Guangzhou Institute of Geochemistry
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Are South China granites special in forming ion-adsorption REE deposits
No full textIon-adsorption REE deposits associated with clay minerals are the main global HREE producer. The majority of these deposits are formed by the weathering of granites in South China, but whether there is any fundamental difference between the granites in and outside South China is still unclear. Besides, an effective evaluation system of granite mineralization potential is urgently needed for HREE exploration. To answer this question, we compiled a global granite geochemical dataset from within (n = 1932) and outside (n = 6109) South China, together with a dataset of representative REE deposits in South China (n = 128). The geochemical comparation shows that the South China granites share similar REE contents with those of many granites from places outside South China. Such similarity has also been found between REE ore-related and ore-barren granites in South China. This shows that granites from outside South China could also have ore-forming potential. Warm humid climate and quasi-equalized crustal state promote chemical weathering to continuously leach REEs and store them in the weathering crust. The enrichment ratio (Rx) can be used to quantify the climatic effect between orebodies and parent rocks. The calculated average Enrichment Ratios (Rx) of LREE-and HREE-rich deposits are 2.41 and 2.68, respectively. Sufficient REE content in granite is the prerequisite for mineralization, and we propose that the combination of the minimum REE + Y (172 and 108 ppm in LREE-and HREE-rich parent rocks, respectively) and REE oxide ratio (1.32) can reveal the granite metallogenic potential. Together with the suitable tropical and temperate climate area with ion-adsorption REE deposits, we further identified certain regions with high REE mineralization potential outside South China to assist future exploration. (c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved
Are South China granites special in forming ion-adsorption REE deposits
No full textIon-adsorption REE deposits associated with clay minerals are the main global HREE producer. The majority of these deposits are formed by the weathering of granites in South China, but whether there is any fundamental difference between the granites in and outside South China is still unclear. Besides, an effective evaluation system of granite mineralization potential is urgently needed for HREE exploration. To answer this question, we compiled a global granite geochemical dataset from within (n = 1932) and outside (n = 6109) South China, together with a dataset of representative REE deposits in South China (n = 128). The geochemical comparation shows that the South China granites share similar REE contents with those of many granites from places outside South China. Such similarity has also been found between REE ore-related and ore-barren granites in South China. This shows that granites from outside South China could also have ore-forming potential. Warm humid climate and quasi-equalized crustal state promote chemical weathering to continuously leach REEs and store them in the weathering crust. The enrichment ratio (Rx) can be used to quantify the climatic effect between orebodies and parent rocks. The calculated average Enrichment Ratios (Rx) of LREE-and HREE-rich deposits are 2.41 and 2.68, respectively. Sufficient REE content in granite is the prerequisite for mineralization, and we propose that the combination of the minimum REE + Y (172 and 108 ppm in LREE-and HREE-rich parent rocks, respectively) and REE oxide ratio (1.32) can reveal the granite metallogenic potential. Together with the suitable tropical and temperate climate area with ion-adsorption REE deposits, we further identified certain regions with high REE mineralization potential outside South China to assist future exploration. (c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved
Molybdenum Isotopic Signatures of Forearc Serpentinites: Origin and Contribution to the Subduction Zone Mo Cycle
No full textSerpentinites, as important reservoirs for volatile and fluid-mobile elements, have been increasingly recognized as playing a critical role in global geochemical cycles. However, direct evidence for their dominance in the molybdenum (Mo) cycle in subduction zones has been elusive. Here, we address this issue by comprehensively investigating the Mo isotope systematics of serpentinites and accompanying metabasites recovered from the Mariana forearc. Forearc serpentinites under low-pressure conditions (blue- and lizardite-serpentinites) show substantial enrichments in Mo/Ce ratios (0.42 to 27.34) with high delta 98/95Mo values (-0.03 parts per thousand to 2.48 parts per thousand), which arise from not only the incorporation of shallow forearc slab-derived fluids but also late low-temperature metasomatism by seawater during clast exhumation. Subducted oceanic crust represented by metabasites has low Mo/Ce ratios (0.004 to 0.049) and delta 98/95Mo values (-1.13 parts per thousand to -0.61 parts per thousand), indicating that the loss of Mo during oceanic crust alteration in the early or before subduction stage tends to decrease the Mo isotopic compositions. Combined Mo-Sr-Pb isotope systematics indicate that the high delta 98/95Mo values in some arc lavas cannot be ascribed simply to the incorporation of slab-derived fluids at subarc depths; instead, the injection of forearc serpentinite-derived fluid into their mantle source is noteworthy. We propose that the mobilization of Mo by shallow slab-derived fluids during the early subduction stage generated forearc lizardite-bearing serpentinites enriched in heavy Mo isotopes. Subsequently, dehydration and melting of these serpentinites, dragged by the subducting slab down to the subarc region, might have contributed to the Mo systematics in arc lavas. This study demonstrated that forearc serpentinites may be important reservoirs for arc lavas with high Mo isotopic compositions and may contribute to the Mo cycling in subduction zones.
Serpentinites, as important reservoirs of volatile elements and mobile elements, play key roles in geochemical cycles. However, direct evidence that these rocks dominate the Mo cycle in subduction zones has been elusive. In this paper, we solve this problem by studying the molybdenum (Mo) isotope system of serpentinites and associated metabasites recovered from the Mariana forearc. The forearc serpentinites have high delta 98/95Mo values due to modification by slab-derived fluids and seawater. The delta 98/95Mo values of the metabasites are relatively low, indicating that Mo isotope changes occurred during oceanic crust alteration. The forearc serpentinites with heavy Mo isotopes that experiencing dehydration and melting were dragged below the arc by the subducting slab, which have contributed to the Mo system in arc lava. This study showed that forearc serpentinite may act as an indispensable reservoir in the Mo cycle in subduction zones.
Forearc serpentinites show high Mo/Ce ratios and delta 98/95Mo values Lizardite-serpentinites are influenced by shallow slab-derived fluid, while blue-serpentinites are influenced by late seawater metasomatism Forearc serpentinites may contribute significantly to the Mo systematics in arc lava
Petrogenesis of Miocene high Ba-Sr granitoids from the Central Pamir: Implications for continental growth
No full textHigh Ba-Sr granitoids differ from the I-, Sand A-type granitoids, and their petrogenesis and role in the evolution of the continental crust remain enigmatic. This paper reports a study of whole-rock geochemistry, and Sr-Nd isotopes, zircon U-Pb geochronology, and Lu-Hf isotopes of the Zankan high Ba-Sr intrusion in the Central Pamir. U-Pb dating of zircons suggests that the pluton was emplaced during the Miocene (10.2 +/- 0.1 Ma). The Zankan rocks have high contents of K2O (3.83 to 12.3 wt%), Rb (212-483 ppm), Ba (701-6910 ppm), and Sr (503-3371 ppm). They have several geochemical characteristics that are consistent with A-type granitoids, such as high Na2O + K2O (8.10-14.2 wt%) and Zr + Nb + Ce + Y (336-1393 ppm) contents. All samples have enriched Sr-Nd-Hf isotope compositions, with 87Sr/86Sri = 0.7097 to 0.7126, epsilon Nd(T) = -9.3 to -8.4, and epsilon Hf(T) = -12.2 to -4.0. Their isotopic compositions differ from those of mafic lower crust in the Central Pamir. Alternatively, the Zankan rocks may have been derived from an enriched lithospheric mantle. Combining our new isotopic results with data from the literature, we propose that a shift from isotopically juvenile to more isotopically evolved compositions in mantle-derived magmas took place from the Eocene to Miocene. The isotopic shift reveals that South Pamir lower crust was underthrusted beneath the Central Pamir lithosphere during the Miocene. Although high Ba-Sr granitoids generally exhibit "crust-like" isotopic characteristics, our data indicate that they play a role in continental growth
Tissue-Specific Distribution and Maternal Transfer of Persistent Organic Halogenated Pollutants in Frogs
No full textPersistent organic pollutants pose a great threat to amphibian populations, but information on the bioaccumulation of contaminants in amphibians remains scarce. To examine the tissue distribution and maternal transfer of organic halogenated pollutants (OHPs) in frogs, seven types of tissues from black-spotted frog (muscle, liver, kidney, stomach, intestine, heart, and egg) were collected from an e-waste-polluted area in South China. Among the seven frog tissues, median total OHP concentrations of 2.3 to 9.7 mu g/g lipid weight were found (in 31 polychlorinated biphenyl [PCB] individuals and 15 polybrominated diphenyl ether [PBDE], dechlorane plus [syn-DP and anti-DP], bexabromobenzene [HBB], polybrominated biphenyl] PBB153 and -209], and decabromodiphenyl ethane [DBDPE] individuals). Sex-specific differences in contaminant concentration and compound compositions were observed among the frog tissues, and eggs had a significantly higher contaminant burden on the whole body of female frogs. In addition, a significant sex difference in the concentration ratios of other tissues to the liver was observed in most tissues except for muscle. These results suggest that egg production may involve the mobilization of other maternal tissues besides muscle, which resulted in the sex-specific distribution. Different parental tissues had similar maternal transfer mechanisms; factors other than lipophilicity (e.g., molecular size and proteinophilic characteristics) could influence the maternal transfer of OHPs in frogs. Environ Toxicol Chem 2024;00:1-12. (c) 2024 SETA
A novel approach to making composite photocatalyst by peroxide sol-gel deposition of TiO<sub>2</sub> on Al<sub>2</sub>O<sub>3</sub> and ZrO<sub>2</sub> nanosheets
No full textPhotocatalysts are promising materials for removing organic dyes from the environment. TiO2 is one of the most extensively studied photocatalysts; however, its application in the photocatalytic industry has yet to be realized. We contend that fundamental research and the quest for synergy are essential in this field. One approach to enhancing the efficiency of TiO2 is deposition onto porous inert substrates. In this work, we introduce a novel approach by applying TiO2 onto the surfaces of porous nanosized Al2O3 and ZrO2. Employing two soft chemistry methods - the glycol-citrate route for creating a porous and inert substrate and the peroxide route for depositing a TiO2 layer - we have created a technology that allows us to vary the TiO2 concentration on the inert matrix. The developed composite photocatalysts demonstrate competitive efficacy in disintegrating the model dye methylene blue. The most effective photocatalyst was Al2O3@TiO2 (0.26 wt.%) at 1200 degrees C. This material degrades approximately 98.2% of the methylene blue in 5 h, while nanosized TiO2 degrades only 33.5% of the dye under the same conditions. The photocatalytic activity of the material is affected by the concentration of TiO2 in the material due to the dilution of the peroxide solution. Notably, a decrease in the TiO2 concentration enhances the photocatalytic activity of the composite. We assumed that titanium dioxide was distributed in thinner layers at lower concentrations, which increased the area of effective contact and photocatalytic activity. The most efficient aluminum and zirconium oxides decorated with titanium dioxide had surface areas of 12.7 and 16.9 m(2)/g, respectively, while Al2O3 and ZrO2 had surface areas of 31.7 and 34.3 m(2)/g, respectively. Therefore, the decrease in methylene blue concentration was caused by photocatalysis but not by the sorption mechanism. The decomposition of methylene blue in all the samples is consistent with a pseudo-second-order photocatalysis model. The findings of this work lie in the precise application of TiO2 onto the surfaces of inert matrices, which is valuable for developing photocatalytic materials.
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Melanin-mediated accumulation of polycyclic aromatic hydrocarbons in human hair: Insights from biomonitoring and cell exposure studies
No full textWhile human hair is widely used to monitor micro-organic contaminants (MOCs), their incorporation mechanisms are poorly understood. Melanin, known to facilitate the accumulation of drugs in hair, hasn't been studied in the field of MOCs. Here, polycyclic aromatic hydrocarbons (PAHs), a class of priority MOCs, were investigated through hair biomonitoring as well as cell exposure experiments. PAH concentrations and melanin contents were measured in black and white hairs from the same individual. The results showed that five dominant PAHs (phenanthrene, fluoranthene, pyrene, benzo[a]anthracene and chrysene) in black hair (0.66 ng/g - 35.1 ng/g) were significantly higher than those in white hair (0.52 ng/g - 29.6 ng/g). Melanin contents in black hair (14.9 - 48.9 ng/g) were markedly higher than in white hair (0.35 - 2.15 ng/g) and were correlated to PAH concentrations, hinting melanin-mediated accumulation of PAHs in hair. The in vitro experiment using murine melanoma cells demonstrates that PAH levels in cells were affected by melanin, suggesting the affinity of melanin to PAHs. Both biomonitoring and cell exposure experiment implicate the pivotal role of melanin in PAH accumulation in hair. Therefore, to ensure the accuracy of hair biomonitoring for MOCs, attention must be paid to the melanin content uniformity
Global oceans suffer extreme heatwaves intensifying since the early 21st century: A new comprehensive index
No full textAs a result of global warming, major ocean basins have witnessed an increase in the number of extreme warm events and a decrease in the number of extreme cold events, increasing the number of marine heatwave (MHW) events. Previous quantification of MHW events has been limited to simple single metrics, which can only recognize some characteristics from a particular aspect. Here, we propose a new marine Heat Wave Comprehensive Index (HWCI) by fusing multiple metrics to characterize the scalable cumulative intensity of MHWs, which exhibits excellent identification reliability and superiority to effectively monitor the evolutionary patterns of various levels of MHW events. We find that five levels of global MHW events have presented an obvious spatial expansion and temporal enhancement pattern since the early 21st century, with the obvious spatial contraction (32.98 %) of weak events followed by the expansion (19.82 %) of extreme events at the highest growth rate of 0.07, primarily in the mid-low-latitude oceans and the Arctic. The results demonstrate that extreme MHW events dominate global MHW evolution patterns and that the expansion and intensification of such episodes have major implications for the event distribution and level structure. The new indicator is promising for directly measuring and identifying MHWs, and contributes to a more comprehensive understanding of the evolution of MHWs in the context of global climate change
<i>N</i>-nitrosamines in electroplating and printing/dyeing industrial wastewater treatment plants: Removal efficiency, environmental emission, and the influence on drinking water
No full textThe discharge of industrial wastewater containing high concentrations of N -nitrosamines to the aquatic environment can impair downstream source waters and pose potential risks to human health. However, the transport and fate of N -nitrosamines in typical industrial wastewater treatment plants (IWWTPs) and the influence of these effluents on source water and drinking water are still unclear. This study investigated nine N -nitrosamines in four full-scale electroplating (E-) and printing/dyeing (PD-) IWWTPs, two drinking water treatment plants (DWTPs) in the lower reaches of these IWWTPs, and the corresponding tap water in South China. The total concentrations of N -nitrosamines ( & sum;NAs) were 382 - 10,600, 480 - 1920, 494 - 789, and 27.9 - 427 ng/L in influents, effluents, source water, and tap water, respectively. The compositions of N -nitrosamine species in different influents varied a lot, while N -nitrosodi-n-butylamine (NDBA) and N -nitrosodimethylamine (NDMA) dominated in most of the effluents, source water, and tap water. More than 70 % N -nitrosamines were removed by wastewater treatment processes used in E-IWWTPs such as ferric -carbon micro -electrolysis (Fe/C-ME), while only about 50 % of N - nitrosamines were removed in PD-IWWTPs due to the use of chlorine reagent or other inefficient conventional processes such as flocculation by cationic amine -based polymers or bio-contact oxidation. Therefore, the mass fluxes of N -nitrosamines discharged from these industrial wastewaters to the environment in the selected two industrial towns were up to 14,700 mg/day. The results based on correlation and principal component analysis significantly demonstrated correlations between E -and PD -effluents and source water and tap water, suggesting that these effluents can serve as sources of N -nitrosamines to local drinking water systems. This study suggests that N -nitrosamines are prevalent in typical IWWTPs, which may infect drinking water systems. The findings of this study provide a basis data for the scientific evaluation of environmental processes of N -nitrosamines
Ozone and its precursors at an urban site in the Yangtze River Delta since clean air action plan phase II in China
No full textIn response to regional ozone (O 3 ) pollution, Chinese government has implemented air pollution control measures in recent years. Here, a case study was performed at an O 3 -polluted city, Wuhu, in Yangtze River Delta region of China to investigate O 3 variation trend and the relationship to its precursors after implementation of Clean Air Action Plan Phase II, which aims to reduce O 3 pollution. The results showed that peak O 3 concentration was effectively reduced since Clean Air Action Plan Phase II. Due to significant NOx reduction, O 3 formation tended to shift from volatile organic compound (VOC)-limited regimes to NOx-limited regimes during 2018 - 2022. VOC/NOx ratios measured in 2022 revealed that peak O 3 concentration tended to respond positively to NOx. Apart from high -O 3 period, Wuhu was still in a VOC-limited regime. The relationship of maximum daily 8-h ozone average and NO 2 followed a lognormal distribution with an inflection point at 20 mu g m - 3 of NO 2 , suggesting that Wuhu should conduct joint control of VOC and NOx with a focus on VOC reduction before the inflection point. Alkenes and aromatics were suggested to be preferentially controlled due to their higher ozone formation potentials. Using random forest meteorological normalization method, meteorology had a positive effect on O 3 concentration in 2018, 2019 and 2022, but a negative effect in 2020 and 2021. The meteorology could explain 44.0 +/- 19.1% of the O 3 variation during 2018 - 2022. High temperature favors O 3 production and O 3 pollution occurred more easily when temperature was over 25 degrees C, while high relative humidity inhibits O 3 generation and no O 3 pollution was found at relative humidity above 70%. This study unveils some new insights into the trend of urban O 3 pollution in Yangtze River Delta region since Clean Air Action Plan Phase II and the findings provide important references for formulating control strategies against O 3 pollution