Modelling nitrogen and phosphorus cycles and dissolved oxygen in the Zhujiang Estuary Ⅱ. Model results

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 phosphorus and light limit the phytoplankton biomass in the Zhujiang Estuary during the flood season.     

Modelling nitrogen and phosphorus cycles and dissolved oxygen in the Zhujiang Estuary Ⅰ.Model results

rmIoxThe averag annual dischaIge of the Zhujiang Xiver is 3. 32 x l0ll m3, which ranks theZhujiang River just end to the Changjiang River in China. The dischnye occutring duringthe fltal m between APril and ffepteTnber accounts for 80% of the yearly total. The Zhu-jiang hiver has a yeaIy sediment load of about 1 x l08 tons, which also concentrates in theM arn (Zhao, l990; Chen et al., 1998). The Zhujiang Xiver delta,which has l2 cities ofdifferent sizes and more than 40 towns with a po…     

Two-dimensional numerical simulation of vertical distributions of dissolved oxygen in Huanghai Sea

Ｔｗｏ－ｄｉｍｅｎｓｉｏｎａｌｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｏｆｖｅｒｔｉｃａｌｄｉｓｔｒｉｂｕｔｉｏｎｓｏｆｄｉｓｓｏｌｖｅｄｏｘｙｇｅｎｉｎＨｕａｎｇｈａｉＳｅａＬｉｕＫｅｘｉｕ１ａｎｄＺｈａｏＢａｏｒｅｎ１（ＲｅｃｅｉｖｅｄＪａｎｕａｒ...     

Numerical study on residual current and its impact on mass transport in the Hangzhou Bay and the Changjiang Estuary Ⅰ.A3-D joint model of the Hangzhou Bay and the Changjiang Estuary

A 3-D numerical model is set up in a large domain covering the Hang zhou 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.     

On sedimentation of phosphorus in specified area outside of the Changjiang Estuary

ＩＮＴＲＯＤＵＣＴＩＯＮＥｎｖｉｒｏｎｍｅｎｔａｌｐｏｌｌｕｔｉｏｎｈａｓｂｅｃｏｍｅａｖｅｒｙｓｅｒｉｏｕｓｐｒｏｂｌｅｍｗｉｔｈｔｈｅｒａｐｉｄｉｎｄｕｓｔｒｉａｌｉｚａ ｔｉｏｎ .Ｔｈｅｐｏｌｌｕｔｉｏｎｃａｕｓｅｄｂｙｐｏｌｌｕｔａｎｔｓｓｕｃｈａｓｎｕｔｒｉｅｎｔｓ ,ｈｅａｖｙｍｅｔａｌｓａｎｄｏｒｇａｎｉｃｃｏｍｐｏｕｎｄｓ(ｉｎｃｌｕｄｉｎｇｐｅｓｔｉｃｉｄｅｓ)ｅｔｃ .ｃｏｕｌｄｄａｍａｇｅｔｈｅｗｅｌｌ ｂａｌａｎｃｅｄｃｉｒｃｕｌａｔｉｏｎｏｆｎａｔｕｒａｌｅｃｏｓｙｓｔｅｍａｎ…     

Nitrate δ15N and δ18O evidence for active biological transformation in the Changjiang Estuary and the adjacent East China Sea

The Changjiang Estuary has been considered as one of the most polluted estuaries in the world due to high nitrate (NO-3) input, especially in spring and summer. In this study, δ15N and δ18O of NO-3 , along with other chemical parameters in this area, were measured in spring to evaluate NO-3 biogeochemical processes. A simple two end-members mixing model was used to examine the relative contribution of the Changjiang River Diluted Water and marine water to NO-3 sources in the Changjiang Estuary and the adjacent East China Sea. The isotopic signals show that NO-3 behaved relatively and conservatively in Transect F and Transect P where assimilation was weak possibly due to vertical mixing, while active assimilation and weak nitrification occurred in Transect D. Spatial difference in assimilation was indicated by the～1:1 enrichment of δ15N and δ18O in the three transects, while spatial difference in nitrification was reflected by deviations of δ15 N and δ18O from assimilation line. Our results suggest that the input of the Changjiang River Diluted Water promoted NO-3 assimilation possibly by stratifying the water column which favored the phytoplankton growth.     

Distribution of dissolved organic carbon in and near the Prydz Bay, Antarctica

INTRODUCTIONDissolvedorganiccarbon (DOC)makesupthesecondlargestofthebioactivepoolsofcar bonintheocean ,secondtothelargestpoolofdissolvedinorganiccarbon .Theglobaldissolvedorganiccarbonpoolisestimatedtobe 6 85Gt,avaluecomparabletothemassofCO2 intheat mosphere (Hedges,1 992 ) .Thesizeofthereservoir,aswellasitsdynamics ,indicatesthatDOCplaysacentralroleintheoceancarboncycle .AsitrelatestogreenhousegasessuchasCO2 andassociatesclimatecycle ,oceanicDOCbiogeochemicalcycleshavebeenoneoftheh…     

Study on short-range numerical forecasting of ocean current in the East China Sea——Ⅰ Basic problems of ocean current forecasting and structure of the models

Ocean current forecasting is still in explorative stage of study. In the study, we face some problems that have not been met before. The solving of these problems has become fundamental premise for realizing the ocean current forecasting. In the present paper are discussed in depth the physical essence for such basic problems as the predictability of ocean current, the predictable currents, the dynamical basis for studying respectively the tidal current and circulation, the necessity of boundary model, the models on regions with different scales and their link. The foundations and plans to solve the problems are demonstrated. Finally a set of operational numerical forecasting system for ocean current is proposed.     

Nutrient profiles in interstitial water and flux in water-sediment interface of the Zhujiang Estuary of China in summer

I\TRODLCTIO\In ootal enviroaments, the degradation of sedimentaIy organic matter was the main pro-cess of the biQgaxhemistry cyclc of nutrients, which controlled not only the bury efficiency oforganic carbon but a1so the nutrients flux to overlylng water (Aller, l980). The rnain mecha-nism of whneralization of sediment was organic rnatter degradation such a-s biolOgic and redOxprocesses, these reactions oould convert sedirnentary organic rnatter into nutrients, then releaseto the intersti…     

A baroclinic typhoon model with a moving multi-nested grid and variational adjustment initialisation Ⅰ. Numerical method

A baroclinic typhoon model with a moving multi-nested grid is applied in marine environmental forecasts.This paper describes the numerical methods of the model including governing equations, finite differencing, split scheme and time integration.     

Numerical study on residual current and its impact on mass transport in the Hangzhou Bay and the Changjiang Estuary Ⅱ. Residual current and its impact on mass transport in winter

I~IOWIn winter, on the impacts Of the Chriolis force and the current along the shore of the EastChina ho, the residual current from the Changjiang River flows south along the shore and enters the ~ Bay in the north, then it moves out of the bay in the south and flows southin the East China Sea (Su and Wang, 1989; Zhu and Shen, 1997). In recent years, scholars have made further analyse on obSerVed date, and have obtained more profound viewson the residual current and mass transport (Pn …     

Estimating biomass of phytoplankton in the Jiaozhou Bay Ⅰ.Phytoplankton biomass estimated from cell volume and plasma volume

Based on the data of the Jiaozbou Bay Ecosystem Dynamic Research,cell volume and surface area of 87 common phytoplankton species in China sea waters were calculated with assignment of the similar geometric form.The cell plasma volume,live weight,carbon mntent and nitrogen content were also calculated with the methods of Mullin et al.(1966),5trathmann(1967),Eppley et al.(1970),arid Taguchi(1976).After comparing these methods,we chose the method of Eppley et al.(1970) as the best method for calculating phytoplankton carbon content in China sea waters.     

Study on short-range numerical forecasting of ocean current in the East China Sea Ⅱ. Three-dimensional diagnostic model and its application in the Bohai Sea

Ｓｔｕｄｙｏｎｓｈｏｒｔ－ｒａｎｇｅｎｕｍｅｒｉｃａｌｆｏｒｅｃａｓｔｉｎｇｏｆｏｃｅａｎｃｕｒｒｅｎｔｉｎｔｈｅＥａｓｔＣｈｉｎａＳｅａ—ＩＩ．Ｔｈｒｅｅ－ｄｉｍｅｎｓｉｏｎａｌｄｉａｇｎｏｓｔｉｃｍｏｄｅｌａｎｄｉｔｓａｐｐｌｉｃａｔｉｏｎｉｎｔ...     

High resolution oxygen isotope and grayscale records of a medieval fossil giant clam (Tridacna gigas) in the South China Sea：physiological and paleoclimatic implications

Mollusks are well known for their detailed recording of paleoenvironmental and paleoclimatic changes in their carbonate shells. In this study, we constructed 18-year blue color intensity and oxygen isotope profiles of a 14 C dated(AD 990±40) fossil giant clam, Tridacna gigas, from Shidao Island, South China Sea. The δ18O profile of the T. gigas specimen displayed regular annual cycles and was probably controlled by seasonal variations of the climatic parameters. The blue color intensity profile showed good agreement with the δ18O series, and both had 18 clear annual cycles in accordance with the 18 visually identified annual growth bands. The annual shell growth rate determined from the blue color intensity and oxygen isotope profiles indicated that the annual shell increment of the Tridacna specimen was stable after the onset of sexual maturity. Spectral analysis of the δ18O and blue color intensity time series suggested that the El Nio–Southern Oscillation(ENSO) period observed in the instrumental temperature and precipitation records of the South China Sea during the past 50 years also existed in medieval times. Our results showed that fossil giant clams could provide a good archive of historical intra-seasonal to decadal climate variations.     

Characteristics of metals in atmosphere over the western Taiwan Strait-Ⅰ. Concentrations and distributions

INTRODUCTIONTheattentiontothestudyofmetalsinthemarineaerosolparticulatesisincreasingduetotheirenvironmentalecologicaleffectsandcontributiontothebiogeochemicalcycle.Intheaspectofenvironmentalecologicaleffects,first,onthesideofclimate,aerosolswithmetalscanactascloudcondensationoricenuclei,absorbandscattersolarradiation,andaffecttheradiationbudgetontheearth.Therelativelyhighironcontent(5%)ofthedustcanabsorbtheshortwavelengthradiationefficiently.Second,onthesideofecologicaleffects,di~lvedAlse…