Guangzhou Institute of Geochemistry
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Historical Occurrence and Composition of Novel Brominated Flame Retardants and Dechlorane Plus in Sediments from an Electronic Waste Recycling Site in South China
No full textNovel brominated flame retardants (NBFRs) and dechlorane plus (DP) have been widely used as alternatives to traditional BFRs. However, little is known about the temporal trends of NBFR and DP pollution in e-waste recycling sites. In the current study, three composite sediment cores were collected from an e-waste-polluted pond located in a typical e-waste recycling site in South China to investigate the historical occurrence and composition of NBFRs and DP. The NBFRs and DP were detected in all layers of the sediment cores with concentration ranges of 5.71 similar to 180,895 and 4.95 similar to 109,847 ng/g dw, respectively. Except for 2,3,5,6-tetrabromo-p-xylene (pTBX) and 2,3,4,5,6-pentabromoethylbenzene (PBEB), all the NBFR compounds and DP showed a clear increasing trend from the bottom to top layers. These results implied the long-term and severe contamination of NBFRs and DP. Decabromodiphenyl ethane (DBDPE) was the most abundant NBFR with the contribution proportions of 58 +/- 15%, 73 +/- 15%, and 71 +/- 18% in three sediment cores, followed by 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) and pentabromobenzene (HBB). The ratios of BTBPE/Octa-BDEs and DBDPE/Deca-BDEs varied from 0.12 to 60 and from 0.03 to 0.49, respectively, which had no clear increase trends with a decrease in sediment depth. As for DP, the f(anti) values (the concentration ratios of anti-DP to the sum of anti-DP and syn-DP) in sediment cores ranged from 0.41 to 0.83, almost falling in the range of those in DP technical products, suggesting that DP degradation did not occur in sediment cores. The environmental burdens of DBDPE, BTBPE, HBB, PBT, PBEB, pTBX, and DP were estimated to be 34.0, 5.67, 10.1, 0.02, 0.02, 0.01, and 34.8 kg, respectively. This work provides the first insight into the historical contamination status of NBFRs and DP in the sediments of an e-waste recycling site
Genesis of the Wutuogou Ag-Pb-Zn deposit in the Eastern Kunlun Orogenic Belt, NW China: Constraints from calcite U-Pb geochronology, mineral chemistry, and in-situ sulfur isotopes
No full textThe Wutuogou Ag-Pb-Zn deposit, a newly discovered vein-type deposit, is located in the Eastern Kunlun Orogenic Belt (EKOB), northwestern China. The vein-type Ag-Pb-Zn ore bodies are hosted in Middle Triassic granodiorite and monzogranite and are characterized by high-grade Ag, Pb, and Zn (average Ag: 293 g/t, Pb: 3.00 %, Zn: 2.85 %). Three paragenetic stages have been recognized: quartz + pyrite (Py-1) + arsenopyrite (stage I), pyrite (Py-2) + sphalerite + chalcopyrite + tetrahedrite + quartz (substage II-1), galena + pyrargyrite + freibergite + freieslebenite + quartz + calcite (substage II-2), and quartz + calcite (stage III). Except for Ag-bearing minerals (pyrargyrite, freibergite, and freieslebenite), invisible silver is also present in pyrite (1.91-165 ppm), sphalerite (3.86-8806 ppm), and galena (up to 0.21 wt%). The calcite is closely associated with sulfides in substage II-2 and yields a U-Pb age of 210 +/- 7 Ma (MSWD = 2.7), which represents the ore-forming age (lower limit). Py-1 displays higher As contents and lower Co contents than those of Py-2, indicating a decrease in temperature from stage I to stage II. In addition, the Fe/Zn mass ratios (0.025-0.075) of sphalerite estimate the fluid temperature for substage II-1 of 246-284 degrees C, whereas the Ag/(Ag + Cu) and Zn/(Zn + Fe) mole ratios of freibergite estimate the fluid temperature for substage II-2 of 140-270 degrees C, further indicating the decrease of temperature from stage I through substage II-1 to substage II-2. Mineral assemblages of pyrite-chalcopyrite-tetrahedrite in substage II-1 and Ag-sulfosalts in substage II-2 suggest a decrease in sulfur fugacity (fS(2)). Both the decrease in fS(2) and cooling of the mineralizing fluids facilitate silver precipitation. The heterogeneous compositions of the freibergite and the Ag zonation in sphalerite (Sp-1) resulted from retrograde solid-state reactions that redistributed Ag through microscale exsolution. The delta S-34 values (+5.49 to +7.78 parts per thousand) of the sulfides and the low Zn/Cd ratios (107-195) of sphalerite indicate a felsic magma source for the ore-forming materials. Therefore, we concluded that the Wutuogou Ag-Pb-Zn deposit corresponds to a medium- to low-temperature magmatic-hydrothermal deposit associated with Late Triassic magmatism in the Eastern Kunlun Orogenic Belt (EKOB)
Genesis of the Wutuogou Ag-Pb-Zn deposit in the Eastern Kunlun Orogenic Belt, NW China: Constraints from calcite U-Pb geochronology, mineral chemistry, and in-situ sulfur isotopes
No full textThe Wutuogou Ag-Pb-Zn deposit, a newly discovered vein-type deposit, is located in the Eastern Kunlun Orogenic Belt (EKOB), northwestern China. The vein-type Ag-Pb-Zn ore bodies are hosted in Middle Triassic granodiorite and monzogranite and are characterized by high-grade Ag, Pb, and Zn (average Ag: 293 g/t, Pb: 3.00 %, Zn: 2.85 %). Three paragenetic stages have been recognized: quartz + pyrite (Py-1) + arsenopyrite (stage I), pyrite (Py-2) + sphalerite + chalcopyrite + tetrahedrite + quartz (substage II-1), galena + pyrargyrite + freibergite + freieslebenite + quartz + calcite (substage II-2), and quartz + calcite (stage III). Except for Ag-bearing minerals (pyrargyrite, freibergite, and freieslebenite), invisible silver is also present in pyrite (1.91-165 ppm), sphalerite (3.86-8806 ppm), and galena (up to 0.21 wt%). The calcite is closely associated with sulfides in substage II-2 and yields a U-Pb age of 210 +/- 7 Ma (MSWD = 2.7), which represents the ore-forming age (lower limit). Py-1 displays higher As contents and lower Co contents than those of Py-2, indicating a decrease in temperature from stage I to stage II. In addition, the Fe/Zn mass ratios (0.025-0.075) of sphalerite estimate the fluid temperature for substage II-1 of 246-284 degrees C, whereas the Ag/(Ag + Cu) and Zn/(Zn + Fe) mole ratios of freibergite estimate the fluid temperature for substage II-2 of 140-270 degrees C, further indicating the decrease of temperature from stage I through substage II-1 to substage II-2. Mineral assemblages of pyrite-chalcopyrite-tetrahedrite in substage II-1 and Ag-sulfosalts in substage II-2 suggest a decrease in sulfur fugacity (fS(2)). Both the decrease in fS(2) and cooling of the mineralizing fluids facilitate silver precipitation. The heterogeneous compositions of the freibergite and the Ag zonation in sphalerite (Sp-1) resulted from retrograde solid-state reactions that redistributed Ag through microscale exsolution. The delta S-34 values (+5.49 to +7.78 parts per thousand) of the sulfides and the low Zn/Cd ratios (107-195) of sphalerite indicate a felsic magma source for the ore-forming materials. Therefore, we concluded that the Wutuogou Ag-Pb-Zn deposit corresponds to a medium- to low-temperature magmatic-hydrothermal deposit associated with Late Triassic magmatism in the Eastern Kunlun Orogenic Belt (EKOB)
Characteristics and ozone formation potentials of volatile organic compounds in a heavy industrial urban agglomeration of Northeast China
No full textUnderstanding the pollution levels, potential sources, and chemical reactivity of atmospheric volatile organic compounds (VOCs), the key precursors of ozone (O3) and fine particulate matter (PM2.5), is important for emission control and air pollution abatement. This study presents a systematic VOCs analysis in a less studied heavy industrial urban agglomeration located in Northeast China. Using a cruising platform, we conducted real-time monitoring of VOC concentrations and components at Changchun (CC), Jilin (JL), Siping (SP), and Liaoyuan (LY) in Jilin Province. During the observation period, the average VOC concentrations at CC, JL, SP, and LY were 63.38 +/- 127.03, 260.39 +/- 855.76, 18.06 +/- 17.17, and 10.12 +/- 17.48 mu g/m3, respectively. Halocarbons were predominant with a high percentage of contribution (22.4-31.1%) to the total observed VOCs for all cities. Combined with 2020-based anthropogenic VOCs emission inventory of Jilin Province, we concluded that industrial processes had the largest contribution to VOCs concentration in CC, whereas petrochemical emission was the major source of VOCs in JL. The assessment of atmospheric photochemical reactivity indicates the dominant role of aromatics and alkenes in O3 formation potential (OFP). As the second-most abundant species in CC and JL, aromatics contributed over 50% of the OFPs. Alkenes played a dominant role in O3 formation in SP and LY, accounting for nearly half of the total OFPs. Considering the VOC emission characteristics and OFP results, we suggest that reducing aromatics emissions, particularly benzene, toluene, ethylbenzene, and xylene, should be given higher priority to mitigate O3 pollution and prevent health risks. Moreover, industrial-related, and petrochemical sources are crucial in the evolution of O3 pollution, which should be incorporated into heavy industrial urban air quality management and targeted control of O3 pollution in Northeast China
Petrogenesis of the Late Triassic Habake granitic pluton, the West Kunlun Orogen, Western China: Tectonic implications for the evolution of the Paleo-Tethys
No full textRecent discoveries of rare metal pegmatite deposits in the West Kunlun region are believed to be related to Triassic granites. However, the tectonic background of the mineralization in this region is currently unclear. Additionally, the mineralization potential of the granite must be determined to assess whether further exploration is warranted. This paper reports whole-rock elemental and Sr-Nd isotopic compositions, and zircon U-Pb ages and Lu-Hf isotopic compositions for the Habake granitic pluton. The zircon U-Pb dating revealed that these rocks formed in the Late Triassic (210-205 Ma). The two-mica granites are strongly peraluminous high-K calc-alkaline series rocks, with initial Sr-87/Sr-86 ratios of 0.71294 similar to 0.71428, epsilon Nd(t) values of -7.79 similar to -8.15, and epsilon Hf(t) values of -1.77 similar to -32.22; these values are similar to those of Triassic BaryanHar Group graywacke rocks. The other granites are weakly peraluminous high-K calc-alkaline series rocks, with initial Sr-87/Sr-86 ratios of 0.70820 similar to 0.70823 and 0.70942 similar to 0.71041, epsilon Nd(t) of -3.81 similar to -4.11 and -5.33 similar to -5.40, and epsilon Hf(t) of -0.90 to +7.02 and -1.39 to -7.68, indicating that the granodiorite and biotite granite were respectively derived from partial melting of the juvenile crust and older lower crust in continental collision stage. Our new data show that the end of the continental collision between the South Kunlun Terrane (SKT) and Tianshuihai terrane (TST) likely occurred after 209 Ma. After analysis of the ore-forming parent rocks of the rare metal pegmatites, the graywacke-derived Habake two-mica granites, has lower Li contents that too low(<150 ppm), indicating that they did not form the rare metal pegmatites
Na-metasomatism and its contributions to REE enrichment in alkaline granite systems
No full textAlkaline igneous rock is one of the main sources of rare earth resources in the world, especially heavy rare earth resources. Until now, there is a lack of comprehensive and systematic research on key scientific questions such as the super-enrichment mechanism of rare earth (REE) and some high field strength elements (HFSE) in alkaline granite systems and their controlling factors. This paper focuses on Na-metasomatism in the alkaline magmatic-hydrothermal systems, and discusses the mineral replacement reaction processes and the remobilization and migration processes of rare earth elements in the hydrothermal replacement processes, such as albitization, arfvedsonization and aegirinization. In alkaline systems, alkali amphiboles and pyroxenes are considered to be the significant carriers of REE and HFSE, and are also effective tracers of magmatic differentiation and evolution. Taking the Nianzishan alkaline granite in NE China as an example, the late magmatic-hydrothermal metasomatism will lead to the evolution of alkali amphibole and pyroxene from calcium-rich minerals to sodium-rich mineral phases, which will lead to the remobilization and transferring of REE and HFSE in the late hydrothermal stage. In particular, REE and HFSE would be released into the metasomatic fluids, which may be the key controlling factors leading to the super-enrichment and mineralization of these key metal elements in the late hydrothermal stage. Therefore, the sodium index [Na-#=Na/(Na+Ca) molar ratio] of the alkali amphiboles and pyroxenes may be a potential mineral geochemical index, which will provide a new proxy for REE exploration in the alkaline-peralkaline plutons
Influence of goethite nanophase on rare-earth element patterns and enrichment in marine phosphates during early diagenesis
No full textAlthough rare-earth elements (REEs) in authigenic phosphates and carbonates derived from marine sediments are potential proxies (e.g., REE patterns) for reconstructing paleoenvironmental conditions, the REE patterns appear to be inconsistent. Some marine authigenic phosphates show a "bell-shaped" pattern with an enrichment of the middle REEs (MREEs; Nd - Ho), while others exhibit a "modern seawater-like" pattern characterized by a strong depletion in cerium and an enrichment in heavy REEs (Er - Lu, Y, and Sc). Although the origin of the "bellshaped" pattern in phosphates has been extensively debated, the evidence is often ambiguous; therefore, the origin of the pattern remains unclear. In this study, we investigate the microscale and nanoscale mineralogical and geochemical characteristics of the REE-enriched Early Cambrian phosphorites. In situ elemental analyses reveal that the codeposited phosphates ("bell-shaped" REE pattern) and carbonates ("modern seawater-like" pattern) have different REE patterns. A microscale investigation shows that phosphate grains contain some dispersed goethite nanophase, and a nanoscale investigation using transmission electron microscopy coupled with electron energy-loss spectroscopy shows that Fe 2 + is distributed along the rim of the goethite nanophase, indicating that the goethite were reduced. These findings suggest that the REE pattern and concentration in phosphates could have been influenced by the release of REEs during the reduction of Fe (oxyhydr)oxide in the early diagenetic process before the final deposition. Although additional evidence is required, our results are important for understanding the effects of Fe redox cycling on the REE pattern and enrichment in marine authigenic phosphates. In addition, our results suggest that compared with authigenic phosphates, authigenic carbonates would provide a more reliable reconstruction of paleoenvironmental conditions
Formation of In-Cloud Aqueous-Phase Secondary Organic Matter and Related Characteristic Molecules
No full textAtmospheric particles are largely represented by secondary organic aerosols (SOAs) produced by either aqueous- or gas-phase reactions. Recently, the contribution of the former to SOA formation has been shown to substantially increase and even reach that of the latter, which necessitates in-depth mechanistic investigations. For a deeper understanding of aqueous-phase SOA generation, we herein studied the production of these aerosols in the dark from glycolaldehyde (GAld) and ammonium sulfate (AS)/amines (methylamine (MAm) and glycine (Gly)). UV-vis spectroscopy showed that reaction mixtures featured two main absorption bands (at 209-230 and 280-330 nm) that were attributed to the pi-pi* transitions of Schiff bases and the n-pi* transitions of oligomers produced in the above reactions, respectively. Further studies revealed that irrespective of reactant concentration and pH, all the investigated reactions were well fitted by first-order kinetics and were accelerated by increasing AS/MAm concentrations and solution pH under acidic conditions. The reaction rate constants (determined from changes of absorption at 300 nm) followed the order of Gly (k(I) = 2.39 x 10(-6) s(-1)) > MAm (k(I) = 1.19 x 10(-6) s(-1)) > AS (k(I) = 8.33 x 10(-7) s(-1)) at identical low AS/amine concentrations and were in the order of MAm (k(I) = 2.5 x 10(-6) s(-1)) > AS (k(I) = 1.39 x 10(-6) s(-1)) at high AS/MAm concentrations. The main reaction pathways corresponded to the aldol self-condensation of GAld and the nucleophilic attack of AS/amines on GAld followed by dehydration, which afforded imines as the major products. The stronger light absorption of (GAld + Gly) mixtures than that of (glyoxal/methylglyoxal + Gly) mixtures was ascribed to the increased amount of imine- and carbonyl group-containing products produced in the former case
Molecular and carbon isotopic evidence for the possible origin of 13 α (<i> n</i>-alkyl)-tricyclic terpanes in Mesoproterozoic bitumens from the Yanliao Rift, North China
No full textThe Mesoproterozoic Jixian System in the Yanliao Rift of the North China Craton contains organic-rich shales within the Hongshuizhuang, Tieling, and Xiamaling formations. The biomarker composition of these formations is characterized by the dominance of 13 alpha( n -alkyl)-tricyclic terpanes. The distinctive structure and main occurrence of 13 alpha( n -alkyl)-tricyclic terpanes in the Mesoproterozoic Jixian System in the Yanliao Rift have intrigued researchers, raising questions about their origin and formation mechanisms. This study found that 8 13 C values of 13 alpha( n -alkyl)-tricyclic terpanes ranged from -32.7%o to -26.2%o, similar to those of kerogen and n -alkanes, but significantly more depleted in 13 C compared to 13 beta(H),14 alpha(H)-tricyclic terpanes, which ranged from -28.5%o to -25.7%o. The difference in 8 13 C values suggested that 13 alpha( n -alkyl)-tricyclic terpanes were not formed by the same mechanism or precursors as 13 beta(H),14 alpha(H)-tricyclic terpanes. No sterane biomarkers indicative of eukaryotic source input were detected. Instead, the comparable concentrations of 13 alpha( n -alkyl)-tricyclic terpanes and n -alkanes in the samples implied a possible origin from primary organic matter producers, notably cyanobacteria. Moreover, the biomarkers obtained from distinct formations within the Mesoproterozoic Jixian System exhibited an impressive degree of simplicity, similarity and mutual correlation. These findings collectively suggest the prevalence of a cyanobacteria-dominated primitive ecosystem during the Mesoproterozoic Era within the confines of the Yanliao Rift
Tracing Subducted Carbonates in Earth's Mantle Using Zinc and Molybdenum Isotopes
No full textAlthough carbonates are the primary form of carbon subducted into the mantle, their fate during recycling is debated. Here we report the first coupled high-precision Zn and Mo isotope data for Cenozoic intraplate basalts from western China. The exceptionally high delta 66Zn values (+0.39 to +0.50 parts per thousand) of these lavas require involvement of recycled carbonates in the mantle source. Variable delta 98Mo compositions (-0.39 to +0.27 parts per thousand) are positively correlated with Mo/Ce, best interpreted as mixing between isotopically light Mo from dehydrated oceanic crust and heavy Mo from recycled carbonates, which is also supported by positive coupling between delta 66Zn and delta 98Mo. Modeling reveals that involvement of <= 5% carbonate-bearing oceanic crust fully resolves the observed delta 66Zn-delta 98Mo mantle heterogeneity probed by intracontinental basalts. Our study demonstrates that combined delta 66Zn-delta 98Mo data sets for mantle-derived magmas can track recycled surficial carbonates in Earth's interior, providing a powerful geochemical tool for deep carbon science.
Carbon is an element of life and studying its geological cycle is crucial for understanding Earth's evolution including formation of a life-supporting atmosphere. Here we report the first combined high-precision Zn and Mo isotope data for Cenozoic intraplate lavas from western China, showing that the basalts record <= 5% carbonate-bearing oceanic crust components in their mantle source. Our results provide new evidence for surficial carbonates being delivered into the deep upper mantle, which adds to the debate about the deepest extent of the terrestrial carbon cycle.
First combined zinc (Zn) and molybdenum (Mo) isotope data for mantle-derived magmas to track the fate of subducted carbonates Zn-Mo isotopic compositions of Cenozoic Tarim basalts suggest surficial carbonates being delivered into the deep upper mantle We highlight the utility of combined Zn-Mo isotope data as a powerful tool in deep carbon scienc