This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current ...This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current systems by analyzing the thermal infrared imagery with the sediment imagery, which is acquired by correlating the atmosphere corrected AVHRR imagery with in-situ suspended sediment data. The coastal current systems affecting the sediment dispersal mainly include： the Taiwan Warm Current （TWC）, the Huanghai Sea Mixed Water （HSMW）, North Jiangsu near-shore current, and Zhejiang near-shore current etc. In winter, the current systems are stable. Their distribution affects the sediment from north Jiangsu expanding toward the Changjiang estuary in some degree .The front between Zhejiang coastal current and TWC blocks the expanding of sediment toward the sea. In the flood season, apart from the limitation by coastal current systems, the spatial and temporal distribution of suspended sediment is also affected by the runoff, which shows as the jet stream and fresh water. Spring and autumn are the transitional periods of the forming of expanding patterns of flood season and winter respectively. In addition, the re-suspended sediment caused by the wind wave may make the expanding range of near-shore sediment larger.展开更多
Data taken in the two large-scale ocean investigations in China in winter 1959 and 1982 are used to analyze the residual current off the Changjiang (Yangtze) River mouth in this paper. The current in wintertime off th...Data taken in the two large-scale ocean investigations in China in winter 1959 and 1982 are used to analyze the residual current off the Changjiang (Yangtze) River mouth in this paper. The current in wintertime off the river mouth consist of the Changjiang runoff, wind-driven current, coastal current, density-driven current and Taiwan Warm Current (TWC). The TWC occurs in wintertime off the mouth. The surface TWC reaches only to the east side of Dinghai, then turns southeastward. The bottom TWC can flow to the area off the Changjiang mouth along west slop of the submerged river valley (SRV) and to the area off the Subei coast. The simulated currents by 3D model are basically consistent with the observed currents, although the model was run with climatological forces and the observations was done in episodic time manner.展开更多
The Changjiang(Yangtze)River estuary has been subject to a variety of anthropogenic pressures in recent decades.To assess the ecological health of the coastal benthic ecosystem adjacent to the estuary,three surveys we...The Changjiang(Yangtze)River estuary has been subject to a variety of anthropogenic pressures in recent decades.To assess the ecological health of the coastal benthic ecosystem adjacent to the estuary,three surveys were conducted in 2005,2009,and 2010.The AZTI's Marine Biotic Index(AMBI)and multivariate-AMBI(M-AMBI)were used to analyse the benthic ecological status of this coast.The AMBI indicate that the ecological status of the coast adjacent to the Changjiang River estuary was only slightly degraded in all 3 years.In contrast,the M-AMBI indicated that the ecological status was seriously degraded,a result that is most likely due to pollution and eutrophication induced by human activities.The assessment of the coast's ecological status by the AMBI was not in agreement with that of the M-AMBI at some stations because of lower biodiversity values at those sites.The analysis of the two indices integrated with abiotic parameters showed that the M-AMBI could be used as a suitable bio-indicator index to assess the benthic ecological status of the coast adjacent to the Changjiang River estuary.The reference conditions proposed for the coast of the Changjiang River estuary should be further evaluated in future studies.Designation of local species could also provide an important reference for Chinese waters.To improve the reliability of AMBI and M-AMBI,further research into the ecology of local species is required to understand their arrangement in ecological groups.展开更多
Data taken in two large scale ocean observations in China in summer 1959 and 1982 were used to analyze the residual current off the Changjiang (Yangtze) River mouth. The currents at surface off the mouth in July 1959 ...Data taken in two large scale ocean observations in China in summer 1959 and 1982 were used to analyze the residual current off the Changjiang (Yangtze) River mouth. The currents at surface off the mouth in July 1959 and 1982 flow northeastward and eastward due to the river discharge, the current speed was larger in1982 than in 1959. All the bottom currents flow landward due to baroclinic effect. The surface current was controlled by the river runoff and the Taiwan Warm Current (TWC). A return current at surface off the mouth was observed in September 1959. In general, the bottom currents were controlled by the TWC in most study area in addition to the runoff near the mouth. Although driven by 3-D model with the monthly averaged forces (river discharge, wind stress, baroclinic effect, open boundary water volume flux and tidal mixing) in August, the simulated circulations were basically consistent with the observed ones with episodic time manner.展开更多
Nitrogen and phosphorus contents are analyzed in the overlying waters and pore waters taken from the Changjiang Estuary and Shanghai coastal tidal flats in this study. In addition, the diffusion fluxes of nitrogen and...Nitrogen and phosphorus contents are analyzed in the overlying waters and pore waters taken from the Changjiang Estuary and Shanghai coastal tidal flats in this study. In addition, the diffusion fluxes of nitrogen and phosphorus across the sediment-water interface in tidal flats are estimated according to the nutrient concentration gradients at the interface. It has been indicated that the concentrations of ammonium, nitrite, nitrate and dissolved phosphorus in overlying waters range from 0.0082-2.56, 0.03-0.58, 0.69-5.38 and 0.035-0.53 mg/L, respectively, while 0.0025 - 1.35 mg /L for NH^-N, 0. 0055 ~0.20mg/L for NO2-N, 0.61-1.14 mg/L for NO3-N and 0.11~0.53mg/L for DP insurface pore waters.The findings have revealed that ammonium, nitrite, nitrate and dissolved phosphorus diffusionfluxes across the sediment-water interface are between -0.024~0.99, -0.39~ -0.0019, -3.09--0.12 and -0.48- 0.12 ug/ (cm.d ) respectively, showing that the sediment in tidal flats is the source of phosphorus and an important sink for nitrogen in the waters.展开更多
文摘This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current systems by analyzing the thermal infrared imagery with the sediment imagery, which is acquired by correlating the atmosphere corrected AVHRR imagery with in-situ suspended sediment data. The coastal current systems affecting the sediment dispersal mainly include： the Taiwan Warm Current （TWC）, the Huanghai Sea Mixed Water （HSMW）, North Jiangsu near-shore current, and Zhejiang near-shore current etc. In winter, the current systems are stable. Their distribution affects the sediment from north Jiangsu expanding toward the Changjiang estuary in some degree .The front between Zhejiang coastal current and TWC blocks the expanding of sediment toward the sea. In the flood season, apart from the limitation by coastal current systems, the spatial and temporal distribution of suspended sediment is also affected by the runoff, which shows as the jet stream and fresh water. Spring and autumn are the transitional periods of the forming of expanding patterns of flood season and winter respectively. In addition, the re-suspended sediment caused by the wind wave may make the expanding range of near-shore sediment larger.
文摘Data taken in the two large-scale ocean investigations in China in winter 1959 and 1982 are used to analyze the residual current off the Changjiang (Yangtze) River mouth in this paper. The current in wintertime off the river mouth consist of the Changjiang runoff, wind-driven current, coastal current, density-driven current and Taiwan Warm Current (TWC). The TWC occurs in wintertime off the mouth. The surface TWC reaches only to the east side of Dinghai, then turns southeastward. The bottom TWC can flow to the area off the Changjiang mouth along west slop of the submerged river valley (SRV) and to the area off the Subei coast. The simulated currents by 3D model are basically consistent with the observed currents, although the model was run with climatological forces and the observations was done in episodic time manner.
基金Supported by the National Special Research Fund for Non-profit Sector(Environmental Protection)(No.2008467041)the National Natural Science Foundation of China(No.40976086)
文摘The Changjiang(Yangtze)River estuary has been subject to a variety of anthropogenic pressures in recent decades.To assess the ecological health of the coastal benthic ecosystem adjacent to the estuary,three surveys were conducted in 2005,2009,and 2010.The AZTI's Marine Biotic Index(AMBI)and multivariate-AMBI(M-AMBI)were used to analyse the benthic ecological status of this coast.The AMBI indicate that the ecological status of the coast adjacent to the Changjiang River estuary was only slightly degraded in all 3 years.In contrast,the M-AMBI indicated that the ecological status was seriously degraded,a result that is most likely due to pollution and eutrophication induced by human activities.The assessment of the coast's ecological status by the AMBI was not in agreement with that of the M-AMBI at some stations because of lower biodiversity values at those sites.The analysis of the two indices integrated with abiotic parameters showed that the M-AMBI could be used as a suitable bio-indicator index to assess the benthic ecological status of the coast adjacent to the Changjiang River estuary.The reference conditions proposed for the coast of the Changjiang River estuary should be further evaluated in future studies.Designation of local species could also provide an important reference for Chinese waters.To improve the reliability of AMBI and M-AMBI,further research into the ecology of local species is required to understand their arrangement in ecological groups.
文摘Data taken in two large scale ocean observations in China in summer 1959 and 1982 were used to analyze the residual current off the Changjiang (Yangtze) River mouth. The currents at surface off the mouth in July 1959 and 1982 flow northeastward and eastward due to the river discharge, the current speed was larger in1982 than in 1959. All the bottom currents flow landward due to baroclinic effect. The surface current was controlled by the river runoff and the Taiwan Warm Current (TWC). A return current at surface off the mouth was observed in September 1959. In general, the bottom currents were controlled by the TWC in most study area in addition to the runoff near the mouth. Although driven by 3-D model with the monthly averaged forces (river discharge, wind stress, baroclinic effect, open boundary water volume flux and tidal mixing) in August, the simulated circulations were basically consistent with the observed ones with episodic time manner.
基金The work is supported by the National Natural Science Foundation of China(Grant Nos.430100203 and 49801018)the Foundation for University Key Teachers by the Ministry of Education of China.
文摘Nitrogen and phosphorus contents are analyzed in the overlying waters and pore waters taken from the Changjiang Estuary and Shanghai coastal tidal flats in this study. In addition, the diffusion fluxes of nitrogen and phosphorus across the sediment-water interface in tidal flats are estimated according to the nutrient concentration gradients at the interface. It has been indicated that the concentrations of ammonium, nitrite, nitrate and dissolved phosphorus in overlying waters range from 0.0082-2.56, 0.03-0.58, 0.69-5.38 and 0.035-0.53 mg/L, respectively, while 0.0025 - 1.35 mg /L for NH^-N, 0. 0055 ~0.20mg/L for NO2-N, 0.61-1.14 mg/L for NO3-N and 0.11~0.53mg/L for DP insurface pore waters.The findings have revealed that ammonium, nitrite, nitrate and dissolved phosphorus diffusionfluxes across the sediment-water interface are between -0.024~0.99, -0.39~ -0.0019, -3.09--0.12 and -0.48- 0.12 ug/ (cm.d ) respectively, showing that the sediment in tidal flats is the source of phosphorus and an important sink for nitrogen in the waters.
