Guangzhou Institute of Geochemistry
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On the contribution of atmospheric reactive nitrogen deposition to nitrogen burden in a eutrophic Lake in eastern China
No full textAlthough it has been demonstrated that atmospheric reactive nitrogen (i.e., Nr mainly including NH3, NH4+, NOx, NO3- and etc.) deposition has substantial impacts on nitrogen pools in remote and/or sensitive lakes, there is a scarcity of systematic evaluations regarding the impact on nitrogen burden in eutrophic lakes with riverine input as primary nitrogen source. Utilizing a regional atmospheric chemical transport model, combined with observation-based estimates of atmospheric nitrogen deposition fluxes and riverine nitrogen inputs, we investigate the contribution of atmospheric Nr deposition to the fifth largest freshwater lake located in eastern China, i.e., the Chaohu Lake which is facing frequent outbreaks of algal bloom. The results indicate that in the studied year of 2022, riverine total nitrogen (TN) input to the lake was 11553.3 t N yr(-1) and atmospheric TN deposition was 2326.0 t N yr(-1). For Nr species which are directly available for the biosphere supporting algae and plant growth, riverine NH4+ input was 1856.1 t N yr(-1) and atmospheric NHx (NH3 and NH4+) deposition was 824.5 t N yr(-1). The latter accounts for 30.8% of total NHx input to the lake. For NOy (HNO3 and NO3-), riverine NO3- input was estimated as 2621.7 t N yr(-1), while atmospheric NOy deposition was 629.3 t N yr(-1), accounting for 19.4%. In all, atmospheric Nr deposition accounts for 24.5 % of total Nr input to the lake. Our results suggest that even in regions with dense human activities with primary riverine N input, atmospheric deposition of Nr could also contribute significantly to the bio-available nitrogen in lake systems, and addressing eutrophication in Lake Chaohu and other eutrophic lakes will also need to consider the influence of atmospheric Nr deposition which is related to NH3 and NOx (i.e., NO + NO2, the precursor of NOy) emissions, in addition to the mitigation of riverine N input
Molecular characteristics of organic matters in PM 2.5 associated with upregulation of respiratory virus infection<i> in</i><i> vitro</i>
No full textThe extent to which organic matters (OM) in PM 2.5 affect virus infections and the key organic molecules involved in this process remain unclear. Herein, this study utilized ultra-high resolution mass spectrometry coupled with in vitro experiments to identify the organic molecules associated with respiratory virus infection for the first time. Water-soluble organic matters (WSOM) and water-insoluble organic matters (WIOM) were separated from PM 2.5 samples collected at the urban area of Guangzhou, China. Their molecular compositions were analyzed using Fourier transform ion cyclotron resonance mass spectrometry. Subsequently, in vitro experiments were conducted to explore the impact of WSOM and WIOM exposure on the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudo-virus infection in A549 cells. Results revealed that WSOM and WIOM respectively promoted 1.7 to 2.1-fold and 1.9 to 3.5-fold upregulation of SARS-CoV-2 pseudo-virus infection in a concentration- dependent manner (at 25 to 100 mu g mL-1) compared to the virus-only control group. Partial least squares model analysis indicated that the increased virus infection was likely related to phthalate ester and nitro-aromatic molecules in WSOM, as well as LipidC molecules with aliphatic and olefinic structures in WIOM. Interestingly, the molecules responsible for upregulating SARS-CoV-2 receptor angiotensin-converting enzyme 2 ( ACE2 ) expression and virus infection differed. Thus, it was concluded that ACE2 upregulation alone may not fully elucidate the mechanisms underlying increased susceptibility to virus infection. The findings highlight the critical importance of aromatic and lipid molecules found in OM in relation to respiratory virus infection
Deciphering the key drivers of oxidative potential during ammonium nitrate-mediated aqueous-phase photoreaction of methoxyphenols
No full textMethoxyphenols are released in abundance from lignin pyrolysis during biomass burning. Apart from being atmospheric brown carbon components that absorb solar radiation and warm the climate, methoxyphenols also undergo photoreaction in the atmospheric aqueous phase and form secondary organic aerosols (aqSOA). While efforts have been devoted to understanding chemical evolutions and climate-related optical properties of aqSOA, their potential health impacts also require timely investigations. Herein, we used the dithiothreitol (DTT) assay to investigate oxidative potential of the aqSOA formed during the 8-h aqueous-phase photoreaction of two typical methoxyphenols, vanillin and vanillic acid, under pH 2 or 8, and with or without ammonia nitrate. The highest DTT consumption rates (RDTT) were observed for vanillin aqSOA formed in the presence of ammonia nitrate and at pH 8. At pH 2, although RDTT increased rapidly during early photoreaction, it reduced after prolonged illumination. High-resolution mass spectrometry and linear regression analyses were performed to correlate the photoreaction products with the observed RDTT. Results showed that three products that present quinone, lactone and dimer structures, respectively, should be the key drivers of elevated RDTT for aqSOA formed during photoreaction of vanillin and vanillic acid alone, whereas it shifted to the nitrogen-containing aromatic compounds during their photoreaction with ammonia nitrate. Our results have revealed the role of nitrogencontaining aromatic compounds in the oxidative potential and health effects of aqSOA from biomass burning, which was rarely recognized before and warrants immediate assessments
Electrochemically enhanced adsorption of perfluorooctanoic acid (PFOA) on CuO-CNTs composite electrodes
No full textWith the intensification of the global freshwater crisis, seawater desalination has emerged as a vital approach for obtaining freshwater resources. However, the presence of persistent pollutants in seawater poses new challenges to the desalination process. Among these, perfluorooctanoic acid (PFOA) has garnered significant attention due to its stability, bioaccumulative nature, and potential toxicity. While multi-walled carbon nanotubes (CNTs) exhibit high adsorption capacity, their effectiveness in PFOA removal remains limited. To address this, we synthesized copper oxide-modified CNTs (CuO-CNTs) and fabricated electrodes using a straightforward coating technique for electrochemically assisted PFOA adsorption. Our results demonstrate that CuO-CNTs electrodes achieved a 1.26-fold increase in the initial electrosorption rate and a 2.04-fold improvement in removal efficiency, reaching 89.25 % at 0.6 V compared to CNTs. The maximum electrosorption capacity also increased 1.69- fold at 0.6 V relative to 0 V. Furthermore, studies on adsorption mechanism and various ion strengths/ ion types/ pH provide important references for optimizing electrosorption technology in desalination. These findings contribute to improving the efficiency and effectiveness of contaminant removal during desalination, thereby enhancing the quality of desalinated water
Distinct trophic transfer of rare earth elements in adjacent terrestrial and aquatic food webs
No full textGrowing demand and usage of rare earth elements (REEs) lead to significant pollution in wildlife, but trophic transfer of REEs in different food webs has not been well understood. In the present study, bioaccumulation and food web transfer of 16 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc) were investigated in different terrestrial and aquatic species. Median concentrations of REEs in plant, invertebrate, fish, amphibian, reptile, bird, and vole samples were 488-6030, 296-2320, 123-598, 17.5-88.1, 88.0, 14.2-92.0, and 170 mu g/kg, respectively. The REE concentrations decreased as plants > invertebrates > fishes > amphibians and snakes > birds. The biomagnification factors (BMFs) and trophic biomagnification factors of most REEs were lower than 1, indicating trophic dilution of REEs. Most poikilotherms including fishes, amphibians, and snakes presented higher BMFs of REEs than homotherms including birds and voles (p 0.05) in terrestrial organisms, while REE concentrations were negatively correlated with delta N-15 (p 0.05) in aquatic organisms. The result implies diet source and trophic level as key factors affecting the cycling of REEs in terrestrial and aquatic food webs, respectively
Attribute Reduction in a Hybrid Decision Information System Based on Fuzzy Conditional Information Entropy Using Iterative Model and Matrix Operation
No full textAttribute reduction of hybrid decision information systems (HDISs) is a significant research area within the field of machine learning. Due to the presence of nominal attributes, it is difficult to accurately measure the distance between objects in HDISs, which often results in poor attribute reduction for these systems. Rough set theory (RST) is a crucial tool for attribute reduction, but it requires computation of upper and lower approximations, which often leads to computational difficulties. In response to the aforementioned issues, this paper proposes a fast attribute reduction algorithm for HDISs based on fuzzy conditional information entropy that utilizes an iterative model and matrix operations. Firstly, a novel measurement of the distance between nominal attribute values is defined using decision attributes. Subsequently, fuzzy conditional information entropy is calculated from the perspective of "the attribute values is fed back to the attribute set" and its properties are provided. Additionally, an iterative attribute reduction model and difference matrix are established, and two new matrix operations are introduced. Finally, an iterative attribute reduction algorithm is provided. The results of experiments and statistical tests on fifteen UCI datasets, including three large datasets, demonstrate that the proposed algorithm is more effective and efficient than nine state-of-the-art algorithms. This paper not only addresses the issue of difficulty in measuring the distance between nominal attribute values but also significantly improves the computational efficiency of attribute reduction algorithms based on RST, making it possible for them to be applied to large datasets
A continental record of Early Cretaceous (Aptian) vegetation and climate change based on palynology and clay mineralogy from the North China Craton
No full textThe Early Cretaceous Aptian Stage (121.4-113.0 Ma) witnessed significant climate changes and environmental perturbations including Ocean Anoxic Event 1a; however, reconstructions of paleoclimate have predominantly relied on marine records. In this paper, we report palynological and clay mineralogical data from a continuous core (YSDP-4) in the Kazuo Basin of Northeast China to produce a high-resolution terrestrial Aptian record that is correlated with the marine record. In the lowermost part of the Aptian succession (similar to 121 to similar to 120 Ma), vegetation types were dominated by bisaccate conifers (>75%), while smectite and illite clay minerals were co- dominant (each similar to 40-50%), indicating cool and semi-humid to semi-arid conditions with a tendency towards aridity. This was followed by an exceptionally dry and hot climatic event, from similar to 120 Ma to similar to 117.5 Ma, marked by a rapid increase in drought-resistant plants including members of the Cheirolepidiaceae (>60%). During the transition from the early Aptian to the late Aptian (similar to 117.5 to similar to 114 Ma), the clay mineral composition exhibited a complex pattern containing chlorite and kaolinite, and the proportion of vegetation representing relatively cool and moist conditions increased, indicating a gradual transition to a humid climate. By the end of the late Aptian (similar to 114 to similar to 112 Ma), climate became cooler and more humid, as indicated by a sharp increase in Taxodiaceae pollen (similar to 50%). Based on the similar patterns of vegetation and sedimentary records observed in the Kazuo Basin and across the Tethyan Realm, we propose that the early Aptian hot/dry climatic event was synchronous with Oceanic Anoxia Event 1a. The findings of our study provide an important terrestrial sedimentary reference section for future integration of Cretaceous climatic events and biological evolution across the marine-terrestrial spectrum
A prominent oxygenation event in the late Mesoproterozoic broke the calm of the second half of the "Boring Billion"
No full textThe redox conditions on Earth's surface during the so-called "Boring Billion" (ca. 1.8-0.8 Ga) were characterized by an overall low-oxygen background punctuated by pulsed oxygenation events. This viewpoint, however, is primarily based on the redox studies from the first half of the "Boring Billion". Therefore, it remains unclear whether this state continued into the second half. To address this issue, carbonate rocks from the ca. 1.25-1.22 Ga Taizi and Yemahe formations in the Shennongjia area, Yangtze Block, South China, were analyzed using integrated methods. The carbonate rocks in the upper Taizi Formation display persistent and significant negative Ce anomalies (0.50 +/- 0.05, n = 46) and relatively high I/(Ca + Mg) ratios (up to 1.28 mu mol/mol), whereas those from the Yemahe Formation show no negative Ce anomalies (0.99 +/- 0.21, n = 39) and low I/(Ca + Mg) ratios (0.03 +/- 0.04 mu mol/mol, n = 86). These data suggest the occurrence of a significant pulsed oxygenation event in shallow seawater during the deposition of the upper Taizi Formation. A model calculation shows that the shallow seawater oxygen concentrations may have reached up to 41 mu M, accompanied with a rise in atmospheric oxygen levels to 12% PAL (present atmospheric level). In contrast, the reconstructed seawater delta 98Mo value is +1.15 parts per thousand for this interval, lower than that of the modern seawater but similar to those of most mid-Proterozoic values, indicating the global seafloor largely remained anoxic. These findings indicate that the ocean redox state in the second half of the "Boring Billion" was more dynamic than previously thought
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
Lithium isotope and mercury evidence for enhanced continental weathering and intense volcanism during the Ordovician-Silurian transition
No full textThe Ordovician-Silurian transition (OST) was characterised by climatic fluctuations (warming in the Katian and glaciation in the Hirnantian) and mass extinctions. However, the mechanisms driving the climatic and biological variability remain under debate. In order to reveal the relationships between volcanism, climate, and continental weathering, we measured lithium (Li) isotopes and mercury (Hg) concentrations in a carbonate-dominated marine section from South China. The reconstructed S7Liseawater values were generally 21 %o during the Ordovician-Silurian transition, with negative excursions towards 16 %o in the latest Katian and the latest Hirnantian intervals. We infer that changes in continental weathering affected dissolved riverine Li fluxes and S7Li values, and thereby exerted a major control on the seawater S7Li variations, while changes in temperature that influenced isotope fractionation during weathering and reverse weathering exerted a secondary control. In the Late Katian, intense volcanic activity (high Hg/TOC ratios and low S13C values) likely initiated the climatic warming (late Boda warming), which was sustained by enhanced clay formation (S7Liseawater values of 21 %o). The intense volcanism also contributed to the high primary productivity and expansion of ocean anoxia, accounting for the Katian extinction. In the latest Katian and latest Hirnantian, enhanced and more congruent weathering (S7Liseawater values of 16 %o) likely contributed to the initiation of global cooling and further glaciation. Meanwhile, the weathering-induced expansion of euxinic seawater could have driven the Late Ordovician Mass Extinction (LOME) events. During the Hirnantian glacial intervals, decreased and incongruent weathering could have contributed to reduced CO2 drawdown, ultimately allowing warming and climatic recovery. Overall, the climatic fluctuations during the OST were related to changes in continental weathering, while the multiphase biotic extinctions could be attributed to volcanism and/or weathering-induced oceanic anoxia