111 research outputs found
Influence of relative humidity and aging on the optical properties of organic aerosols from burning African biomass fuels
No full textBiomass burning (BB) is a major source of atmospheric fine carbonaceous aerosols, which play a significant, yet uncertain, role in modulating the Earth’s radiation balance. However, accurately representing their optical properties in climate models remains challenging due to factors such as particle size, mixing state, combustion type, chemical composition, aging processes, and relative humidity (RH). In our study, we investigated BB organic-rich aerosols generated from smoldering sub-Saharan African biomass fuels. Fuel samples were collected in Africa and aerosols generated in the laboratory. We quantified key optical parameters, including mass cross-sections for extinction (2.04 ±0.32− 15.5 ±2.48 m2/g), absorption (0.04 ±0.01–0.3 ±0.1 m2/g), and scattering (1.9 ±0.68–15.3 ±5.5 m2/g). Wavelength-dependent properties were used to determine absorption and scattering Ångstro€m exponents. The single scattering albedo of these aerosols ranged from 0.8 ±0.03 to 1.0 ±0.04 and we observed a wavelength-dependent behavior. Extinction emission factors were determined at a wavelength of 550 nm, with values ranging from 42 ±5 to 293 ±32 m2 /kg. Notably, optical properties exhibited fuel-type dependence, with differences observed between hardwood samples and other fuels, such as grass and animal dung. Aging increased mass extinction and scattering cross-sections at 550 nm,while humidity had the opposite effect across all fuels. Nitrate radical oxidation, both in photo and dark aging conditions, also influenced these properties. The findings are expected to close the gap in our understanding of optical properties of BB aerosol emissions in one of the least studied regions of the world – Africa – providing information to climate and air quality models for the region
Quantifying the Light-Absorption Properties and Molecular Composition of Brown Carbon Aerosol from Sub-Saharan African Biomass Combustion
No full text: Sub-Saharan Africa is a hotspot for biomass burning (BB)-derived carbonaceous aerosols, including light-absorbing organic (brown) carbon (BrC). However, the chemically complex nature of BrC in BB aerosols from this region is not fully understood. We generated smoke in a chamber through smoldering combustion of common sub-Saharan African biomass fuels (hardwoods, cow dung, savanna grass, and leaves). We quantified aethalometer-based, real-time light-absorption properties of BrC-containing organic-rich BB aerosols, accounting for variations in wavelength, fuel type, relative humidity, and photochemical aging conditions. In filter samples collected from the chamber and Botswana in the winter, we identified 182 BrC species, classified into lignin pyrolysis products, nitroaromatics, coumarins, stilbenes, and flavonoids. Using an extensive set of standards, we determined species-specific mass and emission factors. Our analysis revealed a linear relationship between the combined BrC species contribution to chamber-measured BB aerosol mass (0.4-14%) and the mass-absorption cross-section at 370 nm (0.2-2.2 m2 g-1). Hierarchical clustering resolved key molecular-level components from the BrC matrix, with photochemically aged emissions from leaf and cow-dung burning showing BrC fingerprints similar to those found in Botswana aerosols. These quantitative findings could potentially help refine climate model predictions, aid in source apportionment, and inform effective air quality management policies for human health and the global climate.: Sub-Saharan Africa is a hotspot for biomass burning (BB)-derived carbonaceous aerosols, including light-absorbing organic (brown) carbon (BrC). However, the chemically complex nature of BrC in BB aerosols from this region is not fully understood. We generated smoke in a chamber through smoldering combustion of common sub-Saharan African biomass fuels (hardwoods, cow dung, savanna grass, and leaves). We quantified aethalometer-based, real-time light-absorption properties of BrC-containing organic-rich BB aerosols, accounting for variations in wavelength, fuel type, relative humidity, and photochemical aging conditions. In filter samples collected from the chamber and Botswana in the winter, we identified 182 BrC species, classified into lignin pyrolysis products, nitroaromatics, coumarins, stilbenes, and flavonoids. Using an extensive set of standards, we determined species-specific mass and emission factors. Our analysis revealed a linear relationship between the combined BrC species contribution to chamber-measured BB aerosol mass (0.4-14%) and the mass-absorption cross-section at 370 nm (0.2-2.2 m2 g-1). Hierarchical clustering resolved key molecular-level components from the BrC matrix, with photochemically aged emissions from leaf and cow-dung burning showing BrC fingerprints similar to those found in Botswana aerosols. These quantitative findings could potentially help refine climate model predictions, aid in source apportionment, and inform effective air quality management policies for human health and the global climate
The Need for Interdisciplinary Research and Education for Sustainable Human Development to Deal with Global Challenges
No full textMajor issues in society - developing alternate sources of energy and a sustainable environment, improving health, and minimizing the effects of climate change require a collective effort by different disciplines working in interdisciplinary groups. Indeed, the boundaries between the different disciplines are becoming increasingly blurred. Society’s responses to major social challenges must be informed by an improved understanding of human perceptions, responses, and of the economic and social impacts of the physical, and biological processes to promote social wellbeing. A comprehensive understanding of the main social challenges requires the collaboration of physical scientists, social scientists, humanities scholars and engineers, and will be highly interdisciplinary. For example climate systems are highly variable, changing in hours, days or years. The need to create a new generation of students who combine a rigorous disciplinary depth with the ability to reach out to other disciplines and work in interdisciplinary teams is more urgent. Because these skills cut across traditional disciplinary boundaries, there is increasing support from government and business for the interdisciplinary programs that focus on identifiable long-term problems in the economy, society, and government, as opposed to department-based programs that focus on academically defined disciplinary paradigms. Interdisciplinary research preparation and education are central to future competitiveness, because knowledge creation and innovation frequently occur at the interface of disciplines. Interdisciplinary programs help to ensure better educational programs, which give students better ability to work in a problem-oriented way and at the same time the ability to think across fields and interact. It responds to the need to prepare students for an increasingly interdisciplinary, collaborative, and global job market. Interdisciplinary programs provide opportunities to strengthen the interaction between the business sector and research, especially in relation to the humanities and social science research and education, where interaction has been especially underdeveloped. There is a consensus that the current academic administrative structure is the most important barrier to interdisciplinary collaboration; other barriers like poor communication, etc., emanate from it. How can interdisciplinary education and research flourish while maintaining strong backgrounds in the disciplines? How can universities lower or remove barriers to faculty participation in interdisciplinary education and research and create porous, flexible, less redundant environment that facilitates the flow of ideas, people and resources across disciplinary boundaries? Is possible to have disciplines without disciplinary departments? In this short paper, the barriers and the challenges for developing interdisciplinary education and research will be summarized, lessons from some successful attempts and failures will be presented, and some approaches will be recommended for newly established institutions of higher education if the developing world such as Africa further discussion
Assessing the Impact of Atmospheric Photochemical Aging on Organic Aerosol Tracers Derived from Burning African Biomass Commonly Found in Botswana
No full textDue to climate change, wildfires are becoming increasingly frequent and intense, leading to substantial production of biomass burning (BB)-derived organic aerosol (BBOA). Although African fires account for over 50% of worldwide BB organic emissions, few studies have systematically analyzed molecular tracers of BBOA in fresh versus photochemically-aged BB emissions representative of African fires. Therefore, using gas chromatography and electron ionization quadrupole mass spectrometry, we analyzed aerosol filter samples collected from both fresh and photochemically-aged BB emissions of six biomass fuel types found in Botswana. The emissions were generated from a furnace mimicking smoldering. For each biomass fuel, 16 known BBOA tracer compounds were quantified and compared between fresh and photochemically-aged BB emissions. Total-suspended atmospheric particulate matter (PM) samples collected from Botswana during fire season were also analyzed. We identified laboratory-generated BBOA constituents (e.g., D-pinitol) that were also found in Botswana PM that could plausibly serve as unique tracers for African BBOA.Master of Scienc
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Odd Dynamics of Colloidal Chiral Matter
No full textThe symmetries that underly conventional equilibrium matter provide the grounding for continuum mechanical models. In this work, we engineer a chiral material comprised of millions of spinning colloidal magnets as a testing ground for breaking these symmetries and observing the resulting odd dynamics. By activating the fluid phase at the single unit level, we observe macroscopic flows with no counterpart in conventional fluids. Along a boundary of the fluid, we observe unidirectional free-surface waves that propagate due to an interplay between viscous and odd rotational stresses. These waves are dissipated by both surface tension and odd viscosity, an anomalous transport coefficient permitted through broken time-reversal and parity symmetries. Then, we ask a deceptively simple question: what is the effect of adding transverse interactions on the solid phase? At the system scale, non-reciprocity causes colloidal spinners to organize into crystalline whorls which sustain super-diffusive mass transport that can be controlled over orders of magnitude. By combining experimental measurements with fully-resolved hydrodynamic and minimal model simulations, we find that this phase spontaneously arises from the interplay of intrinsic odd stresses and odd elastic moduli unconstrained by energy conservation, which conspire to enable the self-propulsion of topological defects. Finally, we lift the constraint of isotropy that underlies our viscous and elastic models, enabling spatiotemporal control of the morphology of chiral matter through the time-modulation of the drive
Dynamic Analysis and Optimization of Autorickshaw Suspension System to Improve Rollover Stability During Cornering
No full textThe broadband light analyzer of complex aerosol: characterization and first applications
No full textWe introduce a new instrument to measure spectral light absorption by aerosol particles. BLAnCA (Broadband Light Analyzer of Complex Aerosol) is an automatic laboratory instrument for offline measurement of aerosol collected on suitable media. BLAnCA is equipped with a white light source and a high-resolution spectrometer, and measures in the range between 375 and 1000 nm with a spectral resolution of 5 nm. This allows for the determination of fine structure of the absorption properties of a sampled aerosol, which can lead to improvement in the robustness and scope of source apportionment and the evaluation of climate-relevant properties such as the aerosol mass absorption cross-section. The new instrument has been validated against a multi-wavelength absorbance analyzer, obtaining an agreement of up to 99 % between absorption coefficient measurements. The absorption coefficient limit of detection for BLAnCA has been estimated at 1.20 Mm−1 (2.70 Mm−1) for standard EU (EPA) sampling conditions, corresponding to an elemental carbon detection limit of about 1.3 g cm−2, if a mass absorption cross-section of m2g−1 at 1000 nm is considered. The instrument has been used to characterize several types of aerosol samples, each with its own distinct absorption features, which show the potential for BLAnCA to identify different kinds of particulate matter based on their optical properties
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