Bohai Bay Research Articles

Quantitative Architectural Anatomy of the Meandering Fluvial Deposits of the Neogene Upper Guantao Formation in Zhanhua Sag, Bohai Bay Basin, China

Quantitative Architectural Anatomy of the Meandering Fluvial Deposits of the Neogene Upper Guantao Formation in Zhanhua Sag, Bohai Bay Basin, China

고려 사절의 契丹 使行 여정 검토

This study examines the Itinerary of Goryeo Embassy to Khitan, focusing on the destination and travel route. As Khitan maintained a nomadic lifestyle, emperor traveled seasonally conducing Nabo. Due to this government system, Goryeo envoys to Khitan did not always visit to one set destination. It is found that Goryeo envoys visited various places such as Five Capitals (五京), Guangping Lake (廣平淀), Qingzhou (慶州), and Mt. Yongan (永安山), etc. in their diplomatic trips to Khitan.
 First, Goryeo envoys with various purposes visited the Central Capital often in winter as Emperor Shenzong held winter nabo there during his reign. On the other hand, Goryeo envoys went to the Southern Capital in various seasons. From the Eastern Capital, there was a travel route to the Central Capital passing through the Liaoxi area. From the Eastern Capital to the Southern Capital, there was one route along the Bohai bay and another path going through the Central Capital. Of the two, the coastal route was the faster than the inland route.
 Second, Goryeo envoys visited places in the Supreme Circuit more frequently. As winter nabo was mainly conducted in Guangping Lake near Yongzhou (永州), diverse regular and special envoys headed there. When there was a state funeral of emperor or empress dowager, Goryeo envoys went to Qingzhou to express condolence. In addition, the destination of Goryeo envoys arrival was related to the specific time as the emperor moved every season for nabo. While regular envoys for celebrating New Year and Brithday of an emperor or empress dowager were sent at the end of year, special envoys were dispatched to various destinations as the occasion demands.
 Regarding the travel route, it is assumed that there is one route passing through the Central Capital and another one to the north and along the rivers. However, these presumed routes have limitation as they detoured to the Supreme Circuit. Because there were frequent exchange of envoys between the two, it is presumed that there was a direct route from the Eastern Capital. For the travel of diplomatic trips, it generally took about two to three months. These diplomatic trips to the various destinations was meaningful in that they helped the Goryeo people to increase understanding of the Khitan state and people, which provided the foundation of stable relations between the two states.

Understanding pore space and oil content of liquid-rich shale in the southern Bohai Sea, China

The commercial production of shale oil in onshore Bohai Bay Basin has become a reality, but the potential of offshore shale oil is still unclear. The Bohai Sea, the leading crude oil-producing area in China in 2022, has great potential of shale oil resources, but the shale properties have not been comprehensively studied. The southern Bohai Sea, including the Huanghekou and southwestern Bozhong Sags, was selected. The study was performed on three layers: the third member of Shahejie Formation, first and second members of Shahejie Formation (as a whole), and the third member of Dongying Formation. Twenty-one shale core samples from nine wells, for the first time, were analyzed for sedimentary structure, lithology, pore space, composition of the thermally hydrocarbons and oil content. The content of minerals, pore sizes, and composition of the thermally hydrocarbons were compared with those of shales from other regions of China. The potentially producible oil generated in the organic-rich laminae was found to be accumulated in the silt-grained laminae through micromigration. Mixed and siliceous shale were the main lithofacies. Mineral overgrowths and solid bitumen reduce the volume of former intergranular pores. Honeycomb-like OM pores in samples with higher maturity (Ro > 1.1%) substantially increased pore connectivity from FIB-SEM image datasets. The retained oil was mainly distributed in pores with widths larger than 4 nm. The composition of the thermally hydrocarbons in samples stored at ambient conditions was governed by the maturity and concentration of the OM. Light hydrocarbons, even gaseous hydrocarbons are still retained in the shale with lower maturity and higher TOC for strong sorption of OM. The oil content is 0.50–23.41 mg/g after Rock-Eval S1 correction, with an average of 6.27 mg/g. While average oil content is 1.38 mg/g without correction. Finally, the optimal production intervals for Well B4 and Well B8 were determined. This study provides data and suggestions for the exploration of shale oil resources in the southern Bohai Sea.

Micro formation mechanism of oil–water inversion in reservoirs based on water film theory—An example from the Dawangzhuang Oilfield in Bohai Bay Basin

In oil fields, the inverted oil–water phenomenon of “water above oil”, which cannot be explained by the traditional principle of gravity differentiation. In hydrophilic reservoirs, water films easily form on rock particle surface. Water films reduce the effective pore throat radius and the space between pores and throats, generate disjoining pressure, and significantly reduces the seepage capacity of pore fluids, which leading to the phenomenon of oil water inversion. Based on laboratory experiments, a model of the relationship between the disjoining pressure -water film thickness was established, and the dynamic mechanism of oil–water inversion was studied using water-film theory. The main factor controlling oil–water inversion is the interaction between the dynamic (buoyancy) and resistance (capillary force and disjoining pressure) forces of oil–water migration and the configuration relationship with the average pore throat radius. The effects of the water film thickness and pore throat radius on the disjoining pressure and capillary resistance were quantitatively analysed, and the critical pore radius model for oil–water inversion was determined. Combining the capillary pressure curve and pore throat distribution, a practical and feasible theoretical technology and method for judging whether oil–water inversion occurs in a reservoir was established. 22 sets of experiments were conducted to verify the reliability and sensitivity of the disjoining pressure - water film thickness model. Taking the Dawangzhuang Oilfield, Raoyang Sag, Bohai Bay Basin, China as an example, through laboratory experiments, specific strata and reservoir data were obtained in the study area, and the disjoining pressure, capillary resistance, and buoyancy were calculated using the disjoining pressure - water film thickness model. By comparing the relationship between the buoyancy and the sum of the equilibrium disjoining pressure and capillary resistance, combined with the distribution of the pore throat radius, it is determined whether there is oil water inversion phenomenon. The practical application based on the theory and method of water film thickness has strong promotion potential for medium–low porosity and permeability reservoirs with the phenomenon of oil water inversion distribution of “water above oil ” whcih can effectively guide oil fields to further select favorable exploration and development targets.

Legacy and alternative per-and polyfluoroalkyl substances (PFASs) in the Bohai Bay Rim: Occurrence, partitioning behavior, risk assessment, and emission scenario analysis

The use of alternative per- and polyfluoroalkyl substances (PFASs) has been practiced because of the restrictions on legacy PFASs. However, knowledge gaps exist on the ecological risks of alternatives and relationships between restrictions and emissions. This study systematically analyzed the occurrence characteristics, water-sediment partitioning behaviors, ecological risks, and emissions of legacy and alternative PFASs in the Bohai Bay Rim (BBR). The mean concentration of total PFASs was 46.105 ng/L in surface water and 6.125 ng/g dry weight (dw) in sediments. As an alternative for perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimer acid (GenX) had a concentration second only to PFOA in surface water. In sediments, perfluorobutyric acid (PFBA) and GenX were the two predominant contaminants. In the water-sediment partitioning system, GenX, 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (F-53B), and 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (8:2 Cl-PFESA) tended to be enriched towards sediments. The species sensitivity distribution (SSD) models revealed the low ecological risks of PFASs and their alternatives in the BBR. Moreover, predicted no-effected concentrations (PNECs) indicated that short-chain alternatives like PFBA and perfluorobutane sulfonate (PFBS) were safer for aquatic ecosystems, while caution should be exercised when using GenX and F-53B. Due to the incremental replacement of PFOA by GenX, cumulative emissions of 1317.96 kg PFOA and 667.22 kg GenX were estimated during 2004–2022, in which PFOA emissions were reduced by 59.2 % due to restrictions implemented since 2016. If more stringent restrictions are implemented from 2023 to 2030, PFOA emissions will further decrease by 85.0 %, but GenX emissions will increase by an additional 21.3 %. Simultaneously, GenX concentrations in surface water are forecasted to surge by 2.02 to 2.45 times in 2023. This study deepens the understanding of PFAS alternatives and assists authorities in developing policies to administer PFAS alternatives.

Abundance, distribution and deposition of PM2.5-bound iron in northern China during 2021 dust and dust storm periods

Dust storms have the ability to transport and deposit contaminants and nutrients, such as iron (Fe), to downwind regions through atmospheric processes. However, there is a lack of reported data on the high-resolution variations and deposition of particulate iron in multiple locations during dust storms. This study aimed to address this gap by employing standardized analytical methods to measure the concentrations of PM10, PM2.5, and PM2.5-associated Fe in Taiyuan, Beijing, Tianjin, Ji'nan, and the Bohai Bay of China during the dusty events of 2021. A total of 13 blowing sand or dust storms were recorded, with average PM10 and PM2.5 concentrations of 262 ± 322 and 85 ± 652, 171 ± 403 and 53 ± 448, 153 ± 211 and 57 ± 315, and 207 ± 249 and 63 ± 301 μg/m3 at the above-mentioned sites, respectively. These elevated concentrations were attributed to stronger winds in northern China and severe wind erosion in the sand source areas. During these events, the average concentrations of PM2.5-bound Fe reached 2730.2 ± 4587.9, 2030.2 ± 3877.9, 1342.1 ± 2251.4, and 1785.1 ± 2536.6 ng/m3 in Taiyuan, Beijing, Tianjin, and Ji'nan, respectively, with the highest concentrations recorded as 48.8, 48.0, 29.2, and 22.7 μg/m3. A significant positive correlation was observed between Fe and Si in PM2.5 in the four cities, with higher Fe/Si slopes recorded in or near the source regions, while the homogenized Fe/Si values were observed after long-distance transport. The mean dry deposition fluxes (FFe) of PM2.5-bound Fe were calculated as 0.34 ± 0.64, 0.31 ± 0.91, 0.21 ± 0.56, and 0.17 ± 0.28 mg/m2/d for Taiyuan, Beijing, Tianjin, and Ji'nan, respectively, based on both hourly observation data and model-based calculations of dry deposition velocities. It is worth noting that FFe decreased from west to east in China, consistent with a previous study that showed a decrease in dust deposition rates with increasing transport distances. Peaks in FFe corresponded to the highest concentrations of PM2.5-associated Fe, indicating that these concentrations played a significant role in Fe. Furthermore, the atmospheric deposition of dissolved Fe from blowing sand or dust storm events was found to contribute to carbon fixation in the Bohai region of China, providing a range of 7.8 × 104–3.9 × 106 mol. This research provides valuable insights into the quantitative relationship between atmospheric deposition and marine productivity during dust events.

Sedimentary Characteristics and Depositional Model of Lacustrine Gravity Flows: A Case Study of Paleogene Shahejie Formation in the Gubei Sag, Eastern China

Abstract The genesis and sedimentary architecture of lacustrine gravity flow deposits include ongoing questions affecting the exploration and development of oil and gas, which require attention and investigation. Based on the core description, logging characteristics, and seismic facies in the third member of Paleogene Shahejie formation from the southern Bohai Bay Basin, this study provides some insights regarding lacustrine gravity flows by analyzing the characteristics, distribution patterns, and sedimentary processes of lacustrine gravity flow deposits. Twenty lithofacies are classified into eight bed types which are caused by cohesive flows, inflated flows, concentrated-density flows, or turbidity currents. The characteristics and distributions of different bed types in five sublacustrine fans with two provenance directions and in a slump olistolith reflect two sedimentary processes influenced by sediment supply, basin structure, and climate, including cohesive flow deposits covered by inflated sandflow deposits transforming into concentrated-density flow deposits into hybrid event beds and finally into turbidity current deposits from inner to outer fan, and cohesive flow deposits transforming into inflated sandflow deposits covered by turbidity current deposits into concentrated-density flow deposits into hybrid event beds finally into turbidity current deposits from proximal to distal lobe. Based on the results, a depositional model of lacustrine gravity flow deposits is established, which highlights the change from superimposed channels to anastomosing channels, the distributions and characteristics of hybrid event beds, and distinctive facies in different elements.

Tectonism and fracture-related dissolution induced the formation of the large-scale metamorphic granite reservoir: Implications from Bozhong 26–6 Precambrian bedrock trap, offshore Bohai Bay basin, Northern China

Crystalline rocks in basins are unconventional sites for hydrocarbon exploration. Owing to the lack of primary pores in the bedrock, it remains unclear how later tectonism and dissolution alter crystalline rock within large-scale reservoirs. Notably, the recent discovery of a 200 million-ton oil field of Precambrian metamorphic granite in the Bonan buried hill, Bohai Bay Basin, China provides an important opportunity for exploring this mechanism. Herein, the relationship between fractures and the regional tectonic evolution of this buried metamorphic granite mass, as well as the accompanying phenomena of dissolution and vein filling (which record related fluid interactions contributing to second pore formation from tight crystalline rocks) were investigated. The results indicated that the reservoir space was primarily composed of tectonic fractures and associated dissolution pores (maximum porosity ≤18%). The densely interlaced fractures with dominant NWW-trending flat surfaces indicated that the majority of Precambrian bedrock fractures were induced by Indosinian tectonic compression. The Cenozoic north–south tectonic extensional fault obliquely intersects these NWW-trending fractures, accounting for 73% of the previous dense shearing fractures transformed into open fractures. The dissolution pores were primarily distributed along the fractures and increased the porosity of these fracture-related reservoirs by ≤ 12%. The carbon and oxygen isotopes of the calcite fillings within the fractures suggested that atmospheric freshwater was the primary dissolution fluid, whereas some pores were formed by the dissolution action of deep hydrothermal and organic acid fluids. Thus, regional compressive stress is a necessary tectonic mechanism for the formation of densely interlaced fractures in tight crystalline rocks. The later extensional setting contributing to fracture release and fracture dissolution in the epi-diagenesis stage are two immediate factors in the formation of permeability and storage capacity within buried bedrock traps.

Spatiotemporal distribution, source analysis and ecological risk assessment of polychlorinated biphenyls (PCBs) in the Bohai Bay, China

As a class of persistent organic pollutants (POPs), the spatial and temporal distribution of polychlorinated biphenyls (PCBs) in seawater is important for environmental assessment. Surface water samples were collected from 35 stations during summer and 36 stations during autumn of 2020 in the Bohai Bay. The concentration, composition, distribution and sources of PCBs were analyzed to assess the ecological impact of PCBs. The average concentration of ∑18PCBs was 124.6 ng/L (range of 28.1–445.5 ng/L) in summer and 122.8 ng/L (range of 21.0–581.4 ng/L) in autumn. PCBs in surface seawater of the Bohai Bay showed high near-shore and low far-shore characteristics, indicating the serious influence of land-based sources such as port activities and river inputs. Proportion analysis showed that Tetra-PCBs and Penta-PCBs were the major constituents in most stations. It was assessed as moderate and high risk (MRQ > 0.1) by mixture risk quotient (MRQ) and concentration addition (CA) model in surface seawater of the Bohai Bay. Principal component analysis (PCA) was used to explain the sources of PCBs in the Bohai Bay. PCBs in the Bohai Bay may come from commercial PCBs and their incineration products, municipal landfills, wood and coal combustion, and industrial activities, etc.

Target-based sedimentary diagenesis simulation and three-dimensional diagenesis evolution modeling

Deposition and diagenesis are important factors affecting the quality of oil and gas reservoirs. Previously reported diagenesis studies mainly involve qualitative analysis, such as the determination of diagenetic events and diagenetic evolution sequences and modeling of two-dimensional diagenetic evolution, with less effort devoted to quantitative numerical simulation and three-dimensional diagenetic evolution models. This study proposes a new method for target-based diagenesis simulation by integrating the discrete element method, the quartet structure generation set method, and morphological algorithms. This new hybrid method can quantitatively simulate the effects of mineral grain deposition, compaction, cementation, dissolution, and replacement. Since specific minerals can undergo specific diagenetic alterations through mineral labeling, the sequence and path of diagenesis can be predefined in this method. Taking the sandstone reservoir of Lower Member 3 of the Shahejie Formation in Linnan Sag, Huimin Depression, Bohai Bay Basin, East China as an example, the new simulation method used the constructed diagenetic evolution sequence based on thin section identification and geochemical analysis to systematically simulate deposition and diagenesis in the study area and to construct a three-dimensional diagenetic evolution model. The predicted porosity, permeability, and pore size distribution of the simulated digital rocks are in good agreement with the experimental values, which validates the high accuracy of the simulation method. Based on these three-dimensional multi-mineral evolution models, the evolution trends of porosity and permeability during the sedimentation and diagenesis process were elucidated, revealing the variation in reservoir quality in the studied area and indicating reservoir sweet spots. The constructed 3D diagenesis evolution models are widely applicable and can be used not only for permeability simulation but also for the study of electrical, acoustic, and mechanical properties of reservoirs.

How did submarine volcanic eruptions interact with organic matter to favour hydrocarbon generation in the Bohai Bay Basin, China?

ABSTRACT Based on the geological and geochemical analysis of volcanic rock and their surrounding rocks, combined with palaeontological data and hydrocarbon generation thermal simulation experiments, the mechanism of the impact of volcanic eruptions on the formation of organic matter and hydrocarbon generation in the Dongying Depression is investigated. According to the results, underwater volcanic eruptions play a significant role in promoting biological eruptions and water stratification by introducing heat, minerals, and metal elements. The formation of the basalt source rock symbiotic association went through three evolutionary stages, which were underwater eruption, late eruption, and normal sedimentation. These stages have influenced the generation of hydrocarbons from organic matter in the following ways: (1) The organic acid released from the source rock dissolves the adjacent basalt, and the transitional metal elements in the basalt become activated and enter the source rock, which catalyses the hydrocarbon generation from the source rock. (2) Alteration of olivine in basalt releases hydrogen, improving hydrocarbon generation efficiency of source rock. (3) The existence of a large number of carbonates improves the hydrocarbon generation rate and efficiency of source rocks and reduces the hydrocarbon generation threshold of source rocks.

Investigation of the antimicrobial susceptibility patterns of marine cyanobacteria in Bohai Bay: Cyanobacteria may be important hosts of antibiotic resistance genes in marine environment

Marine cyanobacteria, as widely distributed and photosynthetically autotrophic bacteria in the ocean, may contribute to the global dissemination of antibiotic resistance genes (ARGs) and develop a different antimicrobial susceptibility pattern from heterotrophic bacteria and cyanobacteria from freshwater environments. However, studies on antimicrobial susceptibility and the carriage of ARGs in marine cyanobacteria are still very limited. In this study, the antibiotic resistance characteristics of cyanobacteria in nearshore waters were examined through field monitoring and laboratory investigations, which included PCR detection and ARG transformation. The results showed a positive correlation between marine cyanobacteria and some ARGs in the nearshore waters of Bohai Bay. Moreover, most screened cyanobacteria showed high minimum inhibitory concentration (MIC) values for polymyxins, tetracyclines, kanamycin, and sulfonamides, moderate MIC values for streptomycin, chloramphenicol, rifampicin, and norfloxacin, and low MIC values for roxithromycin and cephalosporins. The blaTEM, blaKPC, sul1, sul2, strA, tetA, tetB, tetC, tetM, mdfA, and intI1 genes were detected in the screened marine cyanobacteria. The highest detection rates were observed for blaTEM (93.3 %), sul1 (56.6 %), sul2 (90 %), and strA (73.3 %). The detection rate of tetA (33.3 %) was the highest among the tetracycline resistance genes, and mdfA, a multidrug-resistant pump gene with resistance to tetracycline, also showed a high detection level (23.3 %). Overall, most of the screened marine cyanobacteria were found to tolerate multiple antibiotics in seawater, and the condition of the ARGs carriage was serious. Furthermore, the screened marine Synechocystis sp. C12-2 demonstrated the ability to accept ARGs on the RP4 plasmid through natural transformation and showed reduced sensitivity to ampicillin, suggesting the possibility that some marine cyanobacteria could acquire ARGs from the environment through horizontal gene transfer. Thus, marine cyanobacteria may play an important role in the propagation of marine ARGs.

Formation mechanisms and resource potential of carbonate geothermal reservoirs in the Beijing-Tianjin-Hebei plain

Investigating the formation mechanisms of carbonate geothermal reservoirs is of theoretical and practical significance for summarizing the formation pattern of geothermal resources and further guiding their effective exploitation. The Beijing-Tianjin-Hebei Plain (BTHP), predominantly located within the Jizhong Depression and Cangxian Uplift in the Bohai Bay Basin, serves as the primary region for geothermal exploitation and utilization in China. More than 1500 geothermal wells have been drilled therein, with water temperature at the wellhead ranging from 55 to 110 °C, single-well flow rate ranging between 80 and 120 m3/h, and cumulative heating area exceeding 100 × 106 m3. However, the exploration and research in the region remain limited overall. As per the previous geothermal and petroleum exploration results and the latest geothermal drilling data, this study comprehensively evaluated the geothermal resources of karst geothermal reservoirs. The results show that two suites of carbonate karst reservoirs, namely the Jxw Formation and the Ordovician strata, have primarily developed in the BTHP, and their formation and evolution can be divided into four stages: the Mesoproterozoic-Early Paleozoic stage with carbonate sedimentation and the development of interlayer karst, the Late Paleozoic stage with the development of direct sedimentary cover, the Mesozoic stage with compressional uplifting and development of buried hill karst, and the Cenozoic stage with regional cover deposition and the modification and finalization of karst geothermal reservoirs. Accordingly, the porosity evolution history of the geothermal reservoirs is composed of three stages, namely a significant decrease followed by a minor increase, a gradual decline, and then a small fluctuation from increase to decrease before slowly rising again. The karstification in geothermal reservoirs can be summarized into quasi-syngenetic karstification, epigenetic karstification, and burial karstification, which can be subdivided into seven subcategories. The carbonate geothermal reservoirs in the study area boast total geothermal resources of 53.821 × 109 GJ, or 184.155 × 109 t of standard coal equivalent (tce), and the annual exploitable geothermal resources in the urban area can heat an area of (400‒500) × 106 m3, indicating great potential of geothermal exploitation.

Differences and identification on multi-time hydrocarbon generation of carboniferous-permian coaly source rocks in the Huanghua Depression, Bohai Bay Basin

Coal is a solid combustible mineral, and coal-bearing strata have important hydrocarbon generation potential and contribute to more than 12% of the global hydrocarbon resources. However, the deposition and hydrocarbon evolution process of ancient coal-bearing strata is characterized by multiple geological times, leading to obvious distinctions in their hydrocarbon generation potential, geological processes, and production, which affect the evaluation and exploration of hydrocarbon resources derived from coaly source rocks worldwide. This study aimed to identify the differences on oil-generated parent macerals and the production of oil generated from different coaly source rocks and through different oil generation processes. Integrating with the analysis of previous tectonic burial history and hydrocarbon generation history, high-temperature and high-pressure thermal simulation experiments, organic geochemistry, and organic petrology were performed on the Carboniferous-Permian (C–P) coaly source rocks in the Huanghua Depression, Bohai Bay Basin. The oil-generated parent macerals of coal’s secondary oil generation process (SOGP) were mainly hydrogen-rich collotelinite, collodetrinite, sporinite, and cutinite, while the oil-generated parent macerals of tertiary oil generation process (TOGP) were the remaining small amount of hydrogen-rich collotelinite, sporinite, and cutinite, as well as dispersed soluble organic matter and unexhausted residual hydrocarbons. Compared with coal, the oil-generated parent macerals of coaly shale SOGP were mostly sporinite and cutinite. And part of hydrogen-poor vitrinite, lacking hydrocarbon-rich macerals, and macerals of the TOGP, in addition to some remaining cutinite and a small amount of crude oil and bitumen from SOGP contributed to the oil yield. The results indicated that the changes in oil yield had a good junction between SOGP and TOGP, both coal and coaly shale had higher SOGP aborted oil yield than TOGP starting yield, and coaly shale TOGP peak oil yield was lower than SOGP peak oil yield. There were significant differences in saturated hydrocarbon and aromatic parameters in coal and coaly shale. Coal SOGP was characterized by a lower Ts/Tm and C31-homohopane22S/(22S+22R) and a higher Pr/nC17 compared to coal TOGP, while the aromatic parameter methyl dibenzothiophene ratio (MDR) exhibited coaly shale TOGP was higher than coaly shale SOGP than coaly TOGP than coaly SOGP, and coal trimethylnaphthalene ratio (TNR) was lower than coaly shale TNR. Thus, we established oil generation processes and discriminative plates. In this way, we distinguished the differences between oil generation parent maceral, oil generation time, and oil production of coaly source rocks, and therefore, we provided important support for the evaluation, prediction, and exploration of oil resources from global ancient coaly source rocks.

Quantitative Retrieval of Chlorophyll-a Concentrations in the Bohai–Yellow Sea Using GOCI Surface Reflectance Products

As an environmental parameter, the chlorophyll-a concentration (Chl-a) is essential for monitoring water quality and managing the marine ecosystem. However, current mainstream Chl-a inversion algorithms have limited accuracy and poor spatial and temporal generalization in Case II waters. In this study, we constructed a quantitative model for retrieving the spatial and temporal distribution of Chl-a in the Bohai–Yellow Sea area using Geostationary Ocean Color Imager (GOCI) spectral remote sensing reflectance (Rrsλ) products. Firstly, the GOCI Rrsλ correction model based on measured spectral data was proposed and evaluated. Then, the feature variables of the band combinations with the highest correlation with Chl-a were selected. Subsequently, Chl-a inversion models were developed using three empirical ocean color algorithms (OC4, OC5, and YOC) and four machine learning methods: BP neural network (BPNN), random forest (RF), AdaBoost, and support vector regression (SVR). The retrieval results showed that the machine learning methods were much more accurate than the empirical algorithms and that the RF model retrieved Chl-a with the best performance and the highest prediction accuracy, with a determination coefficient R2 of 0.916, a root mean square error (RMSE) of 0.212 mg·m−3, and a mean absolute percentage error (MAPE) of 14.27%. Finally, the Chl-a distribution in the Bohai–Yellow Sea using the selected RF model was derived and analyzed. Spatially, Chl-a was high in the Bohai Sea, including in Laizhou Bay, Bohai Bay, and Liaodong Bay, with a value higher than 4 mg·m−3. Chl-a in the Bohai Strait and northern Yellow Sea was relatively low, with a value of less than 3 mg·m−3. Temporally, the inversion results showed that Chl-a was considerably higher in winter and spring compared to autumn and summer. Diurnal variation retrieval effectively demonstrated GOCI’s potential as a capable tool for monitoring intraday changes in chlorophyll-a concentrations.

Applicability of Nuclear Magnetic Resonance Experiment in Analyzing Pore and Fluid Distribution Characteristics of Tight Sandstone: A Case Study in the Julu Area, Bohai Bay Basin, China.

Characterizing the pore and fluid distribution is critical for evaluating the reservoir potential of new areas. Nuclear magnetic resonance (NMR) is considered as an experimental method capable of full-scale characterization of pore characteristics. However, the T2 spectrum of a saturated sample is affected by a combination of sample and experimental parameters, and it is important to confirm whether the T2 spectrum fully reflects the sample pore information. Eight tight sandstone samples from the Julu area were selected for thin section identification, mercury intrusion porosimetry (MIP), NMR, NMR cryoporometry (NMRC), and centrifugation experiments to critically analyze the applicability of the NMR results. Two methods, the similarity method and Kozeny's equation method, were used to calculate surface relaxivity, a critical parameter for converting NMR T2 signals into pore information. The discussion focuses on the applicability of the calculated surface relaxivity and the phenomenon of T2 signal changes in a short relaxation range after centrifugation. The main results are as follows: The surface relaxivity values calculated using the different methods differed significantly. The surface relaxivity calculated using the same method reflected the relative magnitude of the true surface relaxivity of the samples. For the samples with large surface relaxivity, there may be partial misses of the short relaxation signal, the NMR porosity was smaller than the gas-measured porosity, there was a variation in the T2 spectrum in the short relaxation range after centrifugation, and the calculated surface relaxivity was small. The surface relaxivity calculated using Kozeny's equation was nearly accurate, but perhaps smaller than the true value. The T2 spectra mainly reflected macropore information. This study suggests that PSDs converted from T2 spectra of saturated samples should be judged with relative caution rather than solely based on the peak or range correspondence between the two curves, and the minimum centrifugal radius can be used as a constraint.

Occurrence of organotin compounds in food: increasing challenge of phenyltin compounds

Concentrations and distribution for 16 organotin compounds were studied in all kinds of foods, including seafood, agricultural products, and wine. Meanwhile, the degradation of the TBT or TPhT was also evaluated. Concentrations of total organotins in seafood, agricultural products, and wine were 1047.2, 469.4, and 13.5 μg Sn/kg. Meanwhile, the most frequently detected organotin in three kinds of samples were TPhT, MPhT, and MPhT, respectively. The results demonstrated that phenyltin may probably become an emerging organotin pollutant. Regarding seafood, organotin concentrations of fish and mollusks were much higher than those of crustaceans. At the same time, a significant positive correlation was observed between the concentrations of TBT and MBT (p < 0.05), and between DBT and MBT(p < 0.0001). Moreover, TPhT was significantly and positively associated with DPhT (p < 0.0001), suggesting that TPhT was the precursor of DPhT. Apart from the likely illegal use of OTs as biocides in antifouling paints for ships, anthropogenic activity like agricultural activity or industrial activity also caused organotin contamination. Further research and more effective measures should be formulated to protect the food safety. Meanwhile, monitoring of the organotin contamination should not only in Qinhuangdao, but also expand to the cities along Bohai Bay.

Hydrogeochemical Characteristics of Geothermal Water in Ancient Deeply Buried Hills in the Northern Jizhong Depression, Bohai Bay Basin, China

The Jizhong Depression boasts rich geothermal resources with a lengthy history of geothermal exploitation. Buried hill geothermal reservoirs, which serve as primary thermal sources for hydrothermal resource exploitation, are prevalent in this region and have advantages such as extensive development potential, significant geothermal reservoir capacity, superior water quality, and straightforward recharge. This study investigates the formation and evolution of deep geothermal water in the Jizhong Depression by analyzing the hydrochemical and isotopic data of geothermal water samples collected from buried hill geothermal reservoirs in the northern part of the depression. The findings reveal that the subsurface hot water samples from the carbonate geothermal reservoirs in this region were predominantly weakly alkaline water with a pH ranging between 6.61 and 8.87. The hot water samples collected at the wellhead exhibited temperatures varying from 33.9 °C to 123.4 °C and total dissolved solids (TDS) lying between 473.9 mg/L and 3452 mg/L. Based on the δ2H-δ18O stable isotope analysis, the geothermal fluids in the Jizhong Depression are predominantly sourced from atmospheric precipitation and exist in a somewhat isolated hydrogeological environment, exhibiting pronounced water–rock interactions and deep water circulation (with depths ranging from 1324 m to 3455 m). Through a comparison of various methods, it is deduced that the most appropriate geothermometer for deep karst geothermal reservoirs in the Jizhong Depression is a chalcedony geothermometer, and when using it, the deep reservoir temperature was estimated at 63–137.6 °C. The precipitation in the adjacent mountainous areas enables the groundwater to infiltrate and descend deep into the earth along piedmont faults. Subsequently, lateral runoff over extended periods replenishes the groundwater into the depression. This process allows for the groundwater to fully absorb heat from deep heat sources, resulting in the formation of the deep geothermal reservoirs in the northern Jizhong Depression. The insights obtained from this study offer a theoretical and scientific foundation for the exploitation and utilization of regional geothermal resources and the transformation of the energy structure in China.

Lipid Production of Schizochytrium sp. HBW10 Isolated from Coastal Waters of Northern China Cultivated in Food Waste Hydrolysate.

Marine oleaginous thraustochytrids have attracted increasing attention for their great potential in producing high-value active metabolites using various industrial and agricultural waste. Food waste containing abundant nutrients is considered as an excellent feedstock for microbial fermentation. In this study, a thraustochytrid strain Schizochytrium sp. HBW10 was isolated from a water column in Bohai Bay in Northern China for the first time. Further lipid production characteristics of S. sp. HBW10 were investigated utilizing sulfuric acid hydrolysate of food waste (FWH) from two different restaurants (FWH1 and FWH2) with the initial pH value adjusted by NaOH or NaHCO3. Results showed that the highest concentration of total fatty acids (TFAs) was observed in FWH2 medium with the 50% content level on the fifth day, reaching up to 0.34 g/L. A higher initial pH promoted the growth and saturated fatty acid (SFA) accumulation of S. sp. HBW10, achieving nearly 100% of the sum of saturated and monounsaturated fatty acids (SMUFAs) in TFAs with initial pH7 and pH8 in FWH1 medium. This work demonstrates a possible way for lipid production by thraustochytrids using food waste hydrolysate with a higher initial pH (pH7~pH8) adjusted by NaHCO3.

Analysis of the Genetic Model of the Extremely Narrow Channel Shallow Water Delta in DL-A Oilfield, Bohai Bay Basin.

In recent years, the oil and gas reserves discovered in shallow water deltas in China have continued to grow. The research on shallow water delta deposition models and depositional genesis is becoming more and more mature. In this latest discovery, a unique type of extremely narrow channel shallow water delta deposit was found at the top of the V oil group in the lower part of the Minghuazhen Formation during the Neogene period at DL-A Oilfield, located in the Bohai Bay Basin. The width of most single channels in this deposit measures between 100 and 200m, which is relatively rare and differs from existing research. To better understand this unique narrow channel shallow water delta deposit, a range of analysis methods were conducted including trace element analysis, major element analysis, grain size analysis, core observation, casting thin section observation, 3D seismic analysis, and other methods. These analyses were used to determine the sedimentary environment and sedimentary genesis of the deposit in the study area. The results show the following: (1) The top of the V oil group in the lower part of Minghuazhen Formation was deposited with a strong oxidizing environment. In the early stage, the climate was dry and cold, and gradually changed to warm and humid in the late stage. (2) Due to the frequent exposure to the surface, obvious weathered surfaces and sedimentary discontinuities were observed on the cores; the particle size analysis shows that the lamina types developed in the study area are clastic-clay laminae and clay-clastic laminae, which are mostly developed in shallow lakes area. (3) Observations of cores and thin sections also indicated that the hydrodynamic conditions frequently changed in the study area, alternating between strong and weak hydrodynamic conditions in a short period due to the alternating occurrence of flood and dry periods during the rainy season. Weak hydrodynamic conditions and slow water flow result in insufficient undercutting and sidecutting of rivers. The alternating occurrence of flood periods and dry periods has led to the development of crevasse splays and frequent river channel diversions, resulting in the inability of long-term stable development of the river channel. Besides, the change of water level has also led to the rebuilding of the river. Therefore, the multiple effects led to the formation of an extremely narrow channel shallow water delta. The accuracy of the sedimentary model is verified by a comparative study of the Shaliu River and Buha River in the modern Qinghai Lake. The new extremely narrow channels deposition model proposed this time further improves the deposition theory. At the same time, the modern depositional characteristics of the Shaliu River and Buha River also reveal the reservoir deposition between channels that cannot be distinguished by seismic data, providing guidance for the development of oil and gas in the study area.