Under environment with various water contents, the variations in the mixing state and particle size of coated black carbon (BC) aerosols cause changes in optical and radiative effects. In this study, fractal models for thinly, partially, and thickly coated BC under six relative humidities (RHs 1/4 0-95%) are constructed and optically simulated at 1064 and 532 nm. Differential scattering cross-sections are selected to retrieve the mixing state (Dp/Dc) of BC to investigate the possible retrieval errors caused by the nonspherical morphology when using the single-particle soot photometer (SP2). Furthermore, the radiative forcing of BC aerosols at different RHs are analyzed. Results showed that the retrieval errors (REs) of Dp/Dc are negative for coated particles with BC volume fraction smaller than 0.10, indicating that the mixing states of coated fractal BC are underestimated during the hygroscopic growth. The partiallycoated BC has the best retrieval accuracy of the mixing state, followed by the closed-cell and coatedaggregate model, judging from averaged REs. Radiative forcing enhancements for partially-coated aerosols with different BC volume fractions exponentially increase to opposite values, resulting in a warming or cooling effect. This study helps understand the uncertainties in Dp/Dcof BC aerosols retrieved by SP2 and their radiative forcing at different RHs. (c) 2025 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Residual soil widely distributed in Fujian region has the characteristics of strong structure and easy softening in contact with water, which limits the possibility of its beneficial utilization. This study investigates the impact of humid and hot environment on the strength characteristics of residual soil, and how changes in soil microstructure are correlated with strength attenuation. Residual soil with particle size distribution from gravel to clay was subjected to repeated hygroscopic cycle tests. Subsequently, unsaturated triaxial consolidation drainage shear (CD) and nuclear magnetic resonance (NMR) tests were carried out on the samples undergoing 0-7 hygroscopic cycles, and the damage mechanism of the soil was analyzed from macroscopic to microscopic scales. Results showed that the soil shear characteristics were influenced by the number of hygroscopic cycles and had a correlation with stress level (confining pressure and target suction), the greater the cumulative irreversible deformation and the more pronounced shear dilation characteristics of the soil had after more hygroscopic cycles and higher stress levels. The shear strength index of unsaturated soil after repeated hygroscopic paths presented a decreasing trend, but the attenuation of internal friction angle and suction friction angle was limited, and the average values were 21.3 degrees and 14.7 degrees, respectively. The T 2 spectral distribution curve of soil was a trimodal pattern, and the content of small holes consistently decreasing as the cycling process progressed, while the percentage of macropores increased significantly. In view of the continuous dissolution of soluble minerals and cementing materials and the repeated release of suction in the soil, the internal particles of the soil were gradually loosened. Accompanied by the continuous expansion and penetration of intergranular pores, connecting cracks were ultimately formed. The above fatigue damage to the soil pore structure led to the attenuation of its macro-mechanical properties. Throughout the test, the saturated shear strength of the soil continued to decrease due to the interaggregate connection was always broken, while the destruction of the intergranular connection in the aggregate was relatively slow, and the internal friction angle in the soil implied a slow decrease and even stabilized at a later stage. The research results could provide a useful reference for a deeper understanding of the environmental damage effects on the soil macroscopic mechanical properties.
Arundo donax (giant reed or giant cane) is a widely available, perennial, invasive, non-food crop, present worldwide and employed for several uses, including building practices. Considering the increasing demand for sustainable building materials, A. donax can be an efficient solution. This study investigated its properties as a bio-aggregate mixed with a sodium silicate solution as an adhesive. A horizontal analysis that provided a general characterization of the composite was carried out. The results showed that the A. donax-based composite had an apparent density of 517 kg/m3, thermal conductivity of 0.128 W/(m.K), and high hygroscopicity, with a moisture buffering value of 4.33 g/(m2 %RH), property that could be both an advantage for indoor comfort and a drawback. The uncommon sound absorption behaviour can be comparable to granular materials, with the highest sound absorption coefficient values, alpha, between 600 Hz and 700 Hz. Due to the range and the shape of the acoustic absorption property, this material may be helpful in acoustic treatments for speech noise. The me-chanical tests defined flexural and compressive strength, respectively, 0.35 N/mm2 and 0.9 N/mm2, ensuring applicability. Above all, these tests opened new possible solutions for A. donax-based composite production either alone or in combination with other agro-industrial wastes and justified further tests, such as fire resistance and bio-susceptibility.
Soot particles released in the atmosphere have long been investigated for their ability to affect the radiative forcing. Although freshly emitted soot particles are generally considered to yield only positive contributions to the radiative forcing, atmospheric aging can activate them into efficient cloud condensation or ice nuclei, which can trigger the formation of persistent clouds and ultimately provide a negative contribution to the radiative forcing. Depending on their residence time in the atmosphere, soot particles can undergo several physical and chemical aging processes that affect their chemical composition, particle size distribution and morphology, and ultimately their optical and hygroscopic properties. The impact of the physical-chemical aging on the properties of soot particles is still difficult to quantify, as well as their effect on the radiative forcing of the atmosphere.This work investigates the hygroscopic properties of chemically aged soot particles obtained from the combustion of aviation fuel, and in particular the interplay between aging mechanisms initiated by two widespread atmospheric oxidizers (O-3 and SO2). Activation is measured in water supersaturation conditions using a cloud condensation nuclei counter. Once particle morphology and size distribution are taken into account, the hygroscopicity parameter kappa is derived using kappa-K & ouml;hler theory and correlated to the change of the chemical composition of the particles aged in a simulation chamber. While fresh soot particles are poor cloud condensation nuclei (kappa < 10(-4)) and are not significantly affected by either O-3 or SO2 at the timescale of the experiments, rapid activation is observed when they are simultaneously exposed to both oxidizers. Activated particles become efficient cloud condensation nuclei, comparable to the highly hygroscopic particulate matter typically found in the atmosphere (kappa = 0.2-0.6 at RH = 20 %). Statistical analysis reveals a correlation between the activation and sulfur-containing ions detected on the chemically aged particles that are absent from the fresh particles.
The present work investigates the feasibility of producing boards, with unconventional materials, namely hazelnut shells as a high-mass bio-aggregate and a sodium silicate solution as a no-toxic adhesive, and discusses possible applications based on an extensive characterization. The aim is to define a feasible reuse of a largely produced agro-industrial by-product to reduce the high environmental impact caused by both the construction and the agriculture sectors, by proposing a building composite that improves indoor comfort. The presented combination of aggregate-adhesive generated a product with characteristics interesting to explore. The thermal conductivity is moderated, and the composite achieved values of sigma max = 0.39 N/mm2 for flexural strength and sigma max = 2.1 N/mm2 for compressive strength, but it showed high sorption capacity with a moisture buffering value of about 3.45 g/(m2 %RH), and a peak of sound absorption between 700 and 900 Hz. Therefore, the boards' most promising performance parameters seem to be their high hygroscopicity and acoustic absorption behaviour, namely in the frequency range of the human voice. Hence, the proposed composite could improve indoor comfort if applied as an internal coating board.
Aerosols in Southeast Asia (SEA) are entangled with complex land-sea-atmosphere-human interactions, and it is difficult for scientists to understand their dynamic behaviors. This study aims to provide an insightful understanding of aerosols across SEA with respect to their radiative properties using several lines of evidence obtained from remote sensing instruments, including those from onboard Earth observation satellites (MODIS/Terra and MODIS/Aqua, CALIOP/CALIPSO) and from ground-based observation (AERONET). The findings, obtained from cluster analysis of aerosol optical properties, showed seven aerosol types which were dominant across the country, exhibiting diverse radiative forcing potentials. The light-absorbing (prone to warm the atmosphere) aerosols were likely found in mainland SEA, both for background and high-aerosol events. The light-scattering aerosols were associated with aging processes and hygroscopic growth. The neutral potential, which comprised a mixture of oceanic and local anthropogenic aerosols, was predominant in background aerosols in insular SEA. Further studies should focus on carbonaceous aerosols (organic carbons, black carbon, and brown carbon), the aging processes, and the hygroscopic growth of these aerosols, since they play significant roles in the regional aerosol optical properties.
Both the effects of aerosol hygroscopicity and mixing state on aerosol optical properties were analyzed using ground-based measurements and a Mie model in this study. The sized-resolved particle hygroscopic growth factor at RH = 90% (Gf(90%)) and the enhancement factor for the scattering coefficients (f(RH)(sp)) were measured by a self-constructed Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) and two nephelometers in parallel (PNEPs) respectively from 22nd February to 18th March 2014 in the Pearl River Delta, China. In addition, the particle number size distribution (PNSD) and BC mass concentration (M-BC) were measured simultaneously. During the observation period, the f(RH)(sp) increased sharply along with increasing RH (40%-85%) and the value of f(80%)(sp) was 1.77 +/- 0.18. The mean Gf(90%) for all particles are 1.44 (80 nm), 1.48 (110 nm), 1.52 (150 nm) and 1.55 (200 nm), and the mean Gf(90%) for more-hygroscopic particles are 1.58 (80 nm), 1.63 (110 nm), 1.66 (150 nm) and 1.67 (200 nm) respectively. Based on Gf, PNSD and M-BC, the enhancement factor of the aerosol optical properties (extinction (f(RH)(ep)), scattering (f(RH)(sp)), backscattering (f(RH)(hbsp)), absorption (f(RH)(absp)), and hemispheric backscatter fraction (f(RH)(hbsp))) were calculated under three aerosol mixing state assumptions. The results show that the calculated f(80%)(sp) values agreed well with the ones measured by PNEPs, illustrating that the Gf size distribution fittings are reasonable. The f(RH)(ep), f(RH)(sp) and f(RH)(hbsp) increased along with increasing RH for three mixtures, while f(RH)(HBF) decreased. The f(RH)(absp) increased for the homogenously internal mixture, but remained stable for the external mixture. For the core-shell mixture, the f(RH)(absp) increased from RH = 0 to 75% and then decreased, due to a decrease of light entering the BC core. The enhancement factor of aerosol direct radiative forcing (f(RH)(Fr)) increased sharply as the RH elevated for the external mixing state.However, f(RH)(Fr) increased or decreased along with the elevated RH for the homogenously internal mixture and the core-shell mixture depending on initial value of the aerosol direct radiative forcing (Delta F-r) in a dry condition. (C) 2018 Elsevier B.V. All rights reserved.
In this study, the sensitivity of the optical properties of carbonaceous aerosols, especially humic-like substances (HULIS), are investigated based on a one-year measurement of ambient fine atmospheric particulate matter (PM2.5) at a Global Atmospheric Watch (GAW) station in South Korea. The extinction, absorption coefficient, and radiative forcing (RF) are calculated from the analysis data of water soluble (WSOC) and insoluble (WISOC) organic aerosols, elemental carbon (EC), and HULIS. The sensitivity of the optical properties on the variations of refractive index, hygroscopicity, and light absorption properties of HULIS as well as the polydispersity of organic aerosols are studied. The results showed that the seasonal absorption coefficient of HULIS varied from 0.09 to 11.64 Mm(-1) and EC varied from 0.11 to 3.04 Mm(-1) if the geometric mean diameter varied from 0.1 to 1.0 mu m and the geometric standard deviation varied from 1.1 to 2.0, with the imaginary refractive index (IRI) of HULIS varying from 0.006 to 0.3. Subsequently, this study shows that the RF of HULIS was larger than other constituents, which suggested that HULIS contributed significantly to radiative forcing.
The ability of a particle to uptake water and form a cloud droplet depends on its hygroscopicity. To understand its impact on cloud properties and ultimately radiative forcing, knowledge of chemically resolved mixing state information or the one based on hygroscopic growth is crucial. Typically, global models assume either pure internal or external mixing state which might not be true for all conditions and sampling locations. To investigate into this, the current study employed an indirect approach to infer the probable mixing state. The hygroscopic parameters derived from kappa-Kohler theory using size-resolved CCN measurements (kappa(CCN)) and bulk/size-resolved aerosol mass spectrometer (AMS) measurements (kappa(Ams)) were compared. The accumulation mode particles were found to be more hygroscopic (kappa(CCN) = 0.24) than Aitken mode (kappa(CCN) = 0.13), perhaps due to increased ratio of inorganic to organic mass fraction. The activation diameter calculated from size-resolved CCN activity measurements at 5 different supersaturation (SS) levels varied in the range of 115 nm-42 nm with kappa(CCN) = 0.13-0.23 (avg = 0.18 +/- 0.10 (+/- 1 sigma)). Further, kappa(AMS)> kappa(CCN) was observed possibly due to the fact that organic and inorganic mass present in the Aitken mode was not correctly represented by bulk chemical composition and size-resolved fractional contribution of oxidized OA was not accurately accounted. Better correlation of organic fraction (f(org)) and kappa(CCN) at lower SS explained this behaviour. The decrease in kappa(CCN) with the time of the day was more pronounced at lower SS because of the relative mass reduction of soluble inorganic species by similar to 17%. Despite the large differences between kappa measured from two approaches, less over-prediction (up to 18%) between measured and predicted CCN concentration suggested lower impact of chemical composition and mixing state at higher SS. However, at lower SS, presences of externally mixed CCN-inactive aerosols lead to CCN over-prediction reflecting the significance of aerosol mixing state information. Further examination of the effect of biomass burning aerosols (similar to 35% in least oxidized biomass burning organic aerosol (BBOA-2 fraction) on hygroscopicity and CCN activity showed increase in the concentration of all AMS measured species (except NH4+ and SO42-), less O:C ratio, and organic mass fraction (f(org)) peak shift to lower diameter range caused similar to 13% change in critical diameter (Da) and similar to 40% change in kappa(CCN). Increased deviation of similar to 100% between kappa(CCN) and kappa(AMS) due to sudden influx of internally mixed BBOA caused suppressed hygroscopic growth. This study finally suggests the assumption of pure internally mixed aerosol does not completely hold true for this anthropogenically polluted site. (C) 2016 Elsevier Ltd. All rights reserved.
In this study, the influences of water solubility and light absorption on the optical properties of organic aerosols were investigated. A size-resolved model for calculating optical properties was developed by combining thermodynamic hygroscopic growth and aerosol dynamics models. The internal mixtures based on the homogeneous and core shell mixing were compared. The results showed that the radiative forcing (RF) of Water Soluble Organic Carbon (WSOC) aerosol can be estimated to range from -0.07 to -0.49 W/m(2) for core shell mixing and from -0.09 to -0.47 W/m(2) for homogeneous mixing under the simulation conditions (RH = 60%). The light absorption properties of WSOC showed the mass absorption efficiency (MAE) of WSOC can be estimated 0.43-0.5 m(2)/g, which accounts for 5-10% of the MAE of elemental carbon (EC). The effect on MAE of increasing the imaginary refractive index of WSOC was also calculated, and it was found that increasing the imaginary refractive index by 0.001i enhanced WSOC aerosol absorption by approximately 0.02 m(2)/g. Finally, the sensitivity test results revealed that changes in the fine mode fraction (FMF) and in the geometric mean diameter of the acthmulation mode play important roles in estimating RF during hygroscopic growth. (C) 2015 Elsevier Ltd. All rights reserved.