Column Conditions Research Articles

Carbon, iron and sulfur records of lacustrine paleo-environments during the middle Eocene in eastern China

It is widely recognized that anoxic conditions facilitate the preservation of organic carbon in marine sediments. However, the specific geological factors that lead to the development of such conditions in paleo-lakes are less well understood. Owing to their smaller size, paleolakes could experience more frequent and stronger changes in geochemical conditions than oceans. Such changes, such as volcanism, hydrothermal fluids, or ocean transgressions, can also strongly affect the lacustrine organic carbon burial thereby complicating sediment diagenesis record. Here, we used total organic carbon content (TOC), organic carbon isotope (δ13Corg), iron speciation, and pyrite sulfur isotope (δ34Spy) data to establish relationships between organic carbon preservation and anoxic conditions in fine-grained sediments from the middle Eocene lacustrine depositional environments from the Shahejie Formation of the Jiyang Depression, Bohai Bay Basin, eastern China. The results reveal TOC between 1 % and 10 %, highly-reactive iron to total iron ratios >0.38, and most TOC to total sulfur ratios exceeding 2. These data indicate that the organic-rich shales of the Shahejie Formation were formed as a result of high primary productivity during the warm and humid middle Eocene period, coupled with the efficient preservation of organic matter in anoxic bottom waters. Negative δ13Corg and δ34Spy excursions recorded in the Shahejie Formation indicate water column conditions to have been influenced by transient volcanic eruptions. Positive δ13Corg and negative δ34Spy excursions may have been caused by hydrothermal fluids input whereas δ34Spy values approaching 20 ‰ suggest frequent marine transgressions. In particular, despite potential inputs of S into the paleolake by volcanism, hydrothermal fluids, or marine transgressions, bacterial sulfate reduction efficiently depleted the sulfate pool to have created ferruginous geochemistry water conditions for the effective preservation of organic carbon in sediments. Our results establish a direct link between lacustrine shale geochemical signatures and geological phenomena that impact its sedimentation.

Comprehensive study on copper adsorption using an innovative graphene carbonate sand composite adsorbent: Batch, fixed-bed columns, and CFD modeling insights

This study focused on an innovative graphene carbonate sand composite adsorbent, synthesized from carbonated porous sand and sucrose as raw materials, for the removal of copper ions via the adsorption process. The characteristics of this adsorbent are determined through comprehensive experiments and numerical simulations in batch and fixed-bed column conditions, which has not been extensively explored. Extensive experimentation demonstrated a remarkable 100 % removal efficiency under optimal conditions, which included a copper ion concentration of 3 g/L, a contact time of 10 h, and an adsorbent dosage of 35 g/L. The adsorption kinetics and isotherm results exhibited that the Elovich model (R² = 0.998) and the Langmuir model (R² = 0.996 for linear with qm=123.91 mg g-1, and R² = 0.993 for nonlinear fitting) more effectively described the adsorption of copper onto the adsorbent. In the fixed-bed column studies, among the well-known analytical models, the Log-Gompertz model showed better compatibility (R2 = 0.97∼0.99) between breakthrough curves with experimental results for various copper inlet concentrations. Also, numerical results obtained using computational fluid dynamics and mass transfer simulations with the linear driving force model were successfully validated by experimental results, particularly in the initial and transition zones of the breakthrough curve.

Experiment on selective dynamic extraction of germanium by ultrasonic enhanced N235 extraction resin under complex system

Germanium plays an irreplaceable role in the field of modern high-tech materials and is an important strategic metal resource. N235 extraction resin was used to selectively extract [Ge(C4O6H4)3]2-. Under the condition of ultrasonic power at 120 W in a water bath, the extraction rate of germanium was 97.32%. The extraction rate of zinc was 2.37% under the conditions of a three-stage solid phase extraction column in series (single-stage filling N235 extraction resin 0.8 g), reaction temperature 25 °C, tartaric acid concentration of 2.0 g/L, and the dwell time is 4.1min. The saturated adsorption capacity of the resin is 51.90 mg/g. The extraction rate of germanium increased by 14.4% under ultrasonic-assisted strengthening conditions. The [Ge(C4O6H4)3]2- can be separated from the resin by NaOH solution. The desorption rate of germanium was 94.12% under the condition of water bath ultrasonic power of 120W, 30 ml concentration of 3.5 mol/L NaOH solution, and the dwell time is 5.2min. Under the optimum conditions, the extraction rate of N235 extraction resin was 85.23% after repeated regeneration five times. The results demonstrate that the extraction resin exhibits high selectivity and reproducibility in complex systems, presenting a new method for extracting germanium under complex conditions.

Chemical and isotopic composition of rainwater in the eastern Yucatan peninsula, Mexico

Given that rain is the component of precipitation that reaches the surface of the earth, and aiming to contribute to the global efforts of rainwater monitoring, we present information regarding the origin of ions and their relationship with isotopic patterns and the source of moisture for rainwater in the Mexican Caribbean, which not only may be useful for pollution and atmospheric studies, but also for estimating groundwater recharges, understanding dust nuisances, and offering information about water quality for rainwater harvesting. In this paper, we describe the chemical composition of rainwater in terms of major ions, isotopic composition, and the most probable sources of moisture in the Caribbean coastal zone of Mexico, considering the three main climatic seasons in this area. The chemistry of rainwater displayed a noticeable influence from sea-salt spray, land-blown dust, and anthropogenic impacts such as agriculture and biomass burning. We identified the predominant terrestrial origin of calcium, namely anthropogenic contributions of sulfates and nitrates, plus potassium from sea spray and anthropogenic emissions. The local meteoric water line is δ2H = 8.2 δ18O + 13.8 (R² = 0.9601) suggesting enrichment due to evaporative losses, various moisture sources and local climatic effects. Although isotope composition was not different by site, it was by season, as opposed to water chemistry. We conclude that the water chemistry responds to the local conditions of the air column below the clouds, while the isotope composition is influenced by the origin of moisture and the physical conditions in which water evaporates and condenses as well.

Rapid determination of chlorate and perchlorate in tea by ion exchange chromatography-tandem mass spectrometry

Ion exchange chromatography-tandem mass spectrometry (IEC-MS/MS) has recently become the preferred method for detecting ionic substances in tea. In this study, an IEC-MS/MS method was developed for the rapid determination of chlorate and perchlorate residues in tea samples. The optimal sample extraction process, pretreatment column, and chromatographic and mass spectrometric conditions were systematically investigated. In the optimal process, the tea samples were ultrasonically extracted with methanol-water (13∶7, v/v), and a PRiME HLB SPE column was used to purify the sample extract. An AceChrom Hybri-A IEC column (150 mm×2.1 mm, 5.0 μm) was used for separation, and 100 mmol/L ammonium acetate-acetonitrile (40∶60, v/v) was used as the mobile phase for isocratic elution. The flow rate was 0.3 mL/min, the column temperature was 40 ℃, and the injection volume was 5.0 μL. The mass spectrometric data were collected in negative electrospray ionization mode combined with multiple reaction monitoring (MRM) mode to achieve the rapid and accurate separation and qualitative analysis of the desired chemical components. Quantification was performed using the internal standard (IS) method. The measurement results showed a good linear relationship when the mass concentrations of chlorate and perchlorate were between 2.00-200 and 1.00-100 μg/L, respectively, with correlation coefficients (r2) greater than 0.9990. The average recoveries of chlorate and perchlorate at three spiked levels of low, medium, and high ranged from 88.54% to 97.25% with relative standard deviations (RSDs, n=7) of 3.2%-5.2%. The limits of detection for chlorate and perchlorate were 12.0 and 8.0 μg/kg, respectively, while the limits of quantification were 40.0 and 26.6 μg/kg, respectively. The results of tests conducted to assess the linearity, specificity, accuracy, precision, and applicability of the method to the analysis of chlorate and perchlorate in 15 tea samples collected from a local market demonstrated its validity for the routine analysis of tea samples. The proposed method is simple, rapid, sensitive, and accurate, and can meet requirements for the rapid screening and quantitative analysis of residual trace chlorate and perchlorate in large quantities of tea samples.

Stratigraphic and paleoceanographic alternations within a Mediterranean semi-enclosed, syn-rift basin during Marine Isotope Stage 5: The Gulf of Corinth, Greece

The Gulf of Corinth represents an ideal setting for studying the impact of sea level changes and regional climate on a semi-enclosed, syn-rift basin. Here we investigate the stratigraphic and paleoceanographic variability recorded in the sedimentary succession of the basin over the Marine Isotope Stage (MIS) 5 period when global sea level and climatic conditions along the eastern Mediterranean exhibited pronounced fluctuations. We used sedimentological (granulometry, composition), micropaleontological (planktic and benthic foraminifera), and isotopic (stable δ18O, δ13C, and clumped isotope) proxies on core samples from site M0079A (IODP Expedition 381) combined with additional data from the expedition overview and records from the surrounding area. The sedimentary succession comprises an alternating pattern of a) bioturbated, biogenic-rich deposits associated with increased hemipelagic sedimentation with b) partly bedded, detrital-rich sediments attributed to intercalated sediment gravity flows within the hemipelagic background under low oxic sea-surface conditions, and c) aragonite-rich laminated deposits, indicating either transitional conditions between marine and isolated environment or a highly stratified seawater column and low oxygen seafloor conditions. We find that the Gulf of Corinth lay under marine conditions for nearly the entire MIS 5 period, while the Rion sill would have been possibly shallower, even 10 m, than the current depth. Nevertheless, water exchange was restricted during the MIS 5a – MIS 4 transition when the sea level fluctuated very close to the sill height. The hydrological conditions within the Gulf during most of the highstands MIS 5a, 5c, and 5e reflect higher oxygen levels and/or increased nutrient availability compared to the Holocene and present-day regime. The combined effects of Ionian Sea inflows and enhanced riverine runoff led to increased water column stratification and low oxygen, eutrophic seafloor conditions in the Gulf of Corinth during times of high precipitation in southern Europe and deposition of sapropels S3, S4, and S5 throughout the eastern Mediterranean. In contrast, during periods of widespread cold and arid conditions in the eastern Mediterranean, water column mixing was intense within the Gulf. Prevalent marine conditions are also proposed during the MIS 5b and 5d lowstands, yet associated with predominately bedded-detrital sediments in the Gulf. A complementary investigation in the adjoining Patras Gulf is suggested to fully comprehend the dynamics of climate and sea level changes in complex rift systems.

Geochemical and Organic Petrological Characteristics of the Bituminous Carbonate Succession (Upper Cretaceous Shu'ayb Formation) in Northern Jordan: Implications for Organic Matter Input and Paleosalinity, Paleoredox, and Paleoclimatic Conditions.

Bituminous carbonate rocks of the Upper Cretaceous Shu'ayb Formation from the Ajloun outcrop in Northern Jordan were geochemically and petrologically analyzed in this study. This study integrates kerogen microscopy results with geochemical results (i.e., biomarker, stable carbon isotope, and major elemental compositions) to understand the organic matter (OM) inputs and to reveal the dispositional setting and its effect on the occurrence of OM. The Shu'ayb bituminous carbonate rocks have high total organic carbon (TOC) and sulfur (S) contents, with average values of 12.3 and 4.59 wt %, respectively, indicating redox conditions during their precipitation. The high abundance of alginite (i.e., lamalginite) in the Shu'ayb bituminous carbonate sediments is a further evidence for redox conditions. The finding of mainly marine-derived OM was also demonstrated by the biomarker distribution and carbon isotope composition. The biomarkers are represented by a narrow Pr/Ph ratio of up to 0.97, abundance of tricyclic terpanes, and high C27 regular sterane, indicating that the OM was primarily derived from phytoplankton algae, along with small amounts of land plant-derived materials, and were accumulated under reducing conditions. The studied Shu'ayb bituminous carbonate facies is composed of mainly calcium (CaO; average, 45.10 wt %), with significant amounts of silicon (Si2O3; avg., 9.35 wt %), aluminum (Al2O3; avg., 6.91 wt %), and phosphorus (P2O3; avg., 1.47 wt %) and low amounts of iron (Fe2O3) and titanium (TiO2) of less than 1 wt %, indicating that the detrital influx was low in an open water depth system with higher primary bioproductivity. The geochemical proxy suggests that the Shu'ayb bituminous carbonate facies was established in a saline water environment, with Ca/Ca + Fe and S/TOC values of more than 0.9 and 0.50, respectively, which could be attributed to the increase in reducing conditions of the water column. The chemical index of alteration values of more than 0.8 also indicate that the Shu'ayb bituminous carbonate facies formed during warm and humid climatic conditions, thereby resulting in intense subaerial weathering.

Source rock assessment and organic matter characterization of the Oligocene upper Shahejie and Dongying formations in the Nanpu depression of the saline lacustrine Bohai Bay basin, China: Geochemical, palynological, and mineralogical perspectives

The Bohai Bay Basin, located in eastern China, is a significant petroliferous, non-marine rift basin, underwent intricate tectonic activities throughout the Cenozoic. The Nanpu Depression in the Huanghua sub-basin in the northern part of the basin was controlled by Paleogene rifting and increased subsidence. These geological processes resulted in the deposition of the Shahejie and Dongying formations, which exhibited varying quantities and qualities of organic matter. Eighty drill cuttings samples of the Paleogene First Member (Es1) and the overlying Third (Ed3) and Second (Ed2) members of the Shahejie and Dongying formations, respectively, were investigated. An integrated approach including organic and inorganic geochemistry, palynology, and mineralogy was employed to assess the paleoredox and marine incursion conditions, source rock quality and levels of thermal maturity, and factors that governed organic matter accumulation. Results indicated that the Es1 Member was deposited under anoxic conditions, resulting in the accumulation of organic matter-rich mudstones in the Nanpu Depression. Abundant pollen grains and acritarchs were found in the Es1 Member yielded along with minor occurrences of dinoflagellate cysts, freshwater algae, and spores. Terrestrial palynomorph composition provided evidence of increased terrestrial runoff, while the high abundance of acritarchs, accompanied by some dinoflagellate cysts, confirmed episodes of marine incursion and deposition under hypersaline conditions in the lacustrine Bohai Bay Basin. The Ed2 Member exhibited poor to fair amounts of organic matter and a limited potential of hydrocarbon generation with a variety of kerogen Types, including IV, III, II/III, and II. The Ed3 Member shows fair to good organic matter richness and hydrocarbon potential of kerogen Types III, II/III, and II. The Es1 Member emerged as the most promising source rock within the studied interval, boasting good to excellent organic matter richness, and fair to good hydrocarbon generation potential of kerogen Types III and II/III. Evaluating the thermal maturity of organic matter, based on Tmax and VRo-Eq% and related cross-plots, revealed that the Shahejie and Dongying formations are still in the immature to the early stage of the oil window. The mineralogical composition of the Es1 Member primarily consists of clay and quartz with some carbonate and accessory minerals, such as epigenetic halite, dolomite, and plagioclase. Weak correlations observed between the total organic carbon (TOC) and mineral components indicated that the availability of organic matter was primarily controlled by enhanced production and preservation rather than limited dilution under saline lacustrine, oxygen-deprived, and well-stratified water column conditions. Regional investigations of the Es1 Member confirmed the widespread anoxia and deposition of organic-rich source rocks in the Bohai Bay Basin during the Oligocene.

Accumulation and Quantitative Assessment of Terrigenous Organic Matter in Upper Oligocene to Lower Miocene Marine Source Rocks of the Qiongdongnan Basin.

The intense collision between marine and terrestrial agents results in the dual-source (marine and terrigenous) characteristics of marine source rocks. Our research quantitatively assessed terrestrial organic matter and revealed the crucial role of terrestrial organic materials in the organic matter enrichment of lower Miocene to upper Oligocene marine source rocks in the Qiongdognnan Basin. The quantitative assessment was achieved using partial least-squares analysis with eight biomarker parameters associated with n-alkanes, isoprenoids, bicadinanes, taraxerane, tricyclic terpanes, and gammacerane. Differential unloading of terrestrial organic materials based on sedimentary facies of the delta-marginal sea system were observed through oleanane and bicadinane contents. It should be noted that the diagnostic ratio of oleanane was excluded from the quantitative analysis due to the dual influence from differential unloading and contact with seawater of the terrestrial organic materials. Calculation results show that the terrestrial organic matter was highest in the delta front at 70%, followed by prodelta at 59% and inner shallow marine at 57%. From the late Oligocene to the early Miocene, the proportion of terrestrial organic matter in marine source rocks continuously increased, with the highest average value observed in the second member of the Sanya Formation at 69% and the lowest occurring in the third member of the Lingshui Formation at 46%. Increasing terrestrial organic material inputs and preservation driven by the East Asian summer monsoon provided first-order control of the accumulation of organic carbon in the Qiongdongnan Basin during late Oligocene to early Miocene, rather than the bioproductivity of marine algae. The redox conditions of the water column determine the enrichment extent of organic matter.

Standardization parameters and synergism of source plant materials for the antidiabetic efficacy of the Rauvolfia-Citrus tea

The introduction of glucagon-like peptide 1 (GLP-1)-based therapies has greatly improved the management of type 2 diabetes (T2D), as they ensure good blood glucose control and promote weight loss. Ingestion of standardized herbal remedies that promote the same endogenous metabolic processes affected by the GLP-1-based treatments could provide cheaper alternatives in low- and middle-income countries, where there is currently an increase in the incidence of T2D. The focus in this study was to determine quality control parameters and the prime factors for the Rauvolfia-Citrus tea (RC-tea), as used in Nigerian traditional medicine to treat T2D. We have previously shown that the RC-tea that is made by boiling leaves of Rauvolfia vomitoria Afzel. and fruits of Citrus aurantium L. causes normalization of blood glucose and reduction of ectopic lipid accumulation in genetic diabetic (BKS-db) mice and in humans with T2D. The standardized RC-tea was made by boiling 40 g dried R. vomitoria foliage and 200 g fresh C. aurantium fruits per litre. The resulting golden-brown extract is free of microbial contamination, has pH 5 and contains ca. 230 mg naringin (marker compound for C. aurantium) and 25 mg robinin (marker compound for R. vomitoria) per litre. In addition, the herbal extract has the characteristic HPLC-DAD fingerprint where the marker compounds, naringin and robinin have retention times of approximately 26.3 min and 26.9 min, respectively, when using the outlined column and gradient elution conditions. Comparative evaluations of the antidiabetic effects of the standardized RC-tea and boiling water-extracts made with C. aurantium fruits alone (CA), R. vomitoria foliage alone (RV) and a combination of CA and RV, (CA + RV) in BKS-db mice, indicate that components from R. vomitoria foliage drive the reductions in ectopic lipid accumulation, since CA-treated mice lacked this effect. However, the normalization of blood glucose arises from combination of components from the two source plant materials as administration of either CA or RV resulted in hypoglycaemia. Interestingly, treatment with the CA + RV mixture, generated by mixing individually produced CA and RV plant extracts, resulted in hyperglycaemia, possibly due to drug-drug interactions of the blood glucose-reducing components in either plant extract. Hence, our data show that the best antidiabetic outcome results from the traditional practice of boiling R. vomitoria foliage and C. aurantium fruits together.

The simultaneous removal of technetium and iodine from Hanford tank waste

The simultaneous removal of radionuclides technetium-99 and iodine-129 from an actual decontaminated Hanford tank waste sample (a mixture of decontaminated waste from tanks 241-AP-105 and 241-AP-107) was demonstrated for the first time in this work. A series of commercially available ion exchange resins were evaluated in batch contact tests in the tank waste, and all showed removal of both Tc and I. The highest Tc removal from the tank waste was observed for Purolite A530e while the highest iodine removal was observed for ResinTech SIR-110-MP. Isotherm tests in simulated tank waste with these two resins showed that the SIR-110-HP-MP had consistently higher Kd for both pertechnetate and iodide; with much higher Kd than previous works on Tc removal from Hanford waste. As such, the SIR-110-MP was evaluated in a dual-column (lead/lag) test processing 5.2L of the tank waste mixture showing 50 % breakthrough of Tc on the lead column and no significant breakthrough on the lag after 641 bed volumes (BV, 6 mL size) while significant iodine breakthrough (>50 %) occurred after 28 BV. The limited iodine uptake was attributed to the column conditions generating mass transfer limitations. A fraction of the Tc and I was not captured by the resin (<10 %) in either the batch tests or column tests. The iodine fraction is not iodate and is likely organo-iodide. The fraction of the Tc was identified as a non-pertechnetate species which is the first time non-pertechnetate has been identified in AP-105 and AP-107 tanks. This non-pertechnetate fraction contained Tc(I) and for the first time a stable Tc(VI) species in Hanford waste was identified..

Axial-compression performance and numerical-simulation analysis of steel tube coal gangue concrete column

Coal gangue is a solid waste produced in the process of coal mining, excessive accumulation will occupy land and pollute the environment. It is one of the most effective means to realize comprehensive utilization of coal gangue by replacing some aggregates in concrete and applying it to engineering structures. In this paper, based on C30 concrete, by changing the replacement rate of coal gangue, slenderness ratio, and steel pipe wall thickness, 17 Coal gangue concrete-filled steel tubular (CGC-FST) columns were designed and made, and the axial compression tests were carried out. The results show that the failure mode of the CGC-FST column is similar to that of CFST, and the annular band shear buckling occurs on the wall of the steel pipe, and the higher the slenderness ratio, the more the number of buckling in the middle. With the increase of coal gangue substitution rate, the ultimate bearing capacity of the CGC-FST column decreases gradually, and the ductility of the specimen decreases slightly. The increase in slenderness ratio reduces the ultimate bearing capacity of the member, the failure form changes from material failure to stable failure, and the material properties are not fully utilized. The most obvious way to improve the bearing capacity and ductility of gangue steel tube members is to increase the steel content. Through the finite element simulation analysis of more working conditions of the CGC-FST column, the calculation formula of the bearing capacity of the CGC-FST column is fitted, which can effectively predict the bearing capacity of the CGC-FST column in a certain range.

Distinct oxygenation modes of the Gulf of Oman over the past 43 000 years – a multi-proxy approach

Abstract. Changing climatic conditions can shape the strength and extent of the oxygen minimum zone (OMZ). The presence and variability of the OMZ in the Arabian Sea is of importance to the latter's ecosystem. The state of oxygenation has, for instance, an impact on the pelagic and benthic faunal community or the nitrogen and carbon cycles. It is important to understand the dynamics of the OMZ and related marine environmental conditions because of their climate feedbacks. In this study, we combined three independent proxies to reconstruct the oxygenation state of the water column and bottom water in the Gulf of Oman for the past 43 kyr approximately. This multi-proxy approach is done for the first time at the northeastern Oman margin located in the Gulf of Oman. We used bulk sedimentary nitrogen isotopes (δ15N) and the alkane ratio (lycopane +n-C35)/n-C31 and benthic foraminiferal faunal analysis to reconstruct the strength of the OMZ in the water column and bottom water oxygenation, respectively. Our results show that the Gulf of Oman experienced strong pronounced OMZ and bottom water deoxygenation during the Holocene. In contrast, during Marine Isotope Stage 2 (MIS 2), including the Last Glacial Maximum (LGM), the Gulf of Oman was very well ventilated, with a highly diverse benthic foraminiferal community. This may have been caused by stronger wind-induced mixing and better ventilation by oxygen-rich water masses. Our results also show moderate oxygenation during MIS 3, with deoxygenation events during most of the warmer Dansgaard–Oeschger (D–O) events. We propose two distinct oxygenation modes for the Gulf of Oman: (1) a stable period of either strongly pronounced water column OMZ and bottom water deoxygenation or well-oxygenated water column and bottom water conditions and (2) an unstable period of oscillating oxygenation states between moderately oxygenated (stadials) and deoxygenated (interstadials, D–O events) conditions. The unstable period may be triggered by an interstadial Atlantic meridional overturning circulation (AMOC) mode, which is required to initiate D–O events.

Effects of pockmark activity on iron cycling and mineral composition in continental shelf sediments (southern Baltic Sea)

AbstractPockmarks are formed as a result of gas (methane) or/and groundwater outflow from the sea bottom. Methane, the second most important (after CO2) greenhouse gas, has a significant impact on biogeochemical processes in the bottom sediments by affecting the cycling of some elements, e.g. C, Fe, and S. Active pockmarks may also lead to changes in water column conditions by causing nutrients release from sediments. In the present study, we have focused on the impact of biogeochemical processes in pockmarks (methanogenesis, anaerobic methane oxidation, and groundwater seepage) on the transformation of iron (Fe) and the mineral composition of the sediment. In pore water, concentrations of hydrogen sulfide, phosphate, ammonia, sulfate, chloride, dissolved inorganic carbon, iron, and methane were analyzed. In the sediment, Fe speciation was performed using sequential extraction. The mineral composition was determined using powder X-Ray diffraction and scanning electron microscopy. The results from two pockmarks (with active gas seepage and groundwater infiltration) and two reference stations in the southern Baltic Sea show that geochemical conditions in pockmark sediments are significantly different from those in the typical muddy sea bottom. Pore water in pockmarks is characterized by lower sulfate and higher dissolved carbon concentrations as compared to areas of the seafloor where such structures are absent. This is due to the outflow of groundwater, which was confirmed by lower chloride concentration. In addition, sulfate is used to oxidize methane diffusing from deeper layers. Sediments in pockmarks are enriched in Fe(II) carbonates and depleted in Fe(III) (oxy)hydroxides, resulting from the anaerobic oxidation of methane with Fe(III) (Fe-AOM). Ferrous iron produced in large quantities during Fe-AOM is precipitated with carbonates.

Seismic performance and damage analysis of steel-PVA hybrid fiber cementitious composites encased CFST columns

Using axial compression ratio, core concrete strength, steel tube thickness, and SPC strength as research variables, cyclic loading tests were conducted on 12 steel-polyvinyl alcohol (PVA) hybrid fiber cementitious composites (SPC) encased concrete-filled steel tube（CFST）columns to study the seismic performance of specimens under earthquake action, including failure mode, strength, stiffness, ductility, energy dissipation, and second-order effects. According to the study's findings, fiber bridging enabled SPC-encased CFST columns to effectively prevent cracks and maintain high integrity even after failing. The axial compression ratio, core concrete strength, and lateral bearing capacity were positively correlated, with a maximum bearing capacity increase of 46.9%, but their deformation capacity had decreased to varying degrees. The thickness and SPC strength of the steel tube exhibited excellent performance in terms of deformation capacity and energy consumption, with a maximum ductility coefficient of 6.21. In the overall statistical analysis of research variables, it was found that composite columns with core concrete strength grades higher than outer SPC strength had better seismic performance compared to other specimens. This article proposed an improved Park-Ang damage model that effectively evaluates the damage status of SPC-encased CFST columns. The model complies with the boundary conditions of the composite column, and the damage development trend reflected is consistent with experimental phenomena.

Effects of herbivorous fish on shallow lake ecosystems increase at moderate nutrient conditions

Submerged macrophytes are vital in shallow lakes, as they provide critical ecosystem functions and services and can stabilize the clear-water conditions by various mechanisms. Nutrient enrichment reduces the resilience of macrophyte dominance in shallow lakes, thereby making them susceptible to shifts towards phytoplankton dominance following perturbations. Here, we conducted a mesocosm experiment to examine the individual and combined effects of nutrient enrichment and the addition of grass carp (Ctenopharyngodon idella) on the abundance of submerged macrophytes, epiphyton, and phytoplankton. We hypothesized that moderate nutrient enrichment facilitates macrophyte abundance, but also phytoplankton abundance after macrophyte removal by herbivorous fish. Our data showed that herbivory by grass carp could trigger a shift from macrophytes to algal dominance in mesocosms with moderate nutrient concentrations, but not in those with low nutrient concentrations. Moderate nutrient enrichment alone promoted submerged macrophyte growth, whereas the introduction of grass carp induced a collapse of submerged macrophytes regardless of nutrient conditions. Moreover, the introduction of grass carp showed more negative effects on light conditions of the water column in mesocosms with moderate nutrient concentrations compared to those with low nutrient concentrations. A recovery of submerged macrophytes might thus be limited by low light availability in lakes with moderate nutrient conditions suffering grass carp perturbation. Our results suggest that submerged macrophyte-dominated shallow lakes with moderate nutrient conditions are vulnerable to perturbation by herbivorous fish such as grass carp. In turn, managing the abundance of herbivores in these lakes can support the dominance of macrophytes and associated clear water conditions.

Mediterranean-like “fall dump” events in the Baltic Sea

In the Mediterranean Sea, organic carbon-rich sapropels have been deposited periodically over the last fifteen million years. Some sapropels are characterized by high contents of the mat-forming, planktonic diatom Pseudosolenia calcar-avis and the planktonic diatom Thalassionema nitzschioides as a result of their mass sinking in autumn (the so-called “fall dump”). The present study shows that fall dump events also occurred in the brackish Baltic Sea around 6300–5800 calibrated years before present (cal yr BP; present = AD 1950). In sediments from the northern Baltic Sea these events are evidenced by high contents of a lipid specific for P. calcar-avis (a C25:2 highly branched isoprenoid alkene) and corroborated by fossil remains of both P. calcar-avis and T. nitzschioides. A biomarker index based on long-chain alkyl diol lipids indicates that mat-forming Proboscia diatoms were also present. High contents of calanoid resting eggs further suggest that the copepod population was stressed being unable to feed on such large diatoms. The fall dump events occurred during a complete stratification of the water column and euxinic conditions, as reflected by the redox-sensitive trace metal uranium, allowing upward diffusion of nutrients and the growth of rhizosolenid mat-forming diatoms in a deep chlorophyll maximum. Synchronous remains of P. calcar-avis in the central Baltic Sea further suggest that these events occurred on a basin-wide scale.

Deep learning-based high performance liquid chromatography for food analysis

Abstract This paper presents a study on the determination of synthetic pigments using high performance liquid chromatography (HPLC) method combined. A retention value qualitative approach, combined with an uncertainty assessment algorithm for the determination of pigment content, was used for the simultaneous determination of nine synthetic pigments, namely, lemon yellow, amaranthine red, indigo, carmine, sunset yellow, brilliant blue, seductive red, erythrosine, and seductive red, in foodstuffs by reversed-phase high-performance liquid chromatography (RP-HPLC). The sample pretreatment method was optimized, and the chromatographic conditions were set to investigate the UV determination wavelength, mobile phase, column temperature, and wavelength of synthetic pigments. Under the same mobile phase and column conditions, the results indicated that the components’ retention times did not significantly fluctuate with the change in column temperature. The results showed that the chromatographic response signals of lemon yellow, sunset yellow and seductive red were higher at the UV determination wavelength of 254 nm, so 254 nm was finally determined as the UV detection wavelength in this experiment. Mobile phase A: methanol, B: ammonium acetate (0.02mo/L) using gradient elution, the separation degree R&gt;1.5, and the symmetry and stability of the chromatogram were better. The separation of the components was good, and the peak shape was sharp and symmetric when the column temperature was 35 ℃, so the column temperature was chosen to be 35 ℃, and the establishment of the chromatographic conditions was thus completed.

Nitrogen isotopes and geochemistry of the basal Datangpo Formation: Contrasting redox conditions in the upper and lower water columns during the Cryogenian interglaciation period

The late Neoproterozoic witnessed series of remarkable geological evolutions, including the Sturtian and Marinoan glaciation events during the Cryogenian. A stratified oceanic redox structure has been proposed for this period, and the dynamics of the deep water redox conditions have been well illustrated by trace metals and their isotopes. However, variations in the redox conditions of the upper water column have received much less attention. Sedimentary nitrogen isotopes (δ15N) are critical for reconstructing the redox conditions in the upper water columns of ancient oceans. Existing research on the N cycle during the Cryogenian period is scarce, and the majority of studied samples were collected from shallow and medium water depth facies. To address this paucity of studies, we conducted a high-resolution N isotope study in combination with Fe speciation and Mo concentration data from two deep-water sections of black shales in the basal Datangpo Formation in the Nanhua Basin, a typical organic-rich stratum deposited during the Cryogenian interglaciation period. While the trace metal proxies suggest a fluctuating euxinic–ferruginous bottom water column for the lower interval and a stable euxinic bottom water column for the upper interval, the redox conditions of the upper water column were relatively stable, as indicated by minimal changes in the recorded δ15N values. Furthermore, the δ15N values of black shales in the basal Datangpo Formation of the Nanhua Basin have a limited range (3.1‰ − 5.8‰, average of 4.3‰, standard deviation (SD) = 0.5‰, n = 104) and show no water-depth gradient, indicating the presence of a relatively large and stable nitrate reservoir and a deep redox chemocline in the Nanhua Basin. The characteristic of the nitrate reservoir reflected by these δ15N signals can be roughly analogized to the global interglacial ocean, although only the counterpart northeast Svalbard can be used for comparison. Therefore, the nitrate availability in the marine water column may have had little effect on animal radiation during the Cryogenian interglacial period. These findings help to clarify the N cycle in the Cryogenian Nanhua Basin and shed light on its significance on bioevolution.

Removal of Diclofenac and Heavy Metal Ions from Aqueous Media Using Composite Sorbents in Dynamic Conditions.

Pharmaceuticals and heavy metals pose significant risks to human health and aquatic ecosystems, necessitating their removal from water and wastewater. A promising alternative for this purpose involves their removal by adsorption on composite sorbents prepared using a conventional layer-by-layer (LbL) method or an innovative coacervate direct deposition approach. In this study, four novel composite materials based on a silica core (IS) and a polyelectrolyte coacervate shell were used for the investigation of dynamic adsorption of three heavy metals (lead, nickel and cadmium) and an organic drug model (diclofenac sodium salt, DCF-Na). The four types of composite sorbents were tested for the first time in dynamic conditions (columns with continuous flow), and the column conditions were similar to those used in wastewater treatment plants. The influence of the polyanion nature (poly(acrylic acid) (PAA) vs. poly(sodium methacrylate) (PMAA)), maintaining a constant poly(ethyleneimine) (PEI), and the cross-linking degree (r = 0.1 and r = 1.0) of PEI chains on the immobilization of these pollutants (inorganic vs. organic) on the same type of composite was also studied. The experiments involved both single- and multi-component aqueous solutions. The kinetics of the dynamic adsorption process were examined using two non-linear models: the Thomas and Yoon-Nelson models. The tested sorbents demonstrated good adsorption capacities with affinities for the metal ions in the following order: Pb2+ > Cd2+ > Ni2+. An increase in the initial diclofenac sodium concentration led to an enhanced adsorption capacity of the IS/(PEI-PAA)c-r1 sorbent. The calculated sorption capacities were in good agreement with the adsorption capacity predicted by the Thomas and Yoon-Nelson models. The substantial affinity observed between DCF-Na and a column containing composite microparticles saturated with heavy metal ions was explained.