High-energy Environment Research Articles

Effect of physical and biogeochemical factors on placer gold transformation in mountainous landscapes of Switzerland

In surface environments, placer gold particles are (re)shaped by physical, chemical and biogeochemical processes. This study hypothesizes that in modern landscapes combinations of physical and biogeochemical factors determine placer gold transformation and the composition of biofilm communities living on particle surfaces. Morphology, composition and biofilm communities of placer particles from eight locations in Switzerland were analyzed. Sites reflect a variety of modern-day placer environments in mountainous terrains, ranging from eluvial sites in close proximity to primary sources, to alluvial sites associated with both slow- and fast-moving streams, and to distal glacio-fluvial and depositional lake sediments. Particles are progressively physically and biogeochemically transformed with increasing distance from source. Variable degrees of rounding, gouging and scratching from physical reshaping due to transport and sedimentation processes are evident especially on particles from high energy environments. Surface textures indicative of biogeochemical gold/silver dissolution are common. In low energy/depositional environments and with increasing distance from source overgrowths of gold nano- and micro-particles and aggregates are abundant. These form micro-crystalline layers of secondary gold on particle surfaces covering them to depths of tens of micrometers. Biofilm communities across all sites are dominated by Proteobacteria (669 Operational Taxonomic Units (OTUs), 49.8%), especially β‑Proteobacteria. Other important phyla include Acidobacteria, (172 OTUs, 9.7%), Bacteroidetes (222 OTUs, 11.6%), Cyanobacteria (26 OTUs, 13.7%), and Planctomycetes (125 OTUs, 7.1%). Canonical analysis of principal coordinates demonstrates significant links of community assemblages to biogeochemical transformation and landscape position of collected particles. Increasing specialization towards metallophilic phyla was recorded on particles collected with increasing distance from source, suggesting that Au toxicity resulting from progressing biogeochemical transformation affected bacterial communities. This study ultimately shows that placer gold transformation and biofilm composition within modern landscapes is highly dependent on the interplay of physical and biogeochemical factors.

Recovery of Benthic Microalgal Biomass and Community Structure Following Beach Renourishment at Folly Beach, South Carolina

One method of preserving beaches against the effects of erosion and sea level rise is beach renourishment. While there have been many studies assessing the impact of renourishment on macrofauna, few studies have looked at its effects on microbes. Benthic microalgae (BMA) are important primary producers, representing the basis of nearshore food webs. BMA also secrete extracellular polymeric substances (EPS), which bind sediment and thus help prevent erosion. The objective of this study was to monitor recovery of BMA in terms of relative biomass (estimated as sediment chlorophyll a) and community structure (characterized using high-throughput DNA sequencing) following renourishment of Folly Beach, SC in 2014. We also examined the relationships among biomass, EPS, and erosion. Sediment samples were collected intermittently (n = 9) from two renourished and two control sites within three intertidal zones (high, mid, low) from June 2014 to January 2015. Biomass recovered in sequence from low to high intertidal, corresponding to when the artificially-raised beach once again experienced regular tidal inundation (between 93 and 169 days post-renourishment). Alpha diversity metrics misleadingly indicated recovery around this same time within the high intertidal, but compositional changes through time were unlike those seen in control samples, and these communities had yet to recover at ~ 7 months post-renourishment. Renourishment therefore appears to impact BMA communities via artificial elevation of the beach face. While there were relationships between chl a, EPS, and erosion, BMA most likely play a minimal role in sediment stabilization in high-energy environments like Folly Beach.

Geochemistry and distribution of sediments in the East Indian shelf, SW Bay of Bengal: implications on weathering, transport and depositional environment

Forty-two substrate sediment samples and three cores procured from the shelf region between Chennai and Cuddalore were analyzed to understand the spatial and vertical sediment distribution. Samples subjected to grain size, bulk and clay mineralogical analyses, REE and trace element geochemistry yielded interesting results about the sediment characteristics with respect to the modern day environment. The present study revealed that the study area is characterized by high energy environment marked by predominant composition of medium sand. Results confirmed the evidence of more illite than kaolinite, smectite, and chlorite in the clay mineral assemblage indicating a terrigenous source. Geochemical data also revealed that the enrichment of light rare earth elements (LREE) in the sediments is due to continental source of Precambrian times. High feldspar content in the sediments which is emphasized by bulk mineralogical data displayed positive Eu anomaly. By using the paleoredox index, the area of interest is considered to have undergone no major changes in its depositional settings.

Using differential structure-from-motion photogrammetry to quantify erosion at the Engare Sero footprint site, Tanzania

Hominin footprint sites are excellent sources of data that provide insights into early human physiology, anatomy, and social structures. They are also potential tourist attractions that are often situated in relatively under-developed parts of the world. Unfortunately, many footprint sites are also located in high energy environments and/or are pressed into poorly indurated sediments, which make them highly susceptible to erosion. This paper proposes a non-invasive and low-cost method employing Structure-from-Motion photogrammetry to quantify erosion rates in the absence of permanent ground control points. Using point cloud comparison algorithms between data collected at different times, it is possible to quantitatively analyze the locations, volumes, and rates of material loss. We applied this technique to several footprints within the Engare Sero footprint site in northern Tanzania to assess erosional change between 2010 and 2017. Our comparisons show that prints are vertically eroding at average rates ranging from 0.10 to 0.17 mm/yr with some localized areas experiencing much higher rates over shorter durations. We identify three primary modes of erosion: 1) flaking, 2) abrasion, and 3) boring of holes. Erosion appears to have occurred episodically with major events, such as flooding, separated by periods of relative stability. The methods presented here are valuable for paleoanthropologists to better understand how footprint erosion might adversely affect inferences regarding print-makers, and they are valuable for decision-makers, who can create conservation plans to better protect and maximize the utility of known hominin footprint sites.

Benthic foraminifera in a deep-sea high-energy environment: the Moira Mounds (Porcupine Seabight, SW of Ireland)

Cold-water coral ecosystems represent unique and exceptionally diverse environments in the deep-sea. They are well developed along the Irish margin, varying broadly in shape and size. The Moira Mounds, numerous small-sized mounds, are nestled in the Belgica Mound Province (Porcupine Seabight, North-East Atlantic). The investigation of living (Rose Bengal stained) and dead benthic foraminiferal assemblages from these mounds allowed to describe their distribution patterns and to evaluate their response to environmental variability. Quantitative data was statistically treated to define groups of species/genera associated to specific habitats. The Moira Mounds differ from their larger neighbours by the reduced spatial variability of benthic foraminiferal assemblages, living assemblages only distinguishing coral-rich and coral-barren areas. The ecological needs of corals are highlighted by the abundance of Alabaminella weddellensis and Nonionella iridea, phytodetritus-feeding species in coral supporting sediments. Living foraminifera in sediments from the Moira Mounds concentrate in the upper first centimetre. Infaunal species may be affected by bioturbation and/or reworking by the strong currents in the area. Dead foraminiferal assemblages from the Moira Mounds resemble those described for the sandwave facies in adjacent giant mounds, suggesting similar processes in facies deposition.

Study of the coastal sediments of the Loutraki gulf area

The study of the sedimentological and mineralogical characteristics of the coastal sediments in the Loutraki gulf, included analyses of a large number of samples, that is granulometry, thin section study and x-ray examination. From these data the granulometry paramètres were assessed such as mean grain size, standard deviation σ, skewness SK, and kurtosis KG of the sediments. The study of the sedimentological parameters based on the mean grain size the offshoreline is covered by coarse grain sand, whereas the tidal zone indicates a high energy environment. The longshoredrift is from Ν to S. Most of the sand is loosely graded in the nearschore area, medium graded in the foreshore area and well graded in the backshore area. Their constant declination indicates a trend for a better gradation of sediments southwards. The latter combined with the mean grain size indicate a reduction of kinetic energy from Ν to S. In addition, the beachrocks, were studied together with their, elevation and their mineral composition .

Environmental evolution of western Baltic Sea in the Holocene in the light of multidisciplinary investigations of sediments cores from Arkona Basin

A multidisciplinary investigation performed on gravity cores, supplemented by a new radiocarbon dating of macrofossils, outlined the environmental evolution of Arkona Basin in the Holocene. Studies comprising the analysis of diatoms, geochemistry, grain size, and radiocarbon dating clarified the knowledge about the age and environmental changes during freshwater and marine transgressions and regressions. The acoustic profiling method allowed proper interpretation of the analysis results from sediment cores and created a proper lithostratigraphic model of the investigated basin. Baltic Ice Lake and Yoldia Sea sediment layers were identified acoustically and cores penetrated the final regression surface of the Baltic Ice Lake. The analyses of cores concentrated on Ancylus Lake and Littorina Sea sediments. Two phases of the Ancylus Lake stage were identified. The peaks of loss on ignition in the cores, observed as a strong acoustic reflector, were identified as a marker of Ancylus Lake regression between the first, high-water level phase and the second, shallow-water phase. The age of onset of Littorina transgression was estimated at around 7000–7200 cal BP and was younger than some previous estimations. The retrieved age confirmed the suggestion that the marine environment appeared first in Mecklenburg Bay and then after a few hundred years in Arkona Basin as an intensive transgression. The appearance of Littorina Sea revealed a fast shift of the environment from lacustrine to marine. The first phase of the Littorina stage was recognised as a rapidly increasing water level and high-energy environment; the second showed rapidly increasing salinity in the calmer conditions of sedimentation.

Origination and diversification of Devonian ambocoelioid brachiopods in South China

The superfamily Ambocoelioidea is an important group of the Brachiopoda in the Devonian, both globally and in South China. In the Devonian, this group is also most diverse compared with that in other periods. Based on features of cardinal process and cruralium, three types of cardinalia are recognised, including Ambocoelia-type, Emanuella-type, and Rhyncospirifer-type. Our study shows that the Rhynchospirifer-type cardinalia is a distinct character that distinguishes them from the rest of the Ambocoeliidae; therefore, the Rhynchospiriferinae is re-elevated to the family rank. Guangxiispirifer of the previous Ambocoeliinae is reassigned to the Rhynchospiriferidae while Ambothyris, Choperella, Crurispina, Diazoma, Emanuella, Ilmenia, Ilmospirifer, Ladjia, Moravilla, and Zhonghuacoelia of the previous Rhynchospiriferinae are transferred to the Ambocoeliidae (= previous Ambocoeliinae). Three earliest ambocoelioids in South China are Ambothyris, Amboglossa, and Prolazutkinia in the upper Emsian; their emergences were likely associated with the global Upper Zlichov Event. The upper Emsian occurrences of Amboglossa and Prolazutkinia are their FADs (first appearance datum) globally. These two genera probably gave rise to the Rhynchospiriferidae and the Lazutkiniidae, respectively. After an initial gradual increase in generic richness, the Ambocoelioidea reached the highest diversity (10 genera including four endemic genera) in the late Eifelian and Early Givetian in South China. From then on, the diversity gradually decreased till the end of the Devonian (two genera) and was least affected by the Frasnian–Famennian Event. The Ambocoelioidea is a strongly facies-controlled group. Their temporal and spatial distributions show a close relationship with sea level changes. Ambocoeliids and rhynchospiriferids were adapted to different environments. The former inhabited deeper and partly dysoxic environments, therefore showed greater capabilities to migrate and survive extinctions. On the other hand, the rhynchospiriferids dwelled in a reef-related, high energy, and oxic environments, which were probably more sensitive to environmental changes; they also showed high diversity and endemism and more easily experienced rapid and regional extinctions. Three species representing the three types of cardinalia, Ambocoelia yidadeensis sp. nov., Ambothyris panxiensis, and Rhynchospirifer sp., are described.

Process constraints in sustainable bio-hythane production from wastewater: Technical note

The economy of an industrialized country is greatly dependent on fossil fuels. However, these non-renewable sources of energy are nearing the brink of extinction and which have caused serious adverse impacts on the environment. Hydrogen has emerged as a promising alternative and also has the highest calorific value. Bio-hythane is a hydrogen-methane blend can be produced from different organic substrates by two sequential anaerobic stages: a dark fermentation step followed by a second an anaerobic digestion step, for hydrogen and methane production, respectively. Bio-hythane is considered to be promising approach in sustainable energy sector. The advantages of two-stage technology include; high organic removal, high energy recovery and environment friendly. However, current efforts to recover bio-hythane energy from waste are still at bench scale level. The technical constraints in the fermentation must be removed for the indispensable bio-hythane recovery from waste. This short technical note highlights the two-stage fermentation and the technical barriers to be addressed for bio-hythane scale up from waste.

PLIOCENE BRACHIOPODS FROM RHODES ISLAND (CAPE VAGIA SECTION)

Six brachiopod species (5 terebratulids and 1 craniid) from the upper Pliocene sandy and calcareous deposits of the Cape Vagia (Rhodes Island) are described: Gryphus sp., Terebratulina refusa, Megerlia truncata, Megerlia truncata var. monstruosa, Argyrotheca cordata, Megathiris detruncata and Novocrania anomala. This is the first record of Megerlia truncata var. monstruosa from the Pliocene of Greece and of Megerlia truncata from the Pliocene of Rhodes. Megathiris detruncata, Terebratulina retusa and Argyrotheca cordata are described for the first time from the Pliocene of Rhodes. This brachiopod association displays close affinity with those from the Mediterranean province, where assemblages of similar composition are associated with shallow-water, high energy environments. However, the association of Gryphus sp., Terebratulina retusa and Novocrania anomala corresponds to deeper water moderate environments.

Density functional theory study of uni- and bi-metallic small Pt and Ni clusters for fuel conversion applications

In this work, we employed density functional theory calculations to probe the binding characteristics of C and OH on small uni-metallic (Pt3 and Ni3) and bi-metallic (Pt2Re and Ni2Fe) clusters for energy conversion applications. Both uni-metallic and bi-metallic clusters were found to possess relatively good HOMO-LUMO gaps, indicating that the clusters are electronically stable against excitations and high energy environment. It is found that the introduction of foreign atoms on uni-metallic clusters impacts C and OH binding characteristics, which could be useful in the design and fine-tuning of novel nanocatalysts for energy conversion applications such as CO/CO2 methanation and hydrogenation reactions. It is further inferred that Pt3 and Pt2Re clusters bind C and OH moderately, and could be utilized in further studies concerning energy conversion.

A brief overview of solar and wind energy in Libya: Current trends and the future development

Libya is one of the oil exporters and natural gas exporters to become one of the top lists of primary energy sources in the world. On the other hand, Libya, like other countries in the world suffers from high energy consumption, high conventional energy prices and environment issues, combined with rapid demand growth. As a result, the Renewable Energy Authority of Libya (REAOL) has been founded to promote the development of renewable energy in Libya to increase the utilization of renewable energy from 6% to 10% by the year of 2020. This study corresponds to a revision of the current scenario of energy resources; provide future potential of renewable energy resources in Libya and implementation of the future projects for the utilization of renewable energy. This study shows that there is huge potential for renewable energy in Libya, especially solar and wind. The Libyan government will have to be more aggressive targets to promotion of renewable energy to achieve environmental sustainability in Libya.

Palaeocurrent and environmental implications from anisotropy of magnetic susceptibility (AMS): a case study from Talchir and Barakar formations, Raniganj Basin, West Bengal, India

Oriented cylindrical cores of rock samples were collected from the Talchir and Barakar formations of the Lower Gondwana Supergroup of the Raniganj Basin exposed in and around Kalyaneshwari and Maithon areas. The cores (2.54 cm diameter and 2.2 cm height) were studied in the low field anisotropy of magnetic susceptibility (AMS) measurement to determine the nature of magnetic fabrics, to correlate it with the sedimentological characteristics and to determine the palaeocurrent patterns. The results derived from the statistical parameters (especially the q-factor), the shapes of the susceptibility ellipsoids and directional data of the AMS indicate that the magnetic fabrics within the studied units are primary (depositional) and are correlatable form the palaeoenvironmental features. The orientation of the maximum (K1), intermediate (K2) and minimum (K3) susceptibility axes is dispersed on the lower hemisphere equal area diagram rather than strong clusters which is not because of secondary (tectonic) influence but due to the moderate to high-energy environment of deposition of the sediments in the studied units. Based on the q-factor (which is 0.581 for Barakar Formation and 0.565 for Talchir Formation which are both < 0.7), it is suggested the AMS indicates that the imbrication of the K1 axis is the indicator of palaeocurrent. Also, the magnetic foliation (average value = 1.255) exceeds the magnetic lineation (average value = 1.107) and the shape parameter exceeds 0 in most cases pointing towards an oblate fabric. The palaeocurrent in the present study as indicated by the K1 axis imbrication is very similar in both the units under study and is due SW. However, apart from this precise palaeocurrent direction, there exists a certain degree of randomness of the susceptibility axes which are very clear indication of corresponding depositional environments.

The effect of high-energy environments on the structure of laccase-polymerized poly(catechol)

The laccase polymerization of catechol was performed using different reactors namely a water bath (WB), an ultrasonic bath (US) and a high-pressure homogenizer (HPH). The total content of free OH and the MALDI-TOF spectra of polymers obtained demonstrated that reactions are favored in the presence of high-energy environments. Higher conversion yields and polymerization degrees (DP) were obtained after polymerization using US or HPH. Molecular dynamic simulation studies supported these findings by revealing a more open enzyme active site upon environments with high molecular agitation. The higher mass transport generated by US and HPH is the main feature responsible for a higher substrate accessibility to the enzyme which contributed to produce longer polymers.

Attrition in the kimberlite system

The sustained transportation of particles in a suspension commonly results in particle attrition leading to grain size reduction and shape modification. Particle attrition is a well-studied phenomenon that has mainly focussed on sediments produced in aeolian or fluvial environments. Here, we present analogue experiments designed to explore processes of attrition in the kimberlite system; we focus on olivine as it is the most abundant constituent of kimberlite. The attrition experiments on olivine use separate experimental set-ups to approximate two natural environments relevant to kimberlites. Tumbling mill experiments feature a low energy system supporting near continual particle-particle contact and are relevant to re-sedimentation and dispersal processes. Experiments performed in a fluidized particle bed constitute a substantially higher energy environment pertinent to kimberlite ascent and eruption. The run-products of each experiment are analysed for grain size reduction and shape modification and these data are used to elucidate the rates and extents of olivine attrition as a function of time and energy. Lastly, we model the two experimental datasets with an empirical rate equation that describes the production of daughter products (fines) with time. Both datasets approach a fines production limit, or plateau, at long particle residence times; the fluidized system is much more efficient producing a substantially higher fines content and reaches the plateau faster. Our experimental results and models provide a way to forensically examine a wide range of processes relevant to kimberlite on the basis of olivine size and shape properties.

Estimating similarity in benthic communities over decades and in areas open and closed to fishing in the central Gulf of Maine, USA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 595:15-26 (2018) - DOI: https://doi.org/10.3354/meps12563 Estimating similarity in benthic communities over decades and in areas open and closed to fishing in the central Gulf of Maine, USA Samuel C. Asci1,3,*, Richard W. Langton2, Kevin D. E. Stokesbury1 1School for Marine Science and Technology, University of Massachusetts Dartmouth, 836 South Rodney French Boulevard, New Bedford, MA 02744, USA 2Northeast Fisheries Science Center, Maine Field Station, 17 Godfrey Drive, Suite 1, Orono, ME 04473, USA 3Present address: New England Fishery Management Council, 50 Water Street, Mill 2, Newburyport, MA 01950, USA *Corresponding author: sasci@nefmc.org ABSTRACT: The ledges and banks of the central Gulf of Maine (i.e. Fippennies Ledge, Jeffreys Ledge, Cashes Ledge, and Platts Bank) have supported groundfish and Atlantic sea scallop fisheries for centuries. The benthic community of Fippennies Ledge was evaluated and compared during 2 time periods separated by more than 2 decades, the first based on a series of photographs collected during manned submersible dives conducted in 1986 and 1987 and the second using photographs collected during drop camera video surveys conducted in 2009 to 2014. Further, Fippennies, Jeffreys, and Cashes ledges were permanently closed to fishing in 2002, while Platts Bank remained open, enabling a spatial comparison of benthic communities in open and closed areas along with the examination of changes in the benthos over the 28 yr period on Fippennies Ledge. In the absence of commercial fishing, the scallop population on Fippennies Ledge appeared to be unchanged between 1986 and 2014, while observed differences in other dominant species were attributed to predator-prey relationships and long-term shifts in benthic conditions. Benthos of scallop habitat in the open and closed areas between 2009 and 2014 were similar in spatially dominant species composition and species richness, likely a result of the study area being a high-energy environment and therefore resilient to both natural and fishing perturbations. Understanding change in benthic communities over decades and between open and closed areas helps better define the dynamic nature of the central Gulf of Maine and may inform fisheries management in this region as the ocean climate changes. KEY WORDS: Benthic imaging · Population dynamics · Placopecten magellanicus Full text in pdf format PreviousNextCite this article as: Asci SC, Langton RW, Stokesbury KDE (2018) Estimating similarity in benthic communities over decades and in areas open and closed to fishing in the central Gulf of Maine, USA. Mar Ecol Prog Ser 595:15-26. https://doi.org/10.3354/meps12563 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 595. Online publication date: May 14, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Eocene (Bartonian) benthic foraminifera and paleoenvironmental changes in the Western Tethys

The Eocene was a period of intense climate variability and the response of deep-sea biota is still poorly understood, especially across certain understudied intervals from the middle Eocene. We present new benthic foraminiferal data from a Bartonian marine sequence deposited in the western Tethys Ocean (Torre Cardela section, Spain), and determine the biotic and paleoenvironmental turnover. The assemblages indicate a middle to lower bathyal depth of deposition, and they contain allochthonous taxa (e.g. asterigerinids) that were transported from shallower settings. A Detrended Correspondence Analysis (DCA) performed on the total assemblage differentiates the autochthonous and allochthonous taxa, supporting the idea of different provenience. We suggest that the latter were likely transported downslope by currents. Quantitative analyses of the autochthonous assemblages show a strong dominance of calcareous infaunal taxa, mainly bolivinids, which point to a high flux of organic matter to the seafloor. Bolivinoides crenulata, the most common species, is associated with inputs of refractory organic matter and high-energy environments. Five intervals were differentiated based on changes in the relative abundance of taxa. Two intervals (B and D) show the highest percentages of allochthonous taxa and B. crenulata. We suggest that enhanced current activity not only transported allochthonous taxa, but also brought in refractory organic matter to the seafloor, which was consumed by opportunistic taxa during these two intervals. We conclude that benthic foraminiferal assemblages at Torre Cardela were strongly controlled by the amount and type of organic matter reaching the seafloor, which were in turn affected by sedimentary and, ultimately, by climatic factors.

Composición y estructura de la comunidad de moluscos de fondos blandos de la isla Santa Cruz, golfo de California, México

Background. In the marine environment of San Cruz Island, no published references exist regarding the ecology of soft-bottom mollusks. Thus, it is important to carry out research that broadens and deepens the knowledge of this marine area and contributes to proposals of management methods and alternatives for the sustainable use of insular marine resources. Goals. This study seeks to characterize the community composition and structure of soft-bottom mollusks of the infralitoral zone of Santa Cruz Island, and describe some of the characteristics associated with their habitat. Methods. During August 2010, 32 samples were collected: 16 were biological samples and 16 were sediment samples. The composition, abundance, and diversity of the malacological community were analyzed using ecological indexes. Results. 695 individuals were recorded and grouped in two classes: Gastropoda with 446 organisms (5 orders, 11 families, and 19 species); the most abundant species was Siphonaria maura (18%); the class Bivalvia included 249 organisms (8 orders, 14 families, and 25 species); the most abundant species was Tellina eburnea (10%). The Gastropoda class were more abundant than the Bivalvia, i.e., 64.17% and 35% respectively. The species with major abundances and relative frequencies were the gastropods Siphonaria maura (18%) and the bivalve Septifer seteki (69%). Four trophic categories were identified: filterers (73%), herbivores (20%), carnivores (5%), and ectoparasites, the latter of which were the rarest group (2 %). Conclusions. At this site, the specific richness (44 taxa) was lower compared to other sites from different latitudes of the western Gulf of California, likely derived from the higher energy environment of the study area that allowed only juvenile mollusks and micromollusks to be collected.

Zirconia Doped Ceria Cathodic Interlayer By Atomic Layer Deposition for Low Temperature Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) has the advantages of high energy conversion efficiency, fuel flexibility, and environment friendliness. However, conventional SOFC also has limitations in applying to various fields due to the high operating temperature of 800-1000℃. Therefore, low temperature SOFC (LT-SOFC) (≤ 500 ℃), which can be operated at relatively low temperature, are being widely researched these days. Operation losses of LT-SOFCs, however, have to be minimized to maintain the performance even at low temperature; especially, at low temperature, the activation loss at cathode is the dominant loss due to sluggish oxygen reduction reaction (ORR). The adoption of cathode interlayer such as doped ceria has been researched as an effective method to dramatically lower the cathodic activation loss in LT-SOFCs. In this study, we used zirconia-ceria composite cathodic interlayer fabricated by atomic layer deposition (ALD) to improve the performance of SOFC at low temperature. Ceria-based materials with high oxygen ion conductivity and high oxygen surface exchange coefficient at relatively low temperatures have been widely used as cathodic interlayers for LT-SOFCs, but the relatively low chemical stability has been the practical issue. Zirconia doped ceria (ZDC), on the contrary, is known to have better catalytic properties than pure ceria with even improved chemical stability. We show that the performance of LT-SOFC can be significantly enhanced by using ZDC as cathodic interlayer. The ZDC interlayer was deposited on the cathode side surface of yttria stabilized zirconia (YSZ) electrolyte using ALD. ALD is beneficial in depositing ultra-thin film with the capability to precisely control the composition and the thickness of films. Each interlayer of 20 nm-in-thickness was deposited with different ratios of zirconia and ceria; the molar ratio of zirconia was varied at 0, 30, 50, 80, and 100 mol%, respectively. The composition of the interlayer was analyzed by X-ray Photoelectron Spectroscopy (XPS) and the electrochemical performance was measured at 450℃ by using current-voltage characterization and electrochemical impedance spectroscopy (EIS). The maximum power density of the cell with the ZDC interlayer improved by 50% compared to that of the reference cell without the interlayer, which is even higher those of the cells with zirconia-only or ceria-only interlayers. In addition, the activation resistance of the cell with ZDC was decreased by ~50% in comparison with the cell without interlayers as shown in EIS measurements.

Impact of sequence stratigraphy, depositional facies, diagenesis and CO2 charge on reservoir quality of the lower cretaceous Quantou Formation, Southern Songliao Basin, China

Abstract The fourth member of the Lower Cretaceous Quantou Formation in Southern Fuxin Uplift zone of the Southern Songliao Basin is typical tight oil reservoir which has recently been explored and produced. For effective exploration and development, the evaluation and control factors of the reservoir quality of the K1q4 sandstones should be thoroughly studied. The study focused on the control of the combination of sequence stratigraphy, depositional facies and diagenesis on the reservoir quality, and identified the impact of CO2 charging, based on the core and thin section observation, XRD, SEM, fluid inclusion and isotope testing and analysis. The fourth member of the Lower Cretaceous Quantou Formation consists of lowstand system tracts (LST), transgressive system tracts (TST) and highstand system tracts (HST). The K1q4 sandstones were mostly deposited in distributary channels and crevasse splays of a delta plain within the LST and TST, and underwater distributary channels and sheet sands of a delta front within the HST. The K1q4 sandstones, mostly silt to medium grained, medium to well sorted, and are mostly lithic arkoses and feldspathic litharenites, have undergone significantly diagenetic alterations, such as compaction, quartz cementation, unstable grains (feldspar and volcanic fragments) dissolution, carbonate cementation and clay minerals cementation. The reservoir quality of the K1q4 sandstones are poor with low porosity and permeability, showing variations among the different system tracts and depositional facies, and are influenced by the charging of CO2 and controlled by the combination of sequence stratigraphy, depositional facies and diagenesis. The sandstones with high reservoir quality are mostly deposited in high energy environments, including the (underwater) distributary channel sandstones, especially the LST distributary channel sandstones with the best reservoir quality among the LST, TST and HST sandstones, which can be ascribed to larger grain size and better sorting resulting in larger intergranular pore space after compaction, and less content of carbonate cements, illite and mixed-layer I/S, and more pore-lining chlorite and more effectively dissolution. The poor reservoir quality of sandstones from crevasse splay and sheet sand is due to the small grain size and bad sorting which resulted in extensive compaction and the resulting weak dissolution. The charging of CO2 has dual impact on the reservoir quality of the K1q4 sandstones. The CO2 charging can induce the dissolution of unstable detrital grains and the precipitation of dawsonite. The former create new secondary pore space, while the latter occupy the intergranular pore space. The CO2 charging is harmful to the reservoir quality when the dawsonite content exceeds a threshold of 5%.