20 resultados para zinc dust
em Universidad Politécnica de Madrid
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An intermediate-bandphotovoltaicmaterial, which has an isolated metallic band located between the top of the valence band and bottom of the conduction band of some semiconductors, has been proposed as third generation solar cell to be used in photovoltaic applications. Density functional theory calculations of Zn in CuGaS2:Ti have previously shown that, the intermediate-band position can be modulated in proportion of Zn insertion in such a way that increasing Zn concentration can lead to aband-gap reduction, and an adjustment of the intermediate-band position. This could be interesting in the formation of an intermediate-bandmaterial, that has the maximum efficiency theoretically predicted for the intermediate-band solar cell. In this work, the energetics of several reaction schemes that could lead to the decomposition of the modulated intermediate-bandphotovoltaicmaterial, CuGaS2:Ti:Zn, is studied in order to assess the thermodynamic stability of this material. Calculations of the total free energy and disorder entropy have been taken into account, to get the reaction energy and free energy of the compound decomposition, which is found to be thermodynamically favorable
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In order to determine the presence of Fusarium spp. in atmospheric dust and rainfall dust, samples were collected during September 2007, and July, August, and October 2008. The results reveal the prevalence of airborne Fusarium species coming from the atmosphere of the South East coast of Spain. Five different Fusarium species were isolated from the settling dust: Fusarium oxysporum, F. solani, F. equiseti, F. dimerum, and F. proliferatum. Moreover, rainwater samples were obtained during significant rainfall events in January and February 2009. Using the dilution-plate method, 12 fungal genera were identified from these rainwater samples. Specific analyses of the rainwater revealed the presence of three species of Fusarium: F. oxysporum, F. proliferatum and F. equiseti. A total of 57 isolates of Fusarium spp. obtained from both rainwater and atmospheric rainfall dust sampling were inoculated onto melon (Cucumis melo L.) cv. Piñonet and tomato (Lycopersicon esculentum Mill.) cv. San Pedro. These species were chosen because they are the main herbaceous crops in Almeria province. The results presented in this work indicate strongly that spores or propagules of Fusarium are able to cross the continental barrier carried by winds from the Sahara (Africa) to crop or coastal lands in Europe. Results show differences in the pathogenicity of the isolates tested. Both hosts showed root rot when inoculated with different species of Fusarium, although fresh weight measurements did not bring any information about the pathogenicity. The findings presented above are strong indications that long-distance transmission of Fusarium propagules may occur. Diseases caused by species of Fusarium are common in these areas. They were in the past, and are still today, a problem for greenhouses crops in Almería, and many species have been listed as pathogens on agricultural crops in this region. Saharan air masses dominate the Mediterranean regions. The evidence of long distance dispersal of Fusarium spp. by atmospheric dust and rainwater together with their proved pathogenicity must be taken into account in epidemiological studies.
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Zinc chelates have been widely used to correct deficiencies in this micronutrient in different soil types and under different moisture conditions. The aging of the metal in soil could cause a change in its availability. Over time the most labile forms of Zn could decrease in activity and extractability and change to more stable forms. Various soil parameters, such as redox conditions, time, soil type and moisture conditions, affect the aging process and modify the solubility of the metal. In general, redox conditions influence pH and also the chemical forms dissolved in the soil solution. Soil pH also affects Zn solubility; at high pH values, most of the Zn is present in forms that are not bioavailable to plants. The objective of this study was to determine the changes in Zn over time in a soil solution in a waterlogged acidic soil to which synthetic and natural chelates were applied
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Almendros, P.; Alvarez, J.M.; Gonzalez, D.
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A total of 92 samples of street dust were collected in Luanda, Angola, were sieved below 100 μm, and analysed by ICP-MS for 35 elements after an aqua-regia digestion. The concentration and spatial heterogeneity of trace elements in the street dust of Luanda are generally lower than in most industrialized cities in the Northern hemisphere. These observations reveal a predominantly “natural” origin for the street dust in Luanda, which is also manifested in that some geochemical processes that occur in natural soils are preserved in street dust: the separation of uranium from thorium, and the retention of the former by carbonate materials, or the high correlation between arsenic and vanadium due to their common mode of adsorption on solid particles in the form of oxyanions. The only distinct anthropogenic fingerprint in the composition of Luanda's street dust is the association Pb–Cd–Sb–Cu (and to a lesser extent, Ba–Cr–Zn). The use of risk assessment strategies has proved helpful in identifying the routes of exposure to street dust and the trace elements therein of most concern in terms of potential adverse health effects. In Luanda the highest levels of risk seem to be associated (a) with the presence of As and Pb in the street dust and (b) with the route of ingestion of dust particles, for all the elements included in the study except Hg, for which inhalation of vapours presents a slightly higher risk than ingestion. However, given the large uncertainties associated with the estimates of toxicity values and exposure factors, and the absence of site-specific biometric factors, these results should be regarded as preliminary and further research should be undertaken before any definite conclusions regarding potential health effects are drawn.
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El Zn es un elemento esencial para el crecimiento saludable y reproducción de plantas, animales y humanos. La deficiencia de Zn es una de las carencias de micronutrientes más extendidas en muchos cultivos, afectando a grandes extensiones de suelos en diferentes áreas agrícolas. La biofortificación agronómica de diferentes cultivos, incrementando la concentración de micronutriente Zn en la planta, es un medio para evitar la deficiencia de Zn en animales y humanos. Tradicionalmente se han utilizado fertilizantes de Zn inorgánicos, como el ZnSO4, aunque en los últimos años se están utilizado complejos de Zn como fuentes de este micronutriente, obteniéndose altas concentraciones de Zn soluble y disponible en el suelo. Sin embargo, el envejecimiento de la fuente en el suelo puede causar cambios importantes en su disponibilidad para las plantas. Cuando se añaden al suelo fuentes de Zn inorgánicas, las formas de Zn más solubles pierden actividad y extractabilidad con el paso del tiempo, transformándose a formas más estables y menos biodisponibles. En esta tesis se estudia el efecto residual de diferentes complejos de Zn de origen natural y sintético, aplicados en cultivos previos de judía y lino, bajo dos condiciones de riego distintas (por encima y por debajo de la capacidad de campo, respectivamente) y en dos suelos diferentes (ácido y calizo). Los fertilizantes fueron aplicados al cultivo previo en tres dosis diferentes (0, 5 y 10 mg Zn kg-1 suelo). El Zn fácilmente lixiviable se estimó con la extracción con BaCl2 0,1M. Bajo condiciones de humedad por encima de la capacidad de campo se obtuvieron mayores porcentajes de Zn lixiviado en el suelo calizo que en el suelo ácido. En el caso del cultivo de judía realizado en condiciones de humedad por encima de la capacidad de campo se compararon las cantidades extraídas con el Zn lixiviado real. El análisis de correlación entre el Zn fácilmente lixiviable y el estimado sólo fue válido para complejos con alta movilidad y para cada suelo por separado. Bajo condiciones de humedad por debajo de la capacidad de campo, la concentración de Zn biodisponible fácilmente lixiviable presentó correlaciones positivas y altamente significativas con la concentración de Zn disponible en el suelo. El Zn disponible se estimó con varios métodos de extracción empleados habitualmente: DTPA-TEA, DTPA-AB, Mehlich-3 y LMWOAs. Estas concentraciones fueron mayores en el suelo ácido que en el calizo. Los diferentes métodos utilizados para estimar el Zn disponible presentaron correlaciones positivas y altamente significativas entre sí. La distribución del Zn en las distintas fracciones del suelo fue estimada con diferentes extracciones secuenciales. Las extracciones secuenciales mostraron un descenso entre los dos cultivos (el anterior y el actual) en la fracción de Zn más lábil y un aumento en la concentración de Zn asociado a fracciones menos lábiles, como carbonatos, óxidos y materia orgánica. Se obtuvieron correlaciones positivas y altamente significativas entre las concentraciones de Zn asociado a las fracciones más lábiles (WSEX y WS+EXC, experimento de la judía y lino, respectivamente) y las concentraciones de Zn disponible, estimadas por los diferentes métodos. Con respecto a la planta se determinaron el rendimiento en materia seca y la concentración de Zn en planta. Se observó un aumento del rendimiento y concentraciones con el efecto residual de la dosis mayores (10 mg Zn kg-1) con respecto a la dosis inferior (5 mg Zn 12 kg-1) y de ésta con respecto a la dosis 0 (control). El incremento de la concentración de Zn en todos los tratamientos fertilizantes, respecto al control, fue mayor en el suelo ácido que en el calizo. Las concentraciones de Zn en planta indicaron que, en el suelo calizo, serían convenientes nuevas aplicaciones de Zn en posteriores cultivos para mantener unas adecuadas concentraciones en planta. Las mayores concentraciones de Zn en la planta de judía, cultivada bajo condiciones de humedad por encima de la capacidad de campo, se obtuvieron en el suelo ácido con el efecto residual del Zn-HEDTA a la dosis de 10 mg Zn kg-1 (280,87 mg Zn kg-1) y en el suelo calizo con el efecto residual del Zn-DTPA-HEDTA-EDTA a la dosis de 10 mg Zn kg-1 (49,89 mg Zn kg-1). En el cultivo de lino, cultivado bajo condiciones de humedad por debajo de la capacidad de campo, las mayores concentraciones de Zn en planta ese obtuvieron con el efecto residual del Zn-AML a la dosis de 10 mg Zn kg-1 (224,75 mg Zn kg-1) y en el suelo calizo con el efecto residual del Zn-EDTA a la dosis de 10 mg Zn kg-1 (99,83 mg Zn kg-1). El Zn tomado por la planta fue determinado como combinación del rendimiento y de la concentración en planta. Bajo condiciones de humedad por encima de capacidad de campo, con lixiviación, el Zn tomado por la judía disminuyó en el cultivo actual con respecto al cultivo anterior. Sin embargo, en el cultivo de lino, bajo condiciones de humedad por debajo de la capacidad de campo, se obtuvieron cantidades de Zn tomado superiores en el cultivo actual con respecto al anterior. Esta tendencia también se observó, en ambos casos, con el porcentaje de Zn usado por la planta. Summary Zinc is essential for healthy growth and reproduction of plants, animals and humans. Zinc deficiency is one of the most widespread micronutrient deficiency in different crops, and affect different agricultural areas. Agronomic biofortification of crops produced by an increased of Zn in plant, is one way to avoid Zn deficiency in animals and humans Sources with inorganic Zn, such as ZnSO4, have been used traditionally. Although, in recent years, Zn complexes are used as sources of this micronutrient, the provide high concentrations of soluble and available Zn in soil. However, the aging of the source in the soil could cause significant changes in their availability to plants. When an inorganic source of Zn is added to soil, Zn forms more soluble and extractability lose activity over time, transforming into forms more stable and less bioavailable. This study examines the residual effect of different natural and synthetic Zn complexes on navy bean and flax crops, under two different moisture conditions (above and below field capacity, respectively) and in two different soils (acid and calcareous). Fertilizers were applied to the previous crop in three different doses (0, 5 y 10 mg Zn kg-1 soil). The easily leachable Zn was estimated by extraction with 0.1 M BaCl2. Under conditions of moisture above field capacity, the percentage of leachable Zn in the calcareous soil was higher than in acid soil. In the case of navy bean experiment, performed in moisture conditions of above field capacity, amounts extracted of easily leachable Zn were compared with the real leachable Zn. Correlation analysis between the leachable Zn and the estimate was only valid for complex with high mobility and for each soil separately. Under moisture conditions below field capacity, the concentration of bioavailable easily leachable Zn showed highly significant positive correlations with the concentration of available soil Zn. The available Zn was estimated with several commonly used extraction methods: DTPA-TEA, AB-DTPA, Mehlich-3 and LMWOAs. These concentrations were higher in acidic soil than in the calcareous. The different methods used to estimate the available Zn showed highly significant positive correlations with each other. The distribution of Zn in the different fractions of soil was estimated with different sequential extractions. The sequential extractions showed a decrease between the two crops (the previous and current) at the most labile Zn fraction and an increase in the concentration of Zn associated with the less labile fractions, such as carbonates, oxides and organic matter. A positive and highly significant correlation was obtained between the concentrations of Zn associated with more labile fractions (WSEX and WS + EXC, navy bean and flax experiments, respectively) and available Zn concentrations determined by the different methods. Dry matter yield and Zn concentration in plants were determined in plant. Yield and Zn concentration in plant were higher with the residual concentrations of the higher dose applied (10 mg Zn kg-1) than with the lower dose (5 mg Zn kg-1), also these parameters showed higher values with application of this dose than with not Zn application. The increase of Zn concentration in plant with Zn treatments, respect to the control, was greater in the acid soil than in the calcareous. The Zn concentrations in plant indicated that in the calcareous soil, new applications of Zn are desirable in subsequent crops to maintain suitable concentrations in plant. 15 The highest concentrations of Zn in navy bean plant, performed under moisture conditions above the field capacity, were obtained with the residual effect of Zn-HEDTA at the dose of 10 mg Zn kg-1 (280.87 mg Zn kg-1) in the acid soil, and with the residual effect of Zn- DTPA-HEDTA-EDTA at a dose of 10 mg Zn kg-1 (49.89 mg Zn kg-1) in the calcareous soil. In the flax crop, performed under moisture conditions below field capacity, the highest Zn concentrations in plant were obtained with the residual effect of Zn-AML at the dose of 10 mg Zn kg-1 (224.75 Zn mg kg-1) and with the residual effect of Zn-EDTA at a dose of 10 mg Zn kg-1 (99.83 mg Zn kg-1) in the calcareous soil. The Zn uptake was determined as a combination of yield and Zn concentration in plant. Under moisture conditions above field capacity, with leaching, Zn uptake by navy bean decreased in the current crop, respect to the previous crop. However, in the flax crop, under moisture conditions below field capacity, Zn uptake was higher in the current crop than in the previous. This trend is also observed in both cases, with the percentage of Zn used by the plant
Origin and patterns of distribution of trace elements in street dust. Unleaded petrol and urban lead
Resumo:
The elemental composition, patterns of distribution and possible sources of street dust are not common to all urban environments, but vary according to the peculiarities of each city. The common features and dissimilarities in the origin and nature of street dust were investigated through a series of studies in two widely different cities, Madrid (Spain) and Oslo (Norway), between 1990 and 1994. The most comprehensive sampling campaign was carried out in the Norwegian capital during the summer of 1994. An area of 14 km2, covering most of downtown Oslo and some residential districts to the north of the city, was divided into 1 km2 mapping units, and 16 sampling increments of approximately 150 g were collected from streets and roads in each of them. The fraction below 100 μm was acid-digested and analysed by ICP-MS. Statistical analyses of the results suggest that chemical elements in street dust can be classified into three groups: “urban” elements (Ba, Cd, Co, Cu, Mg, Pb, Sb, Ti, Zn), “natural” elements (Al, Ga, La, Mn, Na, Sr, Th, Y) and elements of a mixed origin or which have undergone geochemical changes from their original sources (Ca, Cs, Fe, Mo, Ni, Rb, Sr, U). Soil resuspension and/or mobilisation appears to be the most important source of “natural” elements, while “urban” elements originate primarily from traffic and from the weathering and corrosion of building materials. The data for Pb seem to prove that the gradual shift from leaded to unleaded petrol as fuel for automobiles has resulted in an almost proportional reduction in the concentration of Pb in dust particles under 100 μm. This fact and the spatial distribution of Pb in the city strongly suggest that lead sources other than traffic (i.e. lead accumulated in urban soil over the years) may contribute as much lead, if not more, to urban street dust.
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The need for a better quantification of the influence of Saharan dust transport processes on the air quality modelling in the Mediterranean basin led to the formulation of a dust emission module (DEM) integrated into the Air Quality Risk Assessment System for the Iberian Peninsula (SERCA). This paper is focused on the formulation of DEM based on the GOCART aerosol model, along with its integration and execution into the air quality model. It also addresses the testing of the module and its evaluation by contrasting results against satellite products such as MODIS and CALIPSO and ground-level observations of aerosol optical thickness (AOT) and concentration levels of PM10 for different periods in July 2007. DEM was found capable of reproducing the spatial (horizontal and vertical) and temporal profiles of Saharan dust outbreaks into the Mediterranean basin and the Atlantic coast of Africa. Moreover, it was observed that its combination with CMAQ increased the correlation degree between observed and modelled PM10 concentrations at the selected monitoring locations. DEM also enhanced CMAQ capabilities to reproduce observed AOT, although significant underestimations remain. The implementation of CMAQ + DEM succeeded in capturing Saharan dust transport into the Iberian Peninsula, with contributions up to 25 and 14 μg m−3 in 1 h and 24 h average PM10 respectively. The general improvement of total PM10 predictions in Spain are however moderate. The analysis of model performance for the main PM components points out that remaining PM10 underestimation is due to dust local sources missing in the inventories and misrepresentation of organic aerosol processes, which constitutes the main areas for future improvement of CMAQ capabilities to simulate particulate matter within SERCA.
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A one-step extraction procedure and a leaching column experiment were performed to assess the effects of citric and tartaric acids on Cu and Zn mobilization in naturally contaminated mine soils to facilitate assisted phytoextraction. A speciation modeling of the soil solution and the metal fractionation of soils were performed to elucidate the chemical processes that affected metal desorption by organic acids. Different extracting solutions were prepared, all of which contained 0.01 M KNO3 and different concentrations of organic acids: control without organic acids, 0.5 mM citric, 0.5 mM tartaric, 10 mM citric, 10 mM tartaric, and 5 mM citric +5 mM tartaric. The results of the extraction procedure showed that higher concentrations of organic acids increased metal desorption, and citric acid was more effective at facilitating metal desorption than tartaric acid. Metal desorption was mainly influenced by the decreasing pH and the dissolution of Fe and Mn oxides, not by the formation of soluble metal–organic complexes as was predicted by the speciation modeling. The results of the column study reported that low concentrations of organic acids did not significantly increase metal mobilization and that higher doses were also not able to mobilize Zn. However, 5–10 mM citric acid significantly promoted Cu mobilization (from 1 mg kg−1 in the control to 42 mg kg−1 with 10 mM citric acid) and reduced the exchangeable (from 21 to 3 mg kg−1) and the Fe and Mn oxides (from 443 to 277 mg kg−1) fractions. Citric acid could efficiently facilitate assisted phytoextraction techniques.
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Particulate matter emissions from paved roads are currently one of the main challenges for a sustainable transport in Europe. Emissions are scarcely estimated due to the lack of knowledge about the resuspension process severely hampering a reliable simulation of PM and heavy metals concentrations in large cities and evaluation of population exposure. In this study the Emission Factors from road dust resuspension on a Mediterranean freeway were estimated per single vehicle category and PM component (OC, EC, mineral dust and metals) by means of the deployment of vertical profiles of passive samplers and terminal concentration estimate. The estimated PM10 emission factors varied from 12 to 47 mg VKT?1 (VKT: Vehicle Kilometer Traveled) with an average value of 22.7 ? 14.2 mg VKT?1. Emission Factors for heavy and light duty vehicles, passenger cars and motorbikes were estimated, based on average fleet composition and EPA ratios, in 187e733 mg VKT?1, 33e131 VKT?1, 9.4e36.9 VKT?1 and 0.8e3.3 VKT?1, respectively. These range of values are lower than previous estimates in Mediterranean urban roads, probably due to the lower dust reservoir on freeways. PM emitted material was dominated by mineral dust (9e10 mg VKT?1), but also OC and EC were found to be major components and approximately 14 e25% and 2e9% of average PM exhaust emissions from diesel passenger cars on highways respectively.
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Estudio de una fábrica para tratamiento de menas españolas de zinc
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Expedición a Asturias en 1897 : La Felguera, Fábrica de Zinc en Arnao, alumbrado eléctrico en Oviedo y El Turón
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Extensive spatial and temporal surveys, over 15 years, have been conducted in soil in urban parks and street dusts in one of the most polluted cities in western Europe, Avilés (NW Spain). The first survey was carried out in 1996, and since then monitoring has been undertaken every five years. Whilst the sampling site is a relatively small town, industrial activities (mainly the steel industry and Zn and Al metallurgy) and other less significant urban sources, such as traffic, strongly affect the load of heavy metals in the urban aerosol. Elemental tracers have been used to characterise the influence of these sources on the composition of soil and dust. Although PM10 has decreased over these years as a result of environmental measures undertaken in the city, some of the “industrial” elements still remain in concentrations of concern for example, up to 4.6% and 0.5% of Zn in dust and soil, respectively. Spatial trends in metals such as Zn and Cd clearly reflect sources from the processing industries. The concentrations of these elements across Europe have reduced over time, however the most recent results from Avilés revealed an upward trend in concentration for Zn, Cd, Hg and As. A risk assessment of the soil highlighted As as an element of concern since its cancer risk in adults was more than double the value above which regulatory agencies deem it to be unacceptable. If children were considered to be the receptors, then the risk nearly doubles from this element.
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An important issue related to future nuclear fusion reactors fueled with deuterium and tritium is the creation of large amounts of dust due to several mechanisms (disruptions, ELMs and VDEs). The dust size expected in nuclear fusion experiments (such as ITER) is in the order of microns (between 0.1 and 1000 μm). Almost the total amount of this dust remains in the vacuum vessel (VV). This radiological dust can re-suspend in case of LOVA (loss of vacuum accident) and these phenomena can cause explosions and serious damages to the health of the operators and to the integrity of the device. The authors have developed a facility, STARDUST, in order to reproduce the thermo fluid-dynamic conditions comparable to those expected inside the VV of the next generation of experiments such as ITER in case of LOVA. The dust used inside the STARDUST facility presents particle sizes and physical characteristics comparable with those that created inside the VV of nuclear fusion experiments. In this facility an experimental campaign has been conducted with the purpose of tracking the dust re-suspended at low pressurization rates (comparable to those expected in case of LOVA in ITER and suggested by the General Safety and Security Report ITER-GSSR) using a fast camera with a frame rate from 1000 to 10,000 images per second. The velocity fields of the mobilized dust are derived from the imaging of a two-dimensional slice of the flow illuminated by optically adapted laser beam. The aim of this work is to demonstrate the possibility of dust tracking by means of image processing with the objective of determining the velocity field values of dust re-suspended during a LOVA.
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La emisión de polvo por efecto del viento desde depósitos de residuos mineros o industriales y el paso de vehículos en vías no pavimentadas, es un problema que afecta las actividades productivas; el ambiente y la salud de las personas que permanecen en el área contaminada. En Chile, en los últimos años la sensibilidad social y las exigencias ambientales han aumentado, así como la oferta de diferentes supresores y tecnologías de aplicación. Se han revisado las causas que provocan emisión de polvo y las tecnologías disponibles en Chile para la supresión de polvo, además de las metodologías y normativa para evaluar el desempeño de los materiales tratados con diferentes supresores. En algunos casos no es posible comparar propiedades de desempeño, como durabilidad, dosis a aplicar y frecuencia de las aplicaciones, entre otros aspectos. Los procedimientos descritos en la norma NCh3266-2012 permiten evaluar la erosión eólica en depósitos de residuos, sitios eriazos y caminos no pavimentados, entre otros, junto con evaluar el desempeño de diferentes tipos de supresores de polvo a partir de datos objetivos comparables. Esto permite seleccionar el supresor más adecuado, mejorar la eficiencia de los tratamientos, optimizar los costos y mejorar los procesos productivos. Palabras clave: Erosión-eólica, supresor de polvo, residuos-mineros, caminos-no pavimentados. Dust emissions by wind effect from mining deposits or industrial waste and passing vehicles on unpaved roads, is a problem that affects the productive activities; the environment and the health of those who remain in the contaminated area. The social sensitivity and environmental requirements on this issue in Chile have increased, as well as offering different suppressors and application technologies. Have been reviewed the causes of dust emission and technologies available in Chile for dust suppression, plus methodologies and standards for assessing the performance of the treated materials with different suppressors. In some cases it is not possible to compare performance properties such as durability, application dose and frequency of applications, among others aspects. The procedures described in the NCh 3266-2012 standard allows the assessment of wind erosion in waste deposits, vacant lots and unpaved roads, among others, along with evaluating the performance of different types of dust suppressants from comparable objective data. This allows selecting the most suitable suppressor, improve efficiency of treatments, optimize costs and improve production processes. Keywords: Wind-erosion, dust-suppressor, mining-waste, unpavedroads