This work was carried out in the framework of the Labex SERENADE (ANR-11-LABX-0064) and the A*MIDEX Project (ANR-11-IDEX-0001-02), funded by the French Government program, Investissements d'Avenir, and managed by the French National Research Agency (ANR). We thank the French Ministry of Environment (DRC 33 and Program 190) and ANSES (Nanodata Project 2012/2/154, APR ANSES 2012) for financing the work. We are equally grateful to Olivier Aguerre-Chariol, Patrice Delalain, Morgane Dalle, Laurent Meunier, Pauline Molina, and Farid Ait-Ben-Ahmad for their cooperation and advice during the experiments.

NOTE: The technique presented in the Protocol here is not only limited to the presented test samples but can be used for other samples as well.
1. Artificial Weathering [CEREGE Platform, Aix en Provence]
<ol>
	<li>Take a 250 ml sample of the deionized and purified water to be sprayed in a beaker. Immerse the tip of the water conductivity meter into the water. Note the water conductivity. Repeat the process and note the water conductivity each time. 
	NOTE: According to the ISO 1647432, it should never be higher than 5 &#181;S/cm.</li>
	<li>After measuring the conductivity, connect the water source to the reservoir of the weathering chamber present underneath the stainless steel hood (shown in Figure 3).</li>
	<li>Connect the overflow spout on the back of the chamber to a drain opening through a hose pipe.</li>
	<li>Place the nanocoating samples to weather into the stainless steel hood and close the door. To enable a statistical evaluation of the results, use a minimum of three identical nanocoating and reference samples.</li>
	<li>On the digital console, present on the front of the weathering chamber, select a 2 hr cycle composed of 120 min of UV light, 102 min dry and 18 min water spray.</li>
	<li>Enter the number of cycles equal to 2658 which corresponds to 7 months.</li>
	<li>Choose the irradiance level of the xenon arc lamp equal to 60 &#177; 5 W/m2.</li>
	<li>Set the ambient temperature at 38 &#176;C.</li>
	<li>Start the weathering test by pressing the LAUNCH button on the console.</li>
</ol>
2. Abrasion and ENM Aerosols Characterization [INERIS S-NANO Platform, Verneuil]
NOTE: Before using, pre-verify the particle aerosol characterizing instruments on a calibration bench of INERIS S-NANO Platform which comprises of separate and already installed reference counter parts. By following a specific protocol, ensure that the instruments are working properly.
<ol>
	<li>Assemble all the units and instruments shown in the experimental set-up and make the necessary connections as shown in Figure 2 (details on the units and setting up of instruments are provided in Shandilya et al.33).</li>
	<li>Switch on the circulation of the particle free air inside the nanosecured workpost by pressing the FLUX ON button.</li>
	<li>Make this particle free air to pass through the emission test chamber by opening the chamber and keeping it open inside the nanosecured work post.</li>
	<li>To set up the experiment, connect the particle counter directly to the emission test chamber to measure the instantaneous number concentration of the particles inside the chamber. Observe the concentration value directly on the display counter.</li>
	<li>While the particle free air is passing through the chamber, continue to monitor this instantaneous number concentration value until it drops to zero. In this way, ensure that the chamber is free of any background particle.</li>
	<li>In the meantime, chamfer the edges of the standard cylindrically shaped abradant by gently turning its one end in a to and fro motion inside the slot of a tool provided with the abrasion apparatus.</li>
	<li>Using a digital balance with a measurement precision of at least 0.001 g, weigh the abradant and sample to be abraded.</li>
	<li>Once done, fix the chamfered abradant to the vertical shaft of the abrasion apparatus through a chuck present at its bottom.</li>
	<li>Place the nanostructured product to be abraded gently beneath the fixed abradant and firmly fix its position on the mounting system.</li>
	<li>Open the aerosol sampler and, by using a tweezer, place a copper mesh grid inside the slot with its brighter side upwards. Put a circular ring over the grid to fix it.</li>
	<li>Close the sampler and connect it to a pump via a filter on one end (i.e., towards darker side of the grid) and to the particle source on the other end (i.e., towards brighter side of the grid). Mount the required normal load on the vertical shaft using the dead weights.</li>
	<li>Through the particle counter, check if the background particles concentration inside the open chamber has dropped to zero. If not, wait for it. If yes, close the door of the emission test chamber.</li>
	<li>Via the digital consoles on the instruments, manually set the flow rates of the particle counter and the sizers as follows: CPC- 1.5 l/min; SMPS- 0.3 l/min; APS- 5 l/min</li>
	<li>Set the total sampling duration at 20 min for all these three instruments. Set the abrasion duration and speed equal to 10 min and 60 cycles per minute respectively in the abrasion apparatus.</li>
	<li>Connect the strain gauge to the dynamic strain gauge amplifier. Connect the dynamic strain gauge amplifier to the computer which shall be used for the data acquisition using software installed in it.</li>
	<li>Open the software.</li>
	<li>Click NEW DAQ PROJECT to open a new data acquisition file.</li>
	<li>Stop the option for live data acquisition by clicking LIVE UPDATE</li>
	<li>Click 0 EXECUTE to set the reference signal value equal to zero.</li>
	<li>Switch back on the live data acquisition by clicking LIVE UPDATE.</li>
	<li>Click VISUALIZATION to choose the real time graphical mode of data representation.</li>
	<li>Click NEW to open the templates.</li>
	<li>Choose the option SCOPE PANEL, for example.</li>
	<li>Start the data acquisition in the particle counters and sizers at once.</li>
	<li>After a delay of approx. 5 min, start the abrasion.</li>
	<li>Click START in the data acquisition software window to acquire the strain gauge signals corresponding to the ongoing abrasion.</li>
	<li>After 2 min, switch on the pump connected to the MPS.</li>
	<li>Keep the pump running for 2 - 4 min depending upon the quantity of the emission of the aerosol particles. NOTE: The number of aerosol particles sampled using MPS should be optimal in number i.e., neither too scarce nor too surplus which might prevent a thorough microscopic analysis.</li>
	<li>Once the abrasion stops, switch off the data acquisition by clicking STOP.</li>
	<li>Save the acquired data by clicking SAVE DATA NOW.</li>
	<li>After the counter and sizers stop acquiring data, open the emission test chamber and weigh again the abradant and abraded nanostructured product.</li>
	<li>Continue the entire process for every abrasion test.</li>
	<li>Once the abrasion tests, once again verify the three particle aerosol characterizing instruments are on the calibration bench of INERIS S-NANO Platform.</li>
</ol>
3. TEM Analysis of the Liquid Suspensions- Drop Deposition Technique [INERIS Calibration Platform, Verneuil]
<ol>
	<li>Prepare a 1% volume diluted aqueous solution of the liquid suspension (i.e.,&#160;the &#39;paint&#39;) by adding 1 part of the coating suspension in 99 parts of the filtered and de-ionized water.</li>
	<li>Open the cover of the glow discharge machine</li>
	<li>Set the following operating conditions: 0.1 mbar, 45 mA, 3 min duration.</li>
	<li>In order to make a TEM copper mesh grid hydrophilic by its plasma treatment, put it on the metal stand. Close the cover and start the motor. After 3 min, it stops automatically.</li>
	<li>Take out the hydrophilic turned mesh grid using a tweezer. Place it gently with its brighter side up. Deposit a drop of the diluted solution (8 &#181;l approx.) onto the hydrophilic mesh grid using a syringe.</li>
	<li>Dry the mesh grid in a closed chamber so that the water content gets evaporated and the constituent particles rest deposited on the grid. Make sure that the mesh grid doesn&#39;t get charged with the stray particles which can be easily identified as circular or strand shapes which are characteristic of oil or soot particles.</li>
	<li>Once ready, put the grid in the TEM probe and carry out the microscopic analysis. [electron accelerating voltage 120 kV, cf] 31.</li>
	<li>If the grid appears too laden with particles to analyze, lower the dilution percentage and volume of the deposited drop. The maximum volume an operator is able to deposit is approximately equal to 12 &#181;l.</li>
</ol>

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The authors have nothing to disclose.

In the present article, an experimental investigation of the nanosafety-by-design of commercial nanostructured products is presented. The nanosafety-by-design of any product can be studied in terms of its PNC and PSD when it is subjected to mechanical stresses and environmental weathering. The products chosen for the study are alumino-silicate brick reinforced with TiO2 nanoparticles, glaze with CeO2 nanoparticles and photocatalytic nanocoatings with TiO2 nanoparticles. These products are...

With a rapid maturity in the nanotechnology, its advancement is driven by rapid commercialization of products containing Engineered Nanomaterials (ENM) with remarkable properties. As described by Potocnick1 in the article 18(5) of Regulation 1169/2011, issued by the European Commission, ENM can be defined as &#34;any intentionally manufactured material, containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm to 100 nm&#34;. Moreover, the products containing ENM, either in their solid bulk or on their solid surfaces or in their liquid suspensions, can be termed as Nanostructured products. Different types of ENM with different formulations and functionalizations are used in such products according to the nature of application and budget. The products can be in the form of coatings, paints, tiles, house bricks, concrete etc.
As far as the research is concerned, one may also find enormous number of publications on the innovations that have been accomplished through nanotechnology. Despite this enormous research, the appealing traits of ENM are under probe for potential health or environmental dangers due to their tendency to get released or emitted in air in the form of aerosols during the use or processing of the nanostructures products (for example Oberdorster et al.2, Le Bihan et al.3 and Houdy et al.4). Kulkarni et al.5 defines an aerosol as the suspension of solid or liquid particles in the gaseous medium. Hsu and Chein6 have demonstrated that during the use or processing of a nanostructured product, a nanostructured product is subjected to various mechanical stresses and environmental weathering which facilitate such an emission.
According to Maynard7, upon exposure, these aerosols of ENM may interact with human organism through inhalation or dermal contacts and get deposited inside the body which consequently may cause various detrimental effects, including the carcinogenic ones. Thus, a thorough understanding of the ENM emission phenomenon is of paramount importance given the unprecedented use of nanostructured products, as mentioned by Shatkin et al.8. This may not only help in avoiding unanticipated health related complications arising from their exposure but also in encouraging public confidence in nanotechnologies.
Nevertheless, the exposure related problem has now started getting attention by the research community and has been recently highlighted by various research units throughout the world (for example, Hsu and Chein6, G&#246;hler et al.9, Allen et al.10, Allen et al.11, Al-Kattan et al.12, Kaegi et al.13, Hirth et al.14, Shandilya et al.15, 31, 33, Wohlleben et al.16, Bouillardet al.17, Ounoughene et al.18). Considering the large scale deployment of nanostructured products in the commercial markets, the most effective approach to tackle the problem would be a preemptive one. In such an approach, a product is designed in such a way that it is &#34;nanosafe-by-design&#34; or &#34;Design for safer Nanotechnology&#34; (Morose19) i.e., low emissive. In other words, it maximizes their benefits in problem solving during its use while emitting a minimum amount of aerosols in the environment.
To test the nanosafety-by-design during the usage phase of a nanostructured product, the authors present an appropriate experimental methodology to do so in the present article. This methodology consists of two types of solicitations: (i) mechanical and (ii) environmental which aim at simulating the real life stresses to which the nanostructured product, a masonry brick, is subjected to during its usage phase.
(i) A linear abrasion apparatus which simulates the mechanical solicitation. Its original and commercial form, as shown in Figure 1A, is referenced in numerous internationally recognized test standards like ASTM D406020, ASTM D603721 and ASTM D104422. According to Golanski et al.23, due to its robust and user-friendly design, its original form is already being used widely in industries for analyzing the performance of products like paint, coating, metal, paper, textile, etc. The stress being applied through this apparatus corresponds to the typical one applied in a domestic setting, for example, walking with shoes and displacement of different objects in a household (Vorbau et al.24 and Hassan et al.25). In Figure 1A, a horizontally displacing bar moves the standard abradant in a to and fro motion over the sample surface. The abrasion wear occurs at the contact surface due to the friction at the contact. The magnitude of the abrasion wear can be varied by varying the normal load (FN) which acts at the top of the abradant. By changing the type of the abradant and normal load value, one may vary the abrasiveness and hence the mechanical stress. Morgeneyer et al.26 have pointed out that the stress tensor to be measured during abrasion is composed of normal and tangential components. The normal stress is the direct result of the normal load, i.e., of FN whereas the tangential stress is the result of the tangentially acting friction process, measured as force (FT) and it acts parallel or anti-parallel to the direction in which abrasion takes place. In the original form of this abrasion apparatus, one cannot determine FT. Therefore, the role of the mechanical stresses during the aerosolization of ENM cannot completely be determined. To eradicate this limitation, as described in details by Morgeneyer et al.26, we have (a) modified it by replacing the already installed horizontal steel bar by a replica in aluminum 2024 alloy and (b) mounted a strain gauge on the top surface of this replicated aluminum alloy bar. This is shown in Figure 1B. This strain gauge has 1.5 mm of active measuring grid length and 5.7 mm of measuring grid carrier length. It is made of a constantan foil having 3.8 &#181;m of thickness and 1.95 &#177; 1.5% of gauge factor. A proper measurement of the mechanical stresses are ensured through a dynamic strain gauge amplifier which is connected in series to the strain gauge, thus allowing a reliable measurement of the strain produced in the gauge. The data transmitted via amplifier is acquired using data acquisition software.
<img alt="Figure 1" src="/files/ftp_upload/53496/53496fig1.jpg" /> 
Figure 1. Abrasion Apparatus and Strain Gauge. The commercial standard form of the Taber abrasion apparatus (A) with abrasion speed, duration and stroke length controls. The originally mounted steel bar was replaced by an aluminum bar and was further equipped with a strain gauge (B) to measure the tangential force (FT). <a href="http://cloudflare.jove.com/files/ftp_upload/53496/53496fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In the Figure 2, the complete experimental set-up is shown where this modified Taber abrasion apparatus is placed under the conformity of a nanosecured work post. A particle free air is constantly circulating inside this work post at a flow rate of 31,000 l/min. It has a particle filter efficiency of 99.99% and has already been successfully employed by Morgeneyer et al.27 in various nanoparticles&#39; dustiness tests.
<img alt="Figure 2" src="/files/ftp_upload/53496/53496fig2.jpg" /> 
Figure 2. Experimental Set-up (Shandilya et al.31). A nanosecured work facility to carry out the abrasion tests and real time characterization (both qualitative and quantitavive) of the generated aerosol particles. A small fraction of the particle free air passes through a slot inside the emission chamber to eliminate its background particles number concentration. <a href="http://cloudflare.jove.com/files/ftp_upload/53496/53496fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The motor of the abrasion apparatus is kept outside and its linearly sliding part is kept inside a self-designed emission test chamber, with dimensions, 0.5 m &#215; 0.3 m &#215; 0.6 m, (details in Le Bihan et al.28). It helps in preventing the abrasion apparatus&#39; motor emissions from interfering in the test results. The sampling of the generated aerosol particles is done inside the proximity of a radial symmetric hood (volume of 713 cm3). By employing such a hood, the aerosol particles losses due to their deposition on the surfaces can be minimized. The other advantage includes increase in the aerosol particles number concentration due to a relatively lower volume of the hood with respect to the emission test chamber. Thanks to this set up, a real time characterization and analysis of the particle aerosols getting generated during the abrasion wear can be done experimentally in terms of their number concentrations, size distributions, elemental compositions and shapes. According to Kulkarni et al.5, the number concentration of ENM aerosols particles can be defined as &#34;the number of ENM present in unit cubic centimeter of air&#34;. Similarly, the size distribution of ENM aerosols is &#34;the relationship expressing the quantity of an ENM property (usually number and mass concentrations) associated with particles in a given size range&#34;.
A particle Counter (measurable size range: 4 nm to 3 &#181;m) measures the aerosol particles number concentration (PNC). The particle sizers (measurable size range: 15 nm - 20 &#181;m) measure the particle size distribution (PSD). An aerosol particles sampler (described in details by R&#39;mili et al.30) is used for the particle collection through filtration technique on a porous copper mesh grid which can be used later in Transmission Electron Microscope (TEM) for various qualitative analyses of the released particles.
(ii) The environmental solicitation can be simulated through accelerated artificial weathering in a weathering chamber, shown in Figure 3. As shown by Shandilya et al.31, the weathering conditions can be kept in conformity with the international standards or be customized depending upon the type of simulation. The UV exposure is provided via xenon arc lamp (300 &#8722; 400 nm) installed with an optical radiation filter. The action of rain is simulated by spraying deionized and purified water onto them. A reservoir is placed beneath the test samples to collect the runoff water. The collected water or leachate can be used later to perform the ENM leaching analysis.
<img alt="Figure 3" src="/files/ftp_upload/53496/53496fig3.jpg" /> 
Figure 3. Weathering Chamber. The commercial form of the Suntest XLS+ weathering chamber contains a stainless steel hood inside which the nanocoated samples are placed. The water reservoir is placed beneath the hood which is the source of the water to be sprayed inside the hood. <a href="http://cloudflare.jove.com/files/ftp_upload/53496/53496fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>Photocal Masonry</td><td>Nanofrance Technologies</td><td></td><td>Test sample</td></tr><tr><td>Masonry brick (ref. 901796)</td><td>Castorama</td><td></td><td>Support for test sample</td></tr><tr><td>Optical microscope (model Imager.M1m)</td><td>Carl Zeiss&lt;br/&gt; MicroImaging GmbH</td><td></td><td>For microcopic analysis</td></tr><tr><td>Energy-dispersion spectroscope (model X-max)</td><td>Oxford Instruments</td><td></td><td>For elemental composition analysis</td></tr><tr><td>Transmission Electron&lt;br/&gt; Microscope (model CM12)</td><td>Philips</td><td></td><td>For microcopic analysis</td></tr><tr><td>Weathering chamber (model Suntest XLS+)</td><td>Atlas</td><td></td><td>For accelerated artificial weathering</td></tr><tr><td>Xenon arc lamp (model NXE 1700)</td><td>Ametek SAS</td><td></td><td>UV rays source</td></tr><tr><td>Inductively Coupled Plasma Mass spectrometer (model 7500cx)</td><td>Agilent Technologies</td><td></td><td>For leachate&lt;br/&gt; water samples analysis</td></tr><tr><td>Taber linear abraser (model 5750)</td><td>Taber Inc.</td><td></td><td>For abrasion</td></tr><tr><td>Taber H38 abradant</td><td>Taber Inc.</td><td></td><td>For abrasion</td></tr><tr><td>Condensation Particle Counter 3775</td><td>TSI</td><td></td><td>For counting number concentration of aerosol particles</td></tr><tr><td>Aerodynamic Particle Sizer 3321</td><td>TSI</td><td></td><td>For measuring the size of aerosol particles&amp;nbsp;</td></tr><tr><td>Differential Mobility Analyzer 3081</td><td>TSI</td><td></td><td>For measuring the size of aerosol particles&amp;nbsp;</td></tr><tr><td>Mini Particle Sampler</td><td>Ecomesure</td><td></td><td>For sampling the aerosol particles</td></tr><tr><td>Gilian LFS-113 Low Flow Personal Air Sampling Pump</td><td>Sensidyne</td><td></td><td>For sampling the aerosol particles</td></tr></tbody></table>

experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering, which is a fundamental element to the approach of nanosafety-by-design of nanostructured products for their durable development. This approach is basically a preemptive one in which the focus is put on minimizing the emission of engineered nanomaterials' aerosols during the usage phase of the product's life cycle. This can be attained by altering its material properties during its design phase without compromising with any of its added benefits. In this article, an experimental protocol is presented to investigate the nanosafety-by-design of three commercial nanostructured products with respect to their mechanical solicitation and environmental weathering. The means chosen for applying the mechanical solicitation is an abrasion process and for the environmental weathering, it is an accelerated UV exposure in the presence of humidity and heat. The eventual emission of engineered nanomaterials is studied in terms of their number concentration, size distribution, morphology and chemical composition. The purpose of the protocol is to study the emission for test samples and experimental conditions which are corresponding to real life situations. It was found that the application of the mechanical stresses alone emits the engineered nanomaterials' aerosols in which the engineered nanomaterial is always embedded inside the product matrix, thus, a representative product element. In such a case, the emitted aerosols comprise of both nanoparticles as well as microparticles. But if the mechanical stresses are coupled with the environmental weathering, the experimental protocol reveals then the eventual deterioration of the product, after a certain weathering duration, may lead to the emission of the free engineered nanomaterial aerosols too.

Test Samples 
The protocols presented in the article were applied to three different commercial nanostructured products. A focus is put here on the details of the experimental approach: 
(a) alumino-silicate brick reinforced with TiO2 nanoparticles, (11 cm x 5 cm x 2 cm). It finds its frequent application in constructing fa&#231;ades, house walls, wall tiles, pavements etc. Its material properties along with a scanning electron microscope ima...

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Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

In this article, an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering is presented. Results on the emission of engineered nanomaterials, in the form of aerosols are presented. The specific experimental set-up is described in detail.

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental ...

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Research

JoVE Journal

Engineering

7.3K Views.  Institut National de l'Environnement Industriel et des Risques (INERIS).  In dit artikel, een experimenteel protocol te onderzoeken deeltje verstuiving van een product in het kader van slijtage en in het kader van het milieu verwering wordt gepresenteerd. Resultaten op de emissie van gemanipuleerde nanomaterialen in de vorm van aërosolen worden gepresenteerd. De specifieke experimentele set-up wordt in detail beschreven. 

Video: Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

We present a technique to achieve low-velocity to intermediate-velocity collisions between fragile dust aggregates in the laboratory. For this purpose, two vacuum drop-tower setups have been developed that allow collision velocities between &#60;0.01 and ~10 m/sec. The collision events are recorded by high-speed imaging.

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust ...

Extraction and Characterization of Surfactants from Atmospheric Aerosols

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth&#39;s atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth&#39;s ecosystems.
In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter &#60;1 &#956;m) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Methods are presented for the targeted extraction of surfactants present in atmospheric aerosols and the determination of their absolute concentrations and surface tension curves in water, including their Critical Micelle Concentration (CMC).

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in ...

Environment

Experimental Methods of Dust Charging and Mobilization on Surfaces with Exposure to Ultraviolet Radiation or Plasmas

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using three recently developed experiments in which dust particles are exposed to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. The UV light source has a narrow bandwidth in wavelength centered at 172 nm. The beam electrons with the energy of 120 eV are created with a negatively biased hot filament. When the vacuum chamber is filled with the argon gas, a thermal plasma is created in addition to the electron beam. Insulating dust particles of a few tens of microns in diameter are used in the experiments. Dust particles are recorded to be lofted to a height up to a few centimeters with a launch speed up to 1 m/s. These experiments demonstrate that photo and/or secondary electron emission from a dusty surface changes the charging mechanism of dust particles. According to the recently developed &#34;patched charge model&#34;, the emitted electrons can be re-absorbed inside microcavities between neighboring dust particles below the surface, causing the accumulation of enhanced negative charges on the surrounding dust particles. The repulsive forces between these negatively charged particles may be large enough to mobilize and lift them off the surface. These experiments present the advanced understanding of dust charging and transport on dusty surfaces, and laid a foundation for future investigations of its role in the surface evolution of airless planetary bodies.

Dust charging and mobilization is demonstrated in three experiments with exposure to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. These experiments present the advanced understanding of electrostatic dust transport and its role in shaping the surfaces of airless planetary bodies.

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using ...

A System to Create Stable Nanoparticle Aerosols from Nanopowders

Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring minimal amounts of test materials (min. 200 mg), for studying powder aerosolization behavior and aerosol properties. The aerosolization procedure follows the concept of the fluidized-bed process, but occurs in the modified volume of a V-shaped aerosol generator. The airborne particle number concentration is adjustable by controlling the air flow rate. The system supplied stable aerosol generation rates and particle size distributions over long periods (0.5-2 hr and possibly longer), which are important, for example, to study aerosol behavior, but also for toxicological studies. Strict adherence to the operating procedures during the aerosolization experiments ensures the generation of reproducible test results. The critical steps in the standard protocol are the preparation of the material and setup, and the aerosolization operations themselves. The system can be used for experiments requiring stable aerosol concentrations and may also be an alternative method for testing dustiness. The controlled aerosolization made possible with this setup occurs using energy inputs (may be characterized by aerosolization air velocity) that are within the ranges commonly found in occupational environments where nanomaterial powders are handled. This setup and its operating protocol are thus helpful for human exposure and risk assessment.

We designed and developed an effective nanopowder aerosolization setup and operating protocol. The system generated nanoparticle aerosols with stable number concentrations and size distributions for long durations, requiring only small quantities of test material (min. 200 mg).

Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring ...

Testing of Nanoparticle Release from a Composite Containing Nanomaterial Using a Chamber System

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products containing nanomaterials is also increasing. Evaluating the nanomaterial release from products containing nanomaterials is a crucial step in assessing the safety of these products, and has resulted in several international efforts to develop consistent and reliable technologies for standardizing the evaluation of nanomaterial release. In this study, the release of nanomaterials from products containing nanomaterials is evaluated using a chamber system that includes a condensation particle counter, optical particle counter, and sampling ports to collect filter samples for electron microscopy analysis. The proposed chamber system is tested using an abrasor and disc-type nanocomposite material specimens to determine whether the nanomaterial release is repeatable and consistent within an acceptable range. The test results indicate that the total number of particles in each test is within 20% from the average after several trials. The release trends are similar and they show very good repeatability. Therefore, the proposed chamber system can be effectively used for nanomaterial release testing of products containing nanomaterials.

Nanoparticle release is tested using a chamber system that includes a condensation particle counter, an optical particle counter and sampling ports to collect filter samples for microscopy analysis. The proposed chamber system can be effectively used for nanomaterial release testing with a repeatable and consistent data range.

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products ...

A New Portable In Vitro Exposure Cassette for Aerosol Sampling

This protocol introduces a new in vitro exposure system, capable of being worn, including its characterization and performance. Air-liquid interface (ALI) in vitro exposure systems are often large and bulky, making transport to the field and operation at the source of emission or within the breathing zone difficult. Through miniaturization of these systems, the lab can be brought to the field, expediting processing time and providing a more appropriate exposure method that does not alter the aerosol prior to contacting the cells. The Portable In vitro Exposure Cassette (PIVEC) adapts a 37 mm filter cassette to allow for in vitro toxicity testing outside of a traditional laboratory setting. The PIVEC was characterized using three sizes of copper nanoparticles to determine deposition efficiency based on gravimetric and particle number concentration analysis. Initial cytotoxicity experiments were performed with exposed lung cells to determine the ability of the system to deposit particles while maintaining cell viability. The PIVEC provides a similar or increased deposition efficiency when comparing to available perpendicular flow in vitro exposure devices. Despite the lower sample throughput, the small size gives some advantages to the current in vitro ALI exposure systems. These include the ability to be worn for personal monitoring, mobility from the laboratory to the source of emission, and the option to set-up multiple systems for spatial resolution while maintaining a lower user cost. The PIVEC is a system capable of collecting aerosols in the field and within the breathing zone onto an air-interfaced, in vitro model.

A New Portable In Vitro Exposure Cassette for Aerosol Sampling

Here, we present a protocol to perform portable cellular aerosol exposures and measure cellular response. The method uses cells, grown at the air-liquid interface, mimicking in vivo physiology. Cellular response to copper nanoparticle aerosols was observed as oxidative stress through reactive oxygen species generation and cytotoxicity as lactate dehydrogenase release.

This protocol introduces a new in vitro exposure system, capable of being worn, including its characterization and performance. Air-liquid interface (ALI) ...

Development of a Nose-only Inhalation Toxicity Test Chamber That Provides Four Exposure Concentrations of Nano-sized Particles

Using a numerical analysis based on computerized fluid dynamics, a nose-only inhalation toxicity chamber with four different exposure concentrations is designed and validated for flow field uniformity and cross-contamination among the exposure ports for each concentration. The designed flow field values are compared with the measured values from exposure ports located horizontally and vertically. For this purpose, nanoscale sodium chloride particles are generated as test particles and introduced to the inhalation chamber to evaluate the cross-contamination and concentration maintenance among the chambers, for each concentration group. The results indicate that the designed multiconcentration inhalation chamber can be used in animal inhalation toxicity testing without cross-contamination among concentration groups. Moreover, the designed multiconcentration inhalation toxicity chamber can also be converted to a single-concentration inhalation chamber. Further testing with gas, organic vapor, or non-nanoscale particles will ensure the use of the chamber in the inhalation testing of other test articles.

A nose-only inhalation toxicity chamber capable of testing inhalation toxicity at four different exposure concentrations was designed and validated for flow field uniformity and cross-contamination between the exposure ports for each concentration. Here, we present a protocol to confirm that the designed chamber is effective for inhalation toxicity testing.

Using a numerical analysis based on computerized fluid dynamics, a nose-only inhalation toxicity chamber with four different exposure concentrations is ...

Enhancing CO2 Sequestration: A Soil Biota Approach to Boost Mineral Weathering

Design and Construction of an Experimental Setup to Enhance Mineral Weathering through the Activity of Soil Organisms

Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies on accelerating the natural process of mineral weathering in soils by manipulating the abiotic variables that govern this process, in particular mineral grain size and exposure to acids dissolved in water. EW mainly aims at reducing atmospheric CO2 concentrations by enhancing inorganic carbon sequestration. Until now, knowledge of EW has been mainly gained through experiments that focused on the abiotic variables known for stimulating mineral weathering, thereby neglecting the potential influence of biotic components. While bacteria, fungi, and earthworms are known to increase mineral weathering rates, the use of soil organisms in the context of EW remains underexplored. 
 This protocol describes the design and construction of an experimental setup developed to enhance mineral weathering rates through soil organisms while concurrently controlling abiotic conditions. The setup is designed to maximize weathering rates while maintaining soil organisms' activity. It consists of a large number of columns filled with rock powder and organic material, located in a climate chamber and with water applied via a downflow irrigation system. Columns are placed above a fridge containing jerrycans to collect the leachate. Representative results demonstrate that this setup is suitable to ensure the activity of soil organisms and quantify their effect on inorganic carbon sequestration. Challenges remain in minimizing leachate losses, ensuring homogeneous ventilation through the climate chamber, and avoiding flooding of the columns. With this setup, an innovative and promising approach is proposed to enhance mineral weathering rates through the activity of soil biota and disentangle the effect of biotic and abiotic factors as drivers of EW.

Author Spotlight: Unraveling the Role of Earthworms in Enhancing Mineral Weathering for CO2 Removal 

Here we present the construction and operation of an experimental setup to enhance mineral weathering through the activity of soil organisms while concurrently manipulating abiotic variables known to stimulate weathering. Representative results from the functioning of the setup and sample analyses are discussed together with points for improvement.

Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies ...

Biochemistry

Whole-Body Nanoparticle Aerosol Inhalation Exposures

Inhalation is the most likely exposure route for individuals working with aerosolizable engineered nano-materials (ENM). To properly perform nanoparticle inhalation toxicology studies, the aerosols in a chamber housing the experimental animals must have: 1) a steady concentration maintained at a desired level for the entire exposure period; 2) a homogenous composition free of contaminants; and 3) a stable size distribution with a geometric mean diameter &lt; 200 nm and a geometric standard deviation &sigma;g &lt; 2.5 5. The generation of aerosols containing nanoparticles is quite challenging because nanoparticles easily agglomerate. This is largely due to very strong inter-particle forces and the formation of large fractal structures in tens or hundreds of microns in size 6, which are difficult to be broken up. Several common aerosol generators, including nebulizers, fluidized beds, Venturi aspirators and the Wright dust feed, were tested; however, none were able to produce nanoparticle aerosols which satisfy all criteria 5.
A whole-body nanoparticle aerosol inhalation exposure system was fabricated, validated and utilized for nano-TiO2 inhalation toxicology studies. Critical components: 1) novel nano-TiO2 aerosol generator; 2) 0.5 m3 whole-body inhalation exposure chamber; and 3) monitor and control system. Nano-TiO2 aerosols generated from bulk dry nano-TiO2 powders (primary diameter of 21 nm, bulk density of 3.8 g/cm3) were delivered into the exposure chamber at a flow rate of 90 LPM (10.8 air changes/hr). Particle size distribution and mass concentration profiles were measured continuously with a scanning mobility particle sizer (SMPS), and an electric low pressure impactor (ELPI). The aerosol mass concentration (C) was verified gravimetrically (mg/m3). The mass (M) of the collected particles was determined as M = (Mpost-Mpre), where Mpre and Mpost are masses of the filter before and after sampling (mg). The mass concentration was calculated as C = M/(Q*t), where Q is sampling flowrate (m3/min), and t is the sampling time (minute). The chamber pressure, temperature, relative humidity (RH), O2 and CO2 concentrations were monitored and controlled continuously. Nano-TiO2 aerosols collected on Nuclepore filters were analyzed with a scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis.
In summary, we report that the nano-particle aerosols generated and delivered to our exposure chamber have: 1) steady mass concentration; 2) homogenous composition free of contaminants; 3) stable particle size distributions with a count-median aerodynamic diameter of 157 nm during aerosol generation. This system reliably and repeatedly creates test atmospheres that simulate occupational, environmental or domestic ENM aerosol exposures.

A whole-body nanoparticle aerosol inhalation exposure facility was constructed for nano-sized titanium dioxide (TiO2) inhalation toxicology studies. This system provides nano-TiO2 aerosol test atmospheres that have: 1) a steady mass concentration; 2) a homogenous composition free of contaminants; and 3) a stable particle size distribution during aerosol generation.

Inhalation is the most likely exposure route for individuals working with aerosolizable engineered nano-materials (ENM). To properly perform nanoparticle ...

Biology

Assessment of the Acute Inhalation Toxicity of Airborne Particles by Exposing Cultivated Human Lung Cells at the Air-Liquid Interface

Here, we present a specially designed modular in vitro exposure system that enables the homogenous exposure of cultivated human lung cells at the ALI to gases, particles or complex atmospheres (e.g., cigarette smoke), thus providing realistic physiological exposure of the apical surface of the human alveolar region to air. In contrast to sequential exposure models with linear aerosol guidance, the modular design of the radial flow system meets all requirements for the continuous generation and transport of the test atmosphere to the cells, a homogenous distribution and deposition of the particles and the continuous removal of the atmosphere. This exposure method is primarily designed for the exposure of cells to airborne particles, but can be adapted to the exposure of liquid aerosols and highly toxic and aggressive gases depending on the aerosol generation method and the material of the exposure modules.
Within the framework of a recently completed validation study, this exposure system was proven as a transferable, reproducible and predictive screening method for the qualitative assessment of the acute pulmonary cytotoxicity of airborne particles, thereby potentially reducing or replacing animal experiments that would normally provide this toxicological assessment.

We present a robust, transferable and predictive in vitro exposure system for the screening and monitoring of airborne particles concerning their acute pulmonary cytotoxicity by exposing cultivated human lung cells at the air-liquid interface (ALI).

Here, we present a specially designed modular in vitro exposure system that enables the homogenous exposure of cultivated human lung cells at the ALI to ...

Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

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