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504 results on '"Sanei, Hamed"'

4. Dispersed organic matter from pre-Devonian marine shales: A review on its composition, origin, evolution, and potential for hydrocarbon prospecting

Author

Luo, Qingyong, Goodarzi, Fariborz, Zhong, Ningning, Qiu, Nansheng, Wang, Xiaomei, Suchý, Václav, Khan, Imran, Zheng, Xiaowei, Liu, Bei, Ardakani, Omid H., Zhang, Ye, Li, Dahua, Wu, Jin, Fang, Zilong, Shi, Ruitan, Skovsted, Christian B., Sanei, Hamed, Xu, Yaohui, Wu, Jia, Hu, Wenxin, and Duan, Guoqiang

Published
2025
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26. Volcanic mercury and mutagenesis in land plants during the end-Triassic mass extinction.

Author

Lindström, Sofie, Sanei, Hamed, van de Schootbrugge, Bas, Pedersen, Gunver K, Lesher, Charles E, Tegner, Christian, Heunisch, Carmen, Dybkjær, Karen, and Outridge, Peter M

Subjects
Ferns, Mercury, Mutagenesis, Fossils, Germany, Extinction, Biological, Stress, Physiological, Volcanic Eruptions, Embryophyta, Scandinavian and Nordic Countries, Extinction, Biological, Stress, Physiological
Abstract

During the past 600 million years of Earth history, four of five major extinction events were synchronous with volcanism in large igneous provinces. Despite improved temporal frameworks for these events, the mechanisms causing extinctions remain unclear. Volcanic emissions of greenhouse gases, SO2, and halocarbons are generally considered as major factors in the biotic crises, resulting in global warming, acid deposition, and ozone layer depletion. Here, we show that pulsed elevated concentrations of mercury in marine and terrestrial sediments across the Triassic-Jurassic boundary in southern Scandinavia and northern Germany correlate with intense volcanic activity in the Central Atlantic Magmatic Province. The increased levels of mercury-the most genotoxic element on Earth-also correlate with high occurrences of abnormal fern spores, indicating severe environmental stress and genetic disturbance in the parent plants. We conclude that this offers compelling evidence that emissions of toxic volcanogenic substances contributed to the end-Triassic biotic crisis.

Published
2019

27. Volcanic mercury and mutagenesis in land plants during the end-Triassic mass extinction.

Author

Tegner, Christian, Heunisch, Carmen, Dybkjær, Karen, Outridge, Peter, Lindström, Sofie, Sanei, Hamed, van de Schootbrugge, Bas, Pedersen, Gunver, and Lesher, Charles

Subjects
Embryophyta, Extinction, Biological, Ferns, Fossils, Germany, Mercury, Mutagenesis, Scandinavian and Nordic Countries, Stress, Physiological, Volcanic Eruptions
Abstract

During the past 600 million years of Earth history, four of five major extinction events were synchronous with volcanism in large igneous provinces. Despite improved temporal frameworks for these events, the mechanisms causing extinctions remain unclear. Volcanic emissions of greenhouse gases, SO2, and halocarbons are generally considered as major factors in the biotic crises, resulting in global warming, acid deposition, and ozone layer depletion. Here, we show that pulsed elevated concentrations of mercury in marine and terrestrial sediments across the Triassic-Jurassic boundary in southern Scandinavia and northern Germany correlate with intense volcanic activity in the Central Atlantic Magmatic Province. The increased levels of mercury-the most genotoxic element on Earth-also correlate with high occurrences of abnormal fern spores, indicating severe environmental stress and genetic disturbance in the parent plants. We conclude that this offers compelling evidence that emissions of toxic volcanogenic substances contributed to the end-Triassic biotic crisis.

Published
2019

33. Evaluating the two-pool decay model for biochar carbon permanence.

Author

Sanei, Hamed, Petersen, Henrik Ingermann, Chiaramonti, David, and Masek, Ondrej

Subjects
*CARBON sequestration, *DECAY constants, *BIOCHAR, *NATIONAL income accounting, *CARBON dioxide
Abstract

Accurate estimation of biochar carbon permanence is essential for assessing its effectiveness as a carbon dioxide removal (CDR) strategy. The widely adopted framework, based on the two-pool carbon exponential decay model, forms the basis of policy guidelines and national CDR accounting. However, our re-analysis of the meta-data used in this model reveals significant deficiencies in its parameterization, leading to two critical issues. First, the current parameterization assigns a disproportionally low percentage of the labile carbon fraction (C1) relative to the recalcitrant fraction (C2), effectively reducing the model to a single-pool approach. Due to the limited duration of incubation experiments, the decay constant of the labile fraction is incorrectly applied to the entire biochar mass, resulting in a considerable overestimation of the biochar decay rate. Second, our analysis reveals a lack of causal correlation between the assigned proportions of C1 and C2 and key carbonization parameters such as production temperature and hydrogen-to-carbon (H/C) ratios, suggesting that the model does not accurately represent the underlying chemistry. This misalignment contradicts the established relationship between increased biochar stability and a higher degree of carbonization. Consequently, the the parameterization of current model may not adequately reflect the carbon sequestration potential of biochar. While a multi-pool decay model is suitable for predicting the permanence of biochar, the primary issue with the current model lies in its parameterization rather than its structure. To address these limitations, we recommend that future research prioritize the development of a revised multi-pool decay model with improved parameterization, supported by empirical decomposition data from a variety of experimental methods, including incubation studies, accelerated aging experiments, and comprehensive physicochemical characterization. This refined approach will improve the accuracy of biochar permanence estimations, strengthening its role in global carbon management strategies. Highlights: Reassessment of biochar decay model reveals key parameterization deficiencies. Current model substantially overestimates biochar decay rates. Model misaligns with the chemistry underlying the decay behavior of biochar. New decay models for biochar permanence need improved parametrization. Enhanced model aims to strengthen biochar's role in carbon management strategies. [ABSTRACT FROM AUTHOR]

Published
2025
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50. Atlas of Microscopic Images of Biochar

Author

Drobniak, Agnieszka, primary, Mastalerz, Maria, additional, Knauth, William, additional, Adarkani, Omid, additional, Dos Santos, Telma, additional, De Faria, Valdeci, additional, Congo, Tara, additional, Hackley, Paul, additional, Hatcherian, Javin, additional, Hower, James, additional, Petersen, Henrik, additional, Reyes, Julito, additional, and Sanei, Hamed, additional

Published
2024
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