Anthropogenic CO2 Research Articles

Anthropogenic CO2 in the Philippine Sea, northwestern Pacific: Distribution, storage, and decadal variations

The Philippine Sea, a deep tropical/subtropical marginal sea in the northwestern Pacific, is influenced by the Kuroshio Current in the west and the Kuroshio Recirculation (KR) in the north. In this study, the seawater carbonate system and related parameters were investigated along 130°/136°E and 21°N transects across the Philippine Sea in 2018–2019, and the inventory of anthropogenic CO2 (CANT) was investigated with details. Results showed that the CANT inventory had a maximum value of 38.8 ± 0.6 mol m−2 at 25°−30°N (KR zone) and decreased southward to 27.8 ± 2.5 mol m−2 at 8°−15°N (tropical zone). In the tropical zone, more than 82% of the CANT inventory was input from extra-tropics through ocean transportation. On a decadal scale, the CANT inventory increased by 0.95 ± 0.10 mol m−2 yr−1 in the KR zone during the 2010s, which is 40% higher than that between 1994 and 2007 (∼0.68 mol m−2 yr−1). This acceleration is also higher than that predicted solely on the basis of increased atmospheric CO2. In the tropical zone, however, the CANT inventory increased by 0.59 ± 0.08 mol m−2 yr−1 during the 2010s, which is similar to the rate between 1994 and 2007 (∼0.54 mol m−2 yr−1). This new high-quality dataset of carbonate system parameters could help the future quantification of the oceanic CANT inventory by increasing spatiotemporal resolution in the Philippine Sea.

Estimating Global Anthropogenic CO2 Gridded Emissions Using a Data-Driven Stacked Random Forest Regression Model

The accurate estimation of anthropogenic carbon emissions is of great significance for understanding the global carbon cycle and guides the setting and implementation of global climate policy and CO2 emission-reduction goals. This study built a data-driven stacked random forest regression model for estimating gridded global fossil fuel CO2 emissions. The driving variables include the annual features of column-averaged CO2 dry-air mole fraction (XCO2) anomalies based on their ecofloristic zone, night-time light data from the Visible Infrared Imaging Radiometer Suite (VIIRS), terrestrial carbon fluxes, and vegetation parameters. A two-layer stacked random forest regression model was built to fit 1° gridded inventory of open-source data inventory for anthropogenic CO2 (ODIAC). Then, the model was trained using the 2014–2018 dataset to estimate emissions in 2019, which provided a higher accuracy compared with a single-layer model with an R2 of 0.766 and an RMSE of 0.359. The predicted gridded emissions are consistent with Global Carbon Grid at 1° scale with an R2 of 0.665, and the national total emissions provided a higher R2 at 0.977 with the Global Carbon Project (GCP) data, as compared to the ODIAC (R2 = 0.956) data, in European countries. This study demonstrates that data-driven random forest regression models are capable of estimating anthropogenic CO2 emissions at a grid scale.

On some possible effects of using renewable oxygenated fuels in a large marine diesel engine

For the continuous reduction of the anthropogenic CO2 large diesel engines require the use of alternative fuels such as oxygenated renewable biofuels. These types of fuels will help in fulfilling future standards of regulated pollutant emissions for industrial, railways or marine applications In this sense, a theoretical investigation has been carried out on a four-stroke large marine diesel engine (nominal power of 2870kW at the rated speed of 1100 rpm). Different mixtures were investigated different mixtures of diesel–ethanol with ethanol volumetric fractions of 5%, 15%, 30%. The same ethanol fractions have been considered while replacing the diesel fuel with biodiesel B20 (20% rapeseed biofuel and 80% diesel fuel in volumetric fractions). The study covers two engine operating conditions characterized by full-load operation at the rated speed of 1100rpm and at mid-speed of 700rpm. It was found that a reasonable compromise can be achieved for an acceptable loss in power of 5% by using the diesel–ethanol15 mixture, which reduces NOx by 9.69%. Using the B20–ethanol05 mixture, will reduces Soot by 19.28% but increases NOx by 21.94% at low speed 700 rpm. At a high engine speed of 1100rpm, for the same both fuels diesel–ethanol15 and B20–ethanol05, Soot increases by 7.84% while NOx decreases by 10.91%, respectively Soot decreases by 17.65% and NOx increases by 37.27%.

Response of Planktic Foraminiferal Shells to Ocean Acidification and Global Warming Assessed Using Micro-X-Ray Computed Tomography

Ocean acidification is now progressing, primarily due to the fact that the oceans have absorbed about 50% of the anthropogenic CO2 emitted since the industrial revolution. Many marine calcifying organisms, such as foraminifers and coccoliths, are known to build their shells using carbonate ions present in the seawaters surrounding them. Carbonate saturation state has a crucial influence on foraminiferal calcification, and foraminiferal shell production is known to be sensitive to increase in ocean pCO2. Moreover, ocean warming is also progressing along with acidification. Therefore, both environmental changes could affect foraminiferal shell formation. However, the relationship between foraminiferal shell parameters (i.e., size, weight, volume, and density) and ocean pCO2 or sea surface temperature (SST), or both, remains unclear. In this study, we used fossil planktic foraminifer Globigerinoides ruber (white) in a late Quaternary sediment core (MD98-2196) from the East China Sea to investigate a relationship between the shell parameters and oceanographic properties estimated based on the proxies from the same core. The foraminiferal shells were scanned using high-resolution micro-X-ray computed tomography (MXCT) to determine shell volume and density. The results showed that the size-normalized weight and the size-normalized volume of the shell had a negative correlation with the SST and atmospheric pCO2. The negative correlation between weight/volume and atmospheric pCO2 agrees with the previous laboratory experiments and geological record during the Pliocene. However, the correlation between weight/volume and SST should be interpreted with caution because it might be an artifact due to the correlation between SST and atmospheric pCO2. On the other hand, shell density is only weakly or insignificantly correlated with SST and pCO2, suggesting that these environmental parameters do not exert any impact on shell density. Thus, future ocean acidification will negatively affect the carbonate productivity of planktic foraminifers, even if it will not affect shell density. The temperature effect on the shell formation of the planktic foraminifers might be much less than ocean acidification considering controversial results of the temperature sensitivity in previous studies.

A green approach towards sorption of CO2 on waste derived biochar

Carbon capture technologies have advanced in recent years to meet the ever-increasing quest to minimize excessive anthropogenic CO2 emissions. The most promising option for CO2 control has been identified as carbon capture and storage. Among the numerous sorbents, char generated from biomass thermal conversion has shown to be an efficient CO2 adsorbent. This study examines various characteristics that can be used to increase the yield of biochar suited for carbon sequestration. This review gives recent research progress in the area, stressing the variations and consequences of various preparation processes on textural features such as surface area, pore size and sorption performance with respect to CO2's sorption capacity. The adjoining gaps discovered in this field have also been highlighted herewith, which will serve as future work possibility. It aims to analyse and describe the possibilities and potential of employing pristine and modified biochar as a medium of CO2 capture. It also examines the parameters that influence biochar's CO2 adsorption ability and pertinent challenges regarding the production of biochar-based CO2 sorbent materials.

CO2 storage potential of basaltic rocks, Mpumalanga: Implications for the Just Transition

South Africa is the largest CO2 emitter on the African continent. These emissions stem from a heavy reliance on coal as the primary energy fuel and contributor toward socio-economic development. The South African government has targeted reducing CO2 emissions by more than half in the next 10 years. To meet climate change mitigation scenarios, while alleviating continued emissions, South Africa will look to technologies such as carbon capture, utilisation and storage. Initial assessments of South Africa’s potential for CO2 storage have focused on deep saline aquifers within volcano-sedimentary sequences along the near and offshore regions. Sustaining the Just Transition will, however, require additional storage capacity. In this study, we make an initial assessment of possible CO2 storage in basaltic sequences of the Ventersdorp Supergroup. Geological and mineralogical information was ascertained from borehole data. The geological information suggests that the subsurface extent of the Ventersdorp Supergroup is at least 80 000 km2 larger than previously mapped, extending beneath major point-source CO2 emitters and active coalfields. Furthermore, petrographic analyses suggest pore space of up to ca 15% with minimal alteration, and preservation of mafic silicate minerals that would enable reactive carbonation of injected CO2. Notable metasomatic and hydrothermal alteration is confined to significant contact horizons, such as the lowermost Ventersdorp Contact Reef. These results suggest that basaltic sequences may exponentially increase South Africa’s CO2 sequestration storage capacity and may have a significant impact on the country’s Just Transition. Significance: This study shows that basaltic sequences may support the permanent storage of anthropogenic CO2 in South Africa, in particular, proximal to significant point-source CO2 emitters. South Africa has voluminous and widespread basaltic sequences, which, in combination, increase South Africa’s geological CO2 storage potential by several orders of magnitude. These storage reservoirs can have a direct impact in South Africa by enabling a sustainable Just Transition toward a low-carbon economy while meeting intended climate change mitigation scenarios.

Contrasting projections of the ENSO-driven CO2flux variability in the equatorial Pacific under high-warming scenario

Abstract. The El Niño–Southern Oscillation (ENSO) widely modulates the global carbon cycle. More specifically, it alters the net uptake of carbon in the tropical ocean. Indeed, over the tropical Pacific less carbon is released by oceans during El Niño, while the opposite is the case for La Niña. Here, the skill of Earth system models (ESMs) from the latest Coupled Model Intercomparison Project (CMIP6) to simulate the observed tropical Pacific CO2 flux variability in response to ENSO is assessed. The temporal amplitude and spatial extent of CO2 flux anomalies vary considerably among models, while the surface temperature signals of El Niño and La Niña phases are generally well represented. Under historical conditions followed by the high-warming Shared Socio-economic Pathway (SSP5-8.5) scenarios, about half the ESMs simulate a reversal in ENSO–CO2 flux relationship. This gradual shift, which occurs as early as the first half of the 21st century, is associated with a high CO2-induced increase in the Revelle factor that leads to stronger sensitivity of partial pressure of CO2 (pCO2) to changes in surface temperature between ENSO phases. At the same time, uptake of anthropogenic CO2 substantially increases upper-ocean dissolved inorganic carbon (DIC) concentrations (reducing its vertical gradient in the thermocline) and weakens the ENSO-modulated surface DIC variability. The response of the ENSO–CO2 flux relationship to future climate change is sensitive to the contemporary mean state of the carbonate ion concentration in the tropics. We present an emergent constraint between the simulated contemporary carbonate concentration with the projected cumulated CO2 fluxes. Models that simulate shifts in the ENSO–CO2 flux relationship simulate positive bias in surface carbonate concentrations.

The Ocean Carbon Cycle

The ocean holds vast quantities of carbon that it continually exchanges with the atmosphere through the air-sea interface. Because of its enormous size and relatively rapid exchange of carbon with the atmosphere, the ocean controls atmospheric CO2 concentration and thereby Earth's climate on timescales of tens to thousands of years. This review examines the basic functions of the ocean's carbon cycle, demonstrating that the ocean carbon inventory is determined primarily by the mass of the ocean, by the chemical speciation of CO2 in seawater, and by the action of the solubility and biological pumps that draw carbon into the ocean's deeper layers, where it can be sequestered for decades to millennia. The ocean also plays a critical role in moderating the impacts of climate change by absorbing an amount of carbon equivalent to about 25% of anthropogenic CO2 emissions over the past several decades. However, this also leads to ocean acidification and reduces the chemical buffering capacity of the ocean and its future ability to take up CO2. This review closes with a look at the uncertain future of the ocean carbon cycle and the scientific challenges that this uncertainty brings.

Recent ocean acidification trends from boron isotope (δ11B) records of coral: Role of oceanographic processes and anthropogenic CO2 forcing

Recent ocean acidification trends from boron isotope (δ11B) records of coral: Role of oceanographic processes and anthropogenic CO2 forcing

Elevated pCO2 Induced Physiological, Molecular and Metabolic Changes in Nannochloropsis Oceanica and Its Effects on Trophic Transfer

The rise of dissolution of anthropogenic CO2 into the ocean alters marine carbonate chemistry and then results in ocean acidification (OA). It has been observed that OA induced different effects on different microalgae. In this study, we explored the physiological and biochemical changes in Nannochloropsis oceanica in response to increased atmospheric carbon dioxide and tested the effect of ocean acidification (OA) on the food web through animal feeding experiments at a laboratory scale. We found that the levels of C, N, C/N, Fv/Fm, and photosynthetic carbon fixation rate of algae cells were increased under high carbon dioxide concentration. Under short-term acidification, soluble carbohydrate, protein, and proportion of unsaturated fatty acids in cells were significantly increased. Under long-term acidification, the proportion of polyunsaturated fatty acids (PUFAs) (~33.83%) increased compared with that in control (~30.89%), but total protein decreased significantly compared with the control. Transcriptome and metabonomics analysis showed that the differential expression of genes in some metabolic pathways was not significant in short-term acidification, but most genes in the Calvin cycle were significantly downregulated. Under long-term acidification, the Calvin cycle, fatty acid biosynthesis, TAG synthesis, and nitrogen assimilation pathways were significantly downregulated, but the fatty acid β-oxidation pathway was significantly upregulated. Metabolome results showed that under long-term acidification, the levels of some amino acids increased significantly, while carbohydrates decreased, and the proportion of PUFAs increased. The rotifer Brachionus plicatilis grew slowly when fed on N. oceanica grown under short and long-term acidification conditions, and fatty acid profile analysis indicated that eicosapentaenoic acid (EPA) levels increased significantly under long-term acidification in both N. oceanica (~9.48%) and its consumer B. Plicatilis (~27.67%). It can be seen that N. oceanica formed a specific adaptation mechanism to OA by regulating carbon and nitrogen metabolism, and at the same time caused changes of cellular metabolic components. Although PUFAs were increased, they still had adverse effects on downstream consumers.

Anthropogenic CO2 emission reduction during the COVID-19 pandemic in Nanchang City, China

China is the largest CO2 emitting country on Earth. During the COVID-19 pandemic, China implemented strict government control measures on both outdoor activity and industrial production. These control measures, therefore, were expected to significantly reduce anthropogenic CO2 emissions. However, large discrepancies still exist in the estimated anthropogenic CO2 emission reduction rate caused by COVID-19 restrictions, with values ranging from 10% to 40% among different approaches. Here, we selected Nanchang city, located in eastern China, to examine the impact of COVID-19 on CO2 emissions. Continuous atmospheric CO2 and ground-level CO observations from January 1st to April 30th, 2019 to 2021 were used with the WRF-STILT atmospheric transport model and a priori emissions. And a multiplicative scaling factor and Bayesian inversion method were applied to constrain anthropogenic CO2 emissions before, during, and after the COVID-19 pandemic. We found a 37.1–40.2% emission reduction when compared to the COVID-19 pandemic in 2020 with the same period in 2019. Carbon dioxide emissions from the power industry and manufacturing industry decreased by 54.5% and 18.9% during the pandemic period. The power industry accounted for 73.9% of total CO2 reductions during COVID-19. Further, emissions in 2021 were 14.3–14.9% larger than in 2019, indicating that economic activity quickly recovered to pre-pandemic conditions.

Spatial and temporal variability of the physical, carbonate and CO2 properties in the Southern Ocean surface waters during austral summer (2005-2019)

In situ measurements of sea surface temperature (SST), salinity (SSS), Total Alkalinity (AT) and Total Carbon (CT) were obtained during austral summer (mid-February to mid-March) from 2005 to 2019 in the Southern Ocean (SO), along a transect between Hobart, Tasmania and Dumont d’Urville French Antarctic Station. The studied transect is divided in four regions from North to South: the Subtropical Zone (STZ), the Subantarctic Region (SAR), the Antarctic Region (AAR) and the Coastal Antarctic Zone (CAZ). Latitudinal distribution of measured SST, SSS, AT, CT as well as calculated pH, CO2 parameters (seawater fugacity of CO2 (fCO2sw), difference between seawater and atmospheric fCO2 (ΔfCO2), CO2 flux (FCO2)) and satellite-derived Chlorophyll a (Chl-a) are discussed. We show that the variability of physical and carbonate parameters in the STZ and north of the SAR are related to the mesoscale activity. In the CAZ, the freshwater inputs from sea-ice melting strongly impact the variability of all parameters. The comparison between physical and carbonate parameters highlights that AT and CT are directly related to the latitudinal variability of SST and SSS. Study of the CO2 parameters shows that the transect is a sink of CO2 during February and March, with a mean FCO2 of −4.0 ± 2.8 mmol m−2 d−1. The most negative values of FCO2 are found in the STZ and SAR north of 50°S and in the AAR south of 62°S, where biological activity is high. New simple empirical relationships are developed for AT from SST and SSS and for CT using SST, SSS and atmospheric fCO2 (fCO2atm) for the austral summer in the studied area. Using high resolution SSS and SST from the SURVOSTRAL program, trends of AT and CT are determined in the SAR and the AAR from 2005 to 2019. SST, SSS and AT increase over this period in the SAR, which might be explained by the southward migration of the Subtropical Front. In the AAR, no clear trend is detected. CT increases by 1.0 ± 0.2 and 0.8 ± 0.3 μmol kg−1 yr−1 in the SAR and AAR respectively. The trend in the AAR is attributed to the increase in anthropogenic CO2 emissions in the atmosphere while, in the SAR, hydrographic changes also contribute to the increase. Using the coefficient associated with fCO2atm in the equation of CT, we estimate the impact of atmospheric CO2 increase on CT at 1.18 ± 0.14 μmol kg−1 yr−1 and 1.07 ± 0.13 μmol kg−1 yr−1 in the SAR and AAR respectively. Decreases in pH are observed in both regions (−0.0018 ± 0.0001 and −0.0026 ± 0.0003 yr−1 in the SAR and AAR respectively), indicating the sensitivity of surface waters in the area towards the development of ocean acidification processes under rising anthropogenic emissions.

Field Application of Automated Spectrophotometric Analyzer for High-Resolution In Situ Monitoring of pH in Dynamic Estuarine and Coastal Waters

High quality pH measurements are required in estuarine and coastal waters to assess the impacts of anthropogenic atmospheric CO2 emissions on the marine carbonate system, including the resulting decrease in pH. In addition, pH measurements are needed to determine impacts on carbonate chemistry of phytoplankton blooms and their breakdown, following enhanced anthropogenic nutrient inputs. The spectrophotometric pH technique provides high quality pH data in seawater, and is advantageous for long-term deployments as it is not prone to drift and does not require in situ calibration. In this study, a field application of a fully automated submersible spectrophotometric analyzer for high-resolution in situ pH measurements in dynamic estuarine and coastal waters is presented. A Lab-on-Chip (LOC) pH sensor was deployed from a pontoon in the inner Kiel Fjord, southwestern Baltic Sea, for a total period of 6 weeks. We present a time-series of in situ pHT (total pH scale) and ancillary data, with sensor validation using discretely collected samples for pHT and laboratory analysis. The difference between the sensor and laboratory analyses of discrete samples was within ±0.015 pHT unit, with a mean difference of 0.001 (n=65), demonstrating that the LOC sensor can provide stable and accurate pHT measurements over several weeks.

The effect of ocean acidification on the escape behaviour of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar

Ocean acidification (OA) driven by sea water uptake of anthropogenic atmospheric CO2 has broad deleterious effects on marine species including modified behavioural interactions such as between predators and prey. Predatory sea stars are key species in many marine ecosystems and often elicit defensive responses in their prey. This study investigated the effect of elevated CO2 on the escape response of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar. In response to touch by M. calcar, P. exigua exhibits a distinct fleeing response. The escape response of P. exigua with respect to velocity and escape trajectory was investigated after both species were acclimated in OA conditions. At pHT 7.6 and 7.8 velocity and escape trajectory of the fleeing response of P. exigua did not differ from that seen in the ambient treatment. However, there was a delay in the time that P. exigua started to flee with the initiation time being 2.8 times slower (10 vs 28 s) at pHT 7.6. This delay may increase the vulnerability of P. exigua to predation by M. calcar and have ecological effects with respect to the role of this species as an algal grazer on rocky shores of southeast Australia where these sea star species co-occur.

Aspen growth is not limited by starch reserves

All photosynthetic organisms balance CO2 assimilation with growth and carbon storage. Stored carbon is used for growth at night and when demand exceeds assimilation. Gaining a mechanistic understanding of carbon partitioning between storage and growth in trees is important for biological studies and for estimating the potential of terrestrial photosynthesis to sequester anthropogenic CO2 emissions.1,2 Starch represents the main carbon storage in plants.3,4 To examine the carbon storage mechanism and role of starch during tree growth, we generated and characterized low-starch hybrid aspen (Populus tremula×tremuloides) trees using CRISPR-Cas9-mediated gene editing of two PHOSPHOGLUCOMUTASE (PGM) genes coding for plastidial PGM isoforms essential for starch biosynthesis. We demonstrate that starch deficiency does not reduce tree growth even in short days, showing that starch is not a critical carbon reserve during diel growth of aspen. The low-starch trees assimilated up to ∼30% less CO2 compared to the wild type under a range of irradiance levels, but this did not reduce growth or wood density. This implies that aspen growth is not limited by carbon assimilation under benign growth conditions. Moreover, the timing of bud set and bud flush in the low-starch trees was not altered, implying that starch reserves are not critical for the seasonal growth-dormancy cycle. The findings are consistent with a passive starch storage mechanism that contrasts with the annual Arabidopsis and indicate that the capacity of the aspen to absorb CO2 is limited by the rate of sink tissue growth.

Recent developments in CO 2 capture, utilization, related materials, and challenges

Anthropogenic activities including the combustion of fossil fuels have led to a dramatic increase in the rate of carbon dioxide (CO2) emission in the last three decades. Since fossil-based fuels are still the predominant energy source for this century, CO2 is a colossal problem. It is emitted as a consequence of combustion and human activities and is a major greenhouse gas (GHG) that significantly contributes to climate change and global warming, making CO2 emission a worldwide problem. The Intergovernmental Panel on Climate Change (IPCC) has proposed a 45% decrease in anthropogenic CO2 emissions by 2030, with a target of “net-zero” CO2 emissions by 2050. Despite its harmful effects, CO2 has the potential to be used for a wide range of different industrial needs, after its capture. CO2 capture technologies are still in the early stage of development because of economic and technological issues. However, in the future, carbon capture and related application technologies and methods may become easier and more accessible due to the new developments in the materials synthesis, strategies and skills and inexpensive utilization, and functioning cost of the employed methods. Furthermore, carbon capture system (CCS) might improve the recent power plan system properties. Concerning climate change, carbon capture is deemed as a promising solution to prevent CO2 emissions. CO2 capture, storage, and utilization are garnering intensive interest from scientists worldwide. This review paper identifies and gave particular attention to the literature on the recent CO2 capture technologies, for example, adsorption, absorption, membrane, and algae-based separation techniques for pre-combustion, oxy-fuel combustion, and post-combustion periods. Aside from all of these capture technologies, the utilization and application of captured CO2 in various industrial fields such as solvents, chemicals, and fuels are evaluated.

Variation of XCO2 anomaly patterns in the Middle East from OCO-2 satellite data

ABSTRACT The anthropogenic CO2 emission is contributed to the rapid increase in CO2 concentration. In the current study the anthropogenic CO2 emission in the Middle East (ME) is investigated using 6 years column-averaged CO2 dry air mole fraction (XCO2) observation from Orbiting Carbon Observatory-2 (OCO-2) satellite. In this way, the XCO2 anomaly (XCO2) as the detrended and deseasonalized term of OCO-2XCO2 product, was computed and compared to provide the direct space-based anthropogenic CO2 emission monitoring. As a result, the high positive and negative XCO2 values have corresponded to the major sources such as oil and gas industries, and growing seasons over ME, respectively. Consequently, the Open-source Data Inventory for Anthropogenic CO2 (ODIAC) emission and the gross primary productivity (GPP) were utilized in exploring the XCO2 relation with human and natural driving factors. The results showed the capability of XCO2 maps in detecting CO2 emission fluctuations in defined periods were detectible in daily to annual periods. The simplicity and accuracy of the method in detecting the man-made and natural driving factors including the main industrial areas, megacities, or local changes due to COVID-19 pandemic or geopolitical situations as well as the vegetation absorption and biomass burning is the key point that provides the environmental managers and policymakers with valuable and accessible information to control and ultimately reduce the CO2 emission over critical regions.

Phycosphere pH of unicellular nano- and micro- phytoplankton cells and consequences for iron speciation

Surface ocean pH is declining due to anthropogenic atmospheric CO2 uptake with a global decline of ~0.3 possible by 2100. Extracellular pH influences a range of biological processes, including nutrient uptake, calcification and silicification. However, there are poor constraints on how pH levels in the extracellular microenvironment surrounding phytoplankton cells (the phycosphere) differ from bulk seawater. This adds uncertainty to biological impacts of environmental change. Furthermore, previous modelling work suggests that phycosphere pH of small cells is close to bulk seawater, and this has not been experimentally verified. Here we observe under 140 μmol photons·m−2·s−1 the phycosphere pH of Chlamydomonas concordia (5 µm diameter), Emiliania huxleyi (5 µm), Coscinodiscus radiatus (50 µm) and C. wailesii (100 µm) are 0.11 ± 0.07, 0.20 ± 0.09, 0.41 ± 0.04 and 0.15 ± 0.20 (mean ± SD) higher than bulk seawater (pH 8.00), respectively. Thickness of the pH boundary layer of C. wailesii increases from 18 ± 4 to 122 ± 17 µm when bulk seawater pH decreases from 8.00 to 7.78. Phycosphere pH is regulated by photosynthesis and extracellular enzymatic transformation of bicarbonate, as well as being influenced by light intensity and seawater pH and buffering capacity. The pH change alters Fe speciation in the phycosphere, and hence Fe availability to phytoplankton is likely better predicted by the phycosphere, rather than bulk seawater. Overall, the precise quantification of chemical conditions in the phycosphere is crucial for assessing the sensitivity of marine phytoplankton to ongoing ocean acidification and Fe limitation in surface oceans.

Insights Provided By Modeling of Electrochemical Hydrogenation and Hydrogenolysis of Furfural on Cu and Side Reactions in Acidic Media

Fine chemicals and fuels can be generated by electrochemical methods as an alternative to the currently in place thermocatalytic methods. The thermocatalytic methods require harsher reaction conditions, such as elevated pressures and temperatures, but also requires hydrogen gas as a reactant for reduction reactions which largely is produced by non-sustainable methods which emit high amounts of CO2. Electrochemical methods, in comparison, use in-situ generated protons in lieu of hydrogen gas which reduces the overall CO2 generation. Electrifying the chemical industry will allow for the reduction in anthropogenic CO2 generation by coupling a neutral or negative carbon emitting process with renewable electricity. Furfural (FF) is a biomass derived platform molecule produced at a scale above 300,000 metric tons annually and can used to produce furfuryl alcohol (FA) and 2-methylfuran (MF) through electrochemical hydrogenation and hydrogenolysis (ECH) respectively. FA is a fine chemical that is highly desirable for use in furanic molds, while MF has been identified as a fuel or fuel precursor. In this work, the kinetics of the FF ECH electrochemical system is decoupled and modeled to understand the conversion of FF.In this work, the electrochemical kinetics and non-electrochemical side reactions investigated in our previous works [1,2,3] are modeled to gain further insights into the mass balance and the longer-term phenomena associated with the FF ECH system. The FF ECH system is modeled as three contributing pieces: the ECH reactions, the non-electrochemical side reactions, and the evaporation of MF to the solvent trap for collection. The desired electrochemical reactions were investigated using a 2 compartment H-cell with a Cu flag electrode in the cathode compartment, and connected to a solvent trap held at -15°C. Experimentation was done in 0.1 and 0.5 M H2SO4 with concentrations of FF between 10 and 120 mM FF. The catholyte had a cosolvent of 80:20 vol% water: acetonitrile and was purged with 60mL/min of nitrogen gas. To study the non-electrochemical reactions, vials of electrolyte with FF, FA, and MF in concentrations matching those found in electrochemical experiments were prepared and sample over time without the presence of any electrochemistry. The vial samples over time showed that mass loss occurred for the three furanics, however much more significantly for FA and MF, the two desired products. Lastly, the evaporation of MF from the catholyte to the solvent trap was studied by preparing the H-cell with a known concentration of MF and sampling over time. By modeling the FF ECH system this way, we were able to show the prominence of the competing side reactions and evaporation of MF to the solvent trap which provides insights into the mass balance and performance of the FF ECH system. We find that while the side reactions are more prevalent in the 0.5M H2SO4 than the 0.1M H2SO4, that a higher MF yield is reached due to the evaporation and collection of MF in the solvent trap. A higher FA yield is found in the 0.1M H2SO4 compared to the 0.5M H2SO4.[1] May, Andrew S., Steven M. Watt, and Elizabeth J. Biddinger. "Kinetics of furfural electrochemical hydrogenation and hydrogenolysis in acidic media on copper." Reaction Chemistry & Engineering 6, no. 11 (2021): 2075-2086[2] Jung, Sungyup, and Elizabeth J. Biddinger. "Electrocatalytic hydrogenation and hydrogenolysis of furfural and the impact of homogeneous side reactions of furanic compounds in acidic electrolytes." ACS Sustainable Chemistry & Engineering 4, no. 12 (2016): 6500-6508[3] Jung, Sungyup, and Elizabeth J. Biddinger. "Controlling competitive side reactions in the electrochemical upgrading of furfural to biofuel." Energy Technology 6, no. 7 (2018): 1370-1379

Return of large fin whale feeding aggregations to historical whaling grounds in the Southern Ocean

Fin whales (Balaenoptera physalus quoyi) of the Southern Hemisphere were brought to near extinction by twentieth century industrial whaling. For decades, they had all but disappeared from previously highly frequented feeding grounds in Antarctic waters. Our dedicated surveys now confirm their return to ancestral feeding grounds, gathering at the Antarctic Peninsula in large aggregations to feed. We report on the results of an abundance survey and present the first scientific documentation of large fin whale feeding aggregations at Elephant Island, Antarctica, including the first ever video documentation. We interpret high densities, re-establishment of historical behaviours and the return to ancestral feeding grounds as signs for a recovering population. Recovery of a large whale population has the potential to augment primary productivity at their feeding grounds through the effects of nutrient recycling, known as 'the whale pump'. The recovery of fin whales in that area could thus restore ecosystem functions crucial for atmospheric carbon regulation in the world's most important ocean region for the uptake of anthropogenic CO2.