Optical characterization of multi-scale morphologically complex heterogeneous media – Application to snow with soot impurities

Abstract

a b s t r a c tA multi-scale methodology for the radiative transfer analysis of heterogeneous media composed of morphologically-complex components on two distinct scales is presented. The methodology incorporates the exact morphology at the various scales and utilizes volume-averaging approaches with the corresponding effective properties to couple the scales. At the continuum level, the volume-averaged coupled radiative transfer equations are solved utilizing ( i ) effective radiative transport properties obtained by direct Monte Carlo simulations at the pore level, and ( ii ) averaged bulk material properties obtained at particle level by Lorenz-Mie theory or discrete dipole approximation calculations. This model is applied to a soot-contaminated snow layer, and is experimentally validated with reflectance measurements of such layers. A quantitative and decoupled understanding of the morphological effect on the radiative transport is achieved, and a significant influence of the dual-scale morphology on the macroscopic optical behavior is observed. Our results show that with a small amount of soot particles, of the order of 1ppb in volume fraction, the reduction in reflectance of a snow layer with large ice grains can reach up to 77% (at a wavelength of 0.3 μm). Soot impurities modeled as compact agglomerates yield 2-3% lower reduction of the reflectance in a thick show layer compared to snow with soot impurities modeled as chain-like agglomerates. Soot impurities modeled as equivalent spherical particles underestimate the reflectance reduction by 2-8%. This study implies that the morphology of the heterogeneities in a media significantly affects the macroscopic optical behavior and, specifically for the soot-contaminated snow, indicates the non-negligible role of soot on the absorption behavior of snow layers. It can be equally used in technical applications for the assessment and optimization of optical performance in multi-scale media.

A Review of Optical and Radiative Properties of Nanoparticle Suspensions: Effects of Particle Stability, Agglomeration, and Sedimentation

“…As there are many particles in a particulate medium, the scattered photon from a particle may interact with those from other particles. This means incident beams can be scattered more than one time and they can be scattered again by the nearby particles (Mishchenko et al, 1999;Dai and Haussener, 2018;Doicu and Mishchenko, 2018;Mishchenko and Dlugach, 2018).…”

“…Also, the constituents of a homogeneous mixture are not easily separated by using mechanical means such as precipitation or centrifugation. A heterogeneous mixture is composed of parts that can be distinguished with the naked eye or by using a microscope (Gibbs, 1879;Dai and Haussener, 2018). Basically, everything except the vacuum is heterogeneous.…”

Characterization of black carbon aerosols over Indian Antarctic station, Maitri and identification of potential source areas

“…[1][2][3][4] It is a carbonaceous material obtained from the incomplete combustion of biomass and fossil fuels via natural and anthropogenic activities and is an excellent marker for air quality and pollution level. 4 Moreover, the BC emissions can occur alongside noxious gases such as carbon monoxide (CO), nitrogen oxides (NO x ), non-methane volatile organic compounds (NMVOC), and sulfur dioxide (SO 2 ) 5 with a negative impact on health, 6,7 modications of cloud characters, ice or snow albedo, 8 visibility and the Earth's energy budget. 9 Moreover, meteorological parameters such as wind speed, wind direction, pressure, temperature and relative humidity govern variations in aerosol distribution and quantities of BC.…”

Оптоакустическое Исследование И Моделирование Оптических Свойств Композитов Циклотриметилентринитрамин-Ультрадисперсные Частицы Никеля

“…Значительная часть элементов данного алгоритма использовалась при моделировании оптических свойств снега с вкраплениями сажи [18], композитов пентаэритрит тетранитрат (PETN)-наночастицы алюминия [13] и циклотриметилентринитрамин (RDX)-наночастицы алюминия типа металлическое ядро-оксидная оболочка [14] и металлическое ядро-воздушная оболочка, связанная с остаточной пористостью материала [15]. Таким образом, данная методика обеспечивает решение прямой и обратной задач спектроскопии систем, содержащих частицы металлов в непоглощающей свет матрице, на количественном уровне.…”