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Clay minerals have different negative effects on the froth flotation process such as low adsorption of collectors on valuable minerals, increased pulp viscosity, and the reduction in recovery and grade concentrates of copper sulfides. This study aims to evaluate the use of polystyrene-based nanoparticles (NPs) for the froth flotation of chalcopyrite and their ability to mitigate the negative effect of montmorillonite on the recovery of this sulfide. The experimental stage consisted of preparing a type of polystyrene-based nanoparticle (St-CTAB-VI), which was analyzed by dynamic night scattering (DLS) to establish its hydrodynamic size. Then, the effect of NPs on chalcopyrite's angle's in the presence and absence of montmorillonite (15%) was evaluated and compared with the contact angle achieved using potassium amyl xanthate (PAX) and a mixture of PAX and NPs. In addition, zeta potential measurements were carried out to investigate the interactions between the chalcopyrite and the montmorillonite or the NPs under fixed concentrations and microflotation tests were performed employing different times to evaluate the chalcopyrite recovery in the presence of montmorillonite, using NPs and mixtures with PAX. Finally, turbidity analysis as a function of time was performed to evaluate the occurrence of sedimentation and flocculation phenomena in suspensions of 15% montmorillonite in the presence and absence of chalcopyrite, nanoparticles, and mixtures of NPs and PAX. The results indicated that the mixture of NPs and PAX contributed to increasing the contact angle of chalcopyrite in the presence of montmorillonite. This can be associated with the presence of molecular and nanometric collectors that generated a higher hydrophobicity on the chalcopyrite particles, contributing to reducing the presence of clay minerals on the mineral surface. In addition, the mixture of NPs and PAX promoted the generation of nanoparticles on the sulfide mineral surface, which helps to detach the slime and facilitate the bubble/mineral attachment step during flotation.

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Spodumene flotation stands as the most commonly used method to concentrate lithium minerals. However, it faces significant challenges related to low collector recoveries and similarity in the surface characteristics of the minerals, which make the effective separation of this valuable mineral difficult. For this reason, numerous researchers have conducted studies to address and confront this problem. In this work, an exhaustive bibliographic search was carried out using keywords and search queries, and the results were structured in three sections according to temporal, methodological, and thematic criteria. The first section covers the period from 1950 to 2004, focusing on experimental tests. The second section covers from 2004 to the present and focuses on flotation tests and measurement analysis. Simultaneously, the third section spans from 2011 to the present and is based on molecular dynamics simulations. Topics covered include spodumene surface properties, the influence of metal ions, pre-treatment techniques, and the use of collectors. Ultimately, molecular dynamics simulations are positioned as a tool that accurately represents experimental phenomena. In this context, specialized software such as Materials Studio or Gromacs prove to be reliable instruments that allow a detailed study of mineral surfaces and other elements to be carried out, which justifies their consideration for future research in this scientific field.

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Renewable cooling via absorption chillers being supplied by various green heat technologies such as solar collectors has been widely studied in the literature, but it is still challenging to get positive economic outcomes from such systems due to the large expenses of solar thermal systems. This study offers the use of a new generation of solar collectors, so-called eccentric reflective solar collectors, for driving single-effect absorption chillers and thereby reducing the levelized cost of cooling. This article develops the most optimal design of this system (based on several different scenarios) using multi-objective optimization techniques and employs them for a case study in Brazil to assess its proficiency compared to conventional solar-driven cooling methods. For making the benchmarking analyses fair, the conventional system is also rigorously optimized in terms of design and operation features. The results show that the eccentric solar collector would enhance the cost-effectiveness by 29%. In addition, using optimally sized storage units would be necessary to get acceptable economic performance from the system, no matter which collector type is used. For the case study, at the optimal sizing and operating conditions, the levelized cost of cooling will be 124 USD/MWh and an emission level of 18.97 kgCO2/MWh.

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Isotope fractionation of metals/metalloids in biological systems is an emerging research area that demands the application of state-of-the-art analytical chemistry tools and provides data of relevance to life sciences. In this work, Se uptake and Se isotope fractionation were measured during the biofortification of baker's yeast (Saccharomyces cerevisiae)-a product widely used in dietary Se supplementation and in cancer prevention. On the other hand, metabolic labeling with 15N is a valuable tool in mass spectrometry-based comparative proteomics. For Se-yeast, such labeling would facilitate the assessment of Se impact on yeast proteome; however, the question arises whether the presence of 15N in the microorganisms affects Se uptake and its isotope fractionation. To address the above-mentioned aspects, extracellularly reduced and cell-incorporated Se fractions were analyzed by hydride generation-multi-collector inductively coupled plasma-mass spectrometry (HG MC ICP-MS). It was found that extracellularly reduced Se was enriched in light isotopes; for cell-incorporated Se, the change was even more pronounced, which provides new evidence of mass fractionation during biological selenite reduction. In the presence of 15N, a weaker preference for light isotopes was observed in both, extracellular and cell-incorporated Se. Furthermore, a significant increase in Se uptake for 15N compared to 14N biomass was found, with good agreement between hydride generation microwave plasma-atomic emission spectrometry (HG MP-AES) and quadrupole ICP-MS results. Biological effects observed for heavy nitrogen suggest 15N-driven alteration at the proteome level, which facilitated Se access to cells with decreased preference for light isotopes.

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Rare earth elements have played a key role in technological advancement, attracting great visibility in the global commodity market. Xenotime, a heavy rare earth resource (YPO4), can be found associated with granitic rocks, as in the Pitinga deposit, located in the Brazilian Amazon region, where the main gangue minerals are quartz, microcline and albite. This research investigates the application of a new collector produced from pracaxi oil, an Amazon oil abundant in Brazil, in the selective flotation between xenotime and its main gangue minerals. The study conducted the synthesis and characterization of the collector, the chemical, mineralogical and surface characterization of minerals, as well as the evaluation of collector adsorption and flotability via microflotation tests, zeta potential measurements, surface tension determination and XRD, WDXRF, ICP-MS, FTIR and XPS analyses. The pracaxi collector was found to be mainly composed of oleic acid (56.2%), linoleic acid (14.1%) and behenic acid (10.6%), in addition to exhibiting a critical micelle concentration (CMC) of approximately 150 mg/L. Microflotation tests indicated that the best condition for selective recovery of xenotime occur at alkaline condition (pH 9.0), presenting selectivity of approximately 90% with collector concentration of 10.0 mg/L. The zeta potential data confirmed a selective adsorption of pracaxi collector onto xenotime, with an increase in the surface charge from -30 mV to -68 mV, whereas no significant changes were detected in the silicates. The FTIR spectra showed the appearance of a band at 1545 cm-1 on the surface of the xenotime after collector adsorption, which indicates, along with the zeta potential data, the chemical nature of the adsorption. The presence of small amounts of iron in the lattice structure of silicate gangues can act as an activator, and therefore, may be responsible for the small flotability of these minerals. The performance of the pracaxi oil collector presented in this study indicates the great potential of this Amazonian oil for application in the selective flotation of xenotime ores found in the region.

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The use of solar energy is considered a potential strategy for the production of electrical energy through thermal heat sources. This article portrays a study framed to be energetic, economic, and environmental fields. This study was carried out in two thermal configurations: the Regenerative Rankine Cycle (RORC) and the Simple Organic Rankine Cycle (SORC), which use solar energy to supply electrical power to a building. The thermodynamic and economic models were proposed for each subsystem of the thermal process, allowing hourly simulations to know the economic indicators such as the payback period (PBP), the levelized cost of energy (LCOE), the specific investment cost (SIC), and the initial investment cost ( C I n v ). The effect of operational variables such as the pressure ratio (rp), the evaporator pinch point temperature (Ap), the condensation pinch point temperature (Tcond), and the solar collector area (Ac) on the Relative Annual Benefit (RAB) were studied. Finally, the Particle Swarm Optimization (PSO) algorithm was implemented to optimize the economic indicators and the environmental impact of the thermal configurations. Results showed that the RORC configuration presented a better performance in terms of generation, purchase, and hourly sale of energy. However, in terms of RAB, the SORC (39,833 USD/year) showed better results in contrast to the RORC (39,604 USD/year) for an evaporator pinch point temperature of 35 °C. Finally, the application of the PSO optimization algorithm allowed the reduction of the LCOE (11.64%), SIC (11.67%), and PBP (11.81%) thermo-economic indicators from the base condition for the SORC, and the reductions obtained in the RORC were LCOE (18.11%), SIC (10.67%), and PBP (11.11%). However, the decrease in environmental Impact for both systems was less than 1% as a consequence of the high contribution of thermal oil in the construction phase of the system.

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This study proposes the use of polymeric nanoparticles (NPs) as collectors for copper sulfide flotation. The experimental phase included the preparation of two types of polystyrene-based NPs: St-CTAB and St-CTAB-VI. These NPs were characterized by Fourier-Transform Infrared (FTIR) spectroscopy and dynamic light scattering (DLS). Then, microflotation tests with chalcopyrite under different pH conditions and nanoparticle dosages were carried out to verify their capabilities as chalcopyrite collectors. In addition, the zeta potential (ZP) measurements of chalcopyrite in the presence and absence of NPs were carried out to study their interaction. Lastly, some Atomic Force Micrographs (AFM) of NPs and Scanning Electronic Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis of NPs on the chalcopyrite surface were conducted to analyze the size, the morphology and their interaction. The results obtained at pH 6 and pH 8 show that the NPs under study can achieve a chalcopyrite recovery near or higher than that obtained with the conventional collector. In this study, it was possible to observe that the NPs functionalized by the imidazole group (St-CTAB-VI) achieved better performance due to the presence of this group in its composition, allowing to achieve a greater affinity with the surface of the mineral.

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Resumen La industria alimentaria utiliza hasta el 15 % del total de la energía eléctrica que demanda el sector industrial, principalmente en procesos de secado. Esto suscita la búsqueda de nuevas alternativas de secado que reduzcan el uso de energía eléctrica. Una opción es el secado solar, principalmente, el de tipo indirecto, a través de captadores solares de placa plana (CSPP). El objetivo de este trabajo fue analizar los recientes desarrollos de los CSPP, características, ventajas, desventajas, eficiencia y diversas tecnologías utilizadas en conjunto, para aumentar la eficiencia térmica en el secado solar. Los CSPP han desarrollado, a través de la hibridación con la utilización de otras fuentes de energía (eléctrica, biomasa, solar), un incremento en su eficiencia que los vuelve cada vez más viables para ser utilizados en procesos comerciales de secado de alimentos.

Abstract The food industry uses up to 15 % of the total electrical energy demanded by the industrial sector, mainly in drying processes. This motivates the search for new drying alternatives that reduce the use of electrical energy. One option is solar drying; mainly indirect type solar drying, that uses flat plate solar collectors (FPSC). The objective of this work was to analyze the recent developments of the FPSC, their characteristics, advantages, disadvantages, efficiency, and the range of technologies used in conjunction with the FPSC to increase their thermal efficiency for solar drying. The FPSC have developed through hybridization with the use of other energy sources (electricity, biomass, solar), an increase in their efficiency, that increasingly turns them into viable options for food drying processes.

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In the present work an intense bibliographic search is developed, with updated information on the microscopic fundamentals that govern the behavior of flotation operations of chalcopyrite, the main copper mineral in nature. In particular, the effect caused by the presence of pyrite, a non-valuable mineral, but challenging for the operation due to its ability to capture a portion of collector and float, decreasing the quality of the concentrate, is addressed. This manuscript discusses the main chemical and physical mechanisms involved in the phenomena of reagent adsorption on the mineral surface, the impact of pH and type of alkalizing agent, and the effect of pyrite depressants, some already used in the industry and others under investigation. Modern collector reagents are also described, for which, although not yet implemented on an industrial scale, promising results have been obtained in the laboratory, including better copper recovery and selectivity, and even some green reagents present biodegradable properties that generate a better environmental perspective for mineral processing.

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A bench-scale tubular photo-reactor was built to evaluate the solar-driven TiO2-based photocatalytic degradation of synthetic polluted water samples. The reactor was designed as a compound-parabolic-collector and operated in batch mode using TiO2 P25 immobilized on a bed of pumice. The immobilization of TiO2 on pumice was carried out using a facile dip impregnation method followed by heat treatment. The obtained material was characterized by SEM, EDS, XRD, and nitrogen adsorption. It was possible to impregnate up to 68.5 mg of TiO2 per gram of pumice stones of 8-14 mm. Conversions of up to 35-40 and 62-69%, after 4 h of treatment and UV doses of 20.8 ± 3.5 kJ L-1, were achieved when the catalyst was used immobilized on pumice stone and in the form of a suspension, respectively. The stability and reusability of the catalyst-coated support was tested through a series of consecutive photocatalytic experiments. After four consecutive runs, the immobilized catalyst showed a decrease in its photoactivity leading to removal levels of 23%.

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Resumo Sabendo que a Epistemologia é o estudo da ciência com implicações sobre as teorias do conhecimento, este artigo não pretende entrar em seu mérito puramente conceitual, mas conjeturar e apresentar os caminhos da ciência, a partir de uma abordagem crítica em torno da Saúde Ambiental, com suas repercussões na profissão de catador. Na tentativa de transcrever os caminhos da ciência com relação ao tema proposto, este estudo tem como objetivo relacionar a problemática dos resíduos sólidos urbanos com a profissão de catador de materiais recicláveis, focando na saúde ambiental e no uso da abordagem do estudo teórico crítico através de uma revisão da literatura. Entende-se que é necessário questionar os caminhos que levam a profissão de catador de materiais recicláveis a não ser protagonista das possíveis soluções do acúmulo dos resíduos sólidos urbanos, proporcionando o enfrentamento das questões econômicas, políticas e tecnológicas pouco eficazes.

Abstract Knowing that epistemology means studying science with a view to its implications for theories of knowledge, this study aims not to enter into its purely conceptual merits but rather to conjecture and show scientific paths from a critical approach to environmental health with its repercussions for waste pickers. In an attempt to transcribe the paths of science regarding the proposed theme, this study aims to relate the problem of urban solid waste with the recyclable material collector profession, focusing on environmental health via a critical theoretical study of literature review. We understand that we need to question the paths leading the recyclable material collector profession toward a leading role in the possible solutions for the accumulation of urban solid waste, confronting ineffective economic, political, and technological issues.

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PURPOSE: The present work aims to study the effects of whole body vibration (WBV) on bus fare collectors through the use of cognitive tests. It is of interest for all individuals working as bus fare collectors or any other activity where logic is of paramount importance and that is performed on a vibrating environment. METHODS: Laboratory simulations were performed in 24 volunteers employing a vibrating platform subjected to vertical vibration. The influence of WBV on cognition was assessed using the performance on a logic game. The frequencies used were 5 Hz and 30 Hz. The acceleration amplitude values were set up as 0.7 m/s2 and 0.2 m/s2. A daily commute was simulated, based on data of the public transport system in the city of Belo Horizonte. A vibration-free test was initially performed to serve as a basis for comparison. RESULTS: The data obtained in all situations were compared and statistically analyzed. At 5 Hz, variation only shows significant after 5 min of vibration ceased as if the residual effect had passed after 5 min of rest. The gender variable was not significant. However, the older the volunteer, the worse the performance. Regarding 30 Hz frequency, the hypotheses did not meet the condition of significance at 5% but showed an opposite tendency indicating, in this situation, a score increase. It is noticed that the female volunteers presented a better performance in relation to the male gender The residual effect lasts for less than 10 min for short exposure intervals, since the score of test 8, in 5 Hz and 30 Hz, show a reduction of performance. CONCLUSIONS: From the results, it was possible to conclude that the frequency of 5 Hz may be related to reduced performance for long exposure times while the 30 Hz frequency has positive effects on cognition as the exposure time increases. In fact, it is a tendency much more than a clear statistical finding. Regarding comfort, most reports related to the frequency of 5 Hz are linked to the sensation of discomfort and difficulty in focusing visually, whereas, for the frequency of 30 Hz, the reports indicate a feeling of muscular comfort and increased easiness of concentration.

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Os catadores de materiais recicláveis podem ser considerados elementos-chave no processo de sustentabilidade ambiental, desempenhando importantes atividades para o tratamento adequado dos resíduos sólidos. Este trabalho visa analisar a dinâmica de trabalho e as condições de saúde dos coletores de lixo no Brasil no ano de 2013 e estabelecer comparações com a totalidade dos trabalhadores ocupados em outras profissões. Foram utilizados os dados quantitativos da Pesquisa Nacional de Saúde 2013 a partir de modelagem estatísticas. Pôde-se constatar que homens, mais velhos, com baixa escolaridade, de cor/raça preta ou parda, com baixa remuneração e que fazem uso do tabaco e/ou do álcool diariamente apresentam mais chances de ocuparem a profissão de catador. Os resultados retratam que os trabalhadores da coleta de materiais recicláveis do Brasil constituem uma fração da força de trabalho bastante vulnerável, sendo necessário que os agentes governamentais de saúde enfrentem a problemática das condições de trabalho e saúde dos catadores

The recyclable materials pickers can be seen as key elements in the process of environmental sustainability, performing important activities for the adequate treatment of solid waste. This study aims to analyze the dynamics of both work and health conditions of waste collectors in Brazil in the year of 2013 and to establish comparisons with the total number of workers in other professions. Was used the quantitative data of the 2013 National Health Survey were explored through statistics models. The results show that men, older, with less education, from black or brown color/race, with low salary and use tabaco and/or drink alcohol on a daily basis present a higher chance of occupying profession of a waste collector. The results show that the workers who collect recyclable materials constitute a fraction of the work force very vulnerable It is necessary that the government health agents face the problematic conditions of both the work and health of the collectors

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In this document, the photocatalytic activity of TiO2/Fe3O4, prepared by the mixing of the pure oxides, was studied. The photocatalytic degradation of aqueous Methylene Blue (MB) solutions (10 and 30 ppm) was performed, the TiO2/Fe3O4 catalysts in 80/20, 50/50 and 20/80 mass ratios were used during the test, artificial sunlight and natural solar radiation were tested at laboratory and pilot plant scale respectively. Besides, the kinetic reactions were evaluated according to the Langmuir-Hinshelwood model, the apparent velocity constants (kapp) were obtained for the TiO2/Fe3O4 catalysts. In the laboratory test, the TiO2/Fe3O4 catalyst (80/20) had a performance for 93.04% of discoloration, kapp = 0.0238 min-1, while for TiO2/Fe3O4 (50/50, 20/80) had an 83.46%, 65.00% for discoloration of MB and the kapp values were 0.0154 min-1 and 0.0098 min-1, respectively. In the solar test at pilot scale, the percentages of discoloration of 24.32%, and 57.78%, with kapp values of 0.00037 min-1, 0.00121 min-1 respectively were obtained for TiO2/Fe3O4 (80/20), a MB solution of 30 ppm, a load of 0.1 g/L and 0.3 g/L of the catalyst respectively.

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RESUMO: Os atuais retratos encontrados no âmbito da saúde mental infanto-juvenil e da Educação convocam a Psicanálise a se (re)inventar a fim de estar em diferentes sítios. Nesse sentido, este artigo busca sustentar a noção do oficineiro/pesquisador-catador-de-restos, problematizando se é possível forjarmos um modo, nas bordas da Psicanálise, Educação e Cinema, que nos auxilie na reinvenção de dispositivos de escuta e intervenção com sujeitos que vivem as nuances da passagem adolescente.

Abstract: The current pictures found in the framework of Mental Health and Education summons Psychoanalysis to (re)think itself in order to be in different places. For that matter, this article aims to support the notion of the workshoppers/researcher collector-of-remains, questioning if it is possible to forge a way, in the borders of Psychoanalysis, Education and Cinema, that can assist us in the reinvention of listening and intervention devices to the subjects who live the shades of the adolescent passage.

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Water fog composition was investigated at a fog harvesting installation in the coast of Atacama (North Chile). Chañaral is historically affected by mining contamination discharges. Hydro-chemical characterization of fog water from top of the mountain (where capture installation is located) and at the bottom of the mountain (after vertical transportation where an aquaponic system is located) revealed many compositional differences that compromise the use of water. High acidity and high concentrations in Cu and As in water collected on top of the mountain were found; meanwhile, acidity and Cu decreased, and As levels overpassed the drinking water standards after the vertical transportation. Collected data was assessed according to national and international regulatory standards, neutralization factors (NF), sodium adsorption ratio (SAR), and ion ratios to determine origin of contamination and suitability of destined for human consumption, irrigation, or aquaculture purposes.

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In the northern coastal and jungle areas of Peru, cocoa beans are dried using artisan methods, such as direct exposure to sunlight. This traditional process is time intensive, leading to a reduction in productivity and, therefore, delays in delivery times. The present study was intended to numerically characterise the thermal behaviour of three configurations of solar air heating collectors in order to determine which demonstrated the best thermal performance under several controlled operating conditions. For this purpose, a computational fluid dynamics model was developed to describe the simultaneous convective and radiative heat transfer phenomena under several operation conditions. The constructed computational fluid dynamics model was firstly validated through comparison with the data measurements of a one-step solar air heating collector. We then simulated two further three-step solar air heating collectors in order to identify which demonstrated the best thermal performance in terms of outlet air temperature and thermal efficiency. The numerical results show that under the same solar irradiation area of exposition and operating conditions, the three-step solar air heating collector with the collector plate mounted between the second and third channels was 67% more thermally efficient compared to the one-step solar air heating collector. This is because the air exposition with the surface of the collector plate for the three-step solar air heating collector former device was twice than the one-step solar air heating collector.

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The purpose of this study was to implement and evaluate a pilot-scale and closed-loop system that synergistically combines solar thermal collector, anaerobic digester, and constructed treatment wetland to simultaneously treat and utilize organic wastes. The system utilizes 863 kg of mixed animal and food wastes to generate 263 MJ renewable energy, produced 28 kg nitrogen and phosphorus fertilizer, and reclaimed 550 kg water per day. The net revenue considering electricity and fertilizer was $2436 annually. The payback period for the system is estimated to be 17.8 years for a relatively dilute waste stream (i.e., 2% total solids). The implemented system has successfully demonstrated a self-efficient and flexible waste utilization and treatment system. It creates a win-win solution to satisfy the energy needs of the community and address environmental concerns of organic wastes disposal in the region.

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Los recolectores de basura, considerados trabajadores de alto riesgo, están expuestos a una variedad de riesgos profesionales y no profesionales. Las tasas de accidentes ocupacionales en este grupo no se conocen en Paraguay. El objetivo del estudio fue estimar y comparar la prevalencia de accidentes de trabajo en los recolectores de basura formales e informales de Asunción, Paraguay, para lo cual se llevó a cabo un estudio transversal. La prevalencia de accidentes de trabajo y su asociación con factores sociodemográficos, condiciones de empleo y trabajo fueron examinadas en 309 trabajadores (186 formales y 123 informales) mediante un cuestionario estructurado. Se utilizó estadística descriptiva, análisis bivariante (test de chi2) y regresión logística ajustada. Los trabajadores formales eran de más edad (57% más de 40 años), todos hombres y mejor educados (82% completo nivel básico) comparado al grupo informal (7% más de 40 años, 68% varones y 30% completo nivel básico). La prevalencia de accidentes de trabajo entre los formales fue de 37.5% vs. 29.5% comparando con los informales (p=0.1). Luego de ajustes con potenciales confusores no se encontró diferencias significativas entre ambos grupos (OR: 1.8; 95% CI= 0.82-3.88). Factores de riesgos significativos fueron el no uso de guantes (OR: 1.84; CI= 1.01-3.05) y peores condiciones de seguridad (OR: 2.44; CI=1.3-4.7). Los factores de riesgo conocidos (educación, condiciones de trabajo, las condiciones de salud, trabajo por turnos) están presentes en ambos grupos, pero no explican los accidentes. Son necesarias más investigaciones e intervenciones en salud ocupacional en esta actividad laboral.

Garbage collector is a high-risk job, with exposure to a variety of occupational and non-occupational factors. Total injury rates of occupational accidents in these workers are not known in Paraguay, the aim of the study was to estimate and to compare the prevalence of accidents at work in formal and informal garbage collectors of Asunción, Paraguay. Across-sectional study was conducted. The 12-months-prevalence of occupational accidents and its association with socio-demographic factors, employment and working conditions were examined using a structured questionnaire. Descriptive statistics, bivariate analysis (chi square test) and adjusted logistic regression models were carried out. Formal workers were older (57% over 40 years old), all men and better educated (82% completed the first grade), compared to the informal group (7% over 40 years, 68% males and 30% completed the first grade). The 12-months-prevalence of occupational accidents among formal garbage collectors was 37.5% vs. 29.5% informal garbage collectors (p=0.1). Likewise, after adjustment for potential confounders no statistically significant difference between the two groups was found (Odds ratio 1.8; 95% CI= 0.82-3.88). Significant risk factors for 12-months prevalence of accidents were lack of gloves (1.84; CI= 1.01-3.05) and poor safetyconditions at the workplace (2.44; CI=1.3-4.7. Risk factors known are present in both groups (education, working condition, health condition, shift work) but not explain accidents. Therefore more researches and interventions on occupational health related on this activity are necessary.

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RESUMO: O objetivo deste estudo foi determinar a suficiência amostral para estudos de impacto ambiental sobre a comunidade de macroinvertebrados bentônicos em arrozais irrigados (Oryza sativa L.). Amostragens de solo foram realizadas com auxílio de coletor cilíndrico, nos anos agrícolas 2007/08 e 2012/13. As amostras foram triadas e os espécimes identificados até o nível de família. Os dados foram submetidos à análise da curva do coletor e os índices de diversidade de Shannon e equabilidade de Pielou foram calculados para o total de amostras e o número de amostras definido pela curva do coletor, em cada ano amostral. Considerando o método de amostragem verificado no presente trabalho, indica-se um mínimo de 12 réplicas para se obter o maior número de famílias sem perda de informação, quando em estudos de impacto ambiental sobre a comunidade de macroinvertebrados bentônicos em área de cultivo de arroz irrigado.

ABSTRACT: The objective of this study was to determine the sample sufficiency in environmental impact studies on the benthic macroinvertebrate community in irrigated rice fields (Oryza sativa L.). Soil samplings were conducted with a cylindrical collector in the agricultural years of 2007/08 and 2012/13. Individuals were sorted out and identified up to family level. Data were analyzed through the collector curve, Shannon's Diversity and Pielou's Evenness Index were calculated for the total number of samples and the number of samples defined by the collector curve in each year. Considering the results observed in this study, we indicate a minimum of 12 replicates to obtain the largest number of families without loss of information, in environmental impact studies on benthic macroinvertebrate community in irrigated rice fields.