In the present study, the ecosystem-based water quality model was applied to the Pearl River (Zhujiang) Estuary. The model results successfully represent the distribution trend of nutrients and dissolved oxygen both i...In the present study, the ecosystem-based water quality model was applied to the Pearl River (Zhujiang) Estuary. The model results successfully represent the distribution trend of nutrients and dissolved oxygen both in the horizontal and vertical planes during the flood season, and it shows that the model has taken into consideration the key part of the dynamical, chemical and biological processes existing in the Zhujiang Estuary. The further studies illustrate that nitrogen is in plenty while phospho- rus and light limit the phytoplankton biomass in the Zhujiang Estuary during the flood season.展开更多
Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. rad...Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. radioactivity, total β radioactivity, artificial radioactive 90Srand 157Cs, and factors inflencing the distribution and the content of U in seawater are studied.The mainly radioactive pollution substances and their sources in the sea area are studied by γ spectra obtained from sediment in the sea area. The results show that the main radioactivity substances are natural radioactivity U,Th series and 40K. which were produced by the modern industry and transported into the sea through the main current of the Zhujiang River.展开更多
Based on data of demersal trawl Samples from 1987 to 1988 in the Zhujiang Estuary and its adjacent waters, relationships between fish community and environmental factors are studied by using clssification , MDS ordina...Based on data of demersal trawl Samples from 1987 to 1988 in the Zhujiang Estuary and its adjacent waters, relationships between fish community and environmental factors are studied by using clssification , MDS ordina-tion and several community parameters. The results shaw that the distribution of fish shoes is zoned by salinty anddivided into three types. The freshwater community which is restricted in the Lianhua Hill - Humen waterway is sim-ple and stable, the coastal community which lives in the shallow waters is complex, and the estuary community whichis idenhfied in the Lingdingyang area and affected by Physical and ecological pinemore greatly greatly has obvious seasonalvariations.展开更多
The Zhujiang (Pearl River) Estuary is a complex water system whose catchments basincovers a very large part of southern China. The large quantity of fresh water carried by the river system flows into the northern coas...The Zhujiang (Pearl River) Estuary is a complex water system whose catchments basincovers a very large part of southern China. The large quantity of fresh water carried by the river system flows into the northern coast of the South China Sea through its eight inlets. The Zhujiang River Delta has experienced the fastest economic growth in China during the past two decades. Rapid population expansion and increased industrial development coupled with insufficient waste management turned the Zhujiang Estuary into waste disposal channels just before entering the coastal waters. The water quality of the estuaries and the coastal oceans has become polluted. During the past two years, an intensive study and monitoring efforts of the pollutions of these waters have been made. A systematic and integrated monitoring task including shore-based measurements, shipboard in-situ measurements, and satellite and radar remote sensing surveys has been completed. Comprehensive collection of physical, chemical and biological parameters has been accomplished and a database has been established. Unlike the previous large scale-monitoring task in which the various pollutant concentrations were the objective, the present study aims to understand the process of the pollution from their initial disposal to their final states. The understanding of the processes makes it possible to evaluate the severity of the pollution with respect to the sustainability. Also the objective is to incorporate these processes into the mathematical models from which a predictive capability of the pollution situation can be realized. The present presentation will describe the planning, methodology and the results of this effort.展开更多
The profiles of nutrient salts in the interstitial water of sediment were analyzed in the Zhu- jiang Estuary in the summer of 1999, and based on the profiles of content and characteristic of nutri- ents, the relations...The profiles of nutrient salts in the interstitial water of sediment were analyzed in the Zhu- jiang Estuary in the summer of 1999, and based on the profiles of content and characteristic of nutri- ents, the relationship between nutrients in the interstitial water and organic matter decomposition in sediment was discussed. The results showed that ammonium with high content was the main existence form of nutrients in the interstital water of sediment, and the organic matter decomposition was com- pleted in anaerobic condition. The increase of ammonium content in the bottom water resulted from the decomposition of organic matter and release of metabolic production, and the ammonium bottom flux was an important resource for nutrients geochemistry in the Zhujiang Estuary.展开更多
INTRODUCTIONThe Zhujiang (Pearl River) Estuary (22°00′-22°45′N, 113°30′-114°00′E), created by the inflow of fresh water from various tributaries of the Zhujiang, is the largest estuarine system...INTRODUCTIONThe Zhujiang (Pearl River) Estuary (22°00′-22°45′N, 113°30′-114°00′E), created by the inflow of fresh water from various tributaries of the Zhujiang, is the largest estuarine system in the southern China with an area of about 2 300 km2 . Average depth of the water body is about展开更多
Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process. Based on prediction of sea level rise over the 21st cent...Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process. Based on prediction of sea level rise over the 21st century, the Zhujiang(Pearl River) Estuary was chosen as a prototype to study the responses of the estuary to potential sea level rise. The numerical model results show that the average salt content, saltwater intrusion distance, and stratification will increase as the sea level rises. The changes of these parameters have obvious seasonal variations. The salt content in the Lingdingyang shows more increase in April and October(the transition periods). The saltwater intrusion distance has larger increase during the low-flow periods than during the highflow periods in the Lingdingyang. The result is just the opposite in Modaomen. The stratification and its increase are larger during the low-flow periods than during the high-flow periods in Lingdingyang. The response results of transport processes to sea level rise demonstrate that:(1) The time of vertical transport has pronounced increase.The increased tidal range and currents would reinforce the vertical mixing, but the increased stratification would weaken the vertical exchange. The impact of stratification changes overwhelms the impact of tidal changes. It would be more difficult for the surface water to reach the bottom.(2) The lengthways estuarine circulation would be strengthened. Both the offshore surface residual current and inshore bottom residual current will be enhanced.The whole meridional resident flow along the transect of the Lingdingyang would be weakened. These phenomena are caused by the decrease of water surface slope(WWS) and the change of static pressure with the increase of water depth under sea level rise.展开更多
Tidal energy budget in the Zhujiang(Pearl River) Estuary(ZE) is evaluated by employing high-resolution baroclinic regional ocean modeling system(ROMS). The results obtained via applying the least square method o...Tidal energy budget in the Zhujiang(Pearl River) Estuary(ZE) is evaluated by employing high-resolution baroclinic regional ocean modeling system(ROMS). The results obtained via applying the least square method on the model elevations are compared against the tidal harmonic constants at 18 tide stations along the ZE and its adjacent coast. The mean absolute errors between the simulation and the observation of M_2, S_2, K_1 and O_1 are 4.6, 2.8, 3.2 and 2.8 cm in amplitudes and 9.8°, 15.0°, 4.6° and 4.6° in phase-lags, respectively. The comparisons between the simulated and observed sea level heights at 11 tide gauge stations also suggest good model performance. The total tidal energy flux incoming the ZE is estimated to be 343.49 MW in the dry season and larger than 336.18 MW in the wet season, which should due to higher mean sea level height and heavier density in the dry season. M_2, K_1, S_2, O_1 and N_2, the top five barotropic tidal energy flux contributors for the ZE,import 242.23(236.79), 52.97(52.08), 24.49(23.96), 16.22(15.91) and 7.10(6.97) MW energy flux into the ZE in dry(wet) season, successively and respectively. The enhanced turbulent mixing induced by eddies around isolated islands and sharp headlands dominated by bottom friction, interaction between tidal currents and sill topography or constricted narrow waterways together account for the five energy dissipation hotspots, which add up to about 38% of the total energy dissipation inside the ZE.展开更多
The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary. This suggests that the area is an emissive source of nitrous oxide. The acetylene inhib...The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary. This suggests that the area is an emissive source of nitrous oxide. The acetylene inhibition technique is employed to evaluate the rates of nitrification, denitrification and nitrate reduction by bacterial activities in the sediments at three sites. The average of nitrification, denitrification and nitrate reduction rates ranges from 0.32 to 2.43, 0.03 to 0.84 and 4.17 to 13.06 mmol/(m2·h), respectively. The ver- tical profiles of the sediments show that the nitrification and denitrification processes mainly take place in the depth from 0 to 4 cm and depend on regional conditions. The rates of nitrification, denitrification and nitrate reduction are dominated by Eh, nitrate and ammoni- um concentrations in sediments and DO in overlay water. There is a coupling between nitrification and denitrification.展开更多
A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pol...A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE ? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water qual展开更多
To investigate organic matter source and reactivity in the Zhujiang River (Pearl River) Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during t...To investigate organic matter source and reactivity in the Zhujiang River (Pearl River) Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during two cruises in July 1999 and July 2000 were measured. The highest POC and PHAA concentration was observed in the waters with maximum Chl a. The spectra distribution, relative content (dry weight in milligram per gram), PHAA-C% POC and other indicators such as the ratios of amino acids vs. amino sugars (AA/AS) and glucosamine vs. galactosamine (Glum/Gal) suggested that particulate amino acids in the water column and sediments in the Zhujiang River Estuary were mainly derived from biogenic processes rather than transported from terrestrial erosion. In inner estuary where high turbidity was often observable, organic matter was mainly contributed by re-suspension of bottom sediments with revealed zooplankton, microbial reworked characteristics, which suggest that these organic matters were relatively 'old'. In the estuarine brackish region, organic matter in water column is mainly contributed by relatively fresh, easily degradable phytoplankton derived organic matter. During physical - biological processes within the eastuary, organic matter derived from phytoplankton was subjected to alteration by zooplankton grazing and bacterial reworking.展开更多
Chemometric approach based on principal component analysis(PCA) was utilized to examine the spatial variances of environmental and ecological characteristics in the Zhujiang River(Pearl River) Estuary and adjacent...Chemometric approach based on principal component analysis(PCA) was utilized to examine the spatial variances of environmental and ecological characteristics in the Zhujiang River(Pearl River) Estuary and adjacent waters(ZREAW) in the South China Sea. The PCA result shows that the ZREAW can be divided into different zones according to the principal components and geographical locations of the study stations,and indicates that there are distinct regional variances on environmental features and the corresponding phytoplankton biomass and community structures among different areas. The spatial distribution of ecological features was implied to be influenced by various degrees of the different water resources,such as the Pearl River discharges,the coastal current and the oceanic water from the South China Sea. The variation of the biomass maximum zone and the complex impacts on the spatial distributions of phytoplankton biomass and production were also evaluated.展开更多
To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21...To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21°N–23.5°N,111°E–117°E).Samples were collected from 65 stations including one for time-series sampling.A total of 212 phytoplankton taxa were identified from 61 genera belonging to 4 phyla.Among them,122 species identified from 42 genera of Bacillariophyta and 83 species from 15 genera of Pyrrophyta.Chain-forming diatoms dominated the phytoplankton community where Pseudonitzschia delicatissima,Guinardia striata,Thalassionema nitzschioides,and P.pungens comprised about 52%of the total abundance.However,higher cell abundances concentrated on both sides of the estuary,because of low salinity and high nutrients brought by diluted water.In addition,Canonical Correspondence Analysis revealed that salinity and dissolved inorganic nitrogen shaped the species composition in the study area.Furthermore,the Jaccard similarity index showed prevailing high similarity in the distribution of species in low-salinity diluted waters,and the Bray-Curtis similarity depicted distinguished grouping for phytoplankton assemblages along the salinity gradient.However,phytoplankton diel vertical cycles showed maximum abundance occurred at 2:00 am,which was mainly contributed by benthic phytoplankton species Pseudo-nitzschia spp.and T.nitzschioides.展开更多
Real-time observations in the field and numerical simulations(with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum(TM) in the Zhujiang(Pearl R...Real-time observations in the field and numerical simulations(with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum(TM) in the Zhujiang(Pearl River) Estuary(ZE). The spatial distribution pattern of the TM varies with the longitudinal distributions of salinity and suspended sediment concentration(SSC). The SSC is enhanced and the TM is intensified during dry seasons,whereas the center of the TM moves upstream by a distance of 10 km during wet seasons. The formation of the TM is influenced by a complex combination of numerous factors, including tides, river discharges and topography, wherein sediment resuspension and vertical circulation dominate the formations and variability of the TM.展开更多
The Zhujiang River Estuary is becoming eutrophic due to the impact of anthropogenic activities in the past decades.To understand nutrient dynamics and fluxes to the Lingdingyang water via four outlets(Humen,Jiaomen,Ho...The Zhujiang River Estuary is becoming eutrophic due to the impact of anthropogenic activities in the past decades.To understand nutrient dynamics and fluxes to the Lingdingyang water via four outlets(Humen,Jiaomen,Hongqimen and Hengmen),we investigated the spatial distribution and seasonal variation of dissolved nutrients in the Zhujiang River Estuary,based on fourteen cruises conducted from March 2015 to October 2017,covering both wet(April to September)and dry(October to March next year)seasons.Our results showed that riverine fluxes of dissolved inorganic nitrogen(DIN)and dissolved silicate(DSi)into the Lingdingyang water through four outlets varied seasonally due to the influence of river discharge,with the highest in spring and the lowest in winter.However,riverine flux of phosphate exhibited little significant seasonal variability.Riverine nutrients into the Lingdingyang water most resulted through Humen Outlet.The estuarine export fluxes of DIN out of the Zhujiang River Estuary derived from a box model were higher than fluxes of riverine nutrients in May,likely due to the influence of local sewage,while lower than riverine flux in August.The export fluxes of phosphate were higher than the fluxes of riverine phosphate in May and August.In contrast,large amounts of DSi were buried in the estuary in May and August.Although excess DIN was delivered into the Zhujiang River Estuary,eutrophication effect was not as severe as expected in the Zhujiang River Estuary,since the light limitation restricted the utilization of nutrients by phytoplankton.展开更多
The contents of total copper, total dissolved copper, particulate copper, and free ion copper in the Zhujiang River Estuary were investigated in July 2002 and January 2003 respectively, and the spatial distribution tr...The contents of total copper, total dissolved copper, particulate copper, and free ion copper in the Zhujiang River Estuary were investigated in July 2002 and January 2003 respectively, and the spatial distribution trend of these species of copper were compared in two cruises. It was found that, in summer, the total copper content in the Zhujiang River Estuary increased with salinity, while the content office ion copper decreased with salinity. However, in winter, the contents of total copper and free ion copper both decreased with salinity. So, it could be concluded that, copper content and speciation in the Zhujiang River Estuary were regulated by other factors than runoffdiffusion such as upwelling current. In order to prove the spatial trend of rice ion copper content in the Zhujiang River Estuary, the cultivation of Dunaliella tertiolecta in waters obtained from sampling stations with different salinities was carried out, and the copper uptake by algae cells was measured then. It was found that, the cells' uptake of copper increased with rice ion copper, not the content of total copper.展开更多
A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang(Pearl)River Estuary(ZRE)from ...A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang(Pearl)River Estuary(ZRE)from 1971 to 2012.It is shown that,during the wavy period,the large wave-induced bottom stress enhances sediment resuspension,resulting in an increase in the area of suspended sediment concentration(SSC)greater than 100 mg/L by 183.4%.On one hand,in spring tide,the change in shoreline reduces the area of SSC greater than 100 mg/L by 17.8%in the west shoal(WS)but increases the SSC,owing to the closer sediment source to the offshore and the stronger residual current at the Hengmeng(HEM)and Hongqili(HQL)outlets.The eastward Eulerian transport is enhanced in the WS and west channel(WC),resulting in a higher SSC there.The reclamation of Longxue Island(LXI)increases SSC on its east side and east shoal(ES)but decreases the SSC on its west and south sides.Moreover,in the WC,the estuarine turbidity maximum(ETM)is located near the saltwater wedge and moves southward,which is caused by the southward movement of the maximum longitudinal Eulerian transport.In neap tide,the changes are similar but relatively weaker.On the other hand,in spring tide,the change in bathymetry makes the SSC in the WS increase,and the area of SSC greater than 100 mg/L increases by 11.4%and expands eastward and southward,which is caused by the increases in wave-induced bottom stress and eastward Eulerian transport.On the east side of the WC,the eastward Eulerian transport decreases significantly,resulting in a smaller SSC in the middle shoal(MS).In addition,in the WC,the maximum SSC is reduced,which is caused by the smaller wave-induced bottom stress and a significant increase of 109.88%in southward Eulerian transport.The results in neap tide are similar to those in spring tide but with smaller changes,and the sediment transports northward in the WC owing to the northward Eulerian transport and vertical shear transport.This study may provide some references for marine ecological environment security and coastal management in the ZRE and other estuaries worldwide affected by strong human interventions.展开更多
The distributions of estuarine colored dissolved organic matter(CDOM)are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ d...The distributions of estuarine colored dissolved organic matter(CDOM)are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ data from four seasonal cruises,an algorithm is developed to estimate CDOM absorption coefficient at 400nm(aCDOM(400))in the Zhujiang(Pearl River)Estuary(ZJE).The algorithm uses band ratios of Rrs(667)/Rrs(443)and Rrs(748)/Rrs(412).By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite(MODIS/Aqua)data from 2002 to 2014,seasonal climatology aCDOM(400)in the ZJE is calculated.CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography.Along the section vertical to a water depth gradient,the seasonal aCDOM(400)exponentially decreased(y=aebx,b〈0),but with great differences among seasons.Riverine fresh water is the primary source of CDOM in the ZJE.Fulvic acid fraction decreases with increasing salinity.Using developed algorithms,conservative CDOM mixing equation,and river discharge,effective riverine end-member concentration and flux of dissolved organic carbon(DOC)in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data.Both effective riverine end-member DOC concentration and flux are positively related to the river discharge,significantly in summer with R-2 of 0.698 for concentration and 0.965 7 for flux.展开更多
1. PREFACE Lingdingyang is a trumpet estuary. It accepts the runoff of the Dongjiang River, the Beijiang River, the Zhengjiang River and the Liusihe River. It also accepts a part of the runoff of the Xijiang River. It...1. PREFACE Lingdingyang is a trumpet estuary. It accepts the runoff of the Dongjiang River, the Beijiang River, the Zhengjiang River and the Liusihe River. It also accepts a part of the runoff of the Xijiang River. Its mean year runoff is 1.742×10" M^3. In resent ten years, industry and agriculture are developing rapidly in Guangzhou City, Dongguan City, Zhongshan City, Shunde County, Panyu County. Lingdingyang’s pollution is increesing. Water quality of lingdingyang is steadily deteriorated. In order to investigate the situation of water environment of Lingdingyang, we study its static environmental capacity of nitrogen and phosphorus. LANDSAT imageries are used in the study. The concentrations of nitrogen and phosphorous is detected by convention method.展开更多
The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determine...The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determined. The method of sequential extraction was used for separating the five bound forms.The main chemical form of the three elements in the sediments of the Zhujiang River and its estuarine zone is the residual one. The exchangeable form exists only in a small fraction.Correlationships between the concentration of a certain form of heavy metals and Eh. pH and salinity were discussed. The principles of geochemistry are used to explain the mechanism of heavy metal transport in the river.It was also found that the distribution rule of the chemical forms of Fe, Al and Mn in sediments in the lower reaches of the Zhujiang River was similar to the one in the lower reaches of the Yamaska River.展开更多
基金The present study was supported by the Pearl River Estuary Pollution Project funded by the Hong Kong AdministrativeDivision Go
文摘In the present study, the ecosystem-based water quality model was applied to the Pearl River (Zhujiang) Estuary. The model results successfully represent the distribution trend of nutrients and dissolved oxygen both in the horizontal and vertical planes during the flood season, and it shows that the model has taken into consideration the key part of the dynamical, chemical and biological processes existing in the Zhujiang Estuary. The further studies illustrate that nitrogen is in plenty while phospho- rus and light limit the phytoplankton biomass in the Zhujiang Estuary during the flood season.
文摘Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. radioactivity, total β radioactivity, artificial radioactive 90Srand 157Cs, and factors inflencing the distribution and the content of U in seawater are studied.The mainly radioactive pollution substances and their sources in the sea area are studied by γ spectra obtained from sediment in the sea area. The results show that the main radioactivity substances are natural radioactivity U,Th series and 40K. which were produced by the modern industry and transported into the sea through the main current of the Zhujiang River.
文摘Based on data of demersal trawl Samples from 1987 to 1988 in the Zhujiang Estuary and its adjacent waters, relationships between fish community and environmental factors are studied by using clssification , MDS ordina-tion and several community parameters. The results shaw that the distribution of fish shoes is zoned by salinty anddivided into three types. The freshwater community which is restricted in the Lianhua Hill - Humen waterway is sim-ple and stable, the coastal community which lives in the shallow waters is complex, and the estuary community whichis idenhfied in the Lingdingyang area and affected by Physical and ecological pinemore greatly greatly has obvious seasonalvariations.
基金This work was supported by the Hong Kong Jockey Club Charity Fund through Chief Executive' s Community Project, "PREPP" the Ministry of Science and Technology of China through 863/818 Project , "Zhujiang Estuary Integrated Ob-servation System".
文摘The Zhujiang (Pearl River) Estuary is a complex water system whose catchments basincovers a very large part of southern China. The large quantity of fresh water carried by the river system flows into the northern coast of the South China Sea through its eight inlets. The Zhujiang River Delta has experienced the fastest economic growth in China during the past two decades. Rapid population expansion and increased industrial development coupled with insufficient waste management turned the Zhujiang Estuary into waste disposal channels just before entering the coastal waters. The water quality of the estuaries and the coastal oceans has become polluted. During the past two years, an intensive study and monitoring efforts of the pollutions of these waters have been made. A systematic and integrated monitoring task including shore-based measurements, shipboard in-situ measurements, and satellite and radar remote sensing surveys has been completed. Comprehensive collection of physical, chemical and biological parameters has been accomplished and a database has been established. Unlike the previous large scale-monitoring task in which the various pollutant concentrations were the objective, the present study aims to understand the process of the pollution from their initial disposal to their final states. The understanding of the processes makes it possible to evaluate the severity of the pollution with respect to the sustainability. Also the objective is to incorporate these processes into the mathematical models from which a predictive capability of the pollution situation can be realized. The present presentation will describe the planning, methodology and the results of this effort.
基金This study was supported by the Science and Technology University of Hong Kong and the State Oceanic Administrationof China.
文摘The profiles of nutrient salts in the interstitial water of sediment were analyzed in the Zhu- jiang Estuary in the summer of 1999, and based on the profiles of content and characteristic of nutri- ents, the relationship between nutrients in the interstitial water and organic matter decomposition in sediment was discussed. The results showed that ammonium with high content was the main existence form of nutrients in the interstital water of sediment, and the organic matter decomposition was com- pleted in anaerobic condition. The increase of ammonium content in the bottom water resulted from the decomposition of organic matter and release of metabolic production, and the ammonium bottom flux was an important resource for nutrients geochemistry in the Zhujiang Estuary.
基金This work was supported by a research grant from the Croucher Foundation, Hong Kong.
文摘INTRODUCTIONThe Zhujiang (Pearl River) Estuary (22°00′-22°45′N, 113°30′-114°00′E), created by the inflow of fresh water from various tributaries of the Zhujiang, is the largest estuarine system in the southern China with an area of about 2 300 km2 . Average depth of the water body is about
基金The National Natural Science Foundation of China under contract No.51409286the Scientific Research Innovation Project of Jiangsu Province Ordinary University Graduate Student under contract No.CXZZ12_0223the Open Fund Project of Zhujiang River Water Resources Commission of the Zhujiang River Water Conservancy Science Research Institute under contract No.[2013]KJ02
文摘Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process. Based on prediction of sea level rise over the 21st century, the Zhujiang(Pearl River) Estuary was chosen as a prototype to study the responses of the estuary to potential sea level rise. The numerical model results show that the average salt content, saltwater intrusion distance, and stratification will increase as the sea level rises. The changes of these parameters have obvious seasonal variations. The salt content in the Lingdingyang shows more increase in April and October(the transition periods). The saltwater intrusion distance has larger increase during the low-flow periods than during the highflow periods in the Lingdingyang. The result is just the opposite in Modaomen. The stratification and its increase are larger during the low-flow periods than during the high-flow periods in Lingdingyang. The response results of transport processes to sea level rise demonstrate that:(1) The time of vertical transport has pronounced increase.The increased tidal range and currents would reinforce the vertical mixing, but the increased stratification would weaken the vertical exchange. The impact of stratification changes overwhelms the impact of tidal changes. It would be more difficult for the surface water to reach the bottom.(2) The lengthways estuarine circulation would be strengthened. Both the offshore surface residual current and inshore bottom residual current will be enhanced.The whole meridional resident flow along the transect of the Lingdingyang would be weakened. These phenomena are caused by the decrease of water surface slope(WWS) and the change of static pressure with the increase of water depth under sea level rise.
基金The National Natural Science Foundation of China under contract No.41476002the Shandong Province Natural Science Foundation under contract No.ZR2014DQ013the Shandong Scientific and Technological Development Program under contract No.2013GHY11502
文摘Tidal energy budget in the Zhujiang(Pearl River) Estuary(ZE) is evaluated by employing high-resolution baroclinic regional ocean modeling system(ROMS). The results obtained via applying the least square method on the model elevations are compared against the tidal harmonic constants at 18 tide stations along the ZE and its adjacent coast. The mean absolute errors between the simulation and the observation of M_2, S_2, K_1 and O_1 are 4.6, 2.8, 3.2 and 2.8 cm in amplitudes and 9.8°, 15.0°, 4.6° and 4.6° in phase-lags, respectively. The comparisons between the simulated and observed sea level heights at 11 tide gauge stations also suggest good model performance. The total tidal energy flux incoming the ZE is estimated to be 343.49 MW in the dry season and larger than 336.18 MW in the wet season, which should due to higher mean sea level height and heavier density in the dry season. M_2, K_1, S_2, O_1 and N_2, the top five barotropic tidal energy flux contributors for the ZE,import 242.23(236.79), 52.97(52.08), 24.49(23.96), 16.22(15.91) and 7.10(6.97) MW energy flux into the ZE in dry(wet) season, successively and respectively. The enhanced turbulent mixing induced by eddies around isolated islands and sharp headlands dominated by bottom friction, interaction between tidal currents and sill topography or constricted narrow waterways together account for the five energy dissipation hotspots, which add up to about 38% of the total energy dissipation inside the ZE.
基金supported by the Knowledge Innovation Engineering of Chinese Academy of Sciences under contract No.KZCX3-SW-214,KSCX2-SW-132the Natural Science Foundation of Guangdong Province under contract No.032622.
文摘The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary. This suggests that the area is an emissive source of nitrous oxide. The acetylene inhibition technique is employed to evaluate the rates of nitrification, denitrification and nitrate reduction by bacterial activities in the sediments at three sites. The average of nitrification, denitrification and nitrate reduction rates ranges from 0.32 to 2.43, 0.03 to 0.84 and 4.17 to 13.06 mmol/(m2·h), respectively. The ver- tical profiles of the sediments show that the nitrification and denitrification processes mainly take place in the depth from 0 to 4 cm and depend on regional conditions. The rates of nitrification, denitrification and nitrate reduction are dominated by Eh, nitrate and ammoni- um concentrations in sediments and DO in overlay water. There is a coupling between nitrification and denitrification.
文摘A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE ? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water qual
文摘To investigate organic matter source and reactivity in the Zhujiang River (Pearl River) Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during two cruises in July 1999 and July 2000 were measured. The highest POC and PHAA concentration was observed in the waters with maximum Chl a. The spectra distribution, relative content (dry weight in milligram per gram), PHAA-C% POC and other indicators such as the ratios of amino acids vs. amino sugars (AA/AS) and glucosamine vs. galactosamine (Glum/Gal) suggested that particulate amino acids in the water column and sediments in the Zhujiang River Estuary were mainly derived from biogenic processes rather than transported from terrestrial erosion. In inner estuary where high turbidity was often observable, organic matter was mainly contributed by re-suspension of bottom sediments with revealed zooplankton, microbial reworked characteristics, which suggest that these organic matters were relatively 'old'. In the estuarine brackish region, organic matter in water column is mainly contributed by relatively fresh, easily degradable phytoplankton derived organic matter. During physical - biological processes within the eastuary, organic matter derived from phytoplankton was subjected to alteration by zooplankton grazing and bacterial reworking.
基金The Knowledge Innovation Project of Chinese Academy of Sciences under contract Nos KZCX2-YW-Q07, KZCX2-YW-T001, KZCX2-YW-213 and SQ200805the National Natural Science Foundation of China under contract Nos U0633007, 40906057 and 40531006
文摘Chemometric approach based on principal component analysis(PCA) was utilized to examine the spatial variances of environmental and ecological characteristics in the Zhujiang River(Pearl River) Estuary and adjacent waters(ZREAW) in the South China Sea. The PCA result shows that the ZREAW can be divided into different zones according to the principal components and geographical locations of the study stations,and indicates that there are distinct regional variances on environmental features and the corresponding phytoplankton biomass and community structures among different areas. The spatial distribution of ecological features was implied to be influenced by various degrees of the different water resources,such as the Pearl River discharges,the coastal current and the oceanic water from the South China Sea. The variation of the biomass maximum zone and the complex impacts on the spatial distributions of phytoplankton biomass and production were also evaluated.
基金Supported by the National Key Research and Development Program of China(No.2015CB954002)the National Natural Science Foundation of China(Nos.41876134,41676112,41276124)+2 种基金the University Innovation Team Training Program for Tianjin(No.TD12-5003)the Tianjin 131 Innovation Team Program(No.20180314)the Changjiang Scholar Program of Chinese Ministry of Education(No.T2014253)to Jun SUN。
文摘To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21°N–23.5°N,111°E–117°E).Samples were collected from 65 stations including one for time-series sampling.A total of 212 phytoplankton taxa were identified from 61 genera belonging to 4 phyla.Among them,122 species identified from 42 genera of Bacillariophyta and 83 species from 15 genera of Pyrrophyta.Chain-forming diatoms dominated the phytoplankton community where Pseudonitzschia delicatissima,Guinardia striata,Thalassionema nitzschioides,and P.pungens comprised about 52%of the total abundance.However,higher cell abundances concentrated on both sides of the estuary,because of low salinity and high nutrients brought by diluted water.In addition,Canonical Correspondence Analysis revealed that salinity and dissolved inorganic nitrogen shaped the species composition in the study area.Furthermore,the Jaccard similarity index showed prevailing high similarity in the distribution of species in low-salinity diluted waters,and the Bray-Curtis similarity depicted distinguished grouping for phytoplankton assemblages along the salinity gradient.However,phytoplankton diel vertical cycles showed maximum abundance occurred at 2:00 am,which was mainly contributed by benthic phytoplankton species Pseudo-nitzschia spp.and T.nitzschioides.
基金The Ocean Special Funds for Scientific Research on Public Causes under contract No.201105001-2the National Basic Research Program(973 Program)of China under contract No.2013CB956502the National Natural Science Foundation of China under contract Nos 41376044,41276083 and 41476049
文摘Real-time observations in the field and numerical simulations(with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum(TM) in the Zhujiang(Pearl River) Estuary(ZE). The spatial distribution pattern of the TM varies with the longitudinal distributions of salinity and suspended sediment concentration(SSC). The SSC is enhanced and the TM is intensified during dry seasons,whereas the center of the TM moves upstream by a distance of 10 km during wet seasons. The formation of the TM is influenced by a complex combination of numerous factors, including tides, river discharges and topography, wherein sediment resuspension and vertical circulation dominate the formations and variability of the TM.
基金The Special Project for Marine Economic Development(Six Major Marine Industries)of Guangdong Province under contract No.GDNRC[2020]064the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract Nos GML2019ZD0303,GML2019ZD0305 and GML2019ZD0402+2 种基金the Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences under contract Nos ISEE2019ZR02 and ISEE2019ZR03the National Natural Science Foundation of China under contract Nos 41676075 and 41706085the Department of Science and Technology of Guangdong Province under contract No.2018B030320005。
文摘The Zhujiang River Estuary is becoming eutrophic due to the impact of anthropogenic activities in the past decades.To understand nutrient dynamics and fluxes to the Lingdingyang water via four outlets(Humen,Jiaomen,Hongqimen and Hengmen),we investigated the spatial distribution and seasonal variation of dissolved nutrients in the Zhujiang River Estuary,based on fourteen cruises conducted from March 2015 to October 2017,covering both wet(April to September)and dry(October to March next year)seasons.Our results showed that riverine fluxes of dissolved inorganic nitrogen(DIN)and dissolved silicate(DSi)into the Lingdingyang water through four outlets varied seasonally due to the influence of river discharge,with the highest in spring and the lowest in winter.However,riverine flux of phosphate exhibited little significant seasonal variability.Riverine nutrients into the Lingdingyang water most resulted through Humen Outlet.The estuarine export fluxes of DIN out of the Zhujiang River Estuary derived from a box model were higher than fluxes of riverine nutrients in May,likely due to the influence of local sewage,while lower than riverine flux in August.The export fluxes of phosphate were higher than the fluxes of riverine phosphate in May and August.In contrast,large amounts of DSi were buried in the estuary in May and August.Although excess DIN was delivered into the Zhujiang River Estuary,eutrophication effect was not as severe as expected in the Zhujiang River Estuary,since the light limitation restricted the utilization of nutrients by phytoplankton.
基金This work was supported by the Innovative Program of Chinese Academy of Sciences under contract No.kzcx3-sw-227 to Dr.Chen ShaoyongGuangdong Province Natural Science Fund under contract Nos 021560,04001313+1 种基金the Innovation Program of South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.50601-32 to Long AiminScience and Technology Planning Program under contract No.2004B33201001 to Dr.Yan Wen and Long Aimin.
文摘The contents of total copper, total dissolved copper, particulate copper, and free ion copper in the Zhujiang River Estuary were investigated in July 2002 and January 2003 respectively, and the spatial distribution trend of these species of copper were compared in two cruises. It was found that, in summer, the total copper content in the Zhujiang River Estuary increased with salinity, while the content office ion copper decreased with salinity. However, in winter, the contents of total copper and free ion copper both decreased with salinity. So, it could be concluded that, copper content and speciation in the Zhujiang River Estuary were regulated by other factors than runoffdiffusion such as upwelling current. In order to prove the spatial trend of rice ion copper content in the Zhujiang River Estuary, the cultivation of Dunaliella tertiolecta in waters obtained from sampling stations with different salinities was carried out, and the copper uptake by algae cells was measured then. It was found that, the cells' uptake of copper increased with rice ion copper, not the content of total copper.
基金The National Natural Science Foundation of China under contract No.41890851the Key Research Program of Frontier Sciences+3 种基金Chinese Academy of Sciences,under contract No.QYZDJ-SSW-DQC034the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0304the fund of Chinese Academy of Sciences under contract No.ISEE2021PY01the project of Department of Natural Resources of Guangdong Province under contract No.[2020]017。
文摘A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang(Pearl)River Estuary(ZRE)from 1971 to 2012.It is shown that,during the wavy period,the large wave-induced bottom stress enhances sediment resuspension,resulting in an increase in the area of suspended sediment concentration(SSC)greater than 100 mg/L by 183.4%.On one hand,in spring tide,the change in shoreline reduces the area of SSC greater than 100 mg/L by 17.8%in the west shoal(WS)but increases the SSC,owing to the closer sediment source to the offshore and the stronger residual current at the Hengmeng(HEM)and Hongqili(HQL)outlets.The eastward Eulerian transport is enhanced in the WS and west channel(WC),resulting in a higher SSC there.The reclamation of Longxue Island(LXI)increases SSC on its east side and east shoal(ES)but decreases the SSC on its west and south sides.Moreover,in the WC,the estuarine turbidity maximum(ETM)is located near the saltwater wedge and moves southward,which is caused by the southward movement of the maximum longitudinal Eulerian transport.In neap tide,the changes are similar but relatively weaker.On the other hand,in spring tide,the change in bathymetry makes the SSC in the WS increase,and the area of SSC greater than 100 mg/L increases by 11.4%and expands eastward and southward,which is caused by the increases in wave-induced bottom stress and eastward Eulerian transport.On the east side of the WC,the eastward Eulerian transport decreases significantly,resulting in a smaller SSC in the middle shoal(MS).In addition,in the WC,the maximum SSC is reduced,which is caused by the smaller wave-induced bottom stress and a significant increase of 109.88%in southward Eulerian transport.The results in neap tide are similar to those in spring tide but with smaller changes,and the sediment transports northward in the WC owing to the northward Eulerian transport and vertical shear transport.This study may provide some references for marine ecological environment security and coastal management in the ZRE and other estuaries worldwide affected by strong human interventions.
基金The National Key Research and Development Progam of China under contract No.2017YFA0603003the National Basic Research Program(973 Program)of China under contract No.2015CB954002+3 种基金the Public Science and Technology Research Funds Project of Ocean under contract No.201505003the National Natural Science Foundation of China under contract Nos41676170,41676172,41476155,41621064 and 41406202the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,State Oceanic Administration of China under contract No.SOEDZZ1801the Research Startup Project of Nanjing Instiute of Geography and Limnology,Chinese Academy of Sciences under contract No.Y7SL051001
文摘The distributions of estuarine colored dissolved organic matter(CDOM)are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ data from four seasonal cruises,an algorithm is developed to estimate CDOM absorption coefficient at 400nm(aCDOM(400))in the Zhujiang(Pearl River)Estuary(ZJE).The algorithm uses band ratios of Rrs(667)/Rrs(443)and Rrs(748)/Rrs(412).By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite(MODIS/Aqua)data from 2002 to 2014,seasonal climatology aCDOM(400)in the ZJE is calculated.CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography.Along the section vertical to a water depth gradient,the seasonal aCDOM(400)exponentially decreased(y=aebx,b〈0),but with great differences among seasons.Riverine fresh water is the primary source of CDOM in the ZJE.Fulvic acid fraction decreases with increasing salinity.Using developed algorithms,conservative CDOM mixing equation,and river discharge,effective riverine end-member concentration and flux of dissolved organic carbon(DOC)in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data.Both effective riverine end-member DOC concentration and flux are positively related to the river discharge,significantly in summer with R-2 of 0.698 for concentration and 0.965 7 for flux.
文摘1. PREFACE Lingdingyang is a trumpet estuary. It accepts the runoff of the Dongjiang River, the Beijiang River, the Zhengjiang River and the Liusihe River. It also accepts a part of the runoff of the Xijiang River. Its mean year runoff is 1.742×10" M^3. In resent ten years, industry and agriculture are developing rapidly in Guangzhou City, Dongguan City, Zhongshan City, Shunde County, Panyu County. Lingdingyang’s pollution is increesing. Water quality of lingdingyang is steadily deteriorated. In order to investigate the situation of water environment of Lingdingyang, we study its static environmental capacity of nitrogen and phosphorus. LANDSAT imageries are used in the study. The concentrations of nitrogen and phosphorous is detected by convention method.
文摘The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determined. The method of sequential extraction was used for separating the five bound forms.The main chemical form of the three elements in the sediments of the Zhujiang River and its estuarine zone is the residual one. The exchangeable form exists only in a small fraction.Correlationships between the concentration of a certain form of heavy metals and Eh. pH and salinity were discussed. The principles of geochemistry are used to explain the mechanism of heavy metal transport in the river.It was also found that the distribution rule of the chemical forms of Fe, Al and Mn in sediments in the lower reaches of the Zhujiang River was similar to the one in the lower reaches of the Yamaska River.