Guangzhou Institute of Geochemistry
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Species-specific accumulation of microplastics in different bird species from South China: A comprehensive analysis
No full textMicroplastics are widespread in many bird species, but the inter-specific variations of microplastic contamination are still unclear. The present study measured microplastics in 24 bird species from South China and investigated the impacts of bird physiological and ecological traits on microplastic contamination. The median abundances of microplastics ranged between 5-167 particles per individual or 0.023-3.58 particles per g body weight. Approximately 60 % of microplastics were within the size range 20-50 mu m, with the primary polymer types of polypropylene (PP) and polyethylene terephthalate (PET). There was no significant correlation between microplastic abundances and bird body weights and trophic levels (delta N-15) in different bird species. Insectivorous birds had significantly higher abundances of microplastics smaller than 0.1 mm than granivorous, piscivorous, and carnivorous birds (p 1 mm) than other bird species. Microplastic contamination in different bird species was more influenced by diet source rather than trophic level and body weight. Potential ecotoxicological risks were observed for most insectivorous species in the preliminary risk assessment. Particular concern should be paid on insectivorous birds, which have been scarcely studied for microplastics but were at high exposure risks of microplastics among bird species
Determination of Thallium Isotope Ratios in Ten Geological Reference Materials, and of Thallium Isotopic Fractionation Effects Related to Sample Digestion by Dry Ashing
No full textWe report for the first time Tl isotope ratios for ten geological reference materials (RMs), namely SGR-1b (from the USGS), and GBW07302, GBW07303a, GBW07401a, GBW03104, GBW07103, GBW07109, GBW07110, GBW07111 and GBW07113 (from China). The principal matrix characteristics of these materials range from sediments to igneous rocks, including stream sediment, soil, shale, granite, nepheline syenite, trachyte, granodiorite and rhyolite. Analytically, the procedure we developed includes a sample digestion step, a simplified single-stage anion exchange matrix separation step and measurements by MC-ICP-MS. For sample digestion we compared a dry ashing-based process with an acid digestion method under high-pressure conditions. We observed that the RMs with high organic content (e.g., SGR-1b = similar to 25%) showed very high values of loss on ignition (LOI) (similar to 40%) during dry ashing. Moreover, Tl isotopic measurement results were heavier after dry ashing than after application of the high-pressure bomb method. We infer that the combustion conditions in case of large amounts of organic matter are probably the cause of Tl isotopic fractionation effects (preferential evaporation of Tl-203). We thus recommend the high-pressure bomb method for the sample digestion step. We validated our entire measurement procedure by applying it to well-documented RMs, including GSP-2 (granodiorite), Nod-A-1 (Marine sediment), Nod-P-1 (Marine sediment) and SCo-1 (shale). Our measurement results were in agreement with literature values
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
Presence and sources of per- and polyfluoroalkyl substances (PFASs) in the three major rivers on Hainan Island
No full textPer- and polyfluoroalkyl substances (PFASs) have attracted considerable attention because of their toxicity, persistence and bioaccumulation potential. With the construction of the Hainan Free Trade Port and the rapid development of economy, environmental pollution on Hainan Island is becoming increasingly prominent. PFASs have been detected in the seawater and sediments of mangrove ecosystems on Hainan Island. As the receiving water of wastewater treatment plants (WWTPs) and industrial wastewater, rivers are inevitably contaminated by PFASs. However, few studies have focused on PFAS pollution in three large rivers (the Nandu, Changhua, and Wanquan rivers) on Hainan Island. In the present study, the pollution status, potential sources, and ecological risks of PFASs in these three major rivers were explored. Perfluorobutanonic acid (PFBA) (48.7%) was found to be the major PFASs in the surface waters, and perfluoroundecanoic acid (PFUnDA) (19.7%) was the major PFASs in the sediments of the three major rivers. The concentrations of & sum;PFASs in the upper-midstream region were low due to minimal human influence and increased in the middle-lower reaches with increasing industrial activity and urbanization, whereas decreased at downstream sites near estuaries where river water was diluted with seawater. WWTP effluent, industrial wastewater discharge, the application and discharge of aqueous firefighting foam, storm runoff and landfill leachate were the major sources of PFASs in the three major rivers. In surface water, perfluorooctanoic acid (PFOA), perfluorooctane sulfonamide (PFOSA) and perfluorooctadecanoic acid (PFODA) posed low-moderate risks at 5.71-85.6% of the sampling sites. PFASs in the sediment posed no ecological risk. This study provides key data regarding the pollution status and potential sources of PFASs in large rivers on subtropical islands
On-line hydropyrolysis gas chromatography-mass spectrometry (HyPy-GC-MS) for kerogen-bound biomarkers
No full textFlash pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) is seldom used to release bound biomarkers, because its hydrogen-poor pyrolysis conditions usually result in a low yield of bound biomarkers and high concentrations of olefins. In this study, by using a Py-GC-MS system and immature kerogen/coal samples, we investigated the effects of heating rate (flash versus 30 degrees C/min), carrier/reaction gas (He versus H-2), hydrogen pressure, and catalyst [(NH4)(2)MoO2S2] on the yields and distributions of bound biomarkers. Also, the bound biomarkers obtained by different pyrolysis conditions were compared with those from catalytic offline hydropyrolysis (HyPy) and free biomarkers from extracted organic matter (EOM). We propose a new technology of hydropyrolysis-gas chromatography-mass spectrometry (HyPy-GC-MS) to be used to release bound biomarkers. HyPy-GC-MS using low-pressure H-2 at slow heating rate can increase the yield of bound biomarkers by 3-9 times, minimize the cracking of the hopanes side chain, better preserve the original sterane and terpane distributions, and have characteristics of lower maturity, compared with conventional flash Py-GC-MS without H-2. Additionally, the steroidal and terpenoid yields by HyPy-GC-MS using low-pressure H-2 at slow heating rate from immature kerogens were 3-6 times that by HyPy. Compared with EOM, biomarker maturity parameter derived from HyPy-GC-MS may not fully represent the actual maturity of samples. Higher hydrogen pressure can significantly facilitate the hydrogenation of unsaturated hydrocarbons into saturated hydrocarbons, but it can also decrease the yields of pyrolysates with higher carbon numbers (i.e., >C-25), leading to a change in the biomarker ratios related to carbon numbers (e.g., the proportion of C-27-C-28-C-29 alpha alpha alpha 20R steranes and TT23/H-30 ratio)
On-line hydropyrolysis gas chromatography-mass spectrometry (HyPy-GC-MS) for kerogen-bound biomarkers
No full textFlash pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) is seldom used to release bound biomarkers, because its hydrogen-poor pyrolysis conditions usually result in a low yield of bound biomarkers and high concentrations of olefins. In this study, by using a Py-GC-MS system and immature kerogen/coal samples, we investigated the effects of heating rate (flash versus 30 degrees C/min), carrier/reaction gas (He versus H-2), hydrogen pressure, and catalyst [(NH4)(2)MoO2S2] on the yields and distributions of bound biomarkers. Also, the bound biomarkers obtained by different pyrolysis conditions were compared with those from catalytic offline hydropyrolysis (HyPy) and free biomarkers from extracted organic matter (EOM). We propose a new technology of hydropyrolysis-gas chromatography-mass spectrometry (HyPy-GC-MS) to be used to release bound biomarkers. HyPy-GC-MS using low-pressure H-2 at slow heating rate can increase the yield of bound biomarkers by 3-9 times, minimize the cracking of the hopanes side chain, better preserve the original sterane and terpane distributions, and have characteristics of lower maturity, compared with conventional flash Py-GC-MS without H-2. Additionally, the steroidal and terpenoid yields by HyPy-GC-MS using low-pressure H-2 at slow heating rate from immature kerogens were 3-6 times that by HyPy. Compared with EOM, biomarker maturity parameter derived from HyPy-GC-MS may not fully represent the actual maturity of samples. Higher hydrogen pressure can significantly facilitate the hydrogenation of unsaturated hydrocarbons into saturated hydrocarbons, but it can also decrease the yields of pyrolysates with higher carbon numbers (i.e., >C-25), leading to a change in the biomarker ratios related to carbon numbers (e.g., the proportion of C-27-C-28-C-29 alpha alpha alpha 20R steranes and TT23/H-30 ratio)
High-temperature structural disorders stabilize hydrous aluminosilicates in the mantle transition zone
No full textHydrous aluminosilicates are important deep water-carriers in sediments subducting into the deep mantle. To date, it remains enigmatic how hydrous aluminosilicates withstand extremely high temperatures in the mantle transition zone. Here we systematically investigate the crystal structures and chemical compositions of typical hydrous aluminosilicates using single-crystal X-ray diffraction, electron probe microanalyzer, and nanoscale secondary ion mass spectrometry. These single crystals are synthesized at 15.5-22.0 GPa and 1400-1700 degrees C, featuring pervasive structural disorders. In particular, Al and Si atoms extensively occupy new tetrahedral and octahedral sites that are nominally vacant in their ordered counterparts. High temperature activates disorders leading to variable local crystal structures and more hydrogen incorporation into the crystal structure. This result suggests that the order-to-disorder transition holds the key to the high thermal stability of hydrous aluminosilicates, significantly affecting the water cycle in the deep mantle
The key constraints on large-scale mineralization of Cenozoic potassic alkaline rocks in the Eastern Tibet-Sanjiang Belt
No full textDuring the Cenozoic Indo-Asian continental collision, a 1500km long, north-south oriented potassium-rich magmatic belt emerged in the Eastern Tibet-Sanjiang region. In this belt's northern sector, magmatic activity produced the extensive Yulong porphyry ore belt, while only sporadic deposits appeared in the central and southern sectors. This study employs SIMS water and oxygen isotope analyses, LA-ICP-MS trace element analyses, and Lu-Hf isotope analyses on primary zircon grains from three potassium-rich, barren rocks located in the middle and southern parts of the Sanjiang Belt. By comparing these with contemporaneous ore-forming porphyries in the Yulong ore belt, we delve into critical factors influencing large-scale porphyry mineralization of potassium-rich rocks in the Eastern Tibet-Sanjiang Belt. Our results reveal that zircon epsilon(Hf)(t) values (-6.00 to 2.70, average -2.94) from the barren rocks are significantly lower than those from fertile porphyries (-3.37 to 6.63, average 2.68), indicating that magmatic sources in the central and southern sectors have more ancient crustal material, while the northern sector's source is enriched with juvenile crustal material. Zircon grains of the three barren rocks display high H2O and OH-contents (average (734 +/- 184)x10(-6) and (14 +/- 4)apfux1000), akin to those from the giant porphyry deposit (average (640 +/- 213)x10(-6) and (12 +/- 5)apfux1000), and much higher than those from the medium-sized porphyry deposit (average (335 +/- 181)x10(-6) and (5.3 +/- 3)apfux1000) in the Yulong belt. Elevated zircon H2O contents in the barren rocks are primarily influenced by high pressures during zircon crystallization, which resulted from the regional high-pressure stress background and deep magmatic storage depths. These factors inhabited early fluid exsolution from the magmas, as indicated by the absence of fluid inclusions in zircons from the barren rocks, subsequently impeding metal extraction and porphyry mineralization. In summary, we propose that juvenile crust-rich sources, extensive regional stress, and early fluid exsolution of water-rich magmas collectively facilitated the large-scale porphyry mineralization of Cenozoic potassium-rich magmas in the Sanjiang Belt's northern segment. Additionally, the inputs of mantle-derived ore-rich potassic magmas controlled the porphyry mineralization and its spatial distribution in the belt's central and southern segments. Moreover, our approach suggests that zircon H2O is regulated by regional stress fields, storage depths, and magmatic water content. Zircons from different tectonic setting formed under different regional stresses, thus caution should be exercised when interpreting the zircon water contents
Combustion-related isoprene contributes substantially to the formation of wintertime secondary organic aerosols
No full textIsoprene is a key reactive organic gas involved in organic aerosol formation. While biogenic isoprene from terrestrial plants has been extensively studied and is recognized as a major contributor to secondary organic aerosol (SOA), high levels of observed SOA, especially in winter, cannot be fully explained by biogenic isoprene alone. In this study, we developed a comprehensive bottom-up emission inventory for isoprene, incorporating both biogenic and combustion sources and modeling their contributions to SOA in China from 2000 to 2016. Combustion-related isoprene emissions from open biomass burning and residential fuel combustion were estimated at 52.0 (39.1-65.7) Gg in 2000, declining to 14.8 (10.6-19.0) Gg by 2016. Open biomass burning contributes similar to 40% of combustion-related isoprene emissions. Though, annually, combustion-related isoprene emissions were much smaller than the biogenic emissions, they did account for 32%-80% of total isoprene emissions in many north and west provinces in the colder months in 2016, and were even higher during the early 2000s owing to more biofuel-burning emissions. Model simulation results indicated that combustion-related isoprene could contribute 25%-40% of winter SOA in northern regions. Wintertime isoprene-derived SOA levels declined since 2000, corresponding with decreased combustion-related isoprene emissions; however, the extent of this decline varied regionally due to the influence of other precursors like nitrogen oxides (NOx). In the northeast region with high NOx levels, while combustion-related isoprene emissions decreased by >80% from 2000 to 2016, isoprene-derived SOA declined by only similar to 20%. These findings highlight the previously underappreciated contributions of combustion-related isoprene to observed high wintertime isoprene-derived SOA levels
A Newly Identified "Proto-Kenting Mélange (S. Taiwan)" Represents a Missing Link for a Continuous Early Cretaceous Paleo-Pacific Subduction-Accretion System
No full textMost m & eacute;langes in exhumed subduction-accretion complexes are polygenetic, recording significant information about the nature of geological processes during their formation. Here, we apply micro-chemical analysis and illite K-Ar dating to constrain the deformation mechanism and timing of the pervasively sheared scaly matrix in the accretionary complex rocks presently known as "Kenting M & eacute;lange" in the Hengchun Peninsula (South Taiwan). Our results reveal that parts of the matrix were formed in Cretaceous (96.7 +/- 8.6 Ma and 108 +/- 18.4 Ma) due to pressure solution. These new, older matrix ages suggest that the Kenting M & eacute;lange, which was considered as Cenozoic and interpreted to have been associated with the subduction of the South China Sea, preserves different primary chaotic units (e.g., m & eacute;lange and/or olistostrome). Our findings imply the Kenting M & eacute;lange is actually polygenetic and allow part of Kenting M & eacute;lange that we named the "proto-Kenting M & eacute;lange" to be interpreted as a remnant of a primary m & eacute;lange, which was mixed and/or juxtaposed in the Cenozoic Kenting M & eacute;lange. The block-in-matrix fabric with a pervasively sheared scaly muddy matrix, along with the preservation of slightly older oceanic crust blocks, suggests that the proto-Kenting M & eacute;lange is most likely an ocean plate stratigraphy m & eacute;lange. This unit initially formed near a Paleo-Pacific subduction margin during the latest Early Cretaceous. Our results reveal a nearly 3000-km-long physical archive of latest Early Cretaceous subduction-accretion processes, which took place adjacent to the continental margin of East Asia during the consumption of Paleo-Pacific ocean floor during the latest Mesozoic