Guangzhou Institute of Geochemistry
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Dominant Contribution of Non-dust Primary Emissions and Secondary Processes to Dissolved Aerosol Iron
No full textSolubility largely determines the impacts of aerosol Fe on marine ecosystems and human health. Currently, modeling studies have large uncertainties in aerosol Fe solubility due to inadequate understanding of the sources of dissolved Fe. This work investigated seasonal variations of Fe solubility in coarse and fine aerosols in Qingdao, a coastal city in the Northwest Pacific, and utilized a receptor model for source apportionment of total and dissolved aerosol Fe. Desert dust was found to be the main source of total Fe, contributing 65 and 81% annually to total Fe in coarse and fine particles, respectively; in contrast, dissolved aerosol Fe originated primarily from combustion, industrial, and secondary sources. The annual average contributions to dissolved Fe in coarse and fine particles were 68 and 47% for the secondary source and 32 and 33% for the combustion source, respectively. Aerosol Fe solubility was found to be highest in summer and lowest in spring, showing seasonal patterns similar to those of aerosol acidity. Increase in Fe solubility in atmospheric particles, when compared to desert dust, was mainly caused by secondary processing and combustion emission, and the effect of secondary processes was dictated by aerosol acidity and liquid water content
Dominant Contribution of Non-dust Primary Emissions and Secondary Processes to Dissolved Aerosol Iron
No full textSolubility largely determines the impacts of aerosol Fe on marine ecosystems and human health. Currently, modeling studies have large uncertainties in aerosol Fe solubility due to inadequate understanding of the sources of dissolved Fe. This work investigated seasonal variations of Fe solubility in coarse and fine aerosols in Qingdao, a coastal city in the Northwest Pacific, and utilized a receptor model for source apportionment of total and dissolved aerosol Fe. Desert dust was found to be the main source of total Fe, contributing 65 and 81% annually to total Fe in coarse and fine particles, respectively; in contrast, dissolved aerosol Fe originated primarily from combustion, industrial, and secondary sources. The annual average contributions to dissolved Fe in coarse and fine particles were 68 and 47% for the secondary source and 32 and 33% for the combustion source, respectively. Aerosol Fe solubility was found to be highest in summer and lowest in spring, showing seasonal patterns similar to those of aerosol acidity. Increase in Fe solubility in atmospheric particles, when compared to desert dust, was mainly caused by secondary processing and combustion emission, and the effect of secondary processes was dictated by aerosol acidity and liquid water content
Excess supply of sulfur mitigates thallium toxicity to rice (<i>Oryza</i><i> sativa</i> L.) growth in hydroponic experiment
No full textSulfur (S) is an essential element for the growth of rice plants (Oryza sativa L.), crucial for enhancing crop yield and grain quality. However, its potential in mitigating thallium (Tl) toxicity in rice remains unclear. In this study, a hydroponic experiment was performed to investigate the effects of low, medium and high S application levels (LS, MS, HS) on Tl accumulation in rice at three Tl exposure levels (0, 0.5 and 1 mgL-1). Our findings reveal that the exogenous S application could alleviate Tl toxicity, enhancing fresh weight and shoot length of rice plant. Additionally, HS (HS, SO42- content was 387.84 mgL-1) group significantly increased chlorophyll and glutathione (GSH) content by 6.46 to 21.38 % and 2.15 to 7.31 % respectively, while reducing malondialdehyde (MDA) levels by 17.43 to 28.48 %, compared to MS (MS, SO42- content was 193.41 mgL-1) group. Fe content in rice roots and iron plaque consistently increased with S provision under Tl-free and Tl-contaminated conditions. In Tl exposure environment, HS and LS (LS, SO42- content was 1.02 mgL-1) groups exhibited significant differences in Fe contents and iron plaque in rice root. Moreover, in Tl exposure environment, S application reduced Tl concentration in iron plaque, root, and shoot, HS treatment showed Tl content reduction from 16.29 % to 25.89 %, compared to LS treatment. Our findings underscore the potential of S application in hydroponic environment to promote rice growth and mitigate Tl accumulation, offering insights for developing effective Tl remediation strategies by using S-contained fertilizers
Geochemistry, zircon U-Pb dating, Hf-Nd isotopic characteristic and geological significance of Late Triassic S -type granite in the Keliya region, West Kunlun Orogen
No full textLithium is a crucial strategic metal resource for modern China. In recent years, significant medium to large high-grade pegmatite-type lithium deposits, such as those at Kalawala, Mulinchang, Kangxiwa, Bailongshan, and Xuefengling, have been discovered in the West Kunlun rare metal metallogenic belt. To identify new rare metal deposits in regions marked by lithium-beryllium geochemical anomalies, this study employs the Bailongshan deposit in the Dahongliutan rare metal ore concentration area on the eastern margin of the West Kunlun orogenic belt as a model. The research establishes a prospecting model that integrates "Late Triassic S-type granite-pegmatite + Bayankala Group strata + emplacement in weak zones of ductile shear belts + lithium-beryllium geochemical anomalies. "To assess the potential for rare metal deposit discovery in the Keliya region, located on the eastern margin of Dahongliutan, this paper utilizes the aforementioned prospecting model as a guiding framework. It combines methodologies such as geochemistry, zircon U-Pb geochronology, and Hf-Nd isotopes in the investigation of the Keliya granite body. Comparative analyses of regional stratigraphy and tectonic settings between the Keliya and Bailongshan deposits reveal that the Keliya body is an S-type monzogranite with an average age of 207 +/- 1. 1Ma, consistent within the margin of error with the S-type two-mica granite of the Bailongshan deposit. Moreover, despite high lithium-beryllium geochemical anomalies, similar exposed strata, pegmatite outcrops, and a post-collisional tectonic setting in both regions, the magma sources of the two areas differ. Based on the above research, this paper concludes that the Keliya region is not suitable for using the prospecting theory modeled after the pegmatite-type lithium deposit of Bailongshan as a guide
Geochemistry, zircon U-Pb dating, Hf-Nd isotopic characteristic and geological significance of Late Triassic S -type granite in the Keliya region, West Kunlun Orogen
No full textLithium is a crucial strategic metal resource for modern China. In recent years, significant medium to large high-grade pegmatite-type lithium deposits, such as those at Kalawala, Mulinchang, Kangxiwa, Bailongshan, and Xuefengling, have been discovered in the West Kunlun rare metal metallogenic belt. To identify new rare metal deposits in regions marked by lithium-beryllium geochemical anomalies, this study employs the Bailongshan deposit in the Dahongliutan rare metal ore concentration area on the eastern margin of the West Kunlun orogenic belt as a model. The research establishes a prospecting model that integrates "Late Triassic S-type granite-pegmatite + Bayankala Group strata + emplacement in weak zones of ductile shear belts + lithium-beryllium geochemical anomalies. "To assess the potential for rare metal deposit discovery in the Keliya region, located on the eastern margin of Dahongliutan, this paper utilizes the aforementioned prospecting model as a guiding framework. It combines methodologies such as geochemistry, zircon U-Pb geochronology, and Hf-Nd isotopes in the investigation of the Keliya granite body. Comparative analyses of regional stratigraphy and tectonic settings between the Keliya and Bailongshan deposits reveal that the Keliya body is an S-type monzogranite with an average age of 207 +/- 1. 1Ma, consistent within the margin of error with the S-type two-mica granite of the Bailongshan deposit. Moreover, despite high lithium-beryllium geochemical anomalies, similar exposed strata, pegmatite outcrops, and a post-collisional tectonic setting in both regions, the magma sources of the two areas differ. Based on the above research, this paper concludes that the Keliya region is not suitable for using the prospecting theory modeled after the pegmatite-type lithium deposit of Bailongshan as a guide
Role of Organic Vapor Precursors in Secondary Organic Aerosol Formation: Concurrent Observations of IVOCs and VOCs in Guangzhou
No full textSecondary organic aerosol (SOA) formed through the atmospheric transformation of organic vapors constitutes a significant portion of fine particulate matter or PM2.5. While recent laboratory studies underscore the importance of intermediate-volatility organic compounds (IVOCs) as key precursors to SOA, field observations that recognize the role of both volatile organic compounds (VOCs) and IVOCs in SOA formation remain scarce. In this study, we conducted concurrent measurements of VOCs and IVOCs in ambient air at urban and suburban sites in Guangzhou during a PM2.5 pollution event in winter 2021. The results reveal that between 12:00-15:00 local time, the photochemically adjusted initial concentrations of VOCs at both sites were approximately 7 times higher than that of IVOCs. However, the SOA formation potential (SOAFP) of primary hydrocarbon IVOCs exceeded that of VOCs by over 3-4 times. Receptor modeling results further indicated that while ship emissions contributed to less than 10% of the C2-C22 primary hydrocarbons concentration (VOCs + primary carbonaceous IVOCs), they accounted for the most significant source (approximately 40%) of SOA formation. This study highlights the substantial role of IVOCs in SOA formation and emphasizes the importance of future PM2.5 pollution control measures targeting major IVOCs contributors, such as ship emissions in harbor cities.
Fine particulate matter (PM2.5) is a critical air pollutant affecting human health, with secondary organic aerosol (SOA) being a significant component. This study investigated the formation of SOA by examining both volatile organic compounds (VOCs) and intermediate-volatility organic compounds (IVOCs) in Guangzhou during a pollution event. Despite VOCs being more abundant, IVOCs showed higher potential to form SOA. Surprisingly, ship emissions, though minor in contributing to C2-C22 primary hydrocarbons, played a major role in SOA formation. This highlights the need to control IVOCs, especially from ships, to combat PM2.5 pollution, particularly in coastal cities.
Concurrent observations of volatile organic compounds (VOCs) and intermediate-volatility organic compounds (IVOCs) were conducted during a PM2.5 pollution event in Guangzhou VOC concentrations were similar to 7 times that of hydrocarbon IVOCs, but their secondary organic aerosol (SOA) formation potentials were less than half that of hydrocarbon IVOCs Ship emissions contributed less than 10% of total VOCs and IVOCs, but could account for up to 40% of SOA formatio
Origin and preservation mechanisms of organic matter in carbonate concretions from Lower Cambrian black shales in South China
No full textCarbonate concretions are widely used in paleoclimate, paleoenvironmental, and paleontological studies, and even in the study of potential life on Mars. These petrological, elemental, isotopic, and lipid biomarker signals in Meso-Cenozoic carbonate concretions (relatively low thermal maturity) can effectively preserve details of seawater conditions and benthic ecosystems during the deposition of their host sediments/rocks. However, such research on Precambrian-Cambrian carbonate concretions under highly mature conditions remains scarce, and the ability of these ancient carbonate concretions to retain their original biogenic information remains uncertain. To achieve that, this study examines two Cambrian carbonate concretions, using samples from the center, transition, and rim of each, and their adjacent host black shales from the Lower Cambrian Qiongzhusi Formation in the Yangtze Block, South China. Organic and inorganic geochemical analyses were combined to elucidate the origin and preservation process of organic matter (OM) in these ancient Cambrian carbonate concretions. The results show that the thermal maturity of OM within these concretions (1.8 % EqVRo) is relatively low compared to their adjacent host shales (2.9 % EqVRo). Hopanes and steranes are detectable in both free and calciteoccluded hydrocarbons within these concretions, with concentrations of individual compounds ranging from 0.001 to 0.800 mu g/g TOC, whereas kerogen-bound hydrocarbons lack detectable biomarkers. The results indicate that the two Cambrian carbonate concretions were formed mainly within the iron reduction and bacterial sulfate reduction zones, extending to depths of 10 to 38 m below the sediment-water interface. The OM within these concretions mainly inherited the initial unaltered signature of OM from the Qiongzhusi host shale. The carbonate concretions protected the internal OM from further thermal and secondary (e.g., biodegradation) alteration processes and might also prevent the formation of the conventional macromolecular skeletal kerogen manifested by the absence of bound biomarkers. The biomarkers, in both free and occluded forms, in the Cambrian carbonate concretions still retained their original source information, providing valuable insights into ancient biogeochemical processes during sediment burial and ancient seawater chemistry during the early Cambrian
Recycled lower oceanic crust signal in early Jurassic A1 1-type granites, South China: Implications for flat-slab subduction and mantle heterogeneity in the continental back-arc region
No full textFlat-slab subduction is a distinctive phenomenon that leads to the development of a wide orogenic zone (>= 800 km) along former continental margins, triggering extensive intraplate magmatism and deformation. However, occurrences of flat-slab subduction on ancient convergent margins are exceptionally rare, possibly owing to multiple episodes of structural destruction and/or poor preservation. Furthermore, the impact of flat-slab subduction on mantle heterogeneity remains ambiguous. In this study, we present comprehensive whole-rock geochemical analyses as well as in-situ zircon U-Pb - Pb dating and Hf-O - O isotopic data for Early Jurassic A-type granites from the Pitou and Shibixia plutons in the interior of the South China Block to investigate the potential influence of flat-slab subduction on intraplate magmatism. The Pitou granites exhibit characteristics consistent with those of A2 2-type granite, displaying zircon epsilon Hf(t) Hf (t) values ranging from-4.9 to +0.3 and elevated delta 18O 18 O values of 6.2-7.6%o. %o . These features suggest that the granites formed through the differentiation of a basaltic parental magma, which underwent varying degrees of crustal contamination. In contrast, the Shibixia granites show A1 1type geochemical features and were derived from basaltic parental magma without significant crustal contamination. The zircons in these granites exhibit positive epsilon Hf(t) Hf (t) values ranging from +6.6 to +10.6 and anomalously low delta 18O 18 O values of 3.3-4.0%o, %o , suggesting the involvement of recycled altered lower oceanic crust components in their mantle source. This provides strong evidence for the occurrence of flat-slab subduction beneath the interior of the South China Block during the early Mesozoic, which was located at least 800 km away from the trench. Combined with the presence of post-delamination ocean island-like intraplate magmatic rocks in the South China interior, it is suggested that the flat-slab delamination at approximately 190 Ma facilitated late Mesozoic intraplate OIB-like magmatism. This process, associated with flat-slab subduction, is expected to exert a significant impact on mantle isotopic heterogeneity within continental back-arc regions
Evolution of mechanical properties of organic-rich shale during thermal maturation
No full textAccurate assessment of the mechanical properties of organic matter, clay matrix, and bulk shale during maturation remains a challenge. Here, we aim to assess the mechanical properties of organic-rich shale during maturation using a combination of nanoindentation methods and various geochemical analyses, i.e., mineral composition, mass loss rate, chemical structure of organic matter, and Rock-Eval analyses. Results show that the evolution of mechanical properties of organic matter in shale during maturation can be divided into: the main oil-generation stage, and the condensate oil and gas generation stage. The stiffening of organic matter in the shale is mainly due to increased aromaticity and condensation of aromatic groups. The clay matrix experiences a slight decrease in hardness and Young's modulus at low maturity levels due to the generation of liquid hydrocarbons. However, overall, the clay matrix becomes stiffer as the shale matures due to shale dehydration, expulsion or cracking of liquid hydrocarbons, transformation of clay minerals, and hardening of organic matter. The Young's modulus and hardness of bulk shale generally increase with increasing maturity. This is closely related to the hardening of organic matter and clay matrix, as well as the development of the more compact and dense microstructure in the shale
Kinetics of Mg-Ni saponite crystallization from precursor mixtures
No full textSmectite growth is of importance across various fields due to its abundance on the surface of both Earth and Mars. However, the impact of the crystallinity of initial materials on smectite growth processes remains poorly understood. In this study, the kinetic processes of smectite growth were examined via experimental synthesis of trioctahedral Mg-Ni saponites. Mg-Ni saponites were synthesized using mixed precursors, specifically end-member Mg-saponite and Ni-saponite, which exhibit different crystallinities. The crystal chemistry and morphology of samples were analyzed using X-ray diffraction, Fourier-transform infrared spectroscopy, and high-angle annular dark-field scanning transmission electron microscopy. The experimental results converge towards these main conclusions: (i) the formation of Mg-Ni saponite solid solutions are promoted when the precursors are small particles, whereas large-particle precursors limit their own dissolution and do not yield Mg-Ni saponite solid solutions under the experimental conditions; (ii) because Ni exhibits a greater stability within the saponite structure compared to Mg, the Mg-Ni-saponite solid solutions formed more easily from the mixture of Ni-saponite germs and well-crystallized Mg-saponite precursors than from the mixture of Mg-saponite germs and well-crystallized Ni-saponite precursors; (iii) the dissolution extent (DE) of precursor mixtures increases with longer synthesis time, higher synthesis temperature, and larger gap between synthesis temperature of precursors and of samples, and stabilizes once it reaches a certain value. Thus DE can be used to estimate the kinetics of Mg-Ni saponite crystallization from precursor mixtures. These results obtained from the experimental Mg-Ni saponite system are useful for predicting the evolution processes of smectite in natural systems