection products. This includes consideration of which species in soil fauna are important to be tested for risk assessment purposes, which ecotoxicological tests should be used, and which exposure models would be suitable, considering Brazilian soils, local agricultural practices, and local biodiversity. In this brief communication, we present proposals and recommendations for the selection of appropriate regulatory exposure assessment techniques to support initial or foundation tier assessment. Integr Environ Assess Manag 2023;19:862-869. © 2022 FMC Corporation, Syngenta, Adama, Bayer AG, BASF SE. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Towards anti-racism: considerations about the pedagogical project of the UFMS/CPTL Law course

The law course, when implemented on Brazilian soil, played an important role in maintaining the oppressive and racist status quo, which remained registered in the first legal curricula. However, with the advent of the 1988 Constitution and the conquest of rights in favor of the black population, a new legal scenario has been redesigned in the face of the racial struggle. Thus, it is necessary to reflect on whether legal curricula have also advanced towards anti-racism. More specifically, we sought to verify whether the Pedagogical Project of the UFMS Law course, Três Lagoas/MS campus, provides for an anti-racist legal education, based on existing anti-racist curricular predictions. For that, a hypothetical-deductive approach and bibliographical and documental research techniques were used, in addition to textual mapping through the use of markers, contributing to the end of the study reaching the understanding that there is no prediction in the local course of an anti-racist legal education, even though it is moving towards that goal.

Biochemical, physiological, and molecular characterisation of a large collection of aerobic endospore-forming bacteria isolated from Brazilian soils

The aerobic endospore-forming bacteria (AEFB) comprise species of Bacillus and related genera and have long been regarded as prominent constituents of the soil bacterial community. The wide diversity of AEFB renders appropriate categorisation and generalisations a challenging task. We previously isolated 312 AEFB strains from Brazilian soils that we designated SDF (Solo do Distrito Federal) strains. To better understand the SDF diversity and explore their biotechnological potential, we addressed the biochemical and physiological profiles of these 312 environmental strains by performing 30 tests in this work. Of these, the 16S rRNA gene sequences segregated 238 SDF strains into four genera in the family Bacillaceae and two in the Paenibacillaceae. Bacillus spp. were the most prevalent, followed by species of Paenibacillus. We summarised the phenotypic test relationships among selected SDF strains using a Pearson correlation-based clustering represented in heatmaps. In practice, biochemical and physiological profiles are often less discriminatory than molecular data and may be unstable because of the loss of traits. Although these test reactions are not universally positive or negative within species, they may define biotypes and be efficient strain markers, enhancing the accuracy of unknown sample identification. It can also help select the most representative phenotypes of samples. Along with the other phenotypic and genotypic data, the present results are of great importance for the robust classification of the SDF strains within the scope of the polyphasic approach.

In-field performance of continuous flight auger (CFA) energy piles with different configurations

In order to face the national energy crisis in Brazil, the use of geothermal energy piles (GEP) integrated with heat pumps is an attractive and cost-effective solution for the building cooling demand. On the other hand, there are very few field studies on the thermal performance of GEP systems in Brazilian soils and climate conditions, and for this reason, the implementation of this technology is still a challenge. Motivated by this need, continuous flight auger (CFA) energy piles were constructed to support a building in São Paulo city, and an experimental study, described in this paper, was carried out to provide useful data for the design of these GEPs. This work examined two key aspects of the design of GEP systems: (1) the influence of the heat exchange pipe configuration, and (2) the thermal response of GEPs and their effect on nearby piles installed in multi-layered ground. For this study, thermal response tests (TRTs) were conducted on four GEPs constructed with different pipe configurations, installed in a saturated sandy deposit intercalated by soft organic clay layers. The results obtained showed that: (i) the influence of pipe configuration on the GEP heat transfer is more significant during the first hours of pile heating process, and decreases with time due to the thermal interference between the pipe loops; (ii) the GEP temperature profile is impacted by the presence of soil layers of highly different thermal conductivities and groundwater flow velocities; and (iii) the temperature variation of nearby piles was also affected by the thermal characteristics of the soil layers, and therefore it should be considered for the structural design of GEPs.