Organic Flux Research Articles

Deep sea paleoceanographic changes in the Southeastern Pacific over the last ~400 kyr and its linkage to the Antarctic Circumpolar Current and Patagonian Ice Sheet

Antarctic Intermediate Water (AAIW) plays a significant role in transporting large volumes of relatively cool water masses to low latitudes and modulating climate. This study investigates the deep sea paleoceanographic evolution of the Southeastern Pacific Ocean (SEP) and the influence of the Patagonian Ice Sheet (PIS) and Antarctic Circumpolar Current (ACC) dynamics in modulating Antarctic Intermediate Water (AAIW) formation. Sediment core samples from International Ocean Discovery Program (IODP) Site U1542, located at ~1100 m deep on the Chilean margin, and under the influence of AAIW, were analysed for benthic foraminifera assemblages, surface productivity, and major minerals to achieve the objectives. Six benthic foraminifera biofacies are delineated using multivariate analyses, suggesting changes in bottom water conditions related to oxygenation and organic flux. Changes in biofacies suggest a change from well-ventilated bottom water with an intermediate flux of organic matter in the SEP from ~400 to 240 ka, followed by a reduction in bottom water oxygenation coupled with higher nutrient and organic flux from ~240 ka through the Holocene, except for a short interval of low productivity and increased ventilation from ~130 to 110 ka. PIS expansion and contraction control the nutrient flux and extent of ACC in the SEP, which modulates the formation of AAIW during various glacial-interglacial periods. ACC variability proxies show a ~ 100 kyr cycle as observed in the Asian monsoon records, whereas SEP bottom water characteristic variability show 44 kyr obliquity cycle, supporting the role of the Southern Ocean in modifying marine carbon reservoirs by influencing AAIW production.

Flux synthesis of two-dimensional covalent organic frameworks.

Covalent organic frameworks (COFs) are crystalline porous polymers constructed from organic building blocks into ordered two- or three-dimensional networks through dynamic covalent bonds. Attributed to their high porosity, well-defined structure, tailored functionality and excellent chemical stability, COFs have been considered ideal sorbents for various separation applications. The synthesis of COFs mainly employs the solvothermal method, which usually requires organic solvents in sealed Pyrex tubes, resulting in unscalable powdery products and environmental pollution that seriously limits their practical applications. Herein, our protocol focuses on an emerging synthesis method for COFs based on organic flux synthesis without adding solvents. The generality of this synthesis protocol has been applied in preparing various types of COFs, including olefin-linked, imide-linked, Schiff-based COFs on both gram and kilogram scales. Furthermore, organic flux synthesis avoids the disadvantages of solvothermal synthesis and enhances the crystallization and porosity of COFs. Typically, COF synthesis takes 3-5 d to complete, and subsequent washing procedures leading to pure COFs need 1 d. The procedure for kilogram-scale production of COFs with commercially available monomers is also provided. The resulting COFs are suitable for separation applications, particularly as adsorbent materials for industrial gas separation and water treatment applications. The protocol is suited for users with prior expertise in the synthesis of inorganic materials and porous organic materials.

Synthetic Leaves Based on Crystalline Olefin-Linked Covalent Organic Frameworks for Efficient CO2 Photoreduction with Water.

We report, for the first time, a new synthetic strategy for the preparation of crystalline two-dimensional olefin-linked covalent organic frameworks (COFs) based on aldol condensation between benzodifurandione and aromatic aldehydes. Olefin-linked COFs can be facilely crystallized through either a pyridine-promoted solvothermal process or a benzoic anhydride-mediated organic flux synthesis. The resultant COF leaf with high in-plane π-conjugation exhibits efficient visible-light-driven photoreduction of carbon dioxide (CO2) with water (H2O) in the absence of any photosensitizer, sacrificial agents, or cocatalysts. The production rate of carbon monoxide (CO) reaches as high as 158.1 μmol g-1 h-1 with near 100% CO selectivity, which is accompanied by the oxidation of H2O to oxygen. Both theoretical and experimental results confirm that the key lies in achieving exceptional photoinduced charge separation and low exciton binding. We anticipate that our findings will facilitate new possibilities for the development of semiconducting COFs with structural diversity and functional variability.

Sustainable and Rapid Water Purification at the Confined Hydrogel Interface.

Emerging organic contaminants in water matrices have challenged ecosystems and human health safety. Persulfate-based advanced oxidation processes (PS-AOPs) have attracted much attention as they address potential water purification challenges. However, overcoming the mass transfer constraint and the catalyst's inherent site agglomeration in the heterogeneous system remains urgent. Herein, the abundant metal-anchored loading (≈6-8g m-2) of alginate hydrogel membranes coupled with cross-flow mode as an efficient strategy for water purification applications is proposed. The organic flux of the confined hydrogel interfaces sharply enlarges with the reduction of the thickness of the boundary layer via the pressure field. The normalized property of the system displays a remarkable organic (sulfonamides) elimination rate of 4.87 × 104mg min-1 mol-1. Furthermore, due to the fast reaction time (<1min), cross-flow mode only reaches a meager energy cost (≈2.21Wh m-3) under the pressure drive field. It is anticipated that this finding provides insight into the novel design with ultrafast organic removal performance and low techno-economic cost (i.e., energy operation cost, material, and reagent cost) for the field of water purification under various PS-AOPs challenging scenarios.

Organic flux synthesis of covalent organic frameworks

Organic flux synthesis of covalent organic frameworks

Microplastics decrease the toxicity of cadmium to methane production from anaerobic digestion of sewage sludge

Microplastics (MPs) and Cd have been proven to inhibit methane production from anaerobic digestion of sewage sludge. However, the published studies mainly focused on their single inhibition. This cannot reflect the real-world situations where MPs and Cd co-exist. This study therefore aims to reveal the combined effect of MPs and Cd on anaerobic digestion of sewage sludge. Experimental results showed that PVC-MPs at environmentally relevant levels (e.g., 1, 10 particles/g total solids (TS)) did not affect methane yield but decrease the toxicity of Cd. When PVC-MPs were 30 particles/g TS, the cumulative methane production recovered from 58.8 % (in the presence of 5 mg Cd/g TS) to 89.7 % of the control. Organic fluxes were significantly increased compared with the control, particularly affecting the content of dissolved substances and short-chain fatty acids during anaerobic digestion. Mechanistic exploration showed that the adsorption of Cd by PVC-MPs was higher than that of sludge-substrate, which reduced the bioavailability of Cd by anaerobes, as evidenced by the increased anaerobes driven carbon flux from solid-phase to bio-methane during anaerobic digestion. Overall, these findings identified important factors in determining the toxicity of pollutants on anaerobic digestion process, providing precise data for toxicity evaluation of MPs and metals in anaerobic environment.

The role of anaerobic methane oxidation on the carbonate authigenesis in sediments of the subtropical Beibu Gulf, South China Sea: A reactive–transport modelling approach

The formation and burial of authigenic carbonate in marine sediment significantly affect the sedimentary carbon cycle and its isotopic mass balance in geological history. Anaerobic oxidation of methane (AOM) is the primary driver of authigenic carbonate precipitation within the sulfate-methane transition zone (SMTZ). Quantitative estimations of the role of AOM on the authigenic carbonate precipitation and its carbon isotope under non-steady-state processes (e.g., changes in methane fluxes at the bottom sediment, sedimentation rates or organic fluxes in the surface sediment), however, are still limited. In this study, we use geochemical data from porewater (e.g., the concentration of sulfate, calcium, magnesium, strontium, dissolved inorganic carbon, total alkalinity) and solid sediment (e.g., organic matter content, and carbonate content) in different depositional environments of the subtropical Beibu Gulf, South China Sea, combined with a diagenetic reactive-transport modelling approach, to estimate the mineralogy of authigenic carbonate, the relationship between AOM and authigenic carbonate precipitation, and the impact of AOM rate on carbon isotope of sediment carbonate (δ13CCar). The results show that high-Mg carbonates (high-Mg calcite and dolomite) are the main type of authigenic carbonate (∼80%) formed in the methane-bearing sediments, leading to higher porewater Sr2+/Ca2+ (>0.02) and Mg2+/Ca2+ (>20) within the SMTZ. Our modelling analysis highlights that the non-steady-state induced by increased methane flux from the underlying sediments can significantly accelerate the authigenic carbonates formation within the SMTZ. Using parametric sensitivity analysis, we observed that even a 1% increase in the authigenic carbonate fraction of sediment carbonates results in significant changes in δ13CCar within the SMTZ (from −1‰ to −2‰), mainly due to lighter carbon isotopes produced by more intensive AOM processes. Noteworthily, the terrestrial-to-marine transition was identified by the sediment and porewater geochemical profiles at site SO-8. Although lower authigenic carbonate precipitation occurs in terrestrial sedimentary environments, the proportion of authigenic carbonate in terrestrial environments (11%) is much higher than that in marine environments (1%), resulting in carbon isotopes of carbonate in terrestrial sediments becoming more negative (−5‰).

Strong Dynamics in Tidal Marsh DOC Export in Response to Natural Cycles and Episodic Events From Continuous Monitoring

AbstractThe role of tidal wetlands as hotspots for carbon and nutrient exchange with adjacent waters has been well documented, but large uncertainties remain regarding the physical and biogeochemical controls on these fluxes, which have significant implications for coastal carbon cycling and budgets. This study elucidates the variability in lateral wetland dissolved organic (DOC) fluxes tidally, seasonally, and during extreme weather events for a brackish wetland within a sub‐estuary of the northwestern Chesapeake Bay, USA. Continuous fluxes from the wetland‐draining tidal creek were calculated based on DOC concentrations ([DOC]) estimated using optical and physicochemical properties measured in situ with concurrent water flow data. Mean export was found to be 8.59 (±1.20) kg C (n = 1,128) tidal cycle−1 and annual flux from the wetland to sub‐estuary was 200.66 (±28.09) g C m−2 yr−1. Peaks in DOC flux were associated with Hurricane Joaquin in 2015, where just two tidal cycles accounted for ∼5% of annual export. Analysis of tidal creek water quality measurements reveal seasonal and tidal dependencies. Highest [DOC] and largest low versus high tide differences were observed in summer, corresponding to more fresh plant biomass and its mobilization, consistent with results from Fourier transform ion cyclotron resonance mass spectrometry. Despite summer highs in tidal creek [DOC], monthly DOC fluxes were greatest in early fall due to higher water flows. The annual flux presented here is higher than fluxes previously reported for this system, highlighting the importance of continuous measurements for monitoring carbon export under a wide range of environmental conditions.

Influence of modern environmental gradients on foraminiferal faunas in the inner Kongsfjorden (Svalbard)

Kongsfjorden (Svalbard archipelago) is subjected to strong environmental gradients creating high physical and geochemical stress on benthic faunas. The present study aims at understanding the environmental drivers governing benthic foraminifera in the innermost part of the fjord. Surface sediments from 9 stations were sampled during August 2018 along a transect starting at ca. 2 km from the tidewater glacier Kronebreen and ending 12 km seaward. Three biozones were identified in response to disturbances linked to the proximity of the Kronebreen front (i.e., high water turbidity, freshwater, and sediment inputs, reduced organic fluxes). Close to the terminus (proximal biozone), few stress-tolerant and glacier proximal species were present (i.e., Capsammina bowmanni and Cassidulina reniforme). At about 6–8 km from the front (medial biozone), reduced turbidity, and increased organic fluxes, resulted in a higher diversity, and a high abundance of the phytodetritus-indicator Nonionellina labradorica. Relatively high diversity persisted until 12 km from the front due to higher organic inputs and reduced stressful conditions. The distal biozone was dominated by the Atlantic Water (AW) indicator Adercotryma glomeratum, in coherence with the presence of warm and salty AW detected far inside the fjord. Physical stress related to the glacier dynamics appears to favour the establishment of opportunistic species close to the terminus, whereas reduced disturbance away from the glacier induces the establishment of diverse assemblages. Our results show that benthic foraminifera may be effective bioindicators to monitor the long-term retreat of tidewater glaciers induced by climate change in Kongsfjorden.

Volatile organic compound fluxes over a winter wheat field by PTR-Qi-TOF-MS and eddy covariance

Abstract. Volatile organic compounds (VOCs) contribute to air pollution through the formation of secondary aerosols and ozone and extend the lifetime of methane in the atmosphere. Tropospheric VOCs originate to 90 % from biogenic sources on a global scale, mainly from forests. Crops are also a potentially large yet poorly characterized source of VOCs (30 % of the VOC emissions in Europe, mostly oxygenated). In this study, we investigated VOC fluxes over a winter wheat field by eddy covariance using a PTR-Qi-TOF-MS with high sensitivity and mass resolution. The study took place near Paris over a 5-week period and included flowering, crop maturity and senescence. We found a total of 123 VOCs with fluxes 3 times above the detection limit. Methanol was the most emitted compound with an average flux of 63 µg m−2 h−1, representing about 52 % of summed VOC emissions on a molar basis (36 % on a mass basis). We also identified ethanol, acetone, acetaldehyde and dimethyl sulfide among the six most emitted compounds. The third most emitted VOC corresponded to the ion m/z 93.033. It was tentatively identified as furan (C6H4O), a compound not previously reported to be strongly emitted by crops. The average summed VOC emissions were about 173 ± 6 µg m2 h−1, while the average VOC depositions were about 109 ± 2 µg m−2 h−1 and hence 63 % of the VOC emissions on a mass basis. The net ecosystem flux of VOCs was an emission of 64 ± 6 µg m−2 h−1 (0.5 ± 0.05 nmol m−2 s−1). The most deposited VOCs were identified as hydroxyacetone, acetic acid and fragments of oxidized VOCs. Overall, our results reveal that wheat fields represent a non-negligible source and sink of VOCs to be considered in regional VOC budgets and underline the usefulness and limitations of eddy covariance measurements with a PTR-Qi-TOF-MS.

Foraminifera of the Faneromeni section (Crete, Greece) reflect the palaeoenvironmental development towards the Messinian salinity crisis

A severe phase of disturbance around 7.17 Ma initiated an ongoing development towards the Messinian salinity crisis (MSC) of the Mediterranean. We present foraminiferal data from the Faneromeni section on Crete to understand how the astronomical cyclicity and the restriction phase starting at 7.17 Ma were reflected in a succession that was deposited on the continental shelf and characterized by a precession-dominated alternation of organic-enriched grey marls and sapropels and light-coloured homogeneous marls. Benthic and planktic abundance data show that the foraminifera are closely associated with precessional cyclicity. Similar as in other Mediterranean sections, the 7.17 Ma shift in benthic assemblages is sedimentologically expressed by the occurrence of the first distinct sapropel (Faneromeni cycle F18). At this level, throughout the Mediterranean a group of open marine benthic species intolerant to oxygen stress abruptly decreased in abundance with several species disappearing at or shortly after 7.17 Ma. These species were replaced by species indicating increasing stress, implying decreasing oxygen content of the bottom waters after 7.17 Ma. The data further suggests that sapropelic sediments dominated by Bolivina dilatata/spathulata were deposited under hypoxic conditions, rather than under continuous organic flux. Our data reflects a second step in the restriction of the Mediterranean between 6.8 and 6.7 Ma, indicated by decreasing benthic diversity and increasing abundances of planktic and benthic taxa considered tolerant of hypersalinity. An increase in water salinity has been suggested before, and if true, appears to have affected the bottom waters and the surface waters around the same time.

Uptake of PCBs into sediment dwellers and trophic transfer in relation to sediment conditions in the Salish Sea

We examined uptake of polychlorinated biphenyls (PCBs) into various marine sediment feeders relative to physical and geochemical factors and transfer to higher trophic levels. PCBs exceeding Canadian Council Ministers of the Environment Guidelines by 6–55× were found in industrialized harbours and some near-outfall sediments, indicating ongoing land input. Sediment PCBs were correlated with organic flux and content. Tissue PCBs were &gt;10× sediment PCBs in all samples and highest in Victoria Harbour infauna, suggesting considerable uptake from these extremely contaminated, organically enriched, chronically disturbed sediments. Sediment PCBs were the primary predictor of tissue lipid PCBs followed by %fines. This results in generally higher tissue PCBs in more depositional regions. The lipid/sediment PCBs (uptake rate) declined with increasing sediment PCBs, acid volatile sulfides and benthos biomass turnover. PCB homologue composition did not change with uptake from sediments or at higher trophic levels, suggesting minimal metabolization in tissues. Trophic bio-magnification occurs since lipid PCBs were 2–100× higher in seal blubber than sediment feeders. PCBs were compared with polybrominated diphenyl ethers (PBDEs) for the same samples. PCBs were highest in industrialized harbours, whereas PBDEs were elevated in harbours but highest near wastewater discharges. This reflects differences in usage history, sediment dynamics, and affinities. PCBs appear to be more bio-accumulative and persistent at higher trophic levels than PBDEs.

The 4GFOR model – Coupling 4G early diagenesis and benthic foraminiferal ecology

The 4GFOR model presented in this paper combines the OMEXDIA model of Soetaert et al. (1996) with four theoretical species of benthic foraminifera. The geochemical part of the model simulates the succession of early diagenetic redox reactions in the superficial sediment layers. The four theoretical foraminiferal species, each representing a group of biological species with comparable microhabitats, differ by their limitations with respect to oxygen and nitrate concentration and their ability to feed on different organic matter types. The foraminiferal model is a transformation model in which different proportions of four types of organic matter with different reactivity are attributed to each of the theoretical species. The model has been manually tuned and tested on a large data set from two stations, at 1000 and 550 m depth, in the Bay of Biscay. The model adequately simulates the vertical distribution of shallow, intermediate and deep infaunal species. The 4GFOR model can be used to test several hypotheses concerning foraminiferal ecology. The model has already allowed us to conclude that it is high unlikely that shallow infaunal taxa feed exclusively on the most labile part of the organic matter flux, since it was unable to reproduce the field observations while using this hypothesis. Another important conclusion based on our preliminary model results is that the absence of deep infaunal taxa close to the sediment surface may be explained by their decreasing competitiveness in well oxygenated environments. In the future, the inversion of the 4GFOR model may yield a powerful paleoceanographic tool, enabling us to reconstruct major limiting environmental factors (oxygen and nitrate concentrations; quantity and quality of the organic flux to the ocean floor) from benthic foraminiferal assemblage data.

Separation of tomato aroma compounds from binary model solutions using PEBA and EPDM membranes in pervaporation: Comparison of membranes performance and investigation of temperature effect

AbstractThe pervaporation separation of four important aroma compounds of tomato juice (1‐hexanol, hexanal, 2‐heptenal, and 6‐methyl‐5‐hepten‐2‐one) was investigated. Ethylene propylene diene monomer (EPDM) and polyether block amide (PEBA) membranes were fabricated and applied to treat binary model solutions containing one of the aroma compounds in water. Results showed that at 25°C, PEBA membrane had higher total flux, organic flux, and pervaporation separation index (PSI) than EPDM membrane, while EPDM performed better in terms of separation factor. For PEBA, the highest total flux (395.93 g/m2hr) was observed in separating 1‐hexanol, and for EPDM, the highest total flux (116.82 g/m2hr) was seen in treating 6‐methyl‐5‐hepten‐2‐one/water at 25°C. Furthermore, the impact of feed temperature on pervaporation performance was investigated. A rise from 25 to 45°C increased the total and organic fluxes for both of the membranes. The separation factors of PEBA and EPDM changed differently with temperature; higher temperatures led to improved separation factor for PEBA and reduced separation factor for EPDM. Moreover, increased feed temperature improved PSI for both membranes, while the change was more significant for PEBA.Practical applicationsIn this study, for the first time, tomato aroma compounds have been separated from their aqueous solutions in a pervaporation process. The findings obtained by the present research can be employed by any plant which processes tomato enabling them the use of aroma compounds in order to reach value added products and therefore increase worth of processing outputs.

Foraminiferal stratigraphy and paleoenvironments of a high latitude marginal marine basin – A Late Cretaceous record from IODP Site U1512 (Great Australian Bight)

The 690 m core recovered at IODP Site U1512 offers unparalleled insights into climate during the peak and demise of the Cretaceous hothouse from the southern high latitudes. A new high-resolution micropaleontological record (notably deep water agglutinated foraminifera, DWAF) combined with additional geochemical data was produced from this locality, with the goal of recognizing benthic foraminiferal biozones, their relationship to the Tethyan realm and associated paleoenvironmental changes.We document a diverse benthic foraminiferal assemblage consisting of 162 taxa (110 agglutinated and 52 calcareous). The most common elements of the DWAF assemblage are tubular (i.e., Kalamopsis grzybowskii, Bathysiphon spp.) and planispiral forms (i.e., Ammodiscus spp., Haplophragmoides spp., Buzasina sp., Labrospira spp.). The Turonian strata yield abundant Bulbobaculites problematicus and Spiroplectammina navarroana. The presence of Uvigerinammina jankoi provides a tie point to the Tethyan DWAF biozonation of Geroch and Nowak (1984). The calcareous foraminiferal assemblage is composed of cosmopolitan deep-water forms including Lenticulina, Dentalina, Gavelinella/Anomalinoides, Praebulimina and Pseudobolivina.Organic geochemical data (notably steranes/hopanes ratios), foraminiferal assemblages, together with an increasing abundance of radiolaria reveal a complex and constantly changing marginal marine paleoenvironment. The prevailing regime (oxic or dysoxic, marine, or terrestrially influenced) was strongly influenced by paleobathymetry, unstable oceanic circulation and terrestrial runoff. These factors caused the paleoenvironment to change five times over 10 million years, each lasting <2 Ma. A major increase in the abundance of radiolaria (>50%) after the mid-Turonian followed a peak in the abundance of tubular epifaunal foraminifera during the lower to mid-Turonian. This is possibly related to an increase in bathymetry, that could correspond to a preceding sea level lowstand, and associated changes in ocean chemistry, such as changes in organic flux or salinity. Foraminiferal and geochemical evidence from Site U1512 allow for far-reaching interpretations of the paleoenvironments of the Great Australian Bight during the Late Cretaceous.

Ross Sea Benthic Ecosystems: Macro- and Mega-faunal Community Patterns From a Multi-environment Survey

The Ross Sea, Antarctica, is amongst the least human-impacted marine environments, and the site of the world’s largest Marine Protected Area. We present research on two components of the Ross Sea benthic fauna: mega-epifauna, and macro-infauna, sampled using video and multicore, respectively, on the continental shelf and in previously unsampled habitats on the northern continental slope and abyssal plain. We describe physical habitat characteristics and community composition, in terms of faunal diversity, abundance, and functional traits, and compare similarities within and between habitats. We also examine relationships between faunal distributions and ice cover and productivity, using summaries of satellite-derived data over the decade prior to our sampling. Clear differences in seafloor characteristics and communities were noted between environments. Seafloor substrates were more diverse on the Slope and Abyss, while taxa were generally more diverse on the Shelf. Mega-epifauna were predominantly suspension feeders across the Shelf and Slope, with deposit feeder-grazers found in higher or equal abundances in the Abyss. In contrast, suspension feeders were the least common macro-infaunal feeding type on the Shelf and Slope. Concordance between the mega-epifauna and macro-infauna data suggests that non-destructive video sampling of mega-epifauna can be used to indicate likely composition of macro-infauna, at larger spatial scales, at least. Primary productivity, seabed organic flux, and sea ice concentrations, and their variability over time, were important structuring factors for both community types. This illustrates the importance of better understanding bentho-pelagic coupling and incorporating this in biogeographic and process-distribution models, to enable meaningful predictions of how these ecosystems may be impacted by projected environmental changes. This study has enhanced our understanding of the distributions and functions of seabed habitats and fauna inside and outside the Ross Sea MPA boundaries, expanding the baseline dataset against which the success of the MPA, as well as variability and change in benthic communities can be evaluated longer term.

Periodic oceanic euxinia and terrestrial fluxes linked to astronomical forcing during the Late Devonian Frasnian–Famennian mass extinction

Oceanic anoxia is considered as the immediate cause of the Frasnian–Famennian mass extinction, yet the frequency of anoxia and associated environmental modulators remains unknown. Here, we demonstrate that astronomical forcing paced oceanic anoxic episodes by mediating land-ocean interactions during the Upper Kellwasser (UKW) Event, using an ultra-high-resolution (one centimeter spacing), multi-proxy geochemical profile of a UKW interval from the Upper Devonian Chattanooga Shale of Tennessee, USA. Organic and inorganic geochemical indices for oceanic anoxia/euxinia, marine primary productivity, terrestrial plant/soil inputs, and clastic sediment inputs show synchronous fluctuations that were paced by the Earth's orbital precession. This study provides the first mechanistic evidence linking the periodicity of Late Devonian oceanic euxinia to astronomical forcing and identifies terrestrial-to-marine inorganic and organic fluxes as the driver of this linkage. These results suggest that astronomical forcing modulated the expression of environmental stressors that led to the Frasnian–Famennian mass extinction.

Development of portable device for measurement of dynamic and static light-emission WOLED characteristics

The research object of this work is the parameters of organic light-emitting diodes, namely power and luminous flux. Determination of these parameters can be carried out using a photodiode and requires measuring the dark current of the sensor (photodiode), measuring the current of the photodiode when illuminated by the LED under investigation. And also take into account the relationship between the light flux received by the sensor and its output current, and take into account the spectral characteristics of the sensor. Calculate the investigated parameters of the LED based on the measurements. Carrying out these measurements requires laboratory instruments and workplace organization, and further calculations are routine work. It is possible to increase the measurement accuracy by improving the existing methods for measuring the required parameters, and it is possible to automate the process of measurements and calculations using a modern microprocessor radioelement base. Microcontrollers are widespread such radioelements. They have the necessary peripherals for independent operation and have sufficient computing power to implement the required measuring device. Its application makes it possible to automate the measurement process, carry out the necessary calculations, save correction constants, accumulate and process the obtained data, analyze these received data, exchange data with a computer, etc. So, the work is aimed at developing a methodology that will allow the simultaneous measurement of power and luminous flux of planar light sources. And also on the feasibility of this technique in the device and software with the ability to measure the power of the light source in an arbitrary band of the spectral visible range. Thus, it is possible to determine what power in watts a light source emits with the dynamics of supply currents in the optical bands, knowing the spectrum of this source without using glass filters. So, the result of applying the technique is to determine the power of light radiation (in watts) or the luminous flux (in lumens) of the emitter (light sources).

The contribution of water radiolysis to marine sedimentary life

Water radiolysis continuously produces H2 and oxidized chemicals in wet sediment and rock. Radiolytic H2 has been identified as the primary electron donor (food) for microorganisms in continental aquifers kilometers below Earth’s surface. Radiolytic products may also be significant for sustaining life in subseafloor sediment and subsurface environments of other planets. However, the extent to which most subsurface ecosystems rely on radiolytic products has been poorly constrained, due to incomplete understanding of radiolytic chemical yields in natural environments. Here we show that all common marine sediment types catalyse radiolytic H2 production, amplifying yields by up to 27X relative to pure water. In electron equivalents, the global rate of radiolytic H2 production in marine sediment appears to be 1-2% of the global organic flux to the seafloor. However, most organic matter is consumed at or near the seafloor, whereas radiolytic H2 is produced at all sediment depths. Comparison of radiolytic H2 consumption rates to organic oxidation rates suggests that water radiolysis is the principal source of biologically accessible energy for microbial communities in marine sediment older than a few million years. Where water permeates similarly catalytic material on other worlds, life may also be sustained by water radiolysis.

Orbital and millennial-scale environmental and hydrological changes of the central Okhotsk Sea over the last 136 kyr inferred from micropaleontological (radiolarian and benthic foraminifera), geochemical and lithological proxies and the mechanisms responsible for them

The response of benthic foraminifera (BF) and radiolarian production in the central Okhotsk Sea (OS) to orbital and millennial changes of climate and environment over the last 136 kyr have been studied on the basis of the sediment core PC-7R, with available productivity, geochemical and lithological records and a modified age model. We used the calculated accumulation rate of microfossils (AR, fluxes) of the main ecological groups and species indicative of radiolarians and of BF as quantity responses in their production, which is related to environmental and hydrological changes of the water column and surface sediment in the central OS and to global and regional climate changes. The responses of the opportunistic BF Alabaminella weddellensis and the suboxic group during the last 136 kyr were mostly related to changes in organic fluxes from the surface, sea ice cover and surface sediment oxygenation at both orbital and millennial time scales. The AR of radiolarians from the surface, dichothermal and mesopelagic groups significantly differed from the AR of BF. The AR has a maximum during the middle and late Marine Isotope Stage 5e and lower values during the earlier Holocene, while the minimum happened during cold Marine Isotope Stages 6, 4 and 2 with maximal ventilation of OS intermediate water. Production of the mesopelagic radiolarian Cycladophora davisiana in the OS was mostly related to the lateral delivery of terrigenous material and OM into the water column from the northwestern shelf and/or from the western subarctic Pacific. Due to the sensitivity of marine organisms to environmental conditions, the production of radiolarians and BF sharply changed with the extinction of Amphimelissa setosa, since Heinrich Stadial 8 is related to the termination of global environment cooling and the hydrology changes of the early last glacial.