Guangzhou Institute of Geochemistry
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Comprehensive review of modified clay minerals for phosphate management and future prospects
No full textPhosphate recovery from water and wastewater serves as a feasible alternative to the exploitation of scarce phosphate rock resources. Currently, phosphate is recovered using adsorption-based techniques due to their desirable features, such as a low running cost, feasible operation, and high efficiency. Clay minerals (CMs), a group of earth-abundant resources, have attracted increasing interest in phosphate management. However, because the surface and crystal lattice of CMs are negatively charged, CMs are inefficient and have been replaced with cost-effective modified CMs (mCMs). This review comprehensively covers the current advances in mCMmediated phosphate recovery. We first discussed the crystal features of natural CMs and the diverse techniques used for mCMs to enhance their phosphate-removal capacity. Subsequently, we covered the processes of mCM-driven phosphate management, namely, ion exchange, hydrogen bonding, crystallization, Lewis acid-base interactions, electrostatic interactions, precipitation, and electrostatic-ligand exchange. Further assessments revealed that mCMs can efficiently remove phosphate through multiple synergistic mechanisms. This review also discussed the effects of anions, humic acids, and cations on the mCMs management of phosphate and analyzed mCMs applications in various water environments, specifically, phosphate passivation materials in lake sediments and the phosphate management of municipal/seawater wastewater. We examined the reutilization of phosphate-loaded mCMs in agriculture from a circular economy perspective, and finally discussed the commercial application prospects of mCMs in environmental pollution remediation, which may help to avert the global phosphate-resource crisis and improve wastewater management
Fluid inclusion calibration of clumped-isotope solid-state reordering in dolomite: Implication for thermal history reconstruction in deeply buried reservoirs
No full textCarbonate clumped -isotope ( A 47 ) paleothermometry offers a novel means of reconstructing the paleoburial temperature of carbonate rocks. However, the application of this thermometer is challenging when applied to thermal history reconstruction in deeply buried reservoirs, due to potential modifications to the A 47 value of carbonate mineral by C-O bond solid-state reordering. Although four reordering models have been proposed based on high -temperature laboratory experiments, the operation of A 47 reordering under geological conditions is still not fully understood. The A 47 and homogenization temperature ( T h ) of primary fluid inclusions trapped within the dolomite cements from the Central Sichuan Basin, China were measured. The A 47 evolution of the dolomite samples were predicted with the four published reordering models under the constraints of independent thermal history reconstruction and T h -derived initial A 47 values. The results of this study demonstrate that T h of fluid inclusion can be a valid indication of precipitation temperature of dolomite cements even when the samples experience peak burial temperature ( T max ) up to -200-240 degrees C. It also indicate current reordering models have overall equivalent ability for A 47 prediction although there are discernible differences between sample types across different models. Both T max and model -determined threshold behavior of A 47 reordering control the reordering pathway for model prediction, and the threshold behaviors of our dolomite samples were explored under geological conditions. In this framework, the threshold temperature (-190 degrees C) for detectable dolomite reordering may be substantially higher than previous model predictions (120-150 degrees C). Moreover, the temperature at which the A 47 temperature fully equilibrates with the ambient temperature during sequential burial could exceed 240-250 degrees C. These threshold behaviors of bond reordering in dolomite under geological conditions are different from previous model calculations. Therefore, T max and threshold temperatures of A 47 reordering for different models should be considered when reconstructing thermal history based clumped -isotope solid-state reordering modeling. Our findings have significant implications for understanding the dolomite clumped -isotope reordering process and reconstructing the thermal history of deeply buried carbonate rocks
Fluid-induced dissolution-reprecipitation of tungsten minerals in the Hongling deposit, South China
No full textTungsten is a critical metal that is predominantly found in magmatic-hydrothermal W-Sn deposits. However, the behavior and controlling factors of tungsten in highly evolved granitic systems are not yet well-known. In this study, we examined the integrated mineral textures and geochemistry of wolframite and scheelite from the Hongling tungsten deposit in the word-class Nanling W-Sn metallogenic belt, South China. Our results reveal that wolframite and scheelite from the muscovite granite of the highly evolved Reshui granite pluton can be classified into three generations formed through a process of coupled dissolution-reprecipitation. Wolframite with altered relict textures was formed during the early magmatic stage, while the two generations of scheelite (Sch-I and SchII) were formed during the magmatic-hydrothermal transitional stage. The formation of Sch-I, which exhibits a notable positive Eu anomaly, required the participation of external Ca-rich reduced fluids within the magmatic exsolved fluids from the highly evolved peraluminous pluton. The porous Sch-II occurs as marginal overgrowth or fracture-filling textures and exhibits a similar negative Eu anomaly as the dissolved wolframite. These three generations of tungsten minerals exhibit distinguishable REE contents and distribution patterns, with increasing LREE and decreasing HREE trends. The fluctuation of oxygen fugacity and the compositional evolution of tungsten minerals from wolframite through Sch-I to Sch-II indicate the involvement of external Ca-rich reduced fluids within the magmatic exsolved fluids from the highly evolved peraluminous pluton. The coupled dissolution of wolframite and the reprecipitation of scheelite were likely induced by intensive fluid-rock interactions, which are critical for the remobilization and enrichment of tungsten in magmatic-hydrothermal deposits. We inferred that such fluid-induced dissolution-reprecipitation of tungsten minerals provides new insights into the formation of the world-class Nanling W-Sn metallogenic belt in South China
Innovative bioremediation of dexamethasone in aquatic ecosystems using<i> Rhodococcus</i> sp. D32: Pathway discovery and reduction of ecotoxicity
No full textIn response to the widespread environmental concern of endocrine disruptors, our research investigated the aerobic biodegradation of dexamethasone (DEX), a widely used synthetic glucocorticoid with endocrinedisrupting properties, by strain Rhodococcus sp. D32. This innovative strain showcases remarkable DEXdegrading capabilities, with the half-life for degrading 500 mu g/L DEX in MH broth being just 7.56 h. Utilizing high -resolution mass spectrometry, we identified six transformation products (TPs) and revealed a unique steroid nucleus -opening pathway marked by A -ring lactonization and subsequent lactone hydrolysis. This newly discovered pathway deviates from the classical steroid 9,10-seco pathways and previous transformations that preserved the intact steroid nucleus, thus expanding our knowledge of microbial steroid transformations. Additionally, the degradation process progressively converts the parent DEX into less ecotoxic products, significantly reducing the overall ecotoxicity of the system. This reduction remains evident when considering the combined toxicity of DEX and its TPs, indicating a promising approach for lessening environmental harm. Strain D32 also proved effective in various authentic aquatic environments, including fishpond water, urban sewage, river water, and reservoir water, where its introduction markedly expedited the dissipation of DEX. Our findings underscore the potential of strain D32 as a powerful tool for the bioremediation of DEX, presenting an efficient and eco-friendly strategy to alleviate the effects of this endocrine disruptor in aquatic ecosystems
Inferring the Paleo-Location of Proto-Arc Magmas During Subduction Infancy in the Izu-Bonin-Mariana
No full textSubduction zones are one of the principal drivers of the modern-day plate tectonics, but the processes that develop as incipient subduction zones mature are yet to be understood. Finding modern analogs for different stages of subduction infancy remains an outstanding challenge to answer questions on how and when an oceanic subduction zone reaches a quasi-steady state to become long-lived. Here, we compare the southern Mariana intra-oceanic arc, in which near-trench spreading and infant arc magmatism developed similar to 3-4 Myr ago, with the Izu-Bonin-Mariana (IBM) proto-arc magmas that formed during subduction infancy similar to 52 Myr ago. Building upon this comparison, we propose that the Southern Mariana may be considered as a modern analog to subduction infancy. The similarities between the Southern Mariana arc magmas and the IBM Eocene proto-arc magmas suggest that the IBM proto-arc crust might have formed within 80-90 km from the paleo-trench (slab at < 90 km paleo-depth), while the Eocene infant arc was likely located at similar to 100 km from the paleo-trench (similar to 100-125 km slab paleo-depth). We use our constraints further to propose a new conceptual model of subduction evolution for IBM. In this model, development of the subduction channel during arc infancy facilitated downward slab penetration and intensified corner flow in the sub-arc asthenosphere of the mantle wedge. As such, cooling and serpentinization of the fore-arc mantle might be considered as the principal drivers of subduction maturation and stabilization over the IBM lifetime
Continuous crustal thinning of the North China Craton in the Early Cretaceous: Evidence from A-type granites
No full textWidespread crust-derived granitoids in North China provide evidence of Mesozoic lithospheric thinning and destruction of the North China Craton. However, the link between lower crust and lithospheric mantle reactivation remains poorly understood. We present whole-rock geochemistry and zircon O-Hf isotopes for Early Cretaceous peralkaline A-type granites (i.e., Xiwanzi, Xiangshan, and Yansehu) from the Yanshan Mountains of the eastern block of the North China Craton. The Xiwanzi granite has a U-Pb age of 134.3 +/- 0.4 Ma, with homogeneous whole-rock Nd isotopes [e(Nd)(t) = -7.7 to -7.5] but highly variable zircon O-Hf isotopes [delta O-18 = 5.1%0 to 7.2%0 and e(Hf)(t) = -7.7 to +9.6]. Such isotopic variations likely resulted from a hybrid juvenile source consisting of partial melting of newly underplated basaltic rocks derived from both the metasomatized ancient and juvenile sub-continental lithospheric mantle. In contrast, the Xiangshan (117.4 +/- 1.0 Ma) and Yansehu (116.3 +/- 1.4 Ma) granites have relatively uniform isotopic compositions [whole-rock e(Nd)(t) = -12.2 to -10.8, zircon delta O-18 = 5.2%0 to 6.4%0, and e(Hf)(t) = -17.1 to -4.7], close to those of the Proterozoic mafic granulite xenoliths from the ancient lower crust. The isotopic variations of the Early Cretaceous A-type granites suggest a continuous change in the melting model from the underplated juvenile lowermost crust to the overlying ancient lower crust at high temperatures in an extensional environment. Our results indicate that A-type reactivation of the lower crust of an Archean craton. Significantly, large-scale continuous thinning of lower continental crust provides key insights into the generation of the wide- spread Mesozoic crust -derived granitoids in North China
Protracted and Progressive Crustal Melting during Continental Collision in the Pamir and Plateau Growth
No full textDetermining crustal melting in parallel with geodynamic evolution provides critical information on plateau crustal thickening and uplift. Here we investigate the timing and duration of crustal melting through in situ analysis of zircon U-Pb ages, trace elements and Hf-O isotopes, and whole-rock elements and Sr-Nd-Hf isotopes for the granites and high-grade metamorphic rocks from the Pamir Plateau. Zircon dates record protracted crustal melting for both Central Pamir (43-33 and 22-12 Ma) and South Pamir (28-10 Ma). The Pamir Cenozoic granites are characterized by significant elemental and isotopic heterogeneity. The elemental variability within the Pamir Cenozoic granites is dominantly attributed to fractional crystallization of K-feldspar and plagioclase with subordinate biotite from a variably fractionated melt, and the accumulation of early crystallized feldspar during magma ascent. Peritectic mineral entrainment and accessory mineral crystallization had some influence on the geochemical characteristics of the garnet-bearing leucogranite dikes. Zircon Hf isotopes and whole-rock Sr-Nd-Hf isotopes show secular variations for both Central and South Pamir granites. The Central Pamir granites show a mild decrease in whole-rock sigma Nd(t) values from Eocene (-4.3 to -4.9) to Miocene (-6.2 to -7.7), and the zircon sigma Hf(t) values decrease from c. 40 Ma (+2 to -5) to c. 10 Ma (-4 to -8). In contrast, the South Pamir granites have highly variable whole-rock Sr-Nd-Hf (87Sr/86Sr(i) = 0.7053 to 0.7830; sigma Nd(t) = -31.5 to +0.2; sigma Hf(t) = -40.0 to +8.2) and zircon Hf isotopes (sigma Hf(t) = -31.7 to +7.5) and display a strong decrease in sigma Nd(t) and sigma Hf(t) values from c. 25 Ma to c. 13 Ma. Geochemical and isotopic data indicate that both the Central and South Pamir experienced crustal melting from juvenile lower crust to ancient lower-middle crustal materials, and Indian crustal materials were incorporated into the melt region of the South Pamir leucogranites from c. 20 Ma. Our study highlights a causal link between a chain of events that includes magma underplating induced by lithosphere thinning and slab breakoff, lithosphere delamination and underthrusting of Indian lithosphere, and formation of the Cenozoic granites in Pamir. This series of processes are incorporated here into a comprehensive model for the geodynamic evolution of the Pamir during the India-Asia collision
A large role of missing volatile organic compound reactivity from anthropogenic emissions in ozone pollution regulation
No full textThere are thousands of volatile organic compound (VOC) species in ambient air, while existing techniques can only detect a small part of them (approximately several hundred). The large number of unmeasured VOCs prevents us from understanding the photochemistry of ozone and aerosols in the atmosphere. The major sources and photochemical effects of these unmeasured VOCs in urban areas remain unclear. The missing VOC reactivity, which is defined as the total OH reactivity of the unmeasured VOCs, is a good indicator for constraining the photochemical effect of unmeasured VOCs. Here, we identified the dominant role of anthropogenic emission sources in the missing VOC reactivity (accounting for up to 70 %) by measuring missing VOC reactivity and tracer-based source analysis in a typical megacity in China. Omitting the missing VOC reactivity from anthropogenic emissions in model simulations will remarkably affect the diagnosis of sensitivity regimes for ozone formation, overestimating the degree of VOC-limited regimes by up to 46 %. Therefore, a thorough quantification of missing VOC reactivity from various anthropogenic emission sources is urgently needed for constraints of air quality models and the development of effective ozone control strategies
Hydrolysis Products of Fe(III)-Si Systems With Different Si/(Si plus Fe) Molar Ratios: Implications to Detection of Ferrihydrite on Mars
No full textFerrihydrite, a nanocrystalline iron (oxyhydr)oxide mineral, is widely distributed in soils and sediments on Earth and is probably an important component and/or precursor of widespread nanophase iron minerals on Mars. Terrestrial ferrihydrite often co-occurs with amorphous silica and/or contains a certain amount of Si in its structure. However, it remains ambiguous how environmental Si concentration affects the formation-evolution and structure-spectral features of ferrihydrite in the Fe(III)-Si systems. To this end, hydrolysis experiments were carried out for Fe-Si systems at an unprecedentedly wide range of initial Si/(Fe + Si) molar ratios (0-0.80), followed by characterizing the products detailly. X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Mossbauer spectroscopy, and transmission electron microscopy results showed that at Si/(Fe + Si) molar ratios = 0.40, ferrihydrite was no longer formed and a novel amorphous Fe-O-Si phase was instead obtained, with the excess Si forming amorphous silica. The visible and near-infrared spectroscopy, the most powerful tool to detect hydrous minerals on the surface of Mars at global or regional scales, showed weakness in identifying ferrihydrite-like materials obtained in the Fe-Si systems. Raman spectroscopy can identify ferrihydrite and Si-containing ferrihydrite but cannot differentiate between them. Mossbauer spectroscopy showed great potential in both identifying and differentiating between ferrihydrite and Si-containing ferrihydrite, and thus can be used to characterize the poorly ordered iron (oxyhydr)oxides on Mars.
On the surface of ancient Mars where liquid water was available, Fe-Si hydrolysis systems were likely common as a result of the high abundances of Fe and Si in the crust of Mars. By performing hydrolysis experiments of Fe-Si systems at an unprecedented wide range of Si/(Fe + Si) molar ratios, we found that the hydrolysis products of Fe-Si systems varied among combinations of ferrihydrite, Si-containing ferrihydrite, an unknown Fe-O-Si phase, and amorphous silica. We also found that the visible and near-infrared reflectance spectroscopy, the most powerful tool to remotely detect hydrous minerals on the surface of Mars at global and regional scales, showed weakness in identifying ferrihydrite, Si-containing ferrihydrite, and the novel Fe-O-Si phase; Raman can be used to identify ferrihydrite-like materials but cannot be used to differentiate between ferrihydrite and Si-containing ferrihydrite; mid-infrared spectroscopy can differentiate ferrihydrite from Si-containing ferrihydrite and the novel Fe-O-Si phase; Mossbauer spectroscopy (recorded at varied temperatures) provided clues to identifying and further differentiating between ferrihydrite-like materials and thus holds great potential for detecting Fe/Si-rich phases on the surface of Mars.
Hydrolysis experiments of Fe(III)-Si systems were performed at an unprecedentedly wide range of initial Si/(Fe + Si) molar ratios (0 similar to 0.80) The environmental Si concentration controls the formation and evolution of ferrihydrite in the Fe(III)-Si systems Mossbauer spectroscopy shows great potential in identifying and differentiating between ferrihydrite-like material
Occurrence, distribution, and ecological risks of polyhalogenated carbazoles in sediments from Daya Bay and Pearl River Estuary, China
No full textPolyhalogenated carbazoles (PHCZs) are a group of emerging organic pollutants attracting increasing concern. In this study, 32 sediment samples were collected from the Pearl River Estuary (PRE) and adjacent Daya Bay (DYB) in China and were investigated for the occurrence and distribution of PHCZs. Total concentration of sedimentary PHCZs ( n-ary sumation PHCZs) ranged from 0.79 to 3.08 ng/g in PRE and 0.89 to 1.95 ng/g in DYB, both containing 3,6dichlorocarbazole as the main component. Higher concentrations of n-ary sumation PHCZs were found in the rivers-mouth and inner part of the PRE indicating their main origins from anthropogenic activities. Notably, concentrations of brominated carbazoles (BCZs) gradually increased offshore, which suggests the potential bio-transformation of BCZs under a saline environment. The toxic equivalent of PHCZs was estimated at 0.13-0.34 pg TEQ/g suggesting limited dioxin-like effects on local organisms