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This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay, silt, and fine sand soils obtained from the Bohai Sea, China. Emphasis is placed on the major factors for predominating the dynamic shear modulus (G) and damping ratio (λ) in the shear strain amplitude (γa) from 10−5 to 10−2, involving depth, sedimentary facies types, and water content of marine soils. The empirical equations of the small-strain shear modulus (Gmax) and damping ratio (λmin) using a single-variable of depth H are established for the three marine soils. A remarkable finding is that the curves of shear modulus reduction (G/Gmax) and the damping ratio (λ) with increasing γa of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content W. This finding is validated by independent experimental data from the literature. At the similar depths, the G value of the marine soils of terrestrial facies is the largest, followed by the neritic facies, and the G value of the marine soils of abyssal facies is the smallest. The sedimentary facies types of the marine soils have slight effect on the λ value. Another significant finding is that the shear modulus reduction curves plotted against the γa of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils, while the damping curves plotted against γa are just the opposite. The results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a radionuclide dispersion model for the nuclear power plants in the Bohai, Yellow, and East China seas (BYECS) characterized by high turbidity and multi-scale circulations, focusing on the comparison of dispersion processes of 137Cs depending upon, in particular, the suspended sediment concentration and erosion/sedimentation processes. The simulations were carried out using a multi-fraction sediment transport model embedded in the semi-implicit Eulerian–Lagrangian finite-element coupled wave-circulation model linked with the model of radionuclide transport, which describes the key radionuclide transfer processes in the system of water–multi-fraction sediments. In contrast to the Eulerian models used for hydrodynamics and sediment transport processes, the Lagrangian technique was applied to simulate the transport of radionuclides. The simulation results for total suspended concentration agreed with in situ measurements and the Geostationary Ocean Color Imager data. The results of the simulation of hypothetical releases of 137Cs from four nuclear power plants (NPPs) placed in BYECS essentially differ from the real release of activity in the Pacific Ocean shelf due to the Fukushima Daiichi accident, which took place at the same time and released activity that was similar. The total amount of bottom contamination of 137Cs in releases from the Sanmen, Hanbit, and Hongyanhe NPPs was about 40% of dissolved component, and the total amount of suspended component was about 20% of dissolved component, in contrast with the Fukushima Daiichi accident, where the particulate component was only 2%. The results demonstrate the importance of erosion processes in the budget of 137Cs in shallow areas around the Sanmen and Hanbit NPPs, where strong wind and tidal currents took place. [ABSTRACT FROM AUTHOR]

Discriminating the provenance of fine-grained sediments is crucial for reconstructing paleogeography, sedimentary processes, and paleoclimate. In this paper, we investigate the South Bohai Coast to better understand source-to-sink systems in East Asia. This region is influenced by both distant sources such as the large-scale Yellow River and small local river sources flowing from the Luzhong Mountain area. Two Holocene sedimentary cores, dated using optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C chronology, were used to investigate the provenance of the fine-grained sediments over the last 7 kyrs. Clay mineralogy and relevant non-linear modeling were employed for provenance discrimination. The results show that the fine-grained sediments along the South Bohai Coast were mainly derived from the Yellow River during the periods of 7.0–5.4 ka and 4.5–2.6 ka, respectively, while the input from the Luzhong Mountain-derived rivers was greater during 5.4–4.5 ka and 2.6–0.2 ka, respectively. Fluvial activities and marine-terrestrial interaction driven by climate factors such as East Asian winter monsoon, temperature, and precipitation in river basins, dominantly influenced the provenance of fine-grained sediments from 7.0 to 2.6 ka. Anthropogenic impact on provenance increased after 2.6 ka. The chronology of the two cores showed extremely rapid sedimentation rate transitions at 5.2 ka and 1.5 ka, respectively, very likely attributed to anthropogenic-induced rapid progradation. Our study provides a model for better understanding the paleoenvironmental and paleogeographic evolution of a coastal area where multiple sources exist. • Anthropogenically high sedimentation rate in the South Bohai Coast in late Holocene. • Provenance discrimination of the fine-grained sediments in the South Bohai Coast since the mid-Holocene. • The major source of the fine-grained sediments in the South Bohai Coast changed episodically. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) plays a pivotal role in sustaining marine ecosystems. The Bohai Sea in China is a semi-enclosed sea, and oxygen-deficit events occur from time to time due to human activities. At present, there is a notable absence of any convenient and precise method for obtaining three-dimensional spatial data on DO, and the exploration of the physical mechanisms influencing oxygen deficit remains incomplete. This investigation uses the linear radial basis function (RBF-Linear) fitting method to conduct three-dimensional spatial interpolation for DO, which demonstrates minimal inaccuracy. Then, the RBF-Linear fitting method is utilized to collect a comprehensive three-dimensional spatial dataset encompassing temperature, salinity, and DO in the Bohai Sea in August from 2016 to 2018. The results indicate discernible interannual variations in the extent, area, and distribution of oxygen deficiency during summer in the Bohai Sea. Mechanism analysis reveals that intense precipitation episodes and an increase in wind stress curl exacerbate oxygen depletion. Additionally, the degree, location, and area of the two oxygen-deficit cores (off the Yellow River Estuary and off the Qinhuangdao) in the Bohai Sea are influenced by several factors, including current velocity, direction, local circulation position, and net horizontal transport rate. Furthermore, the study suggests that oxygen deficiency in the Bohai Sea region is currently in its early stages, with a limited degree of injury and a restricted range of influence. The use of a three-dimensional spatial interpolation method to create a complete DO field in three-dimensional space simplifies the research challenges associated with marine oxygen deficit. Moreover, this study holds particular significance for guiding the development of marine fisheries. [ABSTRACT FROM AUTHOR]

Suspended particulate matter is a crucial component in estuaries and coastal oceans, and a key parameter for evaluating their water quality. The Bohai Sea, a huge marginal sea covering an expanse of 77,000 km² and constantly fed by numerous sediment-laden rivers, has maintained a high level of total suspended particulate matter (TSM). Despite the widespread development and application of TSM retrieval algorithms using commonly available satellite data like Landsat, Sentinel, and MODIS, developing TSM retrieval algorithms for China's Gaofen (GF) series (GF-6 and GF-1) in the Bohai Sea is still a great challenge, mainly due to the limited applicability of empirical algorithms. In this study, 259 in situ measured-TSM samples were collected for algorithm development. The remote sensing reflectance (Rrs) curve demonstrates prominent peaks between 550 and 580 nm. Through conversion to remote sensing reflectance, it was found that single-band data had a weak correlation with TSM, reaching a maximum correlation of 0.44. However, by combining bands of band ratio calculations, the correlation was enhanced. Particularly, the blue and green band equivalent Rrs ratio had a correlation coefficient of 0.81 with TSM, and the proposed TSM inversion exponential algorithm developed based on this factor obtained an R-squared (R²) value of 0.76 and a mean relative error (MRE) of 32.24%. Analysis results indicated that: (1) there are spatial variations in the TSM within the Bohai Sea, Laizhou Bay, and the Yellow River estuary, with higher levels near the coast and lower levels in open waters. The Yellow River estuary experiences seasonal fluctuations higher TSM during spring and winter, and lower variations during summer and autumn, and (2) the dynamics of TSM are affected by Yellow River runoff, with increased runoff leads to higher TSM levels and expanded turbid zones. This study proposes a new algorithm to quantify TSM evolutions and distributions in the Bohai Sea and adjacent regions using China's Gaofen imageries. [ABSTRACT FROM AUTHOR]

Temporal and spatial patterns of inherent optical properties in the Bohai Sea are very complex. In this paper, we used 77 groups of field data of AOPs (apparent optical properties) and IOPs (inherent optical properties) collected in June, August, and September of 2005 in the Bohai Sea, to retrieve the spectral total absorption coefficient a( λ) with the quasi-analytical algorithm (QAA). For QAA implementation, different bands in the region 680-730 nm (in 5 nm intervals) were selected and compared, to determine the optimal band domain of the reference wavelength. On this basis, we proposed a new algorithm (QAA-Com), a combination of QAA-685 and QAA-715, according to turbidity characterized by a(440). The percentage difference of model retrievals in the visible domain was between 4.5%-45.1%, in average of 18.8% for a( λ). The QAA model was then applied to Medium Resolution Imaging Spectrometer (MERIS) radiometric products, which were temporally and spatially matched with in-situ optical measurements. Differences between MERIS retrievals and in-situ values were in the range 9.2%-27.8% for a( λ) in the visible domain. Major errors in satellite retrieval are attributable to uncertainties of QAA model parameters and in-situ measurements, as well as imperfect atmospheric correction of MERIS data by the European Space Agency (ESA). During a storm surge in April 2009, time series of MERIS images together with the QAA model were used to analyze spatial and temporal variability of the total absorption coefficient pattern in the Bohai Sea. It is necessary to collect more independent field data to improve this algorithm. [ABSTRACT FROM AUTHOR]

This paper analyzes the seismicity in Bohai Sea, introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea, a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method, a scheme of two seismic design levels is proposed, and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings, it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000–2500 years, respectively. The validity of these proposed values is discussed. Finally, the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea. [ABSTRACT FROM AUTHOR]

Advances in satellite sensor technology and information systems have contributed to the near real-time availability of high-quality sea ice data in the Bohai Sea. In this paper, the extent of Bohai sea ice and its spatio-temporal changes are analyzed using AVHRR data at visible and infra-red wavelengths. A methodology is put forth to automate the differentiating of sea ice from sea water and land using NOAA-AVHRR band 3 spectral reflectances. It is shown that sea ice is concentrated on the east coast of the Bohai Sea, with the most promising reserves on the eastern coastal region of Liaodong Bay. In particular, the harvesting of Bohai sea ice reserves is estimated to yield a total freshwater volume of approximately 1.585 to 7.089 billion cubic meters (BCM). This corresponds to approximately 33.7 m3 to 150.8 m3 of freshwater per person in the Bohai Sea region. [ABSTRACT FROM AUTHOR]

Spatiotemporal information is crucial for cetacean research and conservation, particularly for wide-ranging and migratory species. Sperm whales (Physeter macrocephalus) are distributed worldwide in deep oceans; however, little is known about the species in the western margin of the Pacific Ocean. Here, we examined the available information related to the occurrence, distribution, and potential habitats of sperm whales in the waters off China. Historical whaling information (18th-20th century) indicates that sperm whales have been captured in the East China Sea (ECS) and South China Sea (SCS). Furthermore, sporadic strandings have been recorded since the 1910s, and more frequently from 1990 onwards. Since 1990, accidental sightings have been documented in the eastern ECS, northeastern and southern SCS, and their adjacent waters. More recently (2019-2022), field encounters have been reported in dedicated ship-based investigations in the Xisha and Nansha waters, providing robust evidence of the regular existence and potential residency of sperm whales in the northwestern and central areas of the SCS. Female nursery groups suggest that the Xisha waters might be an important nursing ground for sperm whales. Satellite tracking data from four adults showed that sperm whales in the SCS might display both fine-scale and long-distance movements. Taken together, it appears that sperm whales are currently active in the waters off China, and that deep waters (depth >200 m) in the ECS and SCS may provide the species with critical habitats. This review provides crucial baseline information on sperm whales in the waters off China, which may help to facilitate future research efforts and conservation initiatives for the species at national and cross-regional scales. More field investigations and other monitoring approaches including acoustic monitoring, biologging, photo-identification, and genetics are required to reveal the distribution, movement, and habitat use patterns of sperm whales in these waters. [ABSTRACT FROM AUTHOR]

Under the influence of glacial-interglacial climate change and regional tectonic activities in the Quaternary, the sedimentary environments of the Bohai Sea changed greatly, providing significant information on transgression-regression events, East Asian monsoon changes and regional tectonic activities. This study analyzed the sedimentological characteristics of the BH1302 core (water depth of 12.3 m, length of 70.2 m) in the southern Bohai Sea based on grain size, foraminiferal assemblages, carbon and oxygen isotopes in foraminiferal shells and element geochemistry, and established a chronological framework based on AMS 14C, optically stimulated luminescence dating and Oxcal age-depth model using Bayesian modeling. The results showed that three interglacial transgressions and one interstadial transgression were revealed in BH1302 since the late Quaternary, corresponding to marine isotope stages (MIS) 7, 5, 3 and 1, and three subinterglacial transgressions were further identified during MIS 7. The sedimentary environments of Laizhou Bay transitioned from an estuary environment dominated by rivers to a neritic environment dominated by marine conditions because of subsidence of the Miaodao uplift in late MIS 7.1. Three subinterstadial transgressions occurred in both MIS5 with two subinterstadial in MIS 3, and the highstand sea level of MIS 3 reached approximately −18 ∼ −21 m. Under the influence of sea level fluctuations and the East Asian monsoon, the sedimentary environments of MIS 1 can be divided into a low salinity tidal-flat environment (12.0–7.0 kyr BP), a low salinity neritic environment (7.0–4.5 kyr BP) and a modern neritic environment (∼4.5 kyr BP). • The isotopes in the foraminifera shells have good indications to the impact of freshwater input on the neritic environments. • Except for 4 interglacial transgressions, the paper further identifies 3 sub-interglacial transgressions in the MIS7 period. [ABSTRACT FROM AUTHOR]

To obtain systematic knowledge on the waterborne pollution status and ecological and human health risk of total petroleum hydrocarbons (TPHs) and metals in the southeastern Bohai Sea, seawater samples were collected in three seasons from 2014 to 2018. TPHs and mercury (Hg) levels were determined by ultraviolet spectrophotometry and cold atomic absorption spectrometry, respectively, and concentrations of copper (Cu), lead (Pb), and cadmium (Cd) were detected by anodic stripping voltammetry. Spatial distribution patterns indicated that these waterborne pollutants are mainly sourced from terrestrial inputs. Temporal variation showed that Pb contents decreased in the past five years, and summer exhibited higher concentrations of Hg, Cu, and Cd than spring and autumn. Spearman's rank correlation coefficients demonstrated that temperature correlated positively with Cu content, while dissolved oxygen, pH, and suspended particulate material correlated negatively with pollutant concentrations. While hazard quotient values were lower than 1 for TPHs, Hg, Pb, and Cd, the hazard quotient of Cu (4.88) was greater than 1, suggesting potential ecological risks of this element in seawater of the southeastern Bohai Sea. The total target hazard quotients of Hg, Cu, Pb, and Cd in seawater of the southeastern Bohai Sea were all lower than 1, which indicated that there was no noncarcinogenic risk caused by heavy metals in seawater of the southeastern Bohai Sea. However, the carcinogenic risk of Cd (1.54 × 10−5) was in the range of 10−6–10−4, which may lead to the occurrence of cancer. This study sounds an alarm for stricter control of metal emissions into this sea area. [ABSTRACT FROM AUTHOR]

Marine zoning and planning are cornerstones of China's marine and coastal management, but are facing challenges in maintaining sustainable development with increasing resource use. Marine functional zoning (MFZ) and marine environmental functional zoning (MEFZ) are existing official Chinese regulations possessing legal force. In contrast, the Marine ecological red line (MERL) refers to a type of marine spatial planning aimed at ecological protection which has been promoted following a 2011 decision of the Chinese State Council to strengthen environmental protection. It has been partially implemented within China, but has only gained legal status in late 2014 and implementation in 2015. The paper compares the two kinds of marine spatial planning providing a general overview, an example in the Bohai Sea, and discussing the marine functional zone and marine ecological red line approaches. The legal status, spatial layout, and control of the systems are compared. The comparison shows that the marine ecological red line has the potential to supplement and strengthen the current marine functional zoning system, and that further improvement should come from recent legal developments. Management will require more ecological information to improve the technical aspects of the MERL approach to enable further MFZ and MERL integration. [ABSTRACT FROM AUTHOR]

Thorough understanding of seabed fluid flow system is of great significance to geohazard identification and hydrocarbon exploration as it can reshape the seabed and act as an indicator of subsurface hydrocarbon resources. For the first time, an integrated study of side‐scan sonar, single‐ and multi‐channel seismic data and magnetic data reveals a complex fluid flow system composed of various seafloor expressions (i.e. pockmarks and mounds) and shallow fluid migration pathways in the central‐west Bohai Sea off northeast China. Gas chimneys, mud diapirs and a dense network of Quaternary faults are the main fluid migration pathways in the shallow subsurface. The gas chimneys can be classified into three categories (Type A formed by relatively rapid gas escape, Type B formed by episodic fluid expulsion and Type C formed by fluid escape from mud diapirs), based on their distribution and seismic character, implying variability in the formation processes. Sediment remobilization and basement‐involved faults contribute to deep fluid migration into shallow depths. As a seal for up‐moving fluids, the nature and thickness of Holocene marine sediments generally decide the permeability and overburden pressure that may control the distribution of pockmarks and mounds since they are almost distributed above relatively thin Holocene deposits (thickness <20 m) and localized coarse surface sediments. The results of the interpretation gain an improved understanding of the geological processes controlling the genesis and spatial distribution of gas chimney formation and show the significance of gas chimney classification. The distribution pattern of different types of gas chimneys may signify the difference of geological background and fluid flow process, like fluid migration through faults or flow of mobilized sediments, that is crucial for the evaluation of global petroleum systems and Carbon Capture and Storage studies. [ABSTRACT FROM AUTHOR]

The shift of diatom dominance to combination of diatom and dinoflagellate dominance in the Bohai Sea (BS), China might be associated with the change of dissolved nitrogen (DN). This study combines field investigation, ship‐based microcosm experiments, a nitrogen biogeochemical model, and statistical analysis to reveal the impact of DN loading on the dominance of diatoms and dinoflagellates in the BS, considering the quantitative relationship between the algal growth/death and nitrogen migration/transformation processes. The diatom to diatom‐dinoflagellate shift was significantly associated with the DN regime shift of oxidized nitrogen (NO3‐N) to reduced nitrogen (NH4‐N and dissolved organic nitrogen [DON]) since the mid‐1990s. This phenomenon was supported by microcosm and numerical experiments: (a) Gonyaulax verior as a dominant dinoflagellate in the BS efficiently absorbed/assimilated NH4‐N, and it can also utilize DON derived from centric diatoms; Chaetoceros densus as dominant centric diatoms in the BS was able to absorb/assimilate NO3‐N, and it can also utilize DON derived from the Xiaoqing River; (b) The change in dinoflagellates/diatoms ratios was reproduced with the change in DN regime from the 1980s to the 2010s by the proposed nitrogen biogeochemical model based on localized parameters in the BS. Moreover, mixotrophism and stronger survival stability, associated with the faster NH4‐N and DONalgal uptake and slower decomposition of G. verior, also supported the shift from diatoms to diatoms–dinoflagellates during high variations in nutrient supply. This study infers the phytoplankton regime shift mechanism associated with the DN structure in coastal waters, providing a credible scientific basis for the shift from water quality‐based to ecosystem‐based environmental management. Plain Language Summary: Changes in amount and proportion of dissolved nitrogen (DN) might lead to the shift of diatoms to diatoms–dinoflagellates in Bohai Sea (BS), which could result in the degradation of primary productivity, the change of zooplankton and subsequent high‐trophic organisms, and then the change of the entire ecosystem, leading to a series of marine ecosystem health problems such as increasing proportion of toxic/harmful algae blooms, jellyfish blooms and the decline of fishery resources. Our study combines field investigation, ship‐based microcosm experiments, a nitrogen biogeochemical model, and statistical analysis to reveal how changes of DN loading influence the dominant algal species structure in BS. According to microcosm and numerical experiments, we found that the DN forms shift of oxidized nitrogen to reduced nitrogen since the mid‐1990s played an important role in the shift of diatoms to diatoms–dinoflagellates. This is because diatoms can absorb/assimilate oxidized nitrogen faster, while dinoflagellates prefer to absorb/assimilate reduced nitrogen. In addition, dinoflagellates have a slower decomposition rate and stronger survival stability. We infer a mechanism that algal community structure in BS shifted from diatoms to diatoms‐dinoflagellates when the amount/proportion of DN changed, providing a credible scientific basis for the ecosystem‐based environmental management. Key Points: We reproduced the shift of diatoms dominance to diatoms‐dinoflagellates dominance in the Bohai Sea by numerical simulationMicrocosm experiments proved that ammonia and algal dissolved organic nitrogen can promote dinoflagellate (Gonyaulax verior) growthThe numerical model emphasized the driving effect of terrestrial dissolved nitrogen input on the shift of diatoms to dinoflagellates [ABSTRACT FROM AUTHOR]

Green tides have increasingly become a nuisance worldwide in recent years, and especially in China. Since 2015, green tides have started recurring in Jinmeng Bay, Qinhuangdao, western Bohai Sea of China, and have severely deteriorated the tourism environment there. In order to investigate the migration process of the green tides in Jinmeng Bay, a hydrodynamic model and a particle-tracking model were applied based on the latest green tide event in August 2021. The hydrodynamic model was applied with triple-level 2DH meshes with different refinements and scales, which provided the hydrodynamics to drive the green macroalgae into the particle-tracking model. From the model results, the semi-enclosed waters surrounded by multiple artificial structures are a low-energy hydrodynamic environment, which is not helpful for water exchange and thus the dispersal of nutrients. The green macroalgae are distributed substantially within the semi-enclosed waters, and few are transported out with low biomass. The effects of wind and artificial structures both increase the coverage of the green macroalgae trajectories; the effect of wind plays a more important role. A sensitivity analysis of the effect of wind showed that 6 m/s wind in ENE led to the maximum coverage of the green macroalgae trajectories in the cases of different magnitudes and directions of winds. This study can provide references for the pre-warning and mitigation of green tides in Jinmeng Bay and other similar places. [ABSTRACT FROM AUTHOR]

Research on the distribution of mantle CO2 should involve comprehensive analysis from CO2 source to accumulation. The crust‐mantle pathway system is the key controlling factor of the distribution of mantle CO2, but has received little attention. The pathway system and controlling factors of CO2 distribution in the Bohai Sea are analyzed using data on fault styles and information on the mantle and lithosphere. The relation between volcanic rocks and the distribution of mantle CO2 is reassessed using age data for CO2 accumulations. The distribution of mantle CO2 is controlled by uplift of the asthenosphere and upper mantle, magma conduits in the mantle and fault systems in the crust. Uplifted regions of the asthenosphere are accumulation areas for CO2. The area with uplift of the Moho exhibits accumulation of mantle CO2 at depth. CO2 was mainly derived from vertical migration through the upper mantle and lower crust. The fault style in the upper crust controls the distance of horizontal migration and the locations of CO2 concentrations. The distribution of mantle CO2 and volcanic rocks are not the same, but both probably followed the same pathways sometimes. Mantle CO2 in the Bohai Sea is concentrated in the Bozhong sag and the surrounding area, particularly in a trap that formed before 5.1 Ma and is connected to crustal faults (the Bozhang faults) and lithospheric faults (the Tanlu faults). [ABSTRACT FROM AUTHOR]

Precise point positioning (PPP) with ambiguity resolution (AR) has been proved to be an effective method to improve the positioning accuracy and shorten the convergence time, which plays an important role in geodetic and geodynamic applications. In this study, the performance achieved based on the BeiDou Navigation Satellite System (BDS-2 and BDS-3) joint PPP-AR with high rate data was considered and the validation of its application to seismic displacement and marine high-precision surveying was evaluated. First, the methods of uncalibrated phase delays (UPDs) estimation and PPP-AR were introduced. Next, the performance achieved based on BDS PPP-AR in both static and simulated real-time kinematic mode was evaluated with hourly data selected from 16 tracking stations over 3 days and data sampling rate of 1 s. After convergence, the positioning accuracies in the east, north, and up directions were 3.4 cm, 1.5 cm, and 5.5 cm, which were improved by 11.9%, 3.8% and 2.2% compared with the float solutions. Finally, a test of applying BDS PPP-AR to marine surveying was carried out with two hours data collected from two independent GNSS receivers installed on a boat sailing along the coast of Bohai Sea, China. The onboard two data set are processed in post-processing kinematic BDS PPP mode. The accuracies were improved from 2.4 cm, 3.5 cm and 4.0 cm to 2.2 cm, 3.1 cm and 3.1 cm in the east, north and up directions by ambiguity resolution, with improvements of 8.3%, 11.4% and 22.5% over the float solutions. The results validated the feasibility of the BDS PPP-AR for high-accuracy maritime applications. [ABSTRACT FROM AUTHOR]

As a key marine economic zone of China, human social and economic activities are very frequent in the Bohai Sea. The timely acquisition of sea ice parameters is of great significance for the prevention and mitigation of sea ice disasters, the utilization of sea ice re-sources, and the design of marine projects in the Bohai Sea. In current, the remote sensing technology has become the most dominant approach of sea ice monitoring. After years of development, sea ice monitoring of Bohai has formed its regional monitoring mode. On the basis of above, literatures related to remote sensing monitoring of sea ice in Bohai were searched and analyzed, and the research advances were summarized. Then the typical characteristics of remote sensing monitoring of sea ice in the Bohai Sea over the past 30 years are obtained. Based on the current status including diverse monitoring requirements, diverse remote sensing methods, and the development of remote sensing technologies, the future research work of sea ice remote sensing monitoring in the Bohai Sea is prospected, in order to provide some ideas for the follow-up research in this field. [ABSTRACT FROM AUTHOR]

Abstract: Gravity data was interpreted in Bohai Sea of China in order to study structural features and find out the distribution rules of oil and gas in this area. This paper, through data processing and synthetic interpretation of the gravity data in Bohai Sea, discusses characteristics of the gravity field and their geological significance, determines the fault system, divides structure unites and analyses the relationship between the features of local gravity anomaly and the distribution of oil and gas fields. The results show that Tanlu fault controlled the regional tectonic evolution and the boundary of the structure units of Bohai Sea in Bohai bay basin. Structurally, this area can be divided into seven units, including Huanghua sag, Chenning uplift, Bozhong sag, Jiyang sag, Liaohe sag, Yanshan fold belt and Jiaoliao uplift. In these sag, a lot of local structures and fault developed, and then many favorable traps and systems of migration and hydrocarbon reservoirs formed. There is a close relationship between the distribution of oil and gas fields and the local gravity highs. The relief areas surrounded by these petroleum generative depressions are the most favorable potential targets for the oil and gas exploration, and the intermediate zones between the depressions and the reliefs are also the significant areas in Bohai Sea. [Copyright &y& Elsevier]

Abstract: River discharges are the important freshwater and nutrient sources for Bohai Sea (BS), and have a profound impact on the local marine environment. In this paper, the annual cycles of nutrient and phytoplankton dynamics in 1980s were reproduced using a coupled biogeochemical–physical model. Based on the validated simulations, the nutrient limitation characters were further investigated by running the model with the riverine nutrient altered, first enriching nitrogen and then phosphorus. It was found that although the riverine N:P ratios in Yellow and Haihe Rivers were much higher than the Redfield number, the nitrogen enrichment was still able to enhance the algae bloom in Laizhou and Bohai Bays. On the other hand, the response of algae growth to phosphorus enrichment was not thus obvious, which suggests that the local phytoplankton dynamics was characterized by the nitrogen limitation. Simulations also show that the nitrogen enrichment is generally accompanied by the phosphorus consumption, so a shift from nitrogen limitation to phosphorus limitation may occur if such a trend continues. [ABSTRACT FROM AUTHOR]

The Bohai Sea is a large, semi-enclosed bay of China with a transport timescale of more than 1 year. Residence time (RT) is an important indicator used to determine the water exchange rate of coastal oceans, and it has a significant influence on coastal ecosystems and the environment. In this study, the RT and its seasonal variability within the Bohai Sea were investigated using a 3-D hydrodynamic model and the adjoint method of the RT. The model results show that the annual mean RT in the Bohai Sea is 3.43 years, and the RT increases from the Bohai Strait to the northwestern coast. The seasonal variability of the RT averaged over the entire Bohai Sea is not obvious; however, the regional RT has a significant seasonal variation, which could be more than 290% on average. When the monsoon winds were removed from the model, the sensitivity experiment showed an annual mean RT increase of ~ 90% with negligible seasonal variations in most areas of the Bohai Sea. The wind-induced residual current controls the seasonal variation in ocean circulation and induces the seasonal variability in RT; thus, monsoon winds play a dominant role in the seasonal variations of the water exchange rate in the Bohai Sea. Sensitivity experiments also suggest that tides can slow the water exchange rate, whereas the baroclinic processes and river runoff can accelerate the water exchange rate in the region near the Yellow River estuary. This study highlights the critical role of monsoon winds in affecting seasonal variabilities in the coastal transport timescale and exchange rate. [ABSTRACT FROM AUTHOR]

There are many important linkages between land, freshwater and oceans. Source-to-sea (S2S) management has been proposed to support environmental management that considers interests along the S2S continuum. This study takes the Bohai and Baltic seas as examples to analyse the legislation system, administrative structure and stakeholders of freshwater and marine management in China and the European Union and presents the related challenges and opportunities for S2S management. The results of this study can provide a basis for designing initiatives to support healthy ecosystems and sustainable green and blue economies, reduce the burdens on water-related ecosystems, and improve economic opportunities and livelihoods. [ABSTRACT FROM AUTHOR]

Abstract: Organic carbon (OC) cycling in coastal seas that connect terrestrial and open oceanic ecosystems is a dynamic and disproportionately important component of oceanic and global carbon cycles. However, OC cycling in coastal seas needs to be better constrained, particularly for geochemically important black carbon (BC). In this study, we conducted multimedium sampling campaigns, including atmospheric deposition, river water, seawater, and sediments in coastal Bohai Sea (BS) in China. We simultaneously quantified particulate OC (POC), particulate BC (PBC), dissolved OC (DOC), and dissolved BC (DBC) and investigated the cycling and budgets of OC and BC. The cycling and budgets of each individual particulate phase (i.e., POC versus PBC) and dissolved phase (i.e., DOC versus DBC) displayed similar patterns, but there were some distinct differences between the particulate and dissolved phases. In the particulate phases, atmospheric and riverine delivery dominated exogenous inputs (>80%), sequestration to sediments dominated removal (~70%), and exchanges in the Bohai Strait resulted in net export. In the dissolved phases, exchanges in the Bohai Strait dominated both import and export and were in a relatively dynamic equilibrium. We found that both natural perturbations, such as spring dust storms, and anthropogenic activity, exerted significant impacts on BS carbon cycling. The integration of regional and global source‐to‐sink process databases made it clear that future BC studies should calculate PBC and DBC fluxes independently. Continuous field observational studies, more details of the biogeochemical processes involved, and consistent BC quantification methods are urgently needed to elucidate coastal OC and BC cycling. [ABSTRACT FROM AUTHOR]

China is one of the largest producers, consumers, and traders for pesticides in the world. Currently, there are more than 600 pesticide-active substances registered in China, whereas few studies were conducted to improve our understanding of the occurrence and environmental impact of current-use pesticides (CUPs) in China's environment. In this work, 72 surface sediment samples were taken from the coastal and offshore of Bohai and Yellow seas and were analyzed for six CUPs (trifluralin, dacthal, quintozene, endosulfan, chlorpyrifos, and dicofol) and two metabolites (pentachloroanisole and endosulfan sulfate). Sediment samples were categorized as estuarine or near-shore sediments (Laizhou Bay, Taozi Bay, Sishili Bay, and Jiaozhou Bay) and offshore sediments. Trifluralin, α-endosulfan, endosulfan sulfate, chlorpyrifos, dicofol, and pentachloroanisole were detected in more than 60 % of the samples. Dicofol was the predominant compound with concentrations mostly higher than 100 pg/g dry weight (dw) with the highest concentration of 18,000 pg/g dw. Concentrations of other compounds were mainly below 100 pg/g dw. CUP levels were much lower than the sediment screening benchmark calculated. The highest levels of α-endosulfan, endosulfan sulfate, trifluralin, and chlorpyrifos existed at Laizhou Bay, whereas pentachloroanisole and dicofol had highest mean concentrations at Jiaozhou Bay. Generally, no correlation between pesticide concentrations and total organic carbon was observed either for offshore samples or for near-shore samples. [ABSTRACT FROM AUTHOR]

The concentration, distribution, and origin of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were investigated in river sediments from the western and southern catchments of the Bohai Sea, China. A toxicity assessment of 28 sediment samples collected from 15 main rivers was conducted by utilizing threshold and probable effect concentrations (TEC and PEC, respectively) derived from consensus-based sediment quality guidelines. The concentrations of total PAHs (∑PAH) ranged from 0.14 to 10,757 μg/kg dry weight (mean = 1,368.6 μg/kg). The high concentrations of PAHs found in Binhai New Area of Tianjin and Binzhou City are likely the result of rapid population and heavy industry growth, resulting in elevated point and nonpoint source inputs of PAHs. Of the samples collected, samples 1 and 10 (7.1 % of the total) were categorized as toxic since some of the PAH concentrations exceeded the corresponding PECs. Twenty samples were classified as nontoxic, with both the individual PAH and the∑PAH concentrations falling below the corresponding TECs. Analyses of selected PAH isomer ratios aided in the identification of PAH origins, allowing for a discrimination between pyrogenic and petrogenic sources. Spatial variability confirmed source heterogeneity within the study area. The most significant PAH-associated contamination was found in the Beitang River and Ji Canal, which are located in Binhai New Area. The magnitude of contamination and the likelihood of an ongoing influx of PAHs support the need for a better understanding of pollution sources and methods for both control and sediment restoration. [ABSTRACT FROM AUTHOR]

The spatiotemporal evolution of sea ice of Bohai Sea in the 2009-2010 winter was studied by time-series remote sensing data, and real-time meteorological data in combination with cumulative freezing degree days (CFDD). Sea ice acreage was determined using a ratio-threshold segmentation together with visual interpretation of daily MODIS 250 m imagery. We found the sea ice acreage soared to 31,849 km on January 23, covering 40.8% of the Bohai Sea. But on February 12, it reached 26,700 km in Liaodong Bay only, covering almost 90.0% of Liaodong Bay. The rapid formation and expansion of sea ice was caused by continuous cold snaps superimposed on a background of anomalously cold weather. CFDD calculated from surrounding cities highly correlated with sea ice acreage in Liaodong Bay ( R = 0.72) suggesting CFDD is one of the significant controlling factors. Sea ice expansion showed 7 days lag with respect to the lowest temperature from surrounding coastal cities, and it mainly occurred close to land, along the coastline, and gradually expanded from the shore outwards. [ABSTRACT FROM AUTHOR]

Seasonal circulation of the Bohai Sea (BS) in 1992 was investigated using Lagrangian particle tracking method. The hydrography of the BS was simulated based on an unstructured grid, finite-volume, three-dimensional primitive equation ocean model. With the use of the unstructured triangular grid, the model can easily fit the irregular coastal boundary of the BS. The simulated tides, tidal current, and thermohaline field agreed well with the observations. The transport of particles has three-dimensional structure in the BS. Compared with central Bohai and Bohai Strait, the differences of particles' transportation between surface and bottom layer in three bays are small. The circulation in the summer is stronger than that in the winter, with the average residual velocity in the surface layer being about 3.7 cm/s during the summer while only 1.8 cm/s during the winter. Using the same model, several well-designed numerical experiments were performed to investigate the effect of oceanic tide, river discharge, wind stress, and thermal stratification on the circulation. It is shown that winds play an important role in the circulation of the BS during both the winter and the summer. Density circulation is important during the summer; however, it is negligible during the winter. River runoff only affects the area around the river mouth. Compared with wind and thermohaline effect, the contribution of tides is small during the summer, and the circulation under only M tidal constituent could not reflect the actual circulation of the BS. [ABSTRACT FROM AUTHOR]

The Tan-Lu Fault zone (TLFZ) is a significant fractural zone in eastern China and also a seismicity belt in North China. Based on total 4000-km-long shallow penetrated single seismic data with high-resolution, structural deformation and fault activity of the TLFZ in the Bohai Sea since the late Pleistocene are discussed in detail. The results show that the TLFZ with a discontinuous distribution and a general NNE-trending consists of 14 active subfaults with an NNE or NE strike in the Bohai Sea. Seismic data reveal that deformation zones along the subfaults in the central Bohai Sea and the Laizhou Bay are wider and more complex than those in the Liaodong Gulf. Related folds and lots of secondary normal faults which are characterized by nearly vertical fault planes and a same or reverse dip construct the fractural zone in the Laizhou Bay and the central Bohai Sea. Usually, micro symmetrical grabens develop on the top of anticlines. In the Liaodong Gulf, subfault fractural zones usually consist of secondary normal faults with the same inclination or opposite inclination. Ages of seismic sequences and cutting relation between subfaults and seismic sequences suggest that the latest faulting age of the TLFZ is the end of the late Pleistocene in the Liaodong Gulf and the early Holocene in the Laizhou Bay and the central Bohai Sea. There is a good match between distribution of earthquakes and that of the subfaults in the Laizhou Bay and the central Bohai. Statistical result shows that total vertical offset of the TLFZ since the late Pleistocene ranges from 6 to 11 m. On the basis of offsets of the subfaults, the vertical slip rate is calculated and results show that average vertical slip rates in the central Bohai Sea are larger than those in the Liaodong Gulf and the Laizhou Bay. Slip rates more than 0.06 mm/a during 23-10 ka B.P. and 85-65 ka B.P. are larger than those in other stages. The TLFZ was mainly dominated by tensional normal component since the late Pleistocene. Synthesizing shallow deformation, activity and distribution of earthquakes, the TLFZ in the Bohai Sea can be divided into three segments: the Laizhou-Bay segment, the Bozhong segment, and the Liaodong-Gulf segment. [ABSTRACT FROM AUTHOR]

Regional Ocean Modeling Systems (ROMS 3.0) and the ?-e turbulence closure scheme has been applied to investigating the seasonal evolution of the thermsocline in the Bohai Sea. The simulation reproduces the stratifications lasting from early April to early September and reveals the existence of marked Asymmetric Dual-Core Cold Bottom Water (ADCCBW) in the south and north depression basin respectively under the thermocline. The bottom temperature in the north depression is about 1-4°C lower than that in the south depression basin which is in good agreement with observations. Model results suggest that the local bathymetry characteristics and inhomogeneous net heat flux due to the latitude difference are the major cause for the early formation of the ADCCBW. Numerical Lagrangian drifter experiments support the finding that the ADCCBW is maintained throughout the stratification periods by the inflow of cold bottom water from the northern Yellow Sea and deep channel in the western side of Liaodong Peninsula. The inflow cold water contributes to the north depression basin distinctively larger than to the south one. Tidal mixing enhances the bottom temperature asymmetry between the two basins. [ABSTRACT FROM AUTHOR]

In 2001 China embarked on an ambitious program to improve water quality through creation of the Clean Bohai Sea Program (CBSP). It is the first regional ocean governance program in China. The joint conference of central and local government units directed CBSP under the leadership of the State Environment Protection Administration. To meet the environmental objectives established by the joint conference local governments must pay for the program and operate it, but to date they have not been able to fully fund the effort. Although data indicate a decline of polluted discharges to the Bohai, one tabulation shows that the area of the sea that is polluted has increased each year from 2001 to 2005. Future enhancement of CBSP depends on revising incentives to better link local environmental programs and development, establishing funding mechanisms to equitably spread costs throughout watersheds, and creating comprehensive monitoring programs to better appraise program results. [ABSTRACT FROM AUTHOR]

The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.

Three new species of marine nematodes belonging to the genera Paranticoma (family Anticomidae) and Parodontophora (family Axonolaimidae) are described from the Bohai Sea and Yellow Sea. Paranticoma tricerviseta sp. nov. is similar to P. bandaense Micoletzky and Kreis, 1930 in the spicules, but can be distinguished by the presence of a ventral projection on the spicules, three regularly arranged cervical setae in both the male and female, and two distinct ventral setae behind the anus. Parodontophora deltensis sp. nov. is close to P. paragranulifera (Timm, 1952) in the length of the amphids, with the ventral arm of the amphid extending past the base of the stoma, but can be separated by the ratio of dorsal arm length to ventral arm (0.36–0.55 versus 0.20–0.25) and the position of the excretory pore (at the middle level versus top level of the stoma), distinctive cervical setae arrangement and a longer renette cell. Parodontophora wuleidaowanensis sp. nov. is close to P. danker Belogurov and Kartavtseva, 1975 in the form of the amphids, but can be distinguished by the longer length of the ventral arm of the amphids and the distinctive arrangement of cervical setae. [ABSTRACT FROM AUTHOR]

We analyzed the distribution of chlorophyll-a (Chla) in the Bohai Sea area based on data from the geosynchronous orbit optical satellite Gaofen-4 (GF-4), which was launched in 2015, carrying a panchromatic multispectral sensor (PMS). This is the first time the geosynchronous orbit optical satellite GF-4 remote-sensing data has been used in China to detect the Chla change details in the Bohai Sea. A new GF-4 retrieved model was established based on the relationship between in situ Chla value and the reflectance combination of 2 and 4 bands, with the R2 of 0.9685 and the total average relative error of 37.42%. Twenty PMS images obtained from 2017 to 2019 were applied to analyze Chla in Bohai sea. The results show that: (1) the new built Chla inversion model PMS-1 for the GF-4 PMS sensor can extract Chla distribution details in the Bohai Sea well. The high Chla content in the Bohai Sea is mainly located in coastal areas, such as the top of Laizhou Bay, Bohai Bay and Liaodong Bay, with the value being around 13 µg/L. The concentration of Chla in the Bohai Strait and northern Yellow Sea is relatively low with the value being around 5 µg/L. (2). Taking full advantage of the continuous observation of geostationary orbit satellite, GF-4 with a high-resolution sensor PMS of 50 m can effectively detect short-term change (changes within 10 min) in Chla concentration. The changes mainly appear at the southwest and northeast costal area as well as in the center of Bohai Sea with the change value of around 3 µg/L. (3) The change of Chla concentration in the Bohai sea is related to the environmental factors such as seawater temperature, salinity, illumination and nutrient salts, as well as the dynamic factors such as wind, flow field and tidal current. [ABSTRACT FROM AUTHOR]

Zhang, D.S.; Pei, S.S.; Duan, G.F.; Feng, X.B.; Zhang, Y.B., and Wu, J., 2020. The pollution level, spatial and temporal distribution trend and risk assessment of heavy metals in Bohai Sea of China. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 354-360. Coconut Creek (Florida), ISSN 0749-0208. In recent years, the rapid industrialization and urbanization of coastal areas have caused serious environmental pressure on the Bohai Sea. The investigator collected the concentration of 7 heavy metals (As, Cu, Cd, Cr, Hg, Pb, Zn) in the Bohai Sea from 2013 to 2017.The results showed that: The main pollution factor of heavy metals in the sea water quality of the study area was Pb. The concentration of Hg increased significantly with the increase of depth. Hg and Cd, due to their high toxicity factors, are the main potential ecological risk factors of surface sediments in the study area. The main heavy metal pollution factor in living creatures is Pb. River discharge, oil exploitation, port area activities and atmospheric subsidence are the main sources of Marine environmental pollution. This study provides ideas for predicting the content of another medium heavy metal in the environment based on one medium. [ABSTRACT FROM AUTHOR]

A storm surge is a complex phenomenon in which waves, tide and current interact. Even though wind is the predominant force driving the surge, waves and tidal phase are also important factors that influence the mass and momentum transport during the surge. Devastating storm surges often occur in the Bohai Sea, a semi-enclosed shallow sea in North China, due to extreme storms. However, the effects of waves on storm surges in the Bohai Sea have not been quantified and the mechanisms responsible for the higher surges that affect part of the Bohai Sea have not been thoroughly studied. In this study, we set up a storm surge model, considering coupled effects of tides and waves on the surges. Validation against measured data shows that the coupled model is capable of simulating storm surges in the Bohai Sea. The simulation results indicate that the longshore currents, which are induced by the large gradient of radiation stress due to wave deformation, are one of the main contributors to the higher surges occurring in some coastal regions. The gently varying bathymetry is another factor contributing to these surges. With such bathymetry, the wave force direction is nearly uniform, and pushes a large amount of water in that direction. Under these conditions, the water accumulates in some parts of the coast, leading to higher surges in nearby coastal regions such as the south coast of the Bohai Bay and the west and south coasts of the Laizhou Bay. Results analysis also shows that the tidal phase at which the surge occurs influences the wave–current interactions, and these interactions are more evident in shallow waters. Neglecting these interactions can lead to inaccurate predictions of the storm surges due to overestimation or underestimation of wave-induced set-up. [ABSTRACT FROM AUTHOR]