Temporal And Spatial Distributions Of Carbon, Nitrogen And Phosphorus In The Changjiang Estuary And Adjacent Sea

The biogenic element cycles are important parts of material-energy cycles in the whole biosphere,so it is of great significance to acquire knowledge about the distributions,transportations and transformations of carbon,nitrogen and phosphorus. In the present thesis,the temporal-spatial distributions of carbon,nitrogen and phosphorus,and the influences of the environmental factors in the Changiiang Estuary and adjacent sea are discussed based on the four seasonal surveys during 2007.The major results are as followed:The spatial distribution of dissolved organic carbon(DOC) has seasonal characteristics in the Changjiang estuary.The appearance of the DOC maximum in the inshore area doesn't only relate to the runoff input,but also to the biological behavior.The particulate organic carbon(POC) concentration decreases with increasing of the offshore-distance,and the high value distribution is located in the south area to the estuarine mouth.The POC concentration both in the channel and the maximum turbidity zone is significantly higher than which in the offshore,the POC distribution is affected by the southern transport of the runoff suspended particulates.The dissolved carbon is mainly component in the organic carbon,while inorganic carbon is predominate in the dissolved carbon.The distribution of DOC and dissolved inorganic carbon(DIC) are stable.Stratification distribution of organic carbon appeares in the various vertical sections in the estuary,and the concentration gradient of organic carbon in shallow waters less than 10m is greater than which in the deep water.There is a significant negative correlation between surface DOC and salinity in the Changjiang estuary.Temperature has significant correlation with DOC both during May and August,with temperature increased and biological activity enhanced,The POC content is significantly positive correlated with suspended particulate amount in the area.The adsorption,desorption and re-suspension of suspended particulates promot transformations and transports between POC and other forms of carbon.The plenty of organic runoff inputs resulte in decreasing trend of dissolved organic phosphorus(DOP) content from the inshore to the offshore.The dissolved phosphorus (DP) distribution is similar to DOP,and the DOP content changes lead to the DP variance.The particulate phosphorus(PP) content decreases with the increasing of the offshore-distance.Dissolved nitrogen(DN) concentration in the inshore is higher than which in the offshore,and is significantly affected by runoff input.Dissolved inorganic nitrogen(DIN) is the dominate form in dissolved nitrogen(DN).The biological behavior,conversing inorganic nitrogen into organic nitrogen,directly affect the dissolved organic nitrogen (DON) horizontal distribution.The particulate nitrogen(PN) distribution has seasonal characteristics,the PN high value in the southern part of the central survey region migrate to the estuarine mouth from summer to spring.The dissolved phosphorus is primary in total phosphorus,and the DP contribution in surface TP is greater than which in the bottom.Dissolved nitrogen plays a dominate role in total nitrogen.The ratio of DON to DN is less than 50%, organic form is dominate in the dissolved nitrogen in the offshore.The correlation between environmental factors and nitrogen,phosphorus is various in different seasons.There are significant correlations between salinity,COD and Nitrogen,phosphorus.Nitrogen and phosphorus are diluted by seawater during the transfer process from the mouth to the open sea,and the physical mixing is predominant in the process,but there is also a clear influence of biological transfers in high productivity areas.