Eutrophication caused by inputs of excess nitrogen(N) has become a serious environmental problem in Hangzhou Bay(China),but the sources of this nitrogen are not well understood.In this study,the August 2019 distributi...Eutrophication caused by inputs of excess nitrogen(N) has become a serious environmental problem in Hangzhou Bay(China),but the sources of this nitrogen are not well understood.In this study,the August 2019 distributions of salinity,nutrients [nitrate(NO_(3)^(-)),nitrite,ammonium,and phosphate],and the stable isotopic composition of NO_(3)^(-)(δ^(15)N and δ^(18)O) were used to investigate sources of dissolved inorganic nitrogen(DIN) to Hangzhou B ay.Spatial distributions of nitrate,salinity,and nitrate δ^(18)O indicate that the Qiantang River,the Changjiang River,and nearshore coastal waters may all contribute nitrate to the bay.Based on the isotopic compositions of nitrate in these potential source waters and conservative mixing of nitrate in our study area,we suggest that the NO_(3)^(- )in Hangzhou B ay was likely derived mainly from soils,synthetic N fertilizer,and manure and sewage.End-member modeling indicates that in the upper half of the bay,the Qiantang River was a very important DIN source,possibly contributing more than 50% of DIN in the bay head area.In the lower half of the bay,DIN was sourced mainly from strongly intruding coastal water.DIN coming directly from the Changjiang River made a relatively small contribution to Hangzhou Bay DIN in August 2019.展开更多
Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally va...Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally variable,but there are limited data on how biological communities respond to this variation.Hangzhou Bay,a mediumsized estuary in China,is an ideal place in which to study the response of plankton to small-scale ocean fronts,because three water masses(Qiantang River Diluted Water,Changjiang River Diluted Water,and the East China Sea current) converge here and form dynamic salinity fronts throughout the year.We investigate zooplankton communities,and temperature,salinity and chlorophyll a(Chl a) in Hangzhou Bay in June(wet perio d) and December(dry period) of 2022 and examine the dominant environmental factors that affect zooplankton community spatial variability.We then match the spatial distributions of zooplankton communities with those of salinity fronts.S alinity is the most important explanatory variable to affect zooplankton community spatial variability during both wet and dry periods,in that it contributes>60% of the variability in community structure.Furthermore,the spatial distributions of zooplankton match well with salinity fronts.During December,with weaker Qiantang River Diluted Water and a stronger secondary Changjiang River Plume,zooplankton communities occur in moderate salinity(MS,salinity range 15.6±2.2) and high salinity(HS,22.4±1.7) regions,and their ecological boundaries closely match the Qiantang River Diluted Water front.In June,different zooplankton communities occur in low salinity(LS,3.9±1.0),MS(11.7±3.6) and HS(21.3±1.9) regions.Although the LS region occurs abnormally in the central bay rather than its apex because of the anomalous influence of rising and falling tides during the sampling perio d,the ecological boundaries still match salinity interfaces.Low-salinity or brackish-water zooplankter taxa are relatively more abundant in LS or MS regions,and the biomass and abundance of zooplankton is higher in the MS region.展开更多
In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydro...In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydrodynamic equations satisfied by two contravariant components of velocity vector and surface elevation in non-orthogonal curvilinear coordinates are used. In each momentum equation the coefficients before the two partial derivatives of surface elevation with respect to variables of alternative direction coordinates have different orders of magnitude, i. e., the derivative with the larger coefficient may play a more important role than that with the smaller one. With this advantage, the ADI scheme can be easily employed. The hydrodynamic factors include tidal current, river runoff and wind-induced current. In terms of tidal current, seven main constituents in the area are considered in the open boundaries. The verifications of surface elevation process and current velocity process in the spring tide and in the neap tide show that the model can preferably reflect current fields in the area. Through the simulation of Lagrangian residual current fields in summer and in winter, the paths of the exchange of water and sediment between the Yangtze Estuary and the Hangzhou Bay are elementarily discussed.展开更多
The distributions of partial pressure of carbon dioxide （pCO2） in the surface waters of the Changjiang River Estuary and adjacent Hangzhou Bay were examined in the summer of 2010. Surface water pCO2 ranged from 751-...The distributions of partial pressure of carbon dioxide （pCO2） in the surface waters of the Changjiang River Estuary and adjacent Hangzhou Bay were examined in the summer of 2010. Surface water pCO2 ranged from 751-2 095/zatm （1 atm=101 325 Pa） in the inner estuary, 177-1 036/zatm in the outer estuary, and 498-1 166 μatm in Hangzhou Bay. Overall, surface pCO2 behaved conservatively during the estuary mixing. In the inner estuary, surface pCO2 was relatively high due to urbanized pollution and a high respiration rate. The lowest pCO2 was observed in the outer estuary, which was apparently induced by a phytoplankton bloom because the dissolved oxygen and chlorophyll a were very high. The Changjiang River Estuary was a significant source of atmospheric CO2 and the degassing fluxes were estimated as 0-230 mmol/（m2.d） [61 mmol/（m2.d） on average] in the inner estuary. In contrast, the outer estuary acted as a CO2 sink.展开更多
Partial pressure of CO2(pCO2) was investigated in the Changjiang(Yangtze River) Estuary,Hangzhou Bay and their adjacent areas during a cruise in August 2004,China.The data show that pCO2 in surface waters of the studi...Partial pressure of CO2(pCO2) was investigated in the Changjiang(Yangtze River) Estuary,Hangzhou Bay and their adjacent areas during a cruise in August 2004,China.The data show that pCO2 in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago.The pCO2 varied from 168 to 2 264 μatm,which fell in the low range compared with those of other estuaries in the world.The calculated sea-air CO2 fluxes decreased offshore and varied from -10.0 to 88.1 mmol m-2 d-1 in average of 24.4 ± 16.5 mmol m-2 d-1.Although the area studied was estimated only 2 × 104 km2,it emitted(5.9 ± 4.0) × 103 tons of carbon to the atmosphere every day.The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.展开更多
The Inductively Coupled Plasma Optical Emission Spectrometer was used to analyze sediment samples collected from the Hangzhou Bay to determine major and trace elemental concentrations. Based on these concentrations, t...The Inductively Coupled Plasma Optical Emission Spectrometer was used to analyze sediment samples collected from the Hangzhou Bay to determine major and trace elemental concentrations. Based on these concentrations, the study area can be classified into three geochemical provinces. Province I covers the northern Hangzhou Bay area and contains high concentrations of A120~, Fe203, MgO, Na20, K20, MnO, Cr, Cu, Ni, Pb, V, Co and Zn. Province III is located in the western Hangzhou Bay, near the Qiantang River mouth, and contains high concentrations of SiO~, Na20, P205~ TiO2, Cr, Sr, Zr. Province II is located in the middle and eastern Hangzhou Bay, with the medium concentrations of major and trace elements. The results also demonstrate that the grain size is the dominating factor controlling the spatial variations of elemental concentrations, and the Changjiang River （Yangtze River） and Qiantang River sediments play an important role in the distribution of these elements. Anthropogenic impact on heavy metal concentrations （especially Cr, Sr and Zr） can be detected in the surface sediments near the Qiantang River mouth.展开更多
This paper presents the sedimentary facies and formation of the Qiantangjiang and Taihu incised valleys, and the characteristics of shallow gas reservoir distribution, based on a large number of data of drilling, stat...This paper presents the sedimentary facies and formation of the Qiantangjiang and Taihu incised valleys, and the characteristics of shallow gas reservoir distribution, based on a large number of data of drilling, static sounding and chemical analysis obtained from the present Hangzhou Bay coastal plain. The incised valleys were formed during the last glacial maximum and were subsequently filled with fluvial facies during the post-glacial period. All commercial gases are stored in the flood plain sand lenses of the incised valleys.展开更多
A 3-D numerical model is set up in a large domain covering the Hangzhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradie...A 3-D numerical model is set up in a large domain covering the Hangzhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradient (BPG)terms and convective terms are improved in the paper according to the characteristics of velocity field and mass transport in the area.The model is validated by the simulations of residual current and salinity transport in the Hangzhou Bay and the Changjiang Estuary.展开更多
Land use change plays an important part in the studies of global environmental change and regional sustainable development. The change of soil quality can particularly reflect the impacts of human socio-economic activ...Land use change plays an important part in the studies of global environmental change and regional sustainable development. The change of soil quality can particularly reflect the impacts of human socio-economic activities on environment. Taking the coastal plain of south Hangzhou Bay as a study case, we analyzed the effects of land use changes on organic matter （OM）, total nitrogen （TN）, total phosphorus （TP）, available phosphorus （AP）, available potassium （AK）, total salinity （TS）, pH value in soil genetic layers, and assessed soil quality change related to different land use types from 1982 to 2003. The results show that： （1） The general change tendency of soil quality in the coastal plain of south Hangzhou Bay declined obviously in A layer and slightly rise in B （or P） layer and C （or W） layer. The contents of TP decreased generally in all soil genetic layers, but the variety difference of other soil quality indices was relatively great. （2） The change of soil quality in the areas where land use changed is far more remarkable than that with land use unchanged. The value of quality variety is A layer 〉B （or P） layer 〉C （or W） layer. （3） The changes of soil tillage, cultivation, fertilization, irrigation and drainage activities related to land use may make some soil-forming processes disappeared and bring in other new processes which will affect the soil quality and soil genetic layers directly.展开更多
Based on Landsat TM images in 2005 and urban planning data of 2005-2020 in Hangzhou Bay Industrial Belt, this paper studied the potential risk of the planned urban construction land extension to the wetlands by employ...Based on Landsat TM images in 2005 and urban planning data of 2005-2020 in Hangzhou Bay Industrial Belt, this paper studied the potential risk of the planned urban construction land extension to the wetlands by employing a GIS spatial analysis method. The results show that： （1） The wetland resources are widely distributed and diverse, with a proximal distribution to present urban construction lands spatially. （2） From 2005 to 2020, the urban construction lands will expand vastly and rapidly, and will take over large areas of wetlands that are mostly the ponds and the aquiculture water areas in the reclamation areas of Hangzhou Bay south coast. Moreover, this change will be spatially uneven obviously, e.g., the most serious recessions of the wetlands are concentrated in Ningbo city, Hangzhou city and Cixi city. （3） Overall, the potential risk to wetlands is very high, and will keep increasing with the trend of urbanization. （4） The quantity and spatial pattern of the planning urban construction land have substantial impacts on the wetland loss. Therefore, some policies and regulations are suggested to coordinate the relationship between urban economic development and wetland resource protection such as adjusting the construction land planning, compensating for wetland occupation as well as constructing wetland parks.展开更多
This study focuses on sedimentary environmental changes offshore of Hangzhou Bay, East China, since the Late Quaternary. AMS ^14C ages from core CJK10, lithologies, distribution of foraminifera, heavy minerals, and S ...This study focuses on sedimentary environmental changes offshore of Hangzhou Bay, East China, since the Late Quaternary. AMS ^14C ages from core CJK10, lithologies, distribution of foraminifera, heavy minerals, and S and C1 elements show a fluvial terrace environment during -23.2-11.0 cal ka BP; a littoral to tidal-flat environment during 11.0-10.2 cal ka BP; and a shallow marine environment with a relatively low sedimentation rate （0.1-0.22 cm/a） since 4.3 cal ka BP. High depositional rates （-1.6 cm/a） from 10.9 to 10.2 cal ka BP resulted from sufficient accommodation space created by rapid sea level rise from -44 m to -33 m, from high sediment delivery by local rivers, and effective trapping of sediments by tidal-flat vegetation. The rate of sea level rise was variable; relatively high from 10.9 to 10.6 cal ka BP （2.1 cm/a）, and lower since 10.6 cal ka BP （1.2 cm/a）. The Changjiang alongshore current crossed the Hangzhou Bay to form the mud wedge on the inner shelf of the East China Sea later than 9.4 cal ka BP. The CJK10 site was a tide-dominated shelf environment and experienced erosion from approximately 9.4-9.2 cal ka BP to 4.3 cal ka BP. The depositional hiatus was caused by the Changjiang alongshore current, which was relatively weak during 9.4-7.5 cal ka BP and increased in strength during -7.5-4 cal ka BP. From -4.3 cal ka BP, a large amount of sediment from the Changjiang River was partly deposited on the continental shelf of Hangzhou Bay with some transported southward. Therefore, this study clarifies the history of Changjiang-derived sediment dispersal and deposition, although a detailed record of the changes in the Chang3iang alongshore current since 4.3 cal ka BP is difficult to obtain because of the scarcity of evidence.展开更多
Since the beginning of the 20th century, tideland reclamation as a huge project has continuously extended from inland to the sea for the socioeconomic development, like Zhejiang, Jiangsu and other coastal regions in C...Since the beginning of the 20th century, tideland reclamation as a huge project has continuously extended from inland to the sea for the socioeconomic development, like Zhejiang, Jiangsu and other coastal regions in China. The increase of land area alleviated the contradiction of supply and demand between human and land, which provided the guarantee for agricultural production and industrial development. However, marine ecological environment has been seriously damaged due to the increasing scale of tideland reclamation. This paper took the Hangzhou Bay in the Yangtze River Delta as a study area to explore the evolution law, socioeconomic effect and eco-environmental effect of reclaimed land from 1985 to 2015. The result showed that as follows:(1) The area of tideland reclamation was 460.67 km^2 with 16.57% cultivated land and 15.93% construction land, and its land use was inefficient;(2) Land use change has spatial and temporal difference, the speed of tideland reclamation had been increasing from 1985 to 2015 in time and the scale of reclaimed land in the southern(84.07%) of Hangzhou Bay was larger than the northern region(15.93%) in space;(3) The evolution law of land use was from tideland to swampland and coastal waters to agricultural facility land, to cultivated land to industrial-mining land to idle land, rural-urban construction land, and formed obviously hierarchical structure;(4) Effect analysis of land use change found that the socio-economic effect had increased but the eco-environmental effect had decreased from 1985 to 2015, it reflected socio-economic effect was acquired through sacrificing eco-environmental effect;(5) It pointed out the existing problems on land extensive inefficient, environmental degradation and economy excessive growth without scientific planning, and offered some suggestions in land comprehensive improvement project, industrial transformation and upgrading and scientific planning and legal safeguardto promote sustainable development in the Hangzhou Bay in the new period.展开更多
Surface sediments from the Changjiang River （Yangtze River） Estuary, Hangzhou Bay, and their adjacent waters were analyzed for their grain size distribution, organic carbon （OC） concentration, and stable carbon is...Surface sediments from the Changjiang River （Yangtze River） Estuary, Hangzhou Bay, and their adjacent waters were analyzed for their grain size distribution, organic carbon （OC） concentration, and stable carbon isotope composition （δ13C）. Based on this analysis, about 36 surface sediment samples were selected from various environments and separated into sand （〉0.250 ram, 0.125-0.250 ram, 0.063-0.125 mm） and silt （0.025-0.063 mm） fractions by wet-sieving fractionation methods, and further into silt- （0.004-0.025 mm） and clay-sized （〈0.004 mm） fractions by centrifugal fractionation. Sediments of six grain size categories were analyzed for their OC and 613C contents to explore the grain size composition and transport paths of sedimentary OC in the study area. From fine to coarse fractions, the OC content was 1.18%, 0.51%, 0.46%, 0.42%, 0.99%, and 0.48%, respectively, while the δ13C was -21.64‰, -22.03‰, -22.52‰, -22.46‰, -22.36‰, and -22.28%0, respectively. In each size category, the OC contribution was 42.96%, 26.06%, 9.82%, 5.75%, 7.09%, and 8.33%, respectively. The OC content in clay and fine silt fractions （〈0.025 ram） was about 69.02%. High OC concentrations were mainly found in offshore modern sediments in the northeast of the Changjiang River Estuary, in modern sediments in the lower estuary of the Changjiang River and Hangzhou Bay, and in Cyclonic Eddy modern sediments to the southwest of the Cheju Island. Integrating the distribution of terrestrial OC content of each grain size category with the δ13C of the bulk sediment indicated that the terrestrial organic material in the Changjiang River Estuary was transported seaward and dispersed to the Cyclonic Eddy modern sediments to the southwest of the Cheju Island via two pathways： one was a result of the Changjiang River Diluted Water （CDW） northeastward extending branch driven by the North Jiangsu Coastal Current and the Yellow Sea Coastal Current, while the other one was the result of the CDW southward extending branch driven by the Taiwan Warm Current.展开更多
-In order to avoid prescribing open boundary condition on the upstream side of the Hangzhou Bay, in numerical simulation of the tides and residual currents of the Bay, a 1-D model for the Qiantang River is connected t...-In order to avoid prescribing open boundary condition on the upstream side of the Hangzhou Bay, in numerical simulation of the tides and residual currents of the Bay, a 1-D model for the Qiantang River is connected to the 2-D model for the Hangzhou Bay. The harmonic constants of diurnal constituent [ (K1+O1)/2],semidiurnal constituent (M2) and shallow water constituent (M4) are obtained. The results produced by the combined model are in better agreement with the observed ones than those produced solely by the original 2-D model. The combined model gives much more reliable results for tide-induced residual water level and current.展开更多
Based on the historical evolution of the Hangzhou Bay, by making use of the conclusions made by the previous research workers and the integration of concrete data, five distinct impact indicators of the sediment from ...Based on the historical evolution of the Hangzhou Bay, by making use of the conclusions made by the previous research workers and the integration of concrete data, five distinct impact indicators of the sediment from the Changjiang Estuary and the East China Sea to the Hangzhou Bay are summarized. Numerical calculation and analysis indicate that the scouring and deposition of seabed in the Hangzhou Bay are subject to the direct impact of the evolution of the Changjiang Estuary, and the growth and decline and the direction of the sandy bar at Nanhuizui give traces to the sediment transport between the Changjiang Estuary and the Hangzhou Bay. The transport of sediment from the Changjiang Estuary to the Hangzhou Bay occurs mainly in winter and spring seasons and the increase of the Changjiang River runoff and the decrease of sediment charge have caused scouring in the northern coast of the Hangzhou Bay and the seabed erosion along the frontal margin of the Changjiang River Delta.展开更多
Based on the COHERENS model (a coupled hydrodynamic ecological model for regional and shelf seas), a numerical hydrodynamic model of the Hangzhou Bay, influenced by tide, regional winds and freshwater from the Yangtze...Based on the COHERENS model (a coupled hydrodynamic ecological model for regional and shelf seas), a numerical hydrodynamic model of the Hangzhou Bay, influenced by tide, regional winds and freshwater from the Yangtze River and the Qiantangjiang River was established. The Lagrangian particle tracking was simulated to provide tracer trajectories. For convenience, the modeling area was divided into 8 subdomains and the modeling focused on March (dry season) and July (wet season). Numerical simulation and analysis indicate that the tracer trajectories originated in different subdomains are quite different. Most particles released in the mouth of the bay move outside the bay quickly and reach the farthest place at 122.5°E; while particles released in the inner part of the bay mostly remain in the same subdomain, with only minor migrations in two opposite directions along the shore. The tracer experiments also indicate that the northwest region of the bay is an area where pollutant can easily accumulate in both wet and dry seasons, and that the southeast region of the bay is another area for pollutant to accumulate in dry season because it is the main path for the contaminant.展开更多
Time-series InSAR analysis（e.g., permanent scatterers（PSInSAR）） has been proven as an effective technology in monitoring ground deformation over urban areas. However, it is a big challenge to apply this technology...Time-series InSAR analysis（e.g., permanent scatterers（PSInSAR）） has been proven as an effective technology in monitoring ground deformation over urban areas. However, it is a big challenge to apply this technology in coastal regions due to the lack of man-made targets. An distributed scatterers interferometric synthetic aperture radar（DSInSAR） is developed to solve the problem of insufficient samples and low reliability in monitoring coastal lowland subsidence, by applying a spatially adaptive filter and an eigendecomposition algorithm to estimating the optimal phase of statistically homogeneous distributed scatterers（DSs）. Twenty-four scenes of COSMO-Sky Med images acquired between 2013 and 2015 are used to retrieve the land subsidence over the Shangyu District on south coast of the Hangzhou Bay, Zhejiang Province, China. The spatial pattern of the land subsidence obtained by the PS-InSAR and the DSInSAR coincides with each other, but the density of the DSs is three point five times higher than the permanent scatterers（PSs）. Validated by precise levelling data over the same period, the DSInSAR method achieves an accuracy of ±5.0 mm/a which is superior to the PS-InSAR with±5.5 mm/a. The land subsidence in the Shangyu District is mainly distributed in the urban areas, industrial towns and land reclamation zones, with a maximum subsidence rate -30.2 mm/a. The analysis of geological data, field investigation and historical reclamation data indicates that human activities and natural compaction of reclamation material are major causes of the detected land subsidence. The results demonstrate that the DSInSAR method has a great potential in monitoring the coastal lowland subsidence and can be used to further investigate subsidence-related environmental issues in coastal regions.展开更多
On the basis of the time series of AVHRR data from NOAA satellites and the geographical information system PURSIS, fluctuations of the plume front and the turbidity maximum in the Hangzhou Bay, reflected by the distri...On the basis of the time series of AVHRR data from NOAA satellites and the geographical information system PURSIS, fluctuations of the plume front and the turbidity maximum in the Hangzhou Bay, reflected by the distributions of temperature and suspended sediment concentration respectively, are studied in view of long-term behaviors or seasonal and tidal cycles. The data suggest that the effect of front plays an important role in the development of the turbidity maximum close to the Changjiang Estuary > while the effect of tide dominates over the development of another very turbid water situated in the shoal areas in the southern Hangzhou Bay.展开更多
In this study, a comparison was made between the Changjiang Estuary and the Hanghzou Bay, in terms of the sources and diagenesis of the sedimentary organic matter (OM). To achieve this purpose, surface sediments from ...In this study, a comparison was made between the Changjiang Estuary and the Hanghzou Bay, in terms of the sources and diagenesis of the sedimentary organic matter (OM). To achieve this purpose, surface sediments from the estuary and bay were analyzed for lignin-derived phenols, stable carbon isotope and TOC/TN (total organic carbon/total nitrogen) molar ratio. The signal of land-derived OM decreased, and the vanillic acid to vanillin ratio, (Ad/Al)v, increased with increasing distance from the Changjiang Estuary and the Hangzhou Bay. These results corresponded with the contribution of the terrigenous OM from the rivers to the coastal zone, and the predominance of marine OM farther offshore, and that the land-derived OM underwent decomposition during transport along the estuary and bay. It should be noted that besides the Qiantang River, Hangzhou Bay is also receiving more than half of its materials from Changjiang Estuary, which flows into the Hangzhou Bay at the north, and leaves via the southern part of the bay. This important aspect of the hydrological cycle in Hangzhou Bay corresponded to higher Λ (total lignin in mg/100 mg OC), higher TOC and C/N ratios and more elevated (Ad/Al)v and (Ad/Al)s values in the bay than the Changjiang Estuary, thus, rendering the bay as a site for the accumulation and rapid cycling of terrigenous OM.展开更多
-low-frequency sea level fluctuations in the Hangzhou Bay in winter and summer, 1973-1974 are analyzed in this paper. The established multi-spectrum response models effectively identify the different dynamical factors...-low-frequency sea level fluctuations in the Hangzhou Bay in winter and summer, 1973-1974 are analyzed in this paper. The established multi-spectrum response models effectively identify the different dynamical factors and their contributions to the low-frequency sea level fluctuations inside the bay. The results show that the Ekman transport due to longshore winds is the major mechanism to induce the sea level fluctuations, more important than the frictional effect of local winds. There also exists obviously the influental effect of the free fluctuations of the continental shelf. In addition ,a simple estimation suggests that the remarkable sea level fluctuation of 0. 4 d-1 in the bay is related to the resonance of the Huanghai Sea and the Bohai Sea (taken as a single bay).展开更多
基金The Zhejiang Provincial Natural Science Foundation of China under contract No.LZ22D060002the Key R&D Program of Zhejiang under contract No.2022C03044the National Key Research and Development Program of China under contract No.2021YFC3101702。
文摘Eutrophication caused by inputs of excess nitrogen(N) has become a serious environmental problem in Hangzhou Bay(China),but the sources of this nitrogen are not well understood.In this study,the August 2019 distributions of salinity,nutrients [nitrate(NO_(3)^(-)),nitrite,ammonium,and phosphate],and the stable isotopic composition of NO_(3)^(-)(δ^(15)N and δ^(18)O) were used to investigate sources of dissolved inorganic nitrogen(DIN) to Hangzhou B ay.Spatial distributions of nitrate,salinity,and nitrate δ^(18)O indicate that the Qiantang River,the Changjiang River,and nearshore coastal waters may all contribute nitrate to the bay.Based on the isotopic compositions of nitrate in these potential source waters and conservative mixing of nitrate in our study area,we suggest that the NO_(3)^(- )in Hangzhou B ay was likely derived mainly from soils,synthetic N fertilizer,and manure and sewage.End-member modeling indicates that in the upper half of the bay,the Qiantang River was a very important DIN source,possibly contributing more than 50% of DIN in the bay head area.In the lower half of the bay,DIN was sourced mainly from strongly intruding coastal water.DIN coming directly from the Changjiang River made a relatively small contribution to Hangzhou Bay DIN in August 2019.
基金The National Key Research and Development Program of China under contact No.2021YFC3101702the Natural Science Foundation of Zhejiang Province under contact Nos LY22D060006 and LY14D060007+1 种基金the Key R&D Program of Zhejiang under contact No.2022C03044the Project of Long-term Observation and Research Plan in the Changjiang Estuary and Adjacent East China Sea (LORCE) under contact No.SZ2001。
文摘Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally variable,but there are limited data on how biological communities respond to this variation.Hangzhou Bay,a mediumsized estuary in China,is an ideal place in which to study the response of plankton to small-scale ocean fronts,because three water masses(Qiantang River Diluted Water,Changjiang River Diluted Water,and the East China Sea current) converge here and form dynamic salinity fronts throughout the year.We investigate zooplankton communities,and temperature,salinity and chlorophyll a(Chl a) in Hangzhou Bay in June(wet perio d) and December(dry period) of 2022 and examine the dominant environmental factors that affect zooplankton community spatial variability.We then match the spatial distributions of zooplankton communities with those of salinity fronts.S alinity is the most important explanatory variable to affect zooplankton community spatial variability during both wet and dry periods,in that it contributes>60% of the variability in community structure.Furthermore,the spatial distributions of zooplankton match well with salinity fronts.During December,with weaker Qiantang River Diluted Water and a stronger secondary Changjiang River Plume,zooplankton communities occur in moderate salinity(MS,salinity range 15.6±2.2) and high salinity(HS,22.4±1.7) regions,and their ecological boundaries closely match the Qiantang River Diluted Water front.In June,different zooplankton communities occur in low salinity(LS,3.9±1.0),MS(11.7±3.6) and HS(21.3±1.9) regions.Although the LS region occurs abnormally in the central bay rather than its apex because of the anomalous influence of rising and falling tides during the sampling perio d,the ecological boundaries still match salinity interfaces.Low-salinity or brackish-water zooplankter taxa are relatively more abundant in LS or MS regions,and the biomass and abundance of zooplankton is higher in the MS region.
基金National Natural Science Foundation of China under contract No.49776279National Excellent Youth Foundation of China under contract No.49825161
文摘In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydrodynamic equations satisfied by two contravariant components of velocity vector and surface elevation in non-orthogonal curvilinear coordinates are used. In each momentum equation the coefficients before the two partial derivatives of surface elevation with respect to variables of alternative direction coordinates have different orders of magnitude, i. e., the derivative with the larger coefficient may play a more important role than that with the smaller one. With this advantage, the ADI scheme can be easily employed. The hydrodynamic factors include tidal current, river runoff and wind-induced current. In terms of tidal current, seven main constituents in the area are considered in the open boundaries. The verifications of surface elevation process and current velocity process in the spring tide and in the neap tide show that the model can preferably reflect current fields in the area. Through the simulation of Lagrangian residual current fields in summer and in winter, the paths of the exchange of water and sediment between the Yangtze Estuary and the Hangzhou Bay are elementarily discussed.
基金The Marine Public Welfare Project of China under contract Nos200805029,200905012,200905025,and 201005034the Scientific Research Fund of the Second Institute of Oceanography,SOA under contract Nos JG0821 and JG1021
文摘The distributions of partial pressure of carbon dioxide （pCO2） in the surface waters of the Changjiang River Estuary and adjacent Hangzhou Bay were examined in the summer of 2010. Surface water pCO2 ranged from 751-2 095/zatm （1 atm=101 325 Pa） in the inner estuary, 177-1 036/zatm in the outer estuary, and 498-1 166 μatm in Hangzhou Bay. Overall, surface pCO2 behaved conservatively during the estuary mixing. In the inner estuary, surface pCO2 was relatively high due to urbanized pollution and a high respiration rate. The lowest pCO2 was observed in the outer estuary, which was apparently induced by a phytoplankton bloom because the dissolved oxygen and chlorophyll a were very high. The Changjiang River Estuary was a significant source of atmospheric CO2 and the degassing fluxes were estimated as 0-230 mmol/（m2.d） [61 mmol/（m2.d） on average] in the inner estuary. In contrast, the outer estuary acted as a CO2 sink.
基金Supported by the National Basic Research Program of China (973 Program, No. 2005CB407305)the open foundation of the Key Laboratory of Marine Sedimentology & Environmental Geology, SOA (No. MASEG200606)+1 种基金the Qingdao Special Program for Leading Scientists (No. 05-2-JC-90)the 100-Talent Project of the Chinese Academy of Sciences
文摘Partial pressure of CO2(pCO2) was investigated in the Changjiang(Yangtze River) Estuary,Hangzhou Bay and their adjacent areas during a cruise in August 2004,China.The data show that pCO2 in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago.The pCO2 varied from 168 to 2 264 μatm,which fell in the low range compared with those of other estuaries in the world.The calculated sea-air CO2 fluxes decreased offshore and varied from -10.0 to 88.1 mmol m-2 d-1 in average of 24.4 ± 16.5 mmol m-2 d-1.Although the area studied was estimated only 2 × 104 km2,it emitted(5.9 ± 4.0) × 103 tons of carbon to the atmosphere every day.The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.
基金The National Natural Science Foundation of China under contract No. 41106063China Postdoctoral Science Foundation under contract No. 20100481304+1 种基金Marine Public Welfare Research Project under contract No. 200805063Coastal Investigation and Research Project of China under contract Nos 908-01-CJ09 and 908-ZC-I-05
文摘The Inductively Coupled Plasma Optical Emission Spectrometer was used to analyze sediment samples collected from the Hangzhou Bay to determine major and trace elemental concentrations. Based on these concentrations, the study area can be classified into three geochemical provinces. Province I covers the northern Hangzhou Bay area and contains high concentrations of A120~, Fe203, MgO, Na20, K20, MnO, Cr, Cu, Ni, Pb, V, Co and Zn. Province III is located in the western Hangzhou Bay, near the Qiantang River mouth, and contains high concentrations of SiO~, Na20, P205~ TiO2, Cr, Sr, Zr. Province II is located in the middle and eastern Hangzhou Bay, with the medium concentrations of major and trace elements. The results also demonstrate that the grain size is the dominating factor controlling the spatial variations of elemental concentrations, and the Changjiang River （Yangtze River） and Qiantang River sediments play an important role in the distribution of these elements. Anthropogenic impact on heavy metal concentrations （especially Cr, Sr and Zr） can be detected in the surface sediments near the Qiantang River mouth.
基金This research is financially supported by the China National Natural Science Foundation(Project No．40272063)
文摘This paper presents the sedimentary facies and formation of the Qiantangjiang and Taihu incised valleys, and the characteristics of shallow gas reservoir distribution, based on a large number of data of drilling, static sounding and chemical analysis obtained from the present Hangzhou Bay coastal plain. The incised valleys were formed during the last glacial maximum and were subsequently filled with fluvial facies during the post-glacial period. All commercial gases are stored in the flood plain sand lenses of the incised valleys.
文摘A 3-D numerical model is set up in a large domain covering the Hangzhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradient (BPG)terms and convective terms are improved in the paper according to the characteristics of velocity field and mass transport in the area.The model is validated by the simulations of residual current and salinity transport in the Hangzhou Bay and the Changjiang Estuary.
基金National Natural Science Foundation of China, No.40701006 Natural Science Foundation of Zhejiang Province, No.Y505032+2 种基金 Natural Science Foundation of Ningbo, No.2006A610077 No.2002C10026 K. C. Wong Magna Fund in Ningbo University
文摘Land use change plays an important part in the studies of global environmental change and regional sustainable development. The change of soil quality can particularly reflect the impacts of human socio-economic activities on environment. Taking the coastal plain of south Hangzhou Bay as a study case, we analyzed the effects of land use changes on organic matter （OM）, total nitrogen （TN）, total phosphorus （TP）, available phosphorus （AP）, available potassium （AK）, total salinity （TS）, pH value in soil genetic layers, and assessed soil quality change related to different land use types from 1982 to 2003. The results show that： （1） The general change tendency of soil quality in the coastal plain of south Hangzhou Bay declined obviously in A layer and slightly rise in B （or P） layer and C （or W） layer. The contents of TP decreased generally in all soil genetic layers, but the variety difference of other soil quality indices was relatively great. （2） The change of soil quality in the areas where land use changed is far more remarkable than that with land use unchanged. The value of quality variety is A layer 〉B （or P） layer 〉C （or W） layer. （3） The changes of soil tillage, cultivation, fertilization, irrigation and drainage activities related to land use may make some soil-forming processes disappeared and bring in other new processes which will affect the soil quality and soil genetic layers directly.
基金Key Project of Zhejiang Provincial Science and Technology Programs, No.2005C23059 National Key Technology R＆D Program of China, No.2006BAJ11B03 National Natural Science Foundation of China, No.40701177 The authors thank Prof. Liu Xinguo from Zhejiang University for his modification of language.
文摘Based on Landsat TM images in 2005 and urban planning data of 2005-2020 in Hangzhou Bay Industrial Belt, this paper studied the potential risk of the planned urban construction land extension to the wetlands by employing a GIS spatial analysis method. The results show that： （1） The wetland resources are widely distributed and diverse, with a proximal distribution to present urban construction lands spatially. （2） From 2005 to 2020, the urban construction lands will expand vastly and rapidly, and will take over large areas of wetlands that are mostly the ponds and the aquiculture water areas in the reclamation areas of Hangzhou Bay south coast. Moreover, this change will be spatially uneven obviously, e.g., the most serious recessions of the wetlands are concentrated in Ningbo city, Hangzhou city and Cixi city. （3） Overall, the potential risk to wetlands is very high, and will keep increasing with the trend of urbanization. （4） The quantity and spatial pattern of the planning urban construction land have substantial impacts on the wetland loss. Therefore, some policies and regulations are suggested to coordinate the relationship between urban economic development and wetland resource protection such as adjusting the construction land planning, compensating for wetland occupation as well as constructing wetland parks.
基金Supported by the National Special Research Fund for Non-Profit Marine Sector(No.200805063)the Continental Shelf Drilling Program(No.GZH201100202)the State Key Laboratory of Marine Geology and Environment,Institute of Oceanology Program(No.MGE2012KG09)
文摘This study focuses on sedimentary environmental changes offshore of Hangzhou Bay, East China, since the Late Quaternary. AMS ^14C ages from core CJK10, lithologies, distribution of foraminifera, heavy minerals, and S and C1 elements show a fluvial terrace environment during -23.2-11.0 cal ka BP; a littoral to tidal-flat environment during 11.0-10.2 cal ka BP; and a shallow marine environment with a relatively low sedimentation rate （0.1-0.22 cm/a） since 4.3 cal ka BP. High depositional rates （-1.6 cm/a） from 10.9 to 10.2 cal ka BP resulted from sufficient accommodation space created by rapid sea level rise from -44 m to -33 m, from high sediment delivery by local rivers, and effective trapping of sediments by tidal-flat vegetation. The rate of sea level rise was variable; relatively high from 10.9 to 10.6 cal ka BP （2.1 cm/a）, and lower since 10.6 cal ka BP （1.2 cm/a）. The Changjiang alongshore current crossed the Hangzhou Bay to form the mud wedge on the inner shelf of the East China Sea later than 9.4 cal ka BP. The CJK10 site was a tide-dominated shelf environment and experienced erosion from approximately 9.4-9.2 cal ka BP to 4.3 cal ka BP. The depositional hiatus was caused by the Changjiang alongshore current, which was relatively weak during 9.4-7.5 cal ka BP and increased in strength during -7.5-4 cal ka BP. From -4.3 cal ka BP, a large amount of sediment from the Changjiang River was partly deposited on the continental shelf of Hangzhou Bay with some transported southward. Therefore, this study clarifies the history of Changjiang-derived sediment dispersal and deposition, although a detailed record of the changes in the Chang3iang alongshore current since 4.3 cal ka BP is difficult to obtain because of the scarcity of evidence.
基金funded by the grants from the Major Project of National Social Science Foundation of China (15ZDA021)National Natural Science Foundation of China (Grant Nos.41130748, 41471143)
文摘Since the beginning of the 20th century, tideland reclamation as a huge project has continuously extended from inland to the sea for the socioeconomic development, like Zhejiang, Jiangsu and other coastal regions in China. The increase of land area alleviated the contradiction of supply and demand between human and land, which provided the guarantee for agricultural production and industrial development. However, marine ecological environment has been seriously damaged due to the increasing scale of tideland reclamation. This paper took the Hangzhou Bay in the Yangtze River Delta as a study area to explore the evolution law, socioeconomic effect and eco-environmental effect of reclaimed land from 1985 to 2015. The result showed that as follows:(1) The area of tideland reclamation was 460.67 km^2 with 16.57% cultivated land and 15.93% construction land, and its land use was inefficient;(2) Land use change has spatial and temporal difference, the speed of tideland reclamation had been increasing from 1985 to 2015 in time and the scale of reclaimed land in the southern(84.07%) of Hangzhou Bay was larger than the northern region(15.93%) in space;(3) The evolution law of land use was from tideland to swampland and coastal waters to agricultural facility land, to cultivated land to industrial-mining land to idle land, rural-urban construction land, and formed obviously hierarchical structure;(4) Effect analysis of land use change found that the socio-economic effect had increased but the eco-environmental effect had decreased from 1985 to 2015, it reflected socio-economic effect was acquired through sacrificing eco-environmental effect;(5) It pointed out the existing problems on land extensive inefficient, environmental degradation and economy excessive growth without scientific planning, and offered some suggestions in land comprehensive improvement project, industrial transformation and upgrading and scientific planning and legal safeguardto promote sustainable development in the Hangzhou Bay in the new period.
基金The National Basic Research Program(973 Program)of China under contract No.2010CB428903the National Natural Science Foundation of China under contract Nos 41106050,41203085 and 41076036+1 种基金the Public Welfare Industry Research Specific Funding of China under contract Nos 201105014,201105012 and 201205008the Basic Scientific Research Fund of the Second Institute of Oceanography of State Oceanic Administration of China under contract Nos JG1108 and JG1219
文摘Surface sediments from the Changjiang River （Yangtze River） Estuary, Hangzhou Bay, and their adjacent waters were analyzed for their grain size distribution, organic carbon （OC） concentration, and stable carbon isotope composition （δ13C）. Based on this analysis, about 36 surface sediment samples were selected from various environments and separated into sand （〉0.250 ram, 0.125-0.250 ram, 0.063-0.125 mm） and silt （0.025-0.063 mm） fractions by wet-sieving fractionation methods, and further into silt- （0.004-0.025 mm） and clay-sized （〈0.004 mm） fractions by centrifugal fractionation. Sediments of six grain size categories were analyzed for their OC and 613C contents to explore the grain size composition and transport paths of sedimentary OC in the study area. From fine to coarse fractions, the OC content was 1.18%, 0.51%, 0.46%, 0.42%, 0.99%, and 0.48%, respectively, while the δ13C was -21.64‰, -22.03‰, -22.52‰, -22.46‰, -22.36‰, and -22.28%0, respectively. In each size category, the OC contribution was 42.96%, 26.06%, 9.82%, 5.75%, 7.09%, and 8.33%, respectively. The OC content in clay and fine silt fractions （〈0.025 ram） was about 69.02%. High OC concentrations were mainly found in offshore modern sediments in the northeast of the Changjiang River Estuary, in modern sediments in the lower estuary of the Changjiang River and Hangzhou Bay, and in Cyclonic Eddy modern sediments to the southwest of the Cheju Island. Integrating the distribution of terrestrial OC content of each grain size category with the δ13C of the bulk sediment indicated that the terrestrial organic material in the Changjiang River Estuary was transported seaward and dispersed to the Cyclonic Eddy modern sediments to the southwest of the Cheju Island via two pathways： one was a result of the Changjiang River Diluted Water （CDW） northeastward extending branch driven by the North Jiangsu Coastal Current and the Yellow Sea Coastal Current, while the other one was the result of the CDW southward extending branch driven by the Taiwan Warm Current.
基金This work was sponsored by the National Natural Science Foundation of China
文摘-In order to avoid prescribing open boundary condition on the upstream side of the Hangzhou Bay, in numerical simulation of the tides and residual currents of the Bay, a 1-D model for the Qiantang River is connected to the 2-D model for the Hangzhou Bay. The harmonic constants of diurnal constituent [ (K1+O1)/2],semidiurnal constituent (M2) and shallow water constituent (M4) are obtained. The results produced by the combined model are in better agreement with the observed ones than those produced solely by the original 2-D model. The combined model gives much more reliable results for tide-induced residual water level and current.
文摘Based on the historical evolution of the Hangzhou Bay, by making use of the conclusions made by the previous research workers and the integration of concrete data, five distinct impact indicators of the sediment from the Changjiang Estuary and the East China Sea to the Hangzhou Bay are summarized. Numerical calculation and analysis indicate that the scouring and deposition of seabed in the Hangzhou Bay are subject to the direct impact of the evolution of the Changjiang Estuary, and the growth and decline and the direction of the sandy bar at Nanhuizui give traces to the sediment transport between the Changjiang Estuary and the Hangzhou Bay. The transport of sediment from the Changjiang Estuary to the Hangzhou Bay occurs mainly in winter and spring seasons and the increase of the Changjiang River runoff and the decrease of sediment charge have caused scouring in the northern coast of the Hangzhou Bay and the seabed erosion along the frontal margin of the Changjiang River Delta.
基金Supported by National Natural Science Foundation of China (No 40576080)National High Technology Research and Development Program of China ("863" Program, No 2007AA12Z182)
文摘Based on the COHERENS model (a coupled hydrodynamic ecological model for regional and shelf seas), a numerical hydrodynamic model of the Hangzhou Bay, influenced by tide, regional winds and freshwater from the Yangtze River and the Qiantangjiang River was established. The Lagrangian particle tracking was simulated to provide tracer trajectories. For convenience, the modeling area was divided into 8 subdomains and the modeling focused on March (dry season) and July (wet season). Numerical simulation and analysis indicate that the tracer trajectories originated in different subdomains are quite different. Most particles released in the mouth of the bay move outside the bay quickly and reach the farthest place at 122.5°E; while particles released in the inner part of the bay mostly remain in the same subdomain, with only minor migrations in two opposite directions along the shore. The tracer experiments also indicate that the northwest region of the bay is an area where pollutant can easily accumulate in both wet and dry seasons, and that the southeast region of the bay is another area for pollutant to accumulate in dry season because it is the main path for the contaminant.
文摘Time-series InSAR analysis（e.g., permanent scatterers（PSInSAR）） has been proven as an effective technology in monitoring ground deformation over urban areas. However, it is a big challenge to apply this technology in coastal regions due to the lack of man-made targets. An distributed scatterers interferometric synthetic aperture radar（DSInSAR） is developed to solve the problem of insufficient samples and low reliability in monitoring coastal lowland subsidence, by applying a spatially adaptive filter and an eigendecomposition algorithm to estimating the optimal phase of statistically homogeneous distributed scatterers（DSs）. Twenty-four scenes of COSMO-Sky Med images acquired between 2013 and 2015 are used to retrieve the land subsidence over the Shangyu District on south coast of the Hangzhou Bay, Zhejiang Province, China. The spatial pattern of the land subsidence obtained by the PS-InSAR and the DSInSAR coincides with each other, but the density of the DSs is three point five times higher than the permanent scatterers（PSs）. Validated by precise levelling data over the same period, the DSInSAR method achieves an accuracy of ±5.0 mm/a which is superior to the PS-InSAR with±5.5 mm/a. The land subsidence in the Shangyu District is mainly distributed in the urban areas, industrial towns and land reclamation zones, with a maximum subsidence rate -30.2 mm/a. The analysis of geological data, field investigation and historical reclamation data indicates that human activities and natural compaction of reclamation material are major causes of the detected land subsidence. The results demonstrate that the DSInSAR method has a great potential in monitoring the coastal lowland subsidence and can be used to further investigate subsidence-related environmental issues in coastal regions.
基金This work is supported by both Grant-4860244 from the National Natural Science Foundation of China and Grant-188011 from the Zhejiang Provincial Natural Science Foundation
文摘On the basis of the time series of AVHRR data from NOAA satellites and the geographical information system PURSIS, fluctuations of the plume front and the turbidity maximum in the Hangzhou Bay, reflected by the distributions of temperature and suspended sediment concentration respectively, are studied in view of long-term behaviors or seasonal and tidal cycles. The data suggest that the effect of front plays an important role in the development of the turbidity maximum close to the Changjiang Estuary > while the effect of tide dominates over the development of another very turbid water situated in the shoal areas in the southern Hangzhou Bay.
文摘In this study, a comparison was made between the Changjiang Estuary and the Hanghzou Bay, in terms of the sources and diagenesis of the sedimentary organic matter (OM). To achieve this purpose, surface sediments from the estuary and bay were analyzed for lignin-derived phenols, stable carbon isotope and TOC/TN (total organic carbon/total nitrogen) molar ratio. The signal of land-derived OM decreased, and the vanillic acid to vanillin ratio, (Ad/Al)v, increased with increasing distance from the Changjiang Estuary and the Hangzhou Bay. These results corresponded with the contribution of the terrigenous OM from the rivers to the coastal zone, and the predominance of marine OM farther offshore, and that the land-derived OM underwent decomposition during transport along the estuary and bay. It should be noted that besides the Qiantang River, Hangzhou Bay is also receiving more than half of its materials from Changjiang Estuary, which flows into the Hangzhou Bay at the north, and leaves via the southern part of the bay. This important aspect of the hydrological cycle in Hangzhou Bay corresponded to higher Λ (total lignin in mg/100 mg OC), higher TOC and C/N ratios and more elevated (Ad/Al)v and (Ad/Al)s values in the bay than the Changjiang Estuary, thus, rendering the bay as a site for the accumulation and rapid cycling of terrigenous OM.
文摘-low-frequency sea level fluctuations in the Hangzhou Bay in winter and summer, 1973-1974 are analyzed in this paper. The established multi-spectrum response models effectively identify the different dynamical factors and their contributions to the low-frequency sea level fluctuations inside the bay. The results show that the Ekman transport due to longshore winds is the major mechanism to induce the sea level fluctuations, more important than the frictional effect of local winds. There also exists obviously the influental effect of the free fluctuations of the continental shelf. In addition ,a simple estimation suggests that the remarkable sea level fluctuation of 0. 4 d-1 in the bay is related to the resonance of the Huanghai Sea and the Bohai Sea (taken as a single bay).
