| 1. |
- Yu, Hua, et al.
(författare)
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Organic coating on sulfate and soot particles during late summer in the Svalbard Archipelago
- 2019
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:15, s. 10433-10446
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Tidskriftsartikel (refereegranskat)abstract
- Interaction of anthropogenic particles with radiation and clouds plays an important role in Arctic climate change. The mixing state of aerosols is a key parameter to influence aerosol radiation and aerosol-cloud interactions. However, little is known of this parameter in the Arctic, preventing an accurate representation of this information in global models. Here we used transmission electron microscopy with energy-dispersive X-ray spectrometry, scanning electron microscopy, nanoscale secondary ion mass spectrometry, and atomic forces microscopy to determine the size and mixing state of individual sulfate and carbonaceous particles at 100 nm to 2 mu m collected in the Svalbard Archipelago in summer. We found that 74% by number of non-sea-salt sulfate particles were coated with organic matter (OM); 20% of sulfate particles also had soot inclusions which only appeared in the OM coating. The OM coating is estimated to contribute 63% of the particle volume on average. To understand how OM coating influences optical properties of sulfate particles, a Mie core-shell model was applied to calculate optical properties of individual sulfate particles. Our result shows that the absorption cross section of individual OM-coated particles significantly increased when assuming the OM coating as light-absorbing brown carbon. Microscopic observations here suggest that OM modulates the mixing structure of fine Arctic sulfate particles, which may determine their hygroscopicity and optical properties.
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| 2. |
- Li, Qiang, et al.
(författare)
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Microbial Necromass, Lignin, and Glycoproteins for Determining and Optimizing Blue Carbon Formation
- 2024
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 58, s. 468-479
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Tidskriftsartikel (refereegranskat)abstract
- Coastal wetlands contribute to the mitigation of climate change through the sequestration of “blue carbon”. Microbial necromass, lignin, and glycoproteins (i.e., glomalin-related soil proteins (GRSP)), as important components of soil organic carbon (SOC), are sensitive to environmental change. However, their contributions to blue carbon formation and the underlying factors remain largely unresolved. To address this paucity of knowledge, we investigated their contributions to blue carbon formation along a salinity gradient in coastal marshes. Our results revealed decreasing contributions of microbial necromass and lignin to blue carbon as the salinity increased, while GRSP showed an opposite trend. Using random forest models, we showed that their contributions to SOC were dependent on microbial biomass and resource stoichiometry. In N-limited saline soils, contributions of microbial necromass to SOC decreased due to increased N-acquisition enzyme activity. Decreases in lignin contributions were linked to reduced mineral protection offered by short-range-ordered Fe (FeSRO). Partial least-squares path modeling (PLS-PM) further indicated that GRSP could increase microbial necromass and lignin formation by enhancing mineral protection. Our findings have implications for improving the accumulation of refractory and mineral-bound organic matter in coastal wetlands, considering the current scenario of heightened nutrient discharge and sea-level rise.
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| 3. |
- Zhang, Jianchao, et al.
(författare)
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Investigating the influence of fly ash on the hydration behavior of cement using an electrochemical method
- 2019
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 222, s. 41-48
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Elsevier Ltd Fly ash is an industrial by-product that is widely used in the cement industry. Traditional methods used to investigate the influence of fly ash on the hydration behavior of cement are destructive and cannot accomplish a continuous tracing of the hydration process. In this study, the influence of fly ash incorporation on the hydration process of cement is evaluated using measured electrochemical data obtained from the electrochemical impedance spectroscopy approach. A novel equivalent circuit model that considers the electrochemical characteristics of cement during the hydration process is proposed to investigate the electrochemical property of the blended cement. The resistance parameter of the model, Rct1, was found to have a positive correlation with hydration degree and compressive strength during hydration. With this parameter, the method can be used to non-destructively trace and characterize the effects of fly ash incorporation on the cement hydration process.
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| 4. |
- Zhang, Jianchao, et al.
(författare)
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Water distribution modelling of capillary absorption in cementitious materials
- 2019
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 216, s. 468-475
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel capillary absorption model is proposed to investigate the capillary absorption process of cementitious materials. This model mainly consider the influence of tortuosity of the capillary pores of cement paste, which is the key factor affecting the capillary absorption process. The proposed model is verified by the capillary absorption process of paste samples with different water/cement ratios. The absorption height and water content profile of testing samples are measured by X-ray computed tomography. The results show that the proposed capillary absorption model that takes the tortuosity of capillary pores into consideration is suitable for investigating the capillary absorption process of water in cementitious materials.
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