Guangzhou Institute of Geochemistry
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Diversities of chromite mineralization induced by chemo-thermal evolution of the mantle during subduction initiation
No full textOphiolites, mostly formed via subduction initiation at proto-forearcs, exhibit a unique variation of mantle-derived magmatism from MORB-like to low-Ti tholeiitic and bainitic-like affinities. Such variation was suggested to form chromite deposits spanning high-Al to high-Cr types. Nevertheless, the origin of diverse magmatism during subduction initiation and their linkages to different chromite deposits has long been enigmatic. Here we show elemental and Os isotopic compositions of different chromitites from the Zambales ophiolite, Philippines. Combined with data from ophiolites worldwide, high-Al and high-Cr chromitites are revealed to result from low-Ti tholeiitic and boninitic-like magmatism, respectively. Proto-forearc mantle had few chromitites generated during MORB-like magmatism, but afterwards, it was modified first by slab fluids and later by continuous asthenospheric upwelling in the context of slab densification and rollback. The latter modification elevated the geothermal gradient and replenished fertile components in the proto-forearc mantle progressively, inducing increasingly higher degrees of mantle melting and Cr-richer magmatism and chromitites.
Varied rates of slab rollback are the fundamental driving force for the evolution of infant subduction zones. Relevant non-uniform motion induces thermo-chemical variations in the underlying mantle, generating diverse magmatism and chromite ores
Excess supply of sulfur mitigates thallium toxicity to rice (<i>Oryza</i><i> sativa</i> L.) growth in hydroponic experiment
No full textSulfur (S) is an essential element for the growth of rice plants (Oryza sativa L.), crucial for enhancing crop yield and grain quality. However, its potential in mitigating thallium (Tl) toxicity in rice remains unclear. In this study, a hydroponic experiment was performed to investigate the effects of low, medium and high S application levels (LS, MS, HS) on Tl accumulation in rice at three Tl exposure levels (0, 0.5 and 1 mgL-1). Our findings reveal that the exogenous S application could alleviate Tl toxicity, enhancing fresh weight and shoot length of rice plant. Additionally, HS (HS, SO42- content was 387.84 mgL-1) group significantly increased chlorophyll and glutathione (GSH) content by 6.46 to 21.38 % and 2.15 to 7.31 % respectively, while reducing malondialdehyde (MDA) levels by 17.43 to 28.48 %, compared to MS (MS, SO42- content was 193.41 mgL-1) group. Fe content in rice roots and iron plaque consistently increased with S provision under Tl-free and Tl-contaminated conditions. In Tl exposure environment, HS and LS (LS, SO42- content was 1.02 mgL-1) groups exhibited significant differences in Fe contents and iron plaque in rice root. Moreover, in Tl exposure environment, S application reduced Tl concentration in iron plaque, root, and shoot, HS treatment showed Tl content reduction from 16.29 % to 25.89 %, compared to LS treatment. Our findings underscore the potential of S application in hydroponic environment to promote rice growth and mitigate Tl accumulation, offering insights for developing effective Tl remediation strategies by using S-contained fertilizers
Presence of polycyclic aromatic compounds in river sediment and surrounding soil: Possible impact from shale gas wastewater
No full textShale gas has been extensively extracted in the Sichuan Basin in China in recent years. To gain insight into the potential impact of shale gas wastewater (SGW) discharge, sediment in a small river receiving treated SGW, as well as cultivated soil and paddy soil irrigated by the river water were collected. The occurrence and distribution of polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and their alkylated/oxygenated derivatives (APAHs/OPAHs), and thiophenes were investigated, the resultant potential ecological risks were assessed subsequently. The total concentration of PACs varied in the range of 1299.9-9286.4, 2069.4-11,512.3, and 475.7-2927.9 ng/g in sediment, cultivated soil and paddy soil, respectively, with thiophenes followed by APAHs being the abundant components in all the studied samples, demonstrating the potential impact of SGW discharge on sediment and surrounding soil environment. Based on the measured concentrations, potential ecological risks posed by PAHs and APAHs were calculated, and moderate to high ecological risks were observed in partial sampling sites, which mainly caused by 3-4 rings PAHs and APAHs
Impact of anthropogenic activities on atmospheric chlorinated paraffins in Ghana using polyurethane foam disk- passive air sampler
No full textChlorinated paraffins (CPs) are a global concern due to their high production, ubiquity in the environment and potential toxicity. In Ghana, there is a significant research gap on the concentration and sources of CPs in the air, as well as insufficient regular monitoring programs to track CP levels over time. This study utilized polyurethane foam-based passive air samplers (PUF-PAS) to examine the concentrations, sources and potential human health risks of CPs in the atmosphere surrounding e-waste sites, urban areas, commercial areas and control/background areas in Ghana. The medium-chain CPs (MCCPs) dominated with an average concentration of 26.0 +/- 40.1 ng/m(3) and ranged from 1.78 to 240 ng/m(3). Short-chain CPs (SCCPs) ranged from 0.05 to 15.2 ng/m(3) and had an average concentration of 3.48 +/- 3.99 ng/m(3). The very short-chain CPs (C9-CPs), had an average concentration of 0.544 +/- 0.524 ng/m(3) and ranged from 0.091 to 2.14 ng/m(3). MCCPs exceeded SCCPs by a factor of 7.5 and C9-CPs by a factor of 48. C14Cl8 was the dominant congener in MCCPs and C10Cl7 was also the dominant congener in SCCPs. E-waste was the main contributor to SCCPs and MCCPs (>30 %) in Ghana. The assessed non-cancer risks associated with CP exposure were within acceptable ranges. For cancer risk, MCCPs indicated high potential health risk but C9-CPs and SCCPs showed low risk. To the best of our knowledge, this is the first study on CPs in Ghana's atmosphere, and e-waste was identified as the country's main source of CPs. This study will help regulatory bodies create policies and procedures to control the use and disposal of chlorinated paraffins
'Super-stable' interlayer organic carbon in soil clay minerals and its impact on soil carbon sequestration
No full textAmbient volatile organic compounds in a typical industrial city in southern China: Impacts of aromatic hydrocarbons from new industry
No full textNew industrial parks, including fine chemical, medical manufacturers, etc., are emerging in modern cities in China, whereas their emissions and impacts have not been fully illuminated. In this study, ambient volatile organic compounds (VOCs) in Huizhou were measured in three functional zones, namely new industrial, roadside, and residential zones. The average mixing ratios of total VOCs were as follow: industrial (56.22 +/- 15.06 ppbv) > roadside (39.30 +/- 12.96 ppbv) > residential (26.03 +/- 7.31 ppbv). The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP) of VOCs in the industrial zone were 1.5-2.3 and 1.7-3.1 times those in the other zones, respectively. Aromatics contributed the most to OFP (39.8 %- 44.8 %) and SOAP (78.9 %- 91.0 %), with much less contributions to VOCs mixing ratios (18.3 %- 21.2 %). Naphthalene was the most abundant aromatic species across the three zones and ranked among the top contributors to OFP and SOAP among all VOCs species. Source apportionment identified that new industrial emissions and solvent use was the largest VOCs contributor in the industrial zone (53.9 %), traffic-related emissions dominated in the roadside zone (40.7 %), while new industrial and traffic-related emissions contributed similar in the residential zone (32.9 % and 34.7 %, respectively). The carcinogenic and non-carcinogenic risks of hazardous VOCs were above the acceptable threshold, primarily due to new industrial and traffic-related emissions. Our results sug- gested to strengthen the control of new industrial emissions and aromatics sources in Huizhou city to improve air quality and protect human health
Using combined texture-element-isotope indicators of sulfides to trace fluid mixing and evolution in Paleozoic IOCG system
No full textGeochemistry of sulfides is widely used to constrain sources and ore-forming processes of various mineral deposits. However, its application on Fe-oxide Cu-Au (IOCG) deposits is not well constrained due to multiphase pyrite and Cu minerals and their complex inheritance relationships. The Shuanglong deposit is an IOCG-like deposit in the Eastern Tianshan characterized by abundant Py1 and Py2 in the Fe mineralization stage (II) and Py3 and Py4 in the Cu mineralization stage (III). Chalcopyrite is divided into three types where Ccp1 is formed by replacing Py1 and Py2, Ccp2 coexists with Py4, and higher grade Ccp3 is in quartz-hematite-chalcopyrite veins without pyrite. Py1 and Py2 are associated with multiphase magnetite in stage II Fe mineralization, whereas Py3 coexists with the early epidote replaced by the late calcite-hematite-Py4-Ccp2 assemblage in stage III Cu mineralization. The increasing Co contents and Co/Ni ratios and decreasing delta 34S values (similar to 8 parts per thousand to 4 parts per thousand) from core to rim in Py1 and Py2 indicate temperature and oxygen fugacity increases during the input of magmatic-hydrothermal fluids. Decreasing Co/Ni, increasing Au, and delta S-34(fluid) (from similar to 6 parts per thousand to 30 parts per thousand) from Py3 to Py4 show fluid mixing between the magmatic-hydrothermal fluid and oxidized non-magmatic sulfur such as seawater or basinal brine sulfate during the stage III Cu mineralization. Ccp1 inherited its sulfur and certain trace elements such as Pb and Zn from pyrite, whereas the addition of external sulfur contributed to local high-grade Cu mineralization. Such external sulfur may be from the seawater or basinal brine sulfate, with an increasing contribution during precipitation of Ccp2 and Ccp3 shown by fluid delta S-34 values (from 26 parts per thousand to 36 parts per thousand). Combined with the decreasing Cd/Zn ratios from Ccp1 to Ccp3 caused by increasing total sulfur in fluids, this suggests that the sulfate sulfur contribution may have played a significant role in the high-grade Cu mineralization in IOCG deposits. This study also highlights the importance of the detailed texture of pyrite using acid etching, coupled with in-situ sulfur isotope and trace elements of pyrite and chalcopyrite for IOCG deposit research
Temporal enrichment of comammox<i> Nitrospira</i> and Ca. Nitrosocosmicus in a coastal plastisphere
No full textPlastic marine debris is known to harbor a unique microbiome (termed the "plastisphere") that can be important in marine biogeochemical cycles. However, the temporal dynamics in the plastisphere and their implications for marine biogeochemistry remain poorly understood. Here, we characterized the temporal dynamics of nitrifying communities in the plastisphere of plastic ropes exposed to a mangrove intertidal zone. The 39-month colonization experiment revealed that the relative abundances of Nitrospira and Candidatus Nitrosocosmicus representatives increased over time according to 16S rRNA gene amplicon sequencing analysis. The relative abundances of amoA genes in metagenomes implied that comammox Nitrospira were the dominant ammonia oxidizers in the plastisphere, and their dominance increased over time. The relative abundances of two metagenome-assembled genomes of comammox Nitrospira also increased with time and positively correlated with extracellular polymeric substances content of the plastisphere but negatively correlated with NH4+ concentration in seawater, indicating the long-term succession of these two parameters significantly influenced the ammonia-oxidizing community in the coastal plastisphere. At the end of the colonization experiment, the plastisphere exhibited high nitrification activity, leading to the release of N2O (2.52 ng N2O N g(-1)) in a 3-day nitrification experiment. The predicted relative contribution of comammox Nitrospira to N2O production (17.9%) was higher than that of ammonia-oxidizing bacteria (4.8%) but lower than that of ammonia-oxidizing archaea (21.4%). These results provide evidence that from a long-term perspective, some coastal plastispheres will become dominated by comammox Nitrospira and thereby act as hotspots of ammonia oxidation and N2O production.
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Early Pleistocene Orbital-Scale Variability in Australian Northwest Shelf Sediments
No full textPaleoclimate proxy records from regions sensitive to humidity/aridity extremes provide crucial insights into the natural forcing mechanisms underlying long-term climate variability in broader regions. One such area is Northwest Australia, where the Australian monsoon impacts its northernmost fringes, which are bordered by the Great Sandy Desert inland. Marine sediments from the Australian Northwest Shelf record fluvial run-off and eolian dust input during the wet and dry seasons, respectively. The location is therefore ideal for investigating long-term variability in the Australian monsoon and Northwest Australian dust flux over orbital timescales. However, there are few continuous, high-resolution paleoclimate records from this region spanning the early Pleistocene, when strong ice-climate feedbacks of the late Pleistocene did not yet dominate global climate. Here, we present geochemical and environmental magnetic proxy records that reveal %CaCO3 and dust-flux variability between 2.9 and 1.6 million years (Myr) ago from International Ocean Discovery Program Expedition 356 Site U1464 on the Australian Northwest Shelf. We establish a new, orbitally-tuned chronology for Site U1464, primarily based on similar to 400 thousand year (kyr) eccentricity cyclicity in %CaCO3, and observe strong obliquity variability (41 and 54 kyr periodicities) but almost no precession signal in the dust-flux records. We propose that the 41 kyr cycle in Northwest Australian dust flux could be a linear response to East Asian winter monsoon intensity and/or the summer inter-tropical insolation gradient (SITIG), whereas the 54 kyr cyclicity might be a non-linear response to obliquity amplitude modulation via the SITIG effect on the cross-equatorial atmospheric circulations.
This study establishes a new orbitally-constrained chronology for International Ocean Discovery Program Site U1464 Australian Northwest shelf sediments preserve similar to 400 kyr eccentricity cycles in %CaCO3 and similar to 41 kyr obliquity cycles in dust proxy records Obliquity in Northwest Australian dust flux may be related to the East Asian winter monsoon and summer inter-tropical insolation gradien
Microtopography and hydrological regulation alter CO2 and CH4 fluxes in urban wetlands: Evidence from the Pearl River Delta, China
No full textInland urban wetlands are significant sources of CO2 2 and CH4. 4 . Wetland carbon fluxes can be influenced by management (e.g., restoration), impacting atmospheric carbon emissions. However, the regulatory mechanisms underlying the variations in CO2 2 and CH4 4 fluxes affected by microtopography and hydrological regulation, such as the water table, remain unclear, and field monitoring is inadequate. This study measured CO2 2 and CH4 4 fluxes and soil physicochemical properties across various micro-terrains in the restored Guangdong Guangzhou Haizhu Wetland in China and analyzed the direct and indirect effects of these factors on carbon flux. The results showed that the CO2 2 flux was lower than most previously reported urban wetland fluxes, with means of 3.41, 2.08, and 1.04 mmol center dot m-- 2 center dot d- 1 for hummocks, transition zones, and hollows, respectively. Similarly, the CH4 4 flux was lower than most previously reported fluxes in natural wetlands, with averages of 0.00027, 0.435, and 0.0087 mmol center dot m-2 center dot d-1- 2 center dot d- 1 for hummocks, transition zones, and hollows, respectively. Microtopography significantly reduced the CO2 2 flux, while saturated regions such as transition zones and hollows released CH4. 4 . Water level fluctuations primarily caused the elevated CO2 2 and CH4 4 emissions from transition zones compared to hollows. Redundancy analysis indicated that hydrolytic enzyme activity (73.85 %) and temperature (70.96 %) explained most of the variation in carbon flux. Path analysis revealed that microtopography influenced soil temperature, iron oxide contents, and enzyme activity via regulating the water level to affect CO2 2 and CH4 4 fluxes indirectly, with total variances of 69 % and 66 %, respectively. Overall, microtopography alters the patterns of CO2/CH4 2 /CH 4 flux, and appropriate hydrological regulation can reduce carbon emissions. Based on the complex changes in urban hydrology, this study emphasizes that wetland restoration strategies must consider topographic structures and hydrological management to mitigate carbon emissions