Guangzhou Institute of Geochemistry
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Algorithm for improving the sizing accuracy in real-time bioaerosol single particle mass spectrometer
No full textThe newly developed bioaerosol single particle mass spectrometer (Bio-SPAMS) has been innovatively designed for its optical sizing system. The first laser beam in the previous single particle mass spectrometer was split into near distance double beams, similar to the design of APS (Aerodynamic Particle Sizer) and SBS-LIBS (Single Beam Splitting-Laser Induced Breakdown Spectroscopy). All the particles focused by the aerodynamic lens can be sized and got number concentration statistic. However, due to the imperfect beam quality and the large scattering intensity of the large-sized particles, there may be some noise in the scattered signals, particle diameter measured by this sizing system was often larger than actual value if the same trigger threshold was set. In this study, when measuring PSL microspheres with diameters of 1.9, 3.1, and 4.9 mu m, the identification rates of the fixed threshold algorithm were only 75.25%, 55.26%, and 0.27%, respectively. To address such issue, we developed a dynamic threshold waveform recognition algorithm based on field programmable gate array (FPGA), which could process the photoelectric signals collected by a photomultiplier tube (PMT) in real time. The algorithm can dynamically adjust the trigger threshold of the collected scattered signals and accurately calculate the interval time between the near distance double beam. For PSL microspheres with diameters of 1.9, 3.1, and 4.9 mu m, the accuracy of the dynamic threshold algorithm increased by 19.09%, 25.72%, and 88.20%, respectively. This algorithm effectively solves the problem of particle sizing deviation, and improves the particle size measurement accuracy of the bioaerosol mass spectrometer in a wide particle size range from 0.3-6 mu m
Seasonal and spatial variability of dissolved organic nitrogen concentration and composition in Daya Bay, China
No full textDissolved organic nitrogen (DON) has recently been recognized as an important nitrogen source for marine phytoplankton. However, the composition, sources, and biogeochemical cycling of DON in coastal ecosystems remain poorly understood. This study investigates the spatial distribution and seasonal variability of DON in Daya Bay, a subtropical semi-enclosed bay in the northern South China Sea. We measured DON concentrations, the DIN:DIP ratio, and the spectral characteristics of dissolved organic matter (DOM), including a(350), SUVA(254), and fluorescence components. Our findings reveal clear seasonal differences in the controlling factors for DON distribution: in summer, land-based sources and biological activities dominate, whereas in winter, oceanic circulation and its associated water mass mixing play a predominant role. The combined spectral indexes suggest that the transformation of DON is significantly more active in summer than in winter. Additionally, most stations exhibited low DIN:DIP ratios (2 mu g/L) during the summer months, while DIP concentrations in Daya Bay remained generally low (<1 mu mol L-1). This suggests that phytoplankton may assimilate DON, potentially leading to algal blooms and changes in population structure. Overall, these findings highlight the potential role of DON in the coastal nitrogen budget and phytoplankton dynamics, emphasizing the need for further investigation
n-Alkanes S<SUP>13</SUP>C and salinity correlation in mangrove Aegiceras corniculatum leaves and surface sediments from Zhanjiang estuaries, China
No full textCarbon isotope ratios (S13C) in plant lipid biomarkers yield insights into historical climates by reflecting plant responses to environmental stressors. Previous research has established a correlation between increased salinity and elevated S13C in Avicennia marina leaf wax n-alkanes, yet it remains unclear if these isotopic signatures are universally applicable across different species and regions or consistently preserved in sedimentary records. We investigated the influence of a 30 ppt salinity gradient on Aegiceras corniculatum in Zhanjiang, China, examining S13C values in leaf wax n-alkanes and adjacent sediments. Leaf wax S13C values ranged from -36.7 %o to -31.4 %o, while sediment n-alkanes ranged from -35.6 %o to -28.2 %o. Sediments consistently exhibited higher S13C values than leaf wax, and their total lipid and n-alkane S13C exhibited a positive correlation with salinity, increasing by 0.06 f 0.02 %o and 0.1 f 0.04 %o per ppt respectively. This positive correlation may be attributed to factors such as marine material input, seasonal variations in lipid synthesis, and plant community succession. In contrast, no significant correlation with salinity was observed in A. corniculatum's bulk leaf tissues or total lipids. This lack of correlation can be attributed to the unique physiological conditions and varying salt exclusion mechanisms among mangrove species, which influence water use efficiency. Accordingly, while sediment S13C values can indicate past vegetation, the variability necessitates caution in using mangrove sediment S13C for paleoenvironmental reconstruction
n-Alkanes S<SUP>13</SUP>C and salinity correlation in mangrove Aegiceras corniculatum leaves and surface sediments from Zhanjiang estuaries, China
No full textCarbon isotope ratios (S13C) in plant lipid biomarkers yield insights into historical climates by reflecting plant responses to environmental stressors. Previous research has established a correlation between increased salinity and elevated S13C in Avicennia marina leaf wax n-alkanes, yet it remains unclear if these isotopic signatures are universally applicable across different species and regions or consistently preserved in sedimentary records. We investigated the influence of a 30 ppt salinity gradient on Aegiceras corniculatum in Zhanjiang, China, examining S13C values in leaf wax n-alkanes and adjacent sediments. Leaf wax S13C values ranged from -36.7 %o to -31.4 %o, while sediment n-alkanes ranged from -35.6 %o to -28.2 %o. Sediments consistently exhibited higher S13C values than leaf wax, and their total lipid and n-alkane S13C exhibited a positive correlation with salinity, increasing by 0.06 f 0.02 %o and 0.1 f 0.04 %o per ppt respectively. This positive correlation may be attributed to factors such as marine material input, seasonal variations in lipid synthesis, and plant community succession. In contrast, no significant correlation with salinity was observed in A. corniculatum's bulk leaf tissues or total lipids. This lack of correlation can be attributed to the unique physiological conditions and varying salt exclusion mechanisms among mangrove species, which influence water use efficiency. Accordingly, while sediment S13C values can indicate past vegetation, the variability necessitates caution in using mangrove sediment S13C for paleoenvironmental reconstruction
Hydrothermal pretreatment for enhanced thermochemical or biochemical conversion of pharmaceutical biowastes into fuels, fertilizers, and carbon materials
No full textPharmaceutical biowastes, rich in organic matter and high in moisture, are typical light industry byproducts with waste and renewable attributes. Thermochemical and biochemical conversion technologies transform these residues into value-added bioproducts, including biofuels, biofertilizers, and bio-carbon materials. Hydrothermal pretreatment effectively removes toxic substances and enhances feedstock for these processes. This review comprehensively examines its role in improving the formation of bioproducts from pharmaceutical biowastes, focusing on (i) upgrading and denitrogenating solid biofuels with better combustion performance; (ii) enhancing biodegradability and gaseous biofuel production via organic matter decomposition; (iii) enriching soluble carbon and nitrogen for liquid biofertilizer; (iv) eliminating antibiotic residues and reducing antibiotic resistance in solid biofertilizers; and (v) stabilizing carbon and nitrogen structures and optimizing pore characteristics for functionalized carbon materials. The review recommends a potential staged thermochemical approach to co-produce nitrogen-enriched liquid biofertilizers and porous carbon materials from pharmaceutical biowastes. Hydrothermal pretreatment emerges as a key technique for facilitating the migration and conversion of essential elements like carbon and nitrogen. This study reveals the potential of hydrothermal pretreatment to address the limitations of pharmaceutical biowastes and offers insights into their valorization
Sedimentary responses to climatic variations and Kuroshio intrusion into the northern South China Sea since the last deglaciation
No full textThe terrigenous sediment source-to-sink processes in marginal seas are governed by intricate interactions among climate, sea level, and ocean currents. The continental slope of the northern South China Sea (SCS) provides an excellent setting to examine these processes due to its substantial terrigenous influx and continuous sedimentation. In this study, we present a high-resolution sedimentary record from the northern SCS continental slope covering the last deglaciation. Analyses of Rare Earth Elements (REEs) and Sr-Nd isotopic compositions in the NH07 core indicate that the predominant source of terrigenous sediment was Taiwan. Grain size-standard deviation analysis identified two sensitive grain size components, with the sensitive component 2 used as a marker of the Kuroshio intrusion into the northern SCS through Luzon Strait. The intensity of the Kuroshio intrusion into the northern SCS was found to be inversely related to that of the open Pacific. The Asian monsoon and El Nino- Southern Oscillation (ENSO) significantly influenced the variability of the Kuroshio Current throughout the deglaciation period. During the interval 16, 000-11, 700 cal yr BP, variations in terrigenous influx were collectively driven by sea level changes and the intensity of the Kuroshio intrusion, while chemical weathering intensity was affected by the reworking of previously exposed shelf sediments due to sea level fluctuations. During the Holocene, however, the East Asian summer monsoon intensity became the primary factor influencing variations in terrigenous influx and chemical weathering
Extensional settings favour initial REE enrichment in the parent granites of ion-adsorption REE deposits: implications from Late Permian to Triassic granites in South China
No full textTo understand the generation of ion-adsorption REE deposits it is important to clarify the mechanism of REE enrichment in granites. We investigated Late Permian to Triassic granites from South China to investigate these issues. Ore-related granites with high REE contents (192-467 ppm) intruded in the Late Permian have high K2O and Zr + Ce + Nb + Y contents, high Ga/Al and K/Na ratios and low CaO contents, and are classified as aluminous A-type granite derived from melting of felsic igneous rocks in a high-temperature extensional setting. Ore-unrelated Triassic Pingtian granite with relatively low REE contents (81.7-127 ppm) is peraluminous with occurrence of muscovite, indicating an S-type affinity. Its high Rb/Sr and low CaO/Na2O ratios indicate magma origin from a metapelitic source related to a compressional setting owing to continental collision. In extensional settings in South China, the high-temperature conditions promoting melting of REE-rich accessory minerals and F-rich conditions improving the solubility of REE in the melts could be the reasons for the initial REE enrichment in these granites. Given that parent rocks for ion-adsorption REE deposits are all generated in extensional settings, it is considered that multiple tectonic stages and long-term extensional setting in South China contributed to generation of the specific ion-adsorption REE deposits in South China
Revisiting the high temperature Darongshan-Shiwandashan granitoids in the South China: A response to slab tearing associated with diachronous collision between Indochina and South China blocks
No full textThe Darongshan-Shiwandashan granite belt (DSGB) is composed of S-type granites and granodiorite intrusions, which are characterized by high- or ultrahigh-temperature cordierite, orthopyroxene, and granulite xenoliths. The petrogenesis of these plutons is a subject of debate, and a thorough overview of regional tectonic evolution and geochemistry is still absent despite the numerous research conducted in this granite belt. This study is a comprehensive overview of geochronology, whole-rock major-trace elements, Sr-Nd isotopes, and zircon Hf-O isotopes in the DSGB, focusing on their petrogenesis and tectonic setting of formation. The geochronological data indicates that DSGB granitoids emplaced at ca. 250 Ma, with a southwestward-younging trend. Moreover, mineral assemblages of cordierite + orthopyroxene suggest that the DSGB was formed in a high-temperature (similar to 850 degrees C) and low-pressure (3.7-6 kbar) tectonic setting. Three main plutons (Darongshan, Jiuzhou, and Taima) of the DSGB exhibit distinctly different compositions. The Darongshan and Taima granitoids display high silica (SiO2 = 68.65-78.10 wt%), low-maficity (FeO + MgO = 1.97-7.28 wt%), along with negative whole-rock epsilon Nd(t) values (-13.9 to -9.7) and elevated initial Sr-87/Sr-86 values (0.71638 to 0.73165). The Jiuzhou granitoids, on the other hand, exhibit relatively low silica (SiO2 = 63.90-72.72 wt%) and high maficity (FeO + MgO = 3.03-9.88 wt%), with largely overlapping but relatively high epsilon Nd(t) values ranging from -12.9 to -9.9 and lower initial Sr-87/Sr-86 values from 0.71453 to 0.72401. Two-component mixing model results indicate these different compositions represent varying degrees of mixing between crust- and mantle-derived magmas, with 0-10 %, 0-20 % and 20-40 % basaltic melts involved for Taima, Darongshan and Jiuzhou plutons, respectively. The subducting slab tearing, induced by the diachronous collision between the South China Block (SCB) and Indochina Block (ICB), provide the most feasible interpretation for the petrogenesis and spatio-temporal geochemical pattern of the granitic rocks in the DSGB. The onset of the diachronous collision initiated at the Hainan-Yunkai massif, southwest of SCB, while the Tethys Ocean still existed in the northwest (Nanpanjiang area), causing notable disparities in the convergence velocities of the subducting ocean slab. The heterogeneous stresses resulting from the different subduction rates were accommodated by bending and tearing of the subducting slab. Then, ultrahigh-temperature basaltic melts derived from the decompression melting of the lithospheric mantle facilitated the melting of metasedimentary rocks, which resulted in the formation of high-temperature S-type granitoids. The Jiuzhou pluton, located at the center of slab tearing, received more mantle contributions than the Darongshan and the Taima plutons, which are emplaced away from the slab tearing center. The younging trend in age from the Darongshan to Jiuzhou and Taima plutons indicates a progressive tearing from the northeast (the far end of the subducting slab) to the southwest
Formation and evolution of supercritical geofluid
No full textIn this work, we provide a comprehensive review on the formation, evolution, properties, and effects of supercritical geofluid. In Earth's interior, enhanced miscibility between H2O and silicate by the addition of special components or by the increase of pressure and temperature gives rise to supercritical geofluid with a significant amount of both H2O and silicate solute. The formation of supercritical geofluid in magmatic-hydrothermal systems, typified by pegmatite system, is governed by meltfluid critical curve. The formation of supercritical geofluid in metamorphic systems, typified by subducted slab, is governed by the second critical end point. Experimental results suggest that the presence of boron and fluorine in pegmatite system makes it possible to form supercritical geofluid at crustal depths, but the release of supercritical geofluid from subducted slab is withheld until almost 100 km depth. A major presence of both H2O and depolymerized structural units (monomers, dimers, etc.) endows supercritical geofluid with unique physical properties including low density, low elastic moduli, low viscosity, high diffusivity, and high electrical conductivity. Supercritical geofluid can effectively mobilize a variety of elements even including high field strength elements and heavy rare earth elements. The chemical signatures of supercritical geofluid can be inherited by metasomatized mantle and mantle-derived melts, and this could give an explanation of the oxidation of arc magmas. Phase separation of supercritical geofluid through the mechanism of spinodal decomposition leads to formation of a melt network. Multiphase fluid inclusions recovered from subduction zone rocks and pegmatites are possible relics of supercritical geofluid. Supercritical geofluid can cause electrical anomaly and low seismic velocity near the top of subducted slab, and can be linked with intermediate-focus earthquakes. Supercritical geofluid may have played a crucial role in the formation of pegmatites and associated ore deposits
Onboard measurements of organic vapor emissions from river vessels under various operational conditions
No full textThe emission factors and characteristics of pollutants from river vessels are critical for understanding the environmental impact of ship emissions, particularly in inland waterways. However, research gaps remain regarding emissions of volatile organic compounds (VOCs) and intermediate-volatility organic compounds (IVOCs) from river vessels. In this study, we collected and analyzed organic vapor emissions, including nonmethane hydrocarbon (NMHCs), oxygenated volatile organic compounds (OVOCs) and IVOCs, from three river vessels under different operating conditions. The results show that the average emission factors of NMHCs, and IVOCs from river vessels are significantly higher than those from ocean-going vessels. Inland waterways' proximity to residential areas increases the risk of pollutant transport to urban environments, heightening the importance of managing river vessel emissions. Notably, older auxiliary engines displayed higher organic vapor emissions compared to main engines, underscoring the need for better control measures for aging engines. By analyzing the emission characteristics of organic vapors from river vessels, it was found that, unlike other pollution sources where C12 n-alkanes are the major contributors of IVOCs, the contributions of C12-C15 nalkanes in river vessel exhaust are similar, with C14 n-alkane having the highest contribution. OVOCs constituted more than 50% to ozone formation potentials of organic vapors, while IVOCs were responsible for over 90% of the secondary organic aerosol (SOA) formation. Given these findings, targeted efforts to reduce OVOCs and IVOCs emissions from river vessels should prioritized to mitigate their environmental impact