Guangzhou Institute of Geochemistry
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On the contribution of atmospheric reactive nitrogen deposition to nitrogen burden in a eutrophic Lake in eastern China
No full textAlthough it has been demonstrated that atmospheric reactive nitrogen (i.e., Nr mainly including NH3, NH4+, NOx, NO3- and etc.) deposition has substantial impacts on nitrogen pools in remote and/or sensitive lakes, there is a scarcity of systematic evaluations regarding the impact on nitrogen burden in eutrophic lakes with riverine input as primary nitrogen source. Utilizing a regional atmospheric chemical transport model, combined with observation-based estimates of atmospheric nitrogen deposition fluxes and riverine nitrogen inputs, we investigate the contribution of atmospheric Nr deposition to the fifth largest freshwater lake located in eastern China, i.e., the Chaohu Lake which is facing frequent outbreaks of algal bloom. The results indicate that in the studied year of 2022, riverine total nitrogen (TN) input to the lake was 11553.3 t N yr(-1) and atmospheric TN deposition was 2326.0 t N yr(-1). For Nr species which are directly available for the biosphere supporting algae and plant growth, riverine NH4+ input was 1856.1 t N yr(-1) and atmospheric NHx (NH3 and NH4+) deposition was 824.5 t N yr(-1). The latter accounts for 30.8% of total NHx input to the lake. For NOy (HNO3 and NO3-), riverine NO3- input was estimated as 2621.7 t N yr(-1), while atmospheric NOy deposition was 629.3 t N yr(-1), accounting for 19.4%. In all, atmospheric Nr deposition accounts for 24.5 % of total Nr input to the lake. Our results suggest that even in regions with dense human activities with primary riverine N input, atmospheric deposition of Nr could also contribute significantly to the bio-available nitrogen in lake systems, and addressing eutrophication in Lake Chaohu and other eutrophic lakes will also need to consider the influence of atmospheric Nr deposition which is related to NH3 and NOx (i.e., NO + NO2, the precursor of NOy) emissions, in addition to the mitigation of riverine N input
P-wave attenuation variations beneath the central and western Tien Shan from teleseismic waves
No full textThe seismic attenuation plays an important role in understanding the subsurface structure and provides complementary information on the mantle dynamic together with seismic velocity information. Here we explore the attenuation structure beneath the central and western Tien Shan using teleseismic P-wave data. Firstly, we map the spatial distribution of relative attenuation parameter using the spectral ratio technique in the frequency band between 0.1 and 1.5 Hz. Our results reveal strong lateral attenuation variations in the lithosphere and asthenosphere underneath the study area. Then we invert for the Qp values using a linear inversion approach. Two high-attenuation regions are observed beneath the middle Tien Shan and western Tarim Basin that could be associated with upwelling hot materials and/or a small plume. Moreover, low-attenuation regions are found beneath the Kazakh Shield and western Tien Shan, which can be attributed to the underthrusted/subducted lithospheric fragments
A new calcite reference material for <i>in situ</i> oxygen isotope analysis using secondary ion mass spectrometry: development and application constraints
No full textThe oxygen isotopic microanalysis of calcite is essential for obtaining high spatial resolution data linked to microstructures, a challenge for conventional techniques. This analysis, however, relies heavily on matrix-matched reference materials, of which only a few calcite standards are available. In this study, an inorganically precipitated calcite vein sample (WS-1) was evaluated through 225 SIMS oxygen isotope analyses and was found to have a homogeneous isotopic composition, with an external reproducibility <= 0.21 parts per thousand (1 sigma), suggesting its potential as a SIMS reference material. The precise delta 18OVPDB value, determined via traditional gas-source IRMS, was -16.52 +/- 0.13 parts per thousand (1SD). Matrix effects were assessed using various carbonates, including abiotic aragonite (VS001/1-A), three abiotic calcites (NBS18, Cal-1, WS-1), and a high-Mg calcite (gorgonian coral). The results revealed negligible matrix effects between abiotic aragonite and calcites but significant differences between calcites and high-Mg calcite, likely due to Mg content or differences in biogenic crystal morphology and trace organic composition. This study demonstrates the utility of in situ oxygen isotopic microanalysis for calcite but emphasizes the need for caution when analyzing high-Mg calcitic skeletons
Sorption of arsenate on cerium oxide: a simulated infrared and Raman spectroscopic identification
No full textCeria (CeO2) is a candidate for arsenic removal, and characterizing its surface speciation is crucial for controlling its removal ability. Here, we focus on arsenates and exploit ab initio calculations to study their interaction with the three most stable surfaces of CeO2. The adsorption of arsenate is stronger on the {100} surface followed by the {110} and {111} surfaces. We find that arsenate can potentially adsorb to CeO2 surfaces, with a range of binding configurations. Interestingly, we discovered a 5-fold coordinated As(v) species in a trigonal bipyramidal coordination, which is stable and displays a strong interaction with the surfaces, pulling oxygen out of the surfaces, which should be a valuable model to address in As adsorption experiments such as EXAFS. We then predict the infrared (IR) and Raman spectral signatures, finding that adsorbed arsenates have a characteristic spectral fingerprint between 200 and 1200 cm-1. Characteristic peaks compared with experiments gives confidence in the modelling. The 5-fold coordinated As species in particular shows potential diagnostic As-O stretching modes between 635-756 cm-1 in IR spectra and 387-521 cm-1 in Raman spectra. While all binding modes for arsenate adsorption on ceria provide IR active modes, interestingly this is not the case for Raman active modes. Here, we provide a set of reference spectra and binding modes for arsenates on CeO2 that can further experimental characterization of arsenate speciation, and provide control of its impact on the removal performance of cerium dioxide
A comprehensive characterization biotransformation of chlorinated paraffin by human and carp liver microsomes via liquid chromatography-high-resolution mass spectrometry and screening algorithm
No full textThe chlorinated paraffin (CP) monomer 1,2,5,6,9,10-Hexachlorodecane (CP-4) was subjected to in vitro biotransformation using human and carp liver microsomes. Five types of CP-4 metabolites (OH-, keto-, enol-, aldehyde- and carboxy-CP-4) were identified in human liver microsomer while only mono-OH-CP-4 was found in the carp liver microsomes. Kinetic studies revealed that the formation of mono-, di-, tri-hydroxylated CP-4, keto-, enol-, and aldehyde-CP-4 in human liver microsomes was best described by substrate inhibition models, whereas the formation of carboxylated CP-4 metabolites best fit the Michaelis-Menten model. Notably, keto-CP-4, enolCP-4 and aldehyde-CP-4 were the predominant metabolites. The estimated Vmax values for these metabolites were significantly higher in the human liver microsomes than in the carp liver microsomes. The intrinsic hepatic clearance (CLint) of CP-4 was higher in humans than in carp, indicating species-specific differences in its metabolism. This study also highlighted potential toxicity concerns, with computational predictions showing varying degrees of acute oral toxicity for CP-4 and its metabolites. These findings indicate significant speciesspecific differences in the biotransformation of CP-4, emphasizing the potential health and environmental risks associated with chlorinated paraffins and their metabolites, and underscore the need for further research to address these concerns
Enrichment and fractionation of rare earth elements (REEs) in ion-adsorption-type REE deposits: Constraints of an iron (hydr)oxide-clay mineral composite
No full textIon-adsorption-type rare earth element (REE) deposits are the source of more than 90% of global heavy REEs (HREEs). Thus, understanding the ore genesis of REEs, particularly the distribution characteristics and enrichment mechanisms of HREEs, is vital for efficient exploration and mining of ion-adsorption-type REE deposits worldwide. The characteristics and petrogenesis of bedrock and the aqueous mobility of REEs are known to be important factors controlling REE accumulation and fractionation in the weathering crust of REE deposits. However, the effect of REE adsorption on secondary minerals, a crucial step in deposit formation, remains poorly understood. This problem was addressed by the study described herein, which involved a systematic analysis of the complete weathering profile (78 m) of the Renju ion-adsorption-type REE deposit in South China and a simulated adsorption experiment. Clay minerals and iron (Fe) (hydr)oxides are the dominant REE adsorbents in the weathering crust and most are micro-to-nanosizedparticles. Thus, the fine-particle fraction (<2 mu m) was separated from field samples to disclose better their effects on the concentration and redistribution of REEs. Phase compositions and morphologies were characterized by X-ray diffraction, M & ouml;ssbauer spectrometry, and scanning/transmission electron microscopy (SEM/TEM), which revealed that various clay minerals and Fe (hydr)oxides form composites along the profile of the deposit. Composites of ferrihydrite-kaolinite, goethite-kaolinite/halloysite, and hematite-kaolinite/halloysite were found to be distributed in the semi-weathered, completely weathered, and topsoil layers, respectively, with different sizes and shapes. The concentrations and partition patterns of REEs in different occurrence states were distinguished after sequential extraction. Ion-exchangeable-REEs were the major state and enriched in the upper completely weathered layer. These species were found to be adsorbed onto kaolinite and halloysite via electrostatic attraction without obvious fractionation. Fe (hydr) oxides were determined to comprise ca. 20% of REEs at most depths and over 50% of REEs in the topsoil and semi-weathered layer. It was found that Fe (hydr)oxides scavenge REEs through complexation and oxidation, resulting in HREE enrichment and a positive cerium (Ce) anomaly, respectively. In addition, compared with crystalline Fe (hydr)oxides, amorphous Fe (hydr)oxides immobilize more REEs but exhibit weaker preferential adsorption of HREEs. The above-described findings are consistent with the results of simulated experiments for REE adsorption onto a clay mineral-Fe (hydr)oxide composite (Bt-60d), which was obtained from hydrothermal processing of biotite. Furthermore, the distributions and stabilities of LREEs and HREEs were distinguished by TEM-energy-dispersive spectroscopy (EDS) of Bt-60d before and after REE extraction by ammonium sulfate. The phase transformation pathways of clay minerals and Fe (hydr)oxides and their different enrichment and fractionation characteristics in REEs were also discussed in terms of the structure and surface properties of minerals, adsorption mechanisms, and variations in chemical properties across the REE group. The results shed new light on how clay minerals and Fe (hydr)oxides affect the enrichment and fractionation of REEs in ion-adsorption-type deposits
First boron isotopes in the southern Jilin TTG series uncover a Neoarchean oceanic arc in the eastern North China Craton
No full textThe Neoarchean evolution of the eastern North China Craton (NCC) is still controversial. This study presents the first B isotopes, together with zircon U-Pb-Hf isotopes and whole-rock geochemical analyses, for the TTG and dioritic series in the Baishan area of the southern Jilin region. LA-ICP-MS zircon U-Pb results uncover the Neoarchean magmatic activities, including granodioritic gneisses (2648 +/- 10 Ma and 2622 +/- 8 Ma), and quartz dioritic gneiss (2539 +/- 7 Ma). The 2.65-2.60 Ga TTG series exhibit intermediate calc-alkaline characteristics, with relatively lower Th/La ratios (0.11-0.41) and positive zircon epsilon Hf(t) values (+3.73 to +7.93), suggesting that the TTG series were likely derived from partial melting of mafic lower crust. By contrast, the 2.54 Ga dioritic series show positive Zr, Hf and Eu anomalies, with relatively lower Nb/Zr ratios (0.013-0.028) and epsilon Hf(t) values (+2.00 to +5.49), indicating that they were possibly produced by mixing of the mantle-derived magma and crustal melts. Importantly, the 2.65-2.60 Ga TTG series are characterized by positive whole-rock delta 11B values of +4.11 to +15.08 %o, resembling the Izu-Bonin-Mariana oceanic arc and South Sandwich Island arc volcanic rocks. The formation of these TTG rocks is attributed to 11B-rich fluids released by subducted oceanic slab and subsequent metasomatism of the subarc mantle wedge. Unlike the oceanic arc TTG series, the 2.54 Ga dioritic series exhibit lighter whole-rock delta 11B values of -4.23 to -4.50 %o, reflecting an arc-continental collision induced by slab breakoff and mantle-derived magma upwelling. Integrated with previous studies, it suggests that the subduction-collision process in the eastern NCC resulted from the co-evolution of oceanic arc and continental margin arc
Impacts of anthropogenic disturbances on antibiotic resistomes in biological soil crusts on the Qinghai-Tibetan Plateau
No full textBiological soil crusts (BSCs) are the main landscape on the Qinghai-Tibetan Plateau and an ecological indicator of human disturbance. Information about antibiotic resistomes in BSCs on the Qinghai-Tibetan Plateau can provide baseline for the risk assessment and management of resistomes and yet to be explored. This work investigated the profiles and geographic patterns of antibiotic resistomes in BSCs along the Lhasa River and their response to anthropogenic activities for the first time. Various antibiotic resistance genes (ARGs) were widely distributed in BSCs, but had relatively lower detection frequency and abundance comparing to soils from human disturbed sites. ARGs profiles in BSCs were separated by altitude from 3860 to 3880 m, possibly attributing to the difference in anthropogenic activities. Above 3860 m, resistomes exhibited lower abundance including total ARGs, aadA, blaSFO and tnpA-04 owing to the rare human activities; at human disturbed sites with altitude <3860 m, the detection frequency and relative abundance of tetG02, oprJ, qacEdelta1-01, and ARGs with the mechanism of efflux pump were higher and viewed as potential indicators of human activities. Anthropogenic activities potentially promoted the horizontal gene transfer of ARGs in BSCs at human disturbed sites from co-occurrence network analysis. Our findings provided fundamental information of antibiotic resistomes in BSCs on the Qinghai-Tibetan Plateau, and unraveled possible mechanisms of human disturbance in shaping antibiotic resistomes
Frequency of Synoptic-Scale Precipitation Events Recorded by Daily Resolved δ<SUP>18</SUP>O of Land Snail Shells
No full textLand snails exhibit the potential for capturing synoptic-scale precipitation events through the delta O-18 records of their shells (delta(18)Oshell), but the application is hindered by the absence of a practical methodology for tracking these events. Here, we developed a statistical methodology to track the synoptic-scale precipitation events from daily resolved snail body fluid delta O-18 (delta O-18(BF)) record. We further tested and verified our approach using daily resolved delta(18)Oshell records of modern Cathaica fasciola from the Chinese Loess Plateau (CLP). The reconstructed 3-day-timescale precipitation events frequencies using first derivations of delta 18OBF and delta 18Oshell shows strong agreement with instrumental data (>85% detection accuracy). The strong correlation between precipitation days in snail-growing-season and annual precipitation amounts across the CLP also permits the reconstruction of synoptical precipitation frequency for investigating the interannual variability of precipitation. Our study paves the avenue in paleoweather study, enabling quantitative reconstructions of past synoptic-scale precipitation events
Magnetotelluric Evidence for Lithospheric Hydration and Thinning Beneath the Youjiang Basin in Southwestern China
No full textDetermining the water content in the lithospheric mantle is crucial for understanding its dynamic evolution. Because the electrical conductivity of mantle minerals is particularly sensitive to water, the magnetotelluric (MT) method becomes a vital tool to determine the water content in the lithospheric mantle. Here we used broadband and long-period MT data collected along a 600-km-long, NS-trending profile to obtain the electrical resistivity structure of the lithosphere across the southwestern South China Block. By combining the results of laboratory electrical conductivity measurements of mantle minerals, xenolith-derived composition, and geotherm information, we further estimated the water content of the lithospheric mantle. The results show that the Youjiang Basin has a relatively thin lithosphere segmented by zones of low-resistivity that spatially coincide with major faults. The relatively conductive mantle lithosphere could be explained by the combined effects of water in nominally anhydrous minerals, sulfide and phlogopite. Combined with regional tectonic context, we proposed that H2O-rich fluids derived from the previously subducted slabs and related metasomatic processes lead to lithospheric hydration and thinning within the Youjiang Basin. Additionally, such processes, together with magmatic-hydrothermal activities, likely contribute to the formation of gold deposits within the basin. By contrast, the lithosphere beneath the Yangtze Craton is characterized by high resistivity extending to a depth of similar to 200 km, representing a typical cratonic lithosphere that has not undergone significant tectonic modification and contains no or very little water