On the source inversion of fugitive surface layer releases. Part II. Complex sources

The experimental measurement of fugitive emissions of particulate matter entails inherent complexity because they are usually discontinuous, of short duration, may be mobile, and are affected by weather conditions. Owing to this complexity, instead of experimental measurements, emission factors are used to inventory such emissions. Unfortunately, emission factor datasets are still very limited at present and are insufficient to identify problematic operations and appropriately select control measures. To extend these datasets, a source inversion methodology (described in Part I of this work) was applied to field campaigns in which operation-specific fugitive particulate matter emission factors were determined for several complex fugitive sources, some of which were mobile. Mobile sources were treated as a superposition of instantaneous sources. The experimental campaigns were conducted at ports (bulk solids terminals), aggregate quarries, and cement factories, encompassing powder handling operations and vehicle circulation on paved and unpaved roads. Emission factors were derived for the operations and materials involved in these scenarios and compared with those available in the emission factor compilations. Significant differences were observed between the emission factors obtained in the studied handling operations. These differences call into question the use of generic emission factors and highlight the need for more detailed studies in this field

Clay hydration mechanisms and their effect on dustiness

Clays are employed in a wide variety of industries such as ceramic industry, manufacture of paper, rubber, etc. In this sense, it is well known that at industrial processes in which clayey materials are used, such as ceramic industry, in order to carry out some specific stages, the wetting of clays is commonly required. Moreover, it is also long established that wetting is an appropriated measure to reduce particulate matter emissions during clays storage and handling. The present study was undertaken to assess the influence of moisture on clay dustiness because, though the complex behaviour of the clay–water system has been known since antiquity, the mechanisms involved in clay hydration and their influence on dustiness are still not well understood. To encompass a wide range of specific surface areas, three clays and a kaolin were studied. Chemical and mineralogical analysis of these four raw materials was performed and their particle size distribution, flowability, true density, plastic limit, and specific surface area were determined. Raw materials dustiness was determined using the continuous drop method. As against what might intuitively be expected, the results showed that the relationship between moisture and dustiness was quite complex and strongly related to the hydration mechanisms. In this regard, to better understand the phenomena involved in the clay hydration process, a specific methodology was developed to estimate the critical points of the clay hydration process (regarding dustiness). This methodology can be readily applied to other clays or even to materials of different nature to predict the optimum moisture and, therefore, it could be employed to propose specific measures which could entail an improvement of outdoor and indoor air quality

Effect of the raw materials processing on their dustiness

En la manipulación y/o procesado de materiales pulverulentos en la industria cerámica, uno de los riesgos más importantes desde el punto de vista ambiental y de higiene laboral es la generación de polvo ambiental. En este sentido, un parámetro de gran interés es el poder de emisión de polvo, que cuantifica la tendencia de los materiales pulverulentos a generar polvo cuando se manipulan. En este trabajo, para determinar el poder de emisión de polvo de una composición cerámica (mezcla de materias primas empleada para la fabricación de baldosas cerámicas) se ha empleado un método de caída continua. Este método se ha seleccionado por ser el que mejor representa las operaciones de manipulación de materiales pulverulentos que tienen lugar en el proceso de fabricación de baldosas cerámicas. Los resultados obtenidos muestran que el poder de emisión de polvo de una misma composición cerámica se modifica sustancialmente durante el proceso productivo dependiendo de su forma de presentación. En este sentido, la muestra procedente de la molienda vía seca presenta un elevado poder de emisión de polvo, pudiéndose reducir significativamente (> 75%) aplicando la humectación y la aglomeración. Los resultados obtenidos muestran que la presentación óptima desde el punto de vista de la minimización de la generación de polvo se alcanza en el proceso de atomización, llegándose a reducir el poder de emisión de polvo en más de un 95%.During the handling and/or processing of powdered materials in the ceramic industry, one of the most important risks regarding the environmental and occupational health is the potential generation of dust. In this regard, a parameter of great interest is the dustiness of the processed materials; this parameter quantifies the tendency of the powdered materials to generate dust when handled. In this study, to determine the dustiness of a ceramic raw material composition (mixture of the body raw materials), the continuous drop method has been used. This test apparatus was selected because it is considered to better simulate how ceramic materials are handled in the ceramic industry. The obtained results show that the dustiness of the same ceramic composition exhibits significant changes during the manufacturing process, depending on the presentation form. In this regard, the dry milling sample presents the highest dustiness, which can be significantly reduced (> 75%) applying the the moisturization and agglomeration. The obtained results also shown that the best presentation form, regarding the minimization of the dust generation, is achieved in the spray-drying process, where the dustiness is reduced by 95%

Modeling of High Nanoparticle Exposure in an Indoor Industrial Scenario with a One-Box Model

Mass balance models have proved to be effective tools for exposure prediction in occupational settings. However, they are still not extensively tested in real-world scenarios, or for particle number concentrations. An industrial scenario characterized by high emissions of unintentionally-generated nanoparticles (NP) was selected to assess the performance of a one-box model. Worker exposure to NPs due to thermal spraying was monitored, and two methods were used to calculate emission rates: the convolution theorem, and the cyclic steady state equation. Monitored concentrations ranged between 4.2 × 104–2.5 × 105 cm−3. Estimated emission rates were comparable with both methods: 1.4 × 1011–1.2 × 1013 min−1 (convolution) and 1.3 × 1012–1.4 × 1013 min−1 (cyclic steady state). Modeled concentrations were 1.4-6 × 104 cm−3 (convolution) and 1.7–7.1 × 104 cm−3 (cyclic steady state). Results indicated a clear underestimation of measured particle concentrations, with ratios modeled/measured between 0.2–0.7. While both model parametrizations provided similar results on average, using convolution emission rates improved performance on a case-by-case basis. Thus, using cyclic steady state emission rates would be advisable for preliminary risk assessment, while for more precise results, the convolution theorem would be a better option. Results show that one-box models may be useful tools for preliminary risk assessment in occupational settings when room air is well mixed

Viabilidad de la implantación de sistemas de cerramiento total para reducir las emisiones difusas de partículas

Following the entry into force of the IPPC directive, the activities that it affects, which include the ceramic sector, have needed to control fugitive particle emissions by implementing corrective measures that often entail significant economic costs. In the most demanding cases, the Integrated Environmental Authorisations (IEA) awarded to companies in the ceramic industry require total enclosure of the raw materials handling operations. This paper evaluates the technical, economic, and environmental feasibility of the implementation of a total enclosure or containment system as a way of reducing fugitive particle emissions, as this is considered one of the Best Available Techniques (BAT). The study was carried out on the raw materials reception, handling, and storage operations at a ceramic company that manufactures spray-dried powder granule

Determinants of workplace exposure and release of ultrafine particles during atmospheric plasma spraying in the ceramic industry

Atmospheric plasma spraying (APS) is a frequently used technique to produce enhanced-property coatings for different materials in the ceramic industry. This work aimed to characterise and quantify the impact of APS on workplace exposure to airborne particles, with a focus on ultrafine particles (UFPs, <100 nm) and nanoparticles (<50 nm). Particle number, mass concentrations, alveolar lung deposited surface area concentration, and size distributions, in the range 10 nm – 20 μm were simultaneously monitored at the emission source, in the worker breathing zone, and in outdoor air. Different input materials (known as feedstock) were tested: (a) micro-sized powders, and (b) suspensions containing submicron- or nano-sized particles. Results evidenced significant UFP emissions (up to 3.3x106/cm3) inside the projection chamber, which impacted exposure in the breathing zone outside the projection chamber (up to 8.3x105/cm3). Environmental release of UFPs was also detected and quantified (3.9x105/cm330 ). Engineered nanoparticle (ENP) release to workplace air was also evidenced by TEM microscopy. UFP emissions were detected during the application of both micro-sized powder and suspensions containing submicron- or nano-sized particles, thus suggesting that emissions were process- (and not material-) dependent. An effective risk prevention protocol was implemented, which resulted in a reduction of worker UFP exposure in the breathing zone. These findings evidence the potential risk of occupational exposure to UFPs during atmospheric plasma spraying, and raise the need for further research on UFP formation mechanisms in high-energy industrial processes

Testing the performance of one and two box models as tools for risk assessment of particle exposure during packing of inorganic fertilizer

Modelling of particle exposure is a useful tool for preliminary exposure assessment in workplaces. However, actual exposure measurements are needed to assess models reliability. Worker exposure was monitored during packing of a complex inorganic granulate fertilizer at industrial scale using small and big bags. Particle concentrations were modelled with one and two box models, where the emission source was estimated with the fertilizer’s dustiness index. The exposure levels were used to calculate inhaled dose rates and test accuracy of the exposure modellings. The particle number concentrations were measured from worker area by using a mobility and optical particle sizer which were used to calculate surface area and mass30 concentrations. The concentrations in the worker area during pre-activity ranged from 63797 - 81073 cm-3, 4.6x106 to 7.5x106 um2 cm-3, and 354 to 634 μg m-3 31 (respirable mass fraction) and during packing from 50300 to 85949 cm-3, 4.3x106 to 7.6x106 um2 32 cm-3, and 279 to 668 μg m-3 33 (respirable mass fraction). Thus, the packing process did not significantly increase the exposure levels. High particle number concentration was partly due to the use of diesel-powered forklifts. The particle surface area deposition rate in respiratory tract was up to 7.6x106 μm2 min-1 during packing, with 52% - 61% of deposition occurring in the alveolar region. Ratios of the modelled and measured concentrations were 0.98 ± 0.19 and 0.84 ± 0.12 for small and big bags, respectively, when using the one box model, and 0.88 ± 0.25 and 0.82 ± 0.12, for small and big bags, respectively, when using the one box model, and 0.88 ± 0.25 and 0.82 ± 0.12, respectively, when using the two box model. The modelling precision improved for both models when outdoor particle concentrations were included. This study shows that exposure concentrations during packing of fertilizers can be predicted with a reasonable accuracy by using a concept of dustiness and mass balance models

Particle release fromrefit operations in shipyards: Exposure, toxicity and environmental implications

European harbours are known to contribute to air quality degradation.While most of the literature focuses on emissions from stacks or logistics operations, ship refit and repair activities are also relevant aerosol sources in EU harbour areas. Main activities include abrasive removal of filler and spray painting with antifouling coatings/primers/topcoats. This work aimed to assess ultrafine particle (UFP) emissions from ship maintenance activities and their links with exposure, toxicity and health risks for humans and the aquatic environment. Aerosol emissions were monitored during mechanical abrasion of surface coatings under real-world operating conditions in two scenarios in the Mallorca harbour (Spain). Different types of UFPs were observed: (1) highly regular (triangular, hexagonal) engineered nanoparticles (Ti-, Zr-, Fe-based), embedded as nano-additives in the coatings, and (2) irregular, incidental particles emitted directly or formed during abrasion. Particle number concentrationsmonitored were in the range of industrial activities such as drilling or welding (up to 5 ∗ 105/cm3, mean diameters <30 nm). The chemical composition of PM4 aerosols was dominated by metallic tracers in the coatings (Ti, Al, Ba, Zn). In vitro toxicity of PM2 aerosols evidenced reduced cell viability and a moderate potential for cytotoxic effects. While best practices (exhaust ventilation, personal protective equipment, dust removal) were in place, it is unlikely that exposures and environmental release can be fully avoided at all times. Thus, it is advisable that health and safety protocols should be comprehensive to minimise exposures in all types of locations (near- andfar-field) and periods (activity and non-activity). Potential release to coastal surface waters of metallic engineered and incidental nanomaterials, as well as fine and coarse particles (in the case of settled dust), should be assessed and avoided

Health risk assessment from exposure to particles during packing in working environments

Packing of raw materials in work environments is a known source of potential health impacts (respiratory, cardiovascular) due to exposure to airborne particles. This activity was selected to test different exposure and risk assessment tools, aiming to understand the effectiveness of source enclosure as a strategy to mitigate particle release. Worker exposure to particle mass and number concentrations was monitored during packing of 7 ceramic materials in 3 packing lines in different settings, with low (L), medium (M) and high (H) degrees of source enclosure. Results showed that packing lines L and M significantly increased exposure concentrations (119-609 μg m-3 respirable, 1150-4705 μg m-3 inhalable, 24755-51645 cm-3 particle number), while nonsignificant increases were detected in line H. These results evidence the effectiveness of source enclosure as a mitigation strategy, in the case of packing of ceramic materials. Total deposited particle surface area during packing ranged between 5.4-11.8x105 μm2 min-1, with particles depositing mainly in the alveoli (51-64%) followed by head airways (27-41%) and trachea bronchi (7-10%). The comparison between the results from different risk assessment tools (Stoffenmanager, ART, NanoSafer) and the actual measured exposure concentrations evidenced that all of the tools overestimated exposure concentrations, by factors of 1.5-8. Further research is necessary to bridge the current gap between measured and modelled health risk assessments

La memoria de los libros. Estudios sobre la historia del escrito y de la lectura en Europa y América. Vol. I

Numerosos artículos sobre aspectos variados de historia del libro y de la lectura, bibliotecas, manuscritos, iluminación e ilustración, etc