An official website of the United States government
Abstract. This study presents a novel analysis of two hailstones collected in central Argentina to provide insights into the size distribution, composition, and potential sources of non-soluble particles within hailstones. Using this new method, non-soluble particles are trapped beneath a thin layer of polyvinyl resin and analyzed with Confocal Laser and Scanning Electron Microscopy combined with Energy-Dispersive Spectroscopy, preserving their in-situ location and physical characteristics. The study characterized these particles' distribution, shape, and size and identified their elemental composition, which is used to interpret possible source regions. Particles ranged in diameter from 1.2 to 256.0 microns, with the largest found in hailstone embryos. Agglomerated mineral and organic particles dominated the elemental composition, followed by organics and quartz, and were present throughout the hailstones. Agglomerated salt particles detected in one sample were traced to a nearby salt lake, while copper chloride and zinc chloride particles found in the second sample were potentially associated with agrochemicals commonly used for pest control and fertilizer, including in Argentina. Various local and regional land-use types, including shrublands, mixed vegetation, croplands, and urban areas, were linked to specific types of particles. This study, therefore, highlights the regional influence of various land use types on hail formation and growth, pointing to the potential impacts of natural and anthropogenic factors on hailstone composition.
more »
« less
Size-controlled Preparation of Alkylamine-stabilized Copper Fine Particles from Cupric Oxide (CuO) Micro-particles
ABSTRACT Size control of copper fine particles is highly important for their application for conductive materials. In this study, easy size tuning of the copper fine particles coated by n-hexylamine was achieved via controlling the ratio of n-hexylamine and the precursor CuO. The obtained particles were stable and had a hydrophobic surface. TG-DTA measurement revealed the formation of thin layer of n-hexylamine on the particles.
more »
« less
- Award ID(s):
- 1846628
- PAR ID:
- 10094664
- Date Published:
- Journal Name:
- MRS Advances
- Volume:
- 4
- Issue:
- 07
- ISSN:
- 2059-8521
- Page Range / eLocation ID:
- 413 to 418
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We present measurements of light scattering intensity from aerosolized, micron sized, irregularly shaped, molybdenum disulfide (MoS 2 ) particles in order to study the effects of a refractive index, m = n + i κ, with large real and imaginary parts. Light scattering was measured over a range of angles from 0.32 °to 157 °. Calibration was achieved by scattering with micron sized, spherical silica particles. Light scattering for both particle types was compared to theoretical Mie scattering calculations using size distributions deter- mined by an aerodynamic particle sizer. Effects of the intensity weighted size distribution are discussed. We find that scattering by these irregularly shaped, highly refractive particles is well described by Mie scattering. We also find that when the quantity κkR, where kR = 2 πR/ λis the size parameter, is greater than one, there is no enhancement in the backscattering. Finally, we show that Guinier analysis of light scattering by highly refractive particles yields intensity weighted mean sizes of reasonable accuracy for any shape.more » « less
-
The index of refraction (n) of particles is an important parameter in optical models that aims to extract particle size and carbon concentrations from light scattering measurements. An inadequate choice ofncan critically affect the characterization and interpretation of optically-derived parameters, including those from satellite-based models which provide the current view of how biogeochemical processes vary over the global ocean. Yet, little is known about hownvaries over time and space to inform such models. Particularly, in situ estimates ofnfor bulk water samples and at diel-resolving time scales are rare. Here, we demonstrate a method to estimatenusing simultaneously and independently collected particulate beam attenuation coefficients, particle size distribution data, and a Mie theory model. We apply this method to surface waters of the North Pacific Subtropical Gyre (NPSG) at hourly resolution. Clear diel cycles innwere observed, marked by minima around local sunrise and maxima around sunset, qualitatively consistent with several laboratory-based estimates ofnfor specific phytoplankton species. A sensitivity analysis showed that the daily oscillation innamplitude was somewhat insensitive to broad variations in method assumptions, ranging from 11.3 ± 4.3% to 16.9 ± 2.9%. Such estimates are crucial for improvement of algorithms that extract the particle size and production from bulk optical measurements, and could potentially help establish a link betweennvariations and changes in cellular composition of in situ particles.more » « less
-
Abstract. The lidar backscattering properties of Asian dust particles, namely the lidar ratio (S) and backscattering depolarization ratio (δ), were studied using a discrete dipole approximation (DDA) model. The three-dimensional morphology of the dust particles was reconstructed in fine detail using the focused ion beam (FIB) tomography technique. An index based on the symmetry of the scattering matrix was developed to assess the convergence of random orientation computation using DDA. Both S and δ exhibit an asymptotic trend with dust particle size: the S initially decreases, while the δ increases with size, before both approach their asymptotic values. The lidar properties were found to have statistically insignificant dependence on effective sphericity. The presence of strongly absorbing minerals, such as magnetite, can greatly reduce the dust's single-scattering albedo and δ. Utilizing the robust asymptotic trend behavior, two parameterization schemes were developed: one to estimate the δ of a single dust particle given its size and the other to estimate the δ of dust particles with a lognormal particle size distribution given the effective radius. The parameterization scheme was compared with results based on the TAMUdust2020 database, showing hexahedrons to reasonably represent realistic geometries with similar physical properties.more » « less
-
Abstract. Acidity, defined as pH, is a central component of aqueouschemistry. In the atmosphere, the acidity of condensed phases (aerosolparticles, cloud water, and fog droplets) governs the phase partitioning ofsemivolatile gases such as HNO3, NH3, HCl, and organic acids andbases as well as chemical reaction rates. It has implications for theatmospheric lifetime of pollutants, deposition, and human health. Despiteits fundamental role in atmospheric processes, only recently has this fieldseen a growth in the number of studies on particle acidity. Even with thisgrowth, many fine-particle pH estimates must be based on thermodynamic modelcalculations since no operational techniques exist for direct measurements.Current information indicates acidic fine particles are ubiquitous, butobservationally constrained pH estimates are limited in spatial and temporalcoverage. Clouds and fogs are also generally acidic, but to a lesser degreethan particles, and have a range of pH that is quite sensitive toanthropogenic emissions of sulfur and nitrogen oxides, as well as ambientammonia. Historical measurements indicate that cloud and fog droplet pH haschanged in recent decades in response to controls on anthropogenicemissions, while the limited trend data for aerosol particles indicateacidity may be relatively constant due to the semivolatile nature of thekey acids and bases and buffering in particles. This paper reviews andsynthesizes the current state of knowledge on the acidity of atmosphericcondensed phases, specifically particles and cloud droplets. It includesrecommendations for estimating acidity and pH, standard nomenclature, asynthesis of current pH estimates based on observations, and new modelcalculations on the local and global scale.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1557/adv.2019.91
