Publications by authors named "Omar Felix"

8 Publications

  • Page 1 of 1

Phytoremediation Reduces Dust Emissions from Metal(loid)-Contaminated Mine Tailings.

Environ Sci Technol 2018 05 27;52(10):5851-5858. Epub 2018 Apr 27.

Environmental and health risk concerns relating to airborne particles from mining operations have focused primarily on smelting activities. However, there are only three active copper smelters and less than a dozen smelters for other metals compared to an estimated 500000 abandoned and unreclaimed hard rock mine tailings in the US that have the potential to generate dust. The problem can also extend to modern tailings impoundments, which may take decades to build and remain barren for the duration before subsequent reclamation. We examined the impact of vegetation cover and irrigation on dust emissions and metal(loid) transport from mine tailings during a phytoremediation field trial at the Iron King Mine and Humboldt Smelter Superfund (IKMHSS) site. Measurements of horizontal dust flux following phytoremediation reveals that vegetated plots with 16% and 32% canopy cover enabled an average dust deposition of 371.7 and 606.1 g m y, respectively, in comparison to the control treatment which emitted dust at an average rate of 2323 g m y. Horizontal dust flux and dust emissions from the vegetated field plots are comparable to emission rates in undisturbed grasslands. Further, phytoremediation was effective at reducing the concentration of fine particulates, including PM, PM, and PM, which represent the airborne particulates with the greatest health risks and the greatest potential for long-distance transport. This study demonstrates that phytoremediation can substantially decrease dust emissions as well as the transport of windblown contaminants from mine tailings.
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http://dx.doi.org/10.1021/acs.est.7b05730DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7025808PMC
May 2018

Windblown Dust Deposition Forecasting and Spread of Contamination around Mine Tailings.

Atmosphere (Basel) 2016 Feb 28;7(2). Epub 2016 Jan 28.

Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ 85721, USA.

Wind erosion, transport and deposition of windblown dust from anthropogenic sources, such as mine tailings impoundments, can have significant effects on the surrounding environment. The lack of vegetation and the vertical protrusion of the mine tailings above the neighboring terrain make the tailings susceptible to wind erosion. Modeling the erosion, transport and deposition of particulate matter from mine tailings is a challenge for many reasons, including heterogeneity of the soil surface, vegetative canopy coverage, dynamic meteorological conditions and topographic influences. In this work, a previously developed Deposition Forecasting Model (DFM) that is specifically designed to model the transport of particulate matter from mine tailings impoundments is verified using dust collection and topsoil measurements. The DFM is initialized using data from an operational Weather Research and Forecasting (WRF) model. The forecast deposition patterns are compared to dust collected by inverted-disc samplers and determined through gravimetric, chemical composition and lead isotopic analysis. The DFM is capable of predicting dust deposition patterns from the tailings impoundment to the surrounding area. The methodology and approach employed in this work can be generalized to other contaminated sites from which dust transport to the local environment can be assessed as a potential route for human exposure.
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http://dx.doi.org/10.3390/atmos7020016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5658141PMC
February 2016

Reconciling PM10 analyses by different sampling methods for Iron King Mine tailings dust.

Rev Environ Health 2016 Mar;31(1):37-41

The overall project objective at the Iron King Mine Superfund site is to determine the level and potential risk associated with heavy metal exposure of the proximate population emanating from the site's tailings pile. To provide sufficient size-fractioned dust for multi-discipline research studies, a dust generator was built and is now being used to generate size-fractioned dust samples for toxicity investigations using in vitro cell culture and animal exposure experiments as well as studies on geochemical characterization and bioassay solubilization with simulated lung and gastric fluid extractants. The objective of this study is to provide a robust method for source identification by comparing the tailing sample produced by dust generator and that collected by MOUDI sampler. As and Pb concentrations of the PM10 fraction in the MOUDI sample were much lower than in tailing samples produced by the dust generator, indicating a dilution of Iron King tailing dust by dust from other sources. For source apportionment purposes, single element concentration method was used based on the assumption that the PM10 fraction comes from a background source plus the Iron King tailing source. The method's conclusion that nearly all arsenic and lead in the PM10 dust fraction originated from the tailings substantiates our previous Pb and Sr isotope study conclusion. As and Pb showed a similar mass fraction from Iron King for all sites suggesting that As and Pb have the same major emission source. Further validation of this simple source apportionment method is needed based on other elements and sites.
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http://dx.doi.org/10.1515/reveh-2015-0061DOI Listing
March 2016

Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model.

Aeolian Res 2014 Sep;14:75-83

Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, United States.

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition.
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http://dx.doi.org/10.1016/j.aeolia.2014.02.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4303573PMC
September 2014

Use of lead isotopes to identify sources of metal and metalloid contaminants in atmospheric aerosol from mining operations.

Chemosphere 2015 Mar 12;122:219-226. Epub 2014 Dec 12.

Department of Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.

Mining operations are a potential source of metal and metalloid contamination by atmospheric particulate generated from smelting activities, as well as from erosion of mine tailings. In this work, we show how lead isotopes can be used for source apportionment of metal and metalloid contaminants from the site of an active copper mine. Analysis of atmospheric aerosol shows two distinct isotopic signatures: one prevalent in fine particles (<1μm aerodynamic diameter) while the other corresponds to coarse particles as well as particles in all size ranges from a nearby urban environment. The lead isotopic ratios found in the fine particles are equal to those of the mine that provides the ore to the smelter. Topsoil samples at the mining site show concentrations of Pb and As decreasing with distance from the smelter. Isotopic ratios for the sample closest to the smelter (650m) and from topsoil at all sample locations, extending to more than 1km from the smelter, were similar to those found in fine particles in atmospheric dust. The results validate the use of lead isotope signatures for source apportionment of metal and metalloid contaminants transported by atmospheric particulate.
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http://dx.doi.org/10.1016/j.chemosphere.2014.11.057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4277909PMC
March 2015

Laboratory dust generation and size-dependent characterization of metal and metalloid-contaminated mine tailings deposits.

J Hazard Mater 2014 Sep 6;280:619-26. Epub 2014 Sep 6.

Department of Chemical and Environmental Engineering, University of Arizona, 1133 E. James E. Rogers Way, Tucson, AZ 85721, USA. Electronic address:

The particle size distribution of mine tailings material has a major impact on the atmospheric transport of metal and metalloid contaminants by dust. Implications to human health should be assessed through a holistic size-resolved characterization involving multidisciplinary research, which requires large uniform samples of dust that are difficult to collect using conventional atmospheric sampling instruments. To address this limitation, we designed a laboratory dust generation and fractionation system capable of producing several grams of dust from bulk materials. The equipment was utilized in the characterization of tailings deposits from the arsenic and lead-contaminated Iron King Superfund site in Dewey-Humboldt, Arizona. Results show that metal and metalloid contaminants are more concentrated in particles of < 10 μm aerodynamic diameter, which are likely to affect surrounding communities and ecosystems. In addition, we traced the transport of contaminated particles from the tailings to surrounding soils by identifying Pb and Sr isotopic signatures in soil samples. The equipment and methods developed for this assessment ensure uniform samples for further multidisciplinary studies, thus providing a tool for comprehensive representation of emission sources and associated risks of exposure.
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http://dx.doi.org/10.1016/j.jhazmat.2014.09.002DOI Listing
September 2014

Size-resolved dust and aerosol contaminants associated with copper and lead smelting emissions: implications for emission management and human health.

Sci Total Environ 2014 Sep 2;493:750-6. Epub 2014 Jul 2.

Department of Atmospheric Sciences, The University of Arizona, Tucson, AZ 85721, USA. Electronic address:

Mining operations, including crushing, grinding, smelting, refining, and tailings management, are a significant source of airborne metal and metalloid contaminants such as As, Pb and other potentially toxic elements. In this work, we show that size-resolved concentrations of As and Pb generally follow a bimodal distribution with the majority of contaminants in the fine size fraction (<1 μm) around mining activities that include smelting operations at various sites in Australia and Arizona. This evidence suggests that contaminated fine particles (<1 μm) are the result of vapor condensation and coagulation from smelting operations while coarse particles are most likely the result of windblown dust from contaminated mine tailings and fugitive emissions from crushing and grinding activities. These results on the size distribution of contaminants around mining operations are reported to demonstrate the ubiquitous nature of this phenomenon so that more effective emission management and practices that minimize health risks associated with metal extraction and processing can be developed.
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http://dx.doi.org/10.1016/j.scitotenv.2014.06.031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4137906PMC
September 2014

Effect of wind speed and relative humidity on atmospheric dust concentrations in semi-arid climates.

Sci Total Environ 2014 Jul 27;487:82-90. Epub 2014 Apr 27.

Department of Atmospheric Sciences, The University of Arizona, Tucson, AZ 85721, United States. Electronic address:

Atmospheric particulate have deleterious impacts on human health. Predicting dust and aerosol emission and transport would be helpful to reduce harmful impacts but, despite numerous studies, prediction of dust events and contaminant transport in dust remains challenging. In this work, we show that relative humidity and wind speed are both determinants in atmospheric dust concentration. Observations of atmospheric dust concentrations in Green Valley, AZ, USA, and Juárez, Chihuahua, México, show that PM10 concentrations are not directly correlated with wind speed or relative humidity separately. However, selecting the data for high wind speeds (>4m/s at 10 m elevation), a definite trend is observed between dust concentration and relative humidity: dust concentration increases with relative humidity, reaching a maximum around 25% and it subsequently decreases with relative humidity. Models for dust storm forecasting may be improved by utilizing atmospheric humidity and wind speed as main drivers for dust generation and transport.
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http://dx.doi.org/10.1016/j.scitotenv.2014.03.138DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072227PMC
July 2014