Guangzhou Institute of Geochemistry
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The terrestrial end-Permian mass extinction in the paleotropics postdates the marine extinction
No full textThe end-Permian mass extinction was the most severe ecological event during the Phanerozoic and has long been presumed contemporaneous across terrestrial and marine realms with global environmental deterioration triggered by the Siberian Traps Large Igneous Province. We present high-precision zircon U-Pb geochronology by the chemical abrasion-isotope dilution-thermal ionization mass spectrometry technique on tuffs from terrestrial to transitional coastal settings in Southwest China, which reveals a protracted collapse of the Cathaysian rainforest beginning after the onset of the end-Permian marine extinction. Integrated with high-resolution geochronology from coeval successions, our results suggest that the terrestrial extinction occurred diachronously with latitude, beginning at high latitudes during the late Changhsingian and progressing to the tropics by the early Induan, spanning a duration of nearly 1 million years. This latitudinal age gradient may have been related to variations in surface warming with more degraded environmental conditions at higher latitudes contributing to higher extinction rates
The Lower Atmospheric Characteristics of Dust Storms Using Ground-Based Sensor Data: A Comparative Analysis of Two Cases in Jinan, China
No full textTwo severe dust storm (DS) events (15-17 March and 28-29 March) hit northern China in 2021 consecutively. The lower atmospheric vertical dynamic and thermal structures during the two cases were compared using the ground-based sensor data from the microwave radiometer and radar wind profiler, combined with the environmental and meteorological observations data in Jinan, China. It was found that both cases occurred under the background of cold vortexes over northeastern China. The dust was transported through the cold air on the northwest route. During the dust period, 2-3 km was the west or northwest airflow, and below 2 km was the northeast wind. The variation in the dynamic structure determined the duration of the DS. During the DS maintenance phase, the vertical wind shear (VWS) below 3 km measured approximately 10 m center dot(s center dot km)-1. The increased VWS during the dust intrusion period facilitated the transportation of dust. In contrast, the more significant VWS was not conducive to the maintenance of DS, and the shift to south wind control in the upper middle layer indicated the weakening of DS. In both cases, we observed a cliff-like decrease in relative humidity as a prominent indicator of dust outbreaks, occurring approximately 2-5 h beforehand. The diurnal difference between the vertical temperature and relative humidity during the dust maintenance period was found to be insignificant
V2O5 modified Mn/SAPO-34 catalyst for the synchronous elimination of NOx and volatile organic compounds
No full textIn this work, a new V-Mn bimetallic multifunctional catalyst based on SAPO-34 zeolite was constructed to achieve synchronous elimination of VOCs and NOx in denitrification zone conditions. The V-Mn/SAPO-34 catalyst exhibited excellent catalytic performance for toluene oxidation and NO reduction and remarkable flue gas tolerance compared to Mn/SAPO-34 and V/SAPO-34. The T90 (265 C) of V-Mn/SAPO-34 for toluene oxidation was 30 C and 125 C lower than that of Mn/SAPO-34 (295 C) and V/SAPO-34, respectively. Moreover, the conversion of NO could reach more than 90% at 138 C. Excellent catalytic activity of the V-Mn/ SAPO-34 was attributed to abundant hierarchical pores, oxygen vacancies and acidic sites owing to ion exchanges of SAPO-34. Meanwhile, the favorable V-Mn synergy effectively facilitated the electron transfer of catalytic reaction. In situ DRIFTS results indicated that the toluene oxidation over it followed the MvK mechanism, while the NH3-SCR followed the E -R mechanism, and the two, proceeding independently, did not interfere with each other during synchronous elimination
Atmospheric ozone destruction and the end-Permian crisis: Evidence from multiple sulfur isotopes
No full textThe end-Permian mass extinction (EPME) is considered the largest biotic crisis of the Phanerozoic. To explain the worldwide destruction and mutation of land plants, previous work has emphasized the role of enhanced UV irradiation linked to volcanism-induced disruption of the ozone shield. However, direct evidence for a link between volcanic SO2 emission and stratospheric ozone deterioration is missing. Previous bulk analysis (i.e., SF6 method) found no Mass-Independent Fractionation of sulfur isotopes (MIF-S, noted A33S). However, possible grain scale sulfur isotope anomaly can be easily overlooked during bulk analysis. To detect possible sulfur isotope anomaly in grain scale, we applied in-situ multiple sulfur isotope analysis of the sulfide using secondary ion mass spectrometry (SIMS). We found a marked positive shift (higher than +0.30%o and up to +0.94%o) just before the end-Permian extinction in the Meishan section. Modelling shows that these positive A33S anomalies cannot be explained by Mass Dependent Fractionation (MDF) processes alone, rather by UV-induced photolysis of volcanic SO2. The formation and preservation of MIF-S anomalies in the atmosphere and subsequent transport to the oceans require intense and prolonged irradiation of the Earth's surface with solar UV, thus fingerprinting severe disruption of the atmospheric ozone balance at the onset of Earth's largest mass extinction
External geodynamic evolution of the Mongolian Accretionary Collage: Insights from petro-chronology of zircon
No full textEvolution of internal or external oceanic domains can bring decisive indications into the mode of formation of supercontinents, which is key to understand the supercontinent cycle. Defining the type of ocean evolving in the Central Asian Orogenic belt (CAOB) is thus critical to better understand the Earth's supercontinental evolution. In this contribution, we provide systematic and combined U-Pb, trace-element in zircon and hafnium-in-zircon analyses of four turbidites of the Altai accretionary wedge. These turbiditic rocks provide constraints into the early Paleozoic subduction-accretionary stages of the Mongolian Accretionary Collage (MAC) and show a major detrital age peak in the Cambro-Ordovician (similar to 490-500 Ma), with minor Neo- and Paleo-Proterozoic to Archean peaks. The zircon trace-elemental patterns are consistent with derivation mostly from magmatic arc (with granitoids affinity), interpreted as detritus sourced from the Ikh-Mongol continental arc system further north-east (present coordinates). The main detrital zircon peak together with the zircon magmatic arc origin suggest that the subduction-accretionary stage was active from 550 to 430 Ma showing mixed epsilon(Hf)(t) values (-20 to + 15). A summary of the detrital zircon epsilon(Hf)(t) values from 550 to 430 Ma suggests a continuous increase of epsilon(Hf)(t) mean values from + 0.2 to + 6.1 towards younger ages. The younging juvenile trend can be compared to the evolution of external orogeny, therefore consistent with a Pacific-type accretionary system facing an external ocean. At last, the results combined with two paleo-geographic reconstructions from the literature imply that the MAC may have been part of the Peri-Siberian accretionary orogeny in the early Paleozoic
Distribution and adsorption-desorption of organophosphate esters from land to sea in the sediments of the Beibu Gulf, South China Sea: Impact of seagoing river input
No full textOrganophosphate esters (OPEs) have been a class of emerging environmental contaminants. However, studies on their environmental behavior, specifically their adsorption-desorption behavior between sediment and seawater in estuarine and coastal areas, remain limited. To address this gap, our study focused on investigating the levels and behavior of 11 OPEs in sediment samples collected from the Beibu Gulf, South China Sea, encompassing estuaries and coastal regions. The total concentrations of 11 OPEs (sigma 11OPEs) in the sediments exhibit a significant decrease in summer, both in seagoing rivers (4.67 +/- 2.74 ng/g dw) and the coastal zone (5.11 +/- 3.71 ng/g dw), compared to winter levels in seagoing rivers (8.26 +/- 4.70 ng/g dw) and the coastal zone (7.71 +/- 3.83 ng/g dw). Chlorinated OPEs dominated the sediments, constituting 63 %-76 % of the total. Particularly, port and mariculture areas showed the highest levels of OPEs. Through load estimation analysis, it was revealed that the sedimentary OPEs in Qinzhou Bay (221 +/- 128 kg) had the highest load, with input from the Qin River identified as a significant source. Chlorinated OPEs showed a trend of desorption from sediments to the water column with increasing salinity, emphasizing the crucial role of land -based OPEs input through suspended particulate matter in rivers as a pathway to the ocean. The impact of strong flow in estuarine environments was highlighted, as it can scour sediments, generate suspended sediments, and release OPEs into the water bodies. Additionally, the results of the ecological risk assessment indicated that most of the OPEs posed low -risk levels. However, attention is warranted for the contamination levels of some chlorinated OPEs, emphasizing the need for ongoing monitoring and assessment
Characteristics of polar organic compounds from diesel truck emissions measured by FT-ICR MS
No full textWater-soluble organic compounds (WSOC) and dichloromethane: methanol-soluble organic compounds (DMSOC) in polar organic compounds (POCs) present in emissions from a diesel truck were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The main compositions and molecular structures of WSOC and DMSOC were investigated and classified into three groups based on their elemental compositions: CHO, CHON, and S-containing compounds (CHONS and CHOS) (namely WSOCCHO; WSOCCHON; WSOCOS; DMSOCCHO; DMSOCCHON and DMSOCOS). The main results are as follows. (1) The order of groups in WSOC and DMSOC in terms of peak response was CHO (WSOC: 52.2% and DMSOC: 64.5%), CHON (WSOC: 43.4% and DMSOC:25.9%), and S-containing compounds (WSOC: 4.35% and DMSOC: 9.57%). (2) The relative response of compounds with low H/C and O/C ratios and double-bond equivalents (DBE) > 10 in WSOCCHO was twice that of DMSOCCHO, indicating that the WSOC emitted by diesel trucks might contain many highly condensed benzene rings. Compounds with H/C = 2 and DBE = 1 in DMSOCCHO showed a strong relative response, presumably due to a fatty-acid structure, which might be used as a tracer to distinguish emissions from diesel trucks and other pollution sources. (3) The strongest relative response in WSOCCHON was for C11H7O5N2 with an aromaticity equivalent (Xc) = 2.5 and DBE = 9, suggesting that dinitrophenol or methyl nitrophenol might be present. Moreover, C39H76O8N1 with Xc = 0 and DBE = 2 was dominant in DMSOCCHON, suggesting the presence of carboxylic acids. (4) In both WSOC and DMSOC, long-chain aliphatic and organic sulfate compounds accounted for the largest proportion of S-containing compounds. However, the contents of condensed hydrocarbons and aromatic rings in DMSOCOS were higher than those in WSOCOS, which suggests that DMSOCOS has a strong optical absorption ability. Thus, this study effectively determined the POC compounds of diesel truck emissions and their possible structures, providing data for assessing the environmental effects of using diesel trucks
Shallow mantle cycle of subducted sedimentary limestone indicated by carbonate xenoliths
No full textIn the subduction zone, carbon (C) release from the subducted plate into the mantle wedge takes place by various mechanisms, including metamorphic degassing, carbonate dissolution, and hydrous melting. Recent studies have highlighted the significant role of buoyant limestone diapirs in facilitating C recycling during subduction processes. Here, we report that the Hannuoba carbonate xenoliths of eastern China were introduced into the shallow mantle in the form of sedimentary limestone diapirs. We conducted a comprehensive study of the Hannuoba carbonate xenoliths using petrological analysis, major- and trace-element analysis, in situ zircon dating, and C-O isotopic analysis techniques. The whole-rock major and trace elements, along with high delta O-18(SMOW) values (22.8 parts per thousand-23.2 parts per thousand), indicate that the protolith of Hannuoba carbonate xenoliths consists of sedimentary limestones. The spectral age peaks of detrital zircons (400-100 Ma, 500-450 Ma, 2.0-1.6 Ga, and 2.8-2.2 Ga) suggest that the primary source of the protolith is the North China Craton. When sedimentary limestone diapirs enter into the mantle wedge, they undergo partial melting under high-temperature conditions. This process results in the melting of low-melting point pelitic components, while leaving behind resistant minerals such as pure calcite. Due to its low density and viscosity, this pure limestone component will continue to migrate upward and assimilate with the mantle peridotite. In this process, the pure calcites are preserved in the shallow mantle in a solid-state form rather than as carbonatitic melts. The discovery of graphite and spinel in the Hannuoba carbonate xenoliths indicates that the depth of formation of the sedimentary limestone diapirs does not exceed 2.5 GPa (<70 km). The calcite in Hannuoba carbonate xenoliths exhibits extremely low delta C-13(VPDB) (-11.8 parts per thousand to -11.0 parts per thousand) and high delta O-18(SMOW) (22.8 parts per thousand-23.2 parts per thousand) contents. This characteristic C-O isotopic signature can be explained by the Rayleigh decarbonation of sedimentary limestones under upper-mantle conditions (<3 GPa). Based on calculations, the Hannuoba carbonate xenoliths are a product of subducted sedimentary limestone experiencing 99% volume decarbonation. Through this metamorphic decarbonation process, limestone diapirs release a significant amount of CO2 into the arc magma system. During subduction processes, sedimentary carbonate rocks can be recycled to the mantle wedge of island arcs as solid limestone diapirs. The C flux released by this mechanism cannot be ignored
Microplastic pollution differences in freshwater river according to stream order: Insights from spatial distribution, annual load, and ecological assessment
No full textMicroplastic (MP) pollution has become a pressing concern in global freshwater ecosystems because rivers serve as essential channels for the transport of terrestrial debris to the ocean. The current researches mostly focus on the large catchments, but the impact on the small catchments remains underexplored. In this study, we employed Strahler 's stream order classification to delineate the catchment structure of the Beijiang River in South China. The distribution pattern of MP contamination and the factors influencing the distribution pattern, were assessed across the streams at different orders. We found that the Beijiang River was moderately polluted compare to other rivers in China, with an average MP abundance of 2.15 +/- 1.65 items/L. MP abundance ranged from 3.17 to 1.45 items/L in the streams at different orders, and significantly decreased with increasing stream order (R 2 = 0.93). This highlights the key role of small rivers as the channels for the transport of MPs from watersheds to main streams. The high abundance of PP and PE fibers, the high correlation between the stream order and the resin proportion (R 2 = 0.89), and the significant correlation between MP abundance and proximity to urban centers (P = 0.02), indicated that MP pollution across the streams at different orders was predominantly influenced by anthropogenic activities, rather than natural environmental factors. By integrating MP data with hydrographic information, the annual MP loads for the streams at Orders 1 to Order 5 were estimated to be 4.63, 39.38, 204.63, 503.06, and 1137.88 tons/yr, respectively. Additionally, an ecological risk assessment indicates that MP pollution led to a low risk in the Beijiang River. Our findings deepen the understanding of MP pollution within freshwater river networks, and emphasize the crucial role of tributary systems in transporting MPs to main river channels
Spatial distribution, trophic magnification, and risk assessment of per- and polyfluoroalkyl substances in Yangtze finless porpoise (<i>Neophocaena</i><i> asiaeorientalis</i><i> asiaeorientalis</i>): Risks of emerging alternatives
No full textThe Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is the only freshwater cetacean found in China. However, per- and polyfluoroalkyl substances (PFASs) risks in YFPs remain unclear. In this study, legacy PFASs, their precursors and alternatives, were determined in YFP muscles (n = 32), liver (n = 29), kidney (n = 24), skin (n = 5), and blubbers (n = 25) collected from Poyang Lake (PL) and Yangtze River (YR) between 2017 and 2023. Perfluorooctane sulfonic acid (PFOS) was the predominant PFAS in all YFP tissues, with a median hepatic concentration of 1700 ng/g wet weight, which is higher than that in other finless porpoises worldwide. PFOS, chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), and perfluoroalkane sulfonamides concentrations in YFP livers from PL were significantly higher than those from YR (p 1. Perfluoroheptane sulfonic acid had the highest BMF value (99), followed by 6:2 Cl-PFESA (94) and PFOS (81). The TMFmuscle and TMFliver values of the total PFASs were 3.4 and 6.6, respectively, and were significantly positively correlated with the fluorinated carbon chain length (p 1, which was higher than that of PFOS (48 %), suggesting a high hepatotoxicity of 6:2 Cl-PFESA to YFPs. Bioaccumulation and biotoxicity of legacy and emerging alternatives in aquatic organisms continue to be a concern, especially for underscoring the vulnerability of the long-lived and endangered species