| As the main channels for transportation of terrigenous materials, estuaries play an important role in the interaction between continental and marine systems. The spatial and time scale changes of physical, chemical and biological processes in estuaries are more severely than those in continent and ocean, which have significant influence on the materials transportation and lead to difference contents and distributions. The Yellow River, famous for its high turbidity, also has high concentration of carbonate because of strong chemical weathering in the basin, meanwhile, the rapid growth of industry and agriculture had brought serious pollution. Based on the reasons above, the transportation of terrigenous materials from continent to adjacent water has important effect on carbon cycle and nutritional status in the adjacent water and even biogeochemical process in the whole Bo Hai Sea. Taking the changes of water and sediment fluxes caused by the water and sediment regulation into account, the study for current status of the Yellow River Estuary is necessary. In combination with the data of hydrology, chemistry and biology collected from the Yellow River Estuary and adjacent water in May 2009, carbon transportation characteristics and eutrophication degree were studied. The main conclusions are drawn as follows:1. The pCO2 ranged from 383 to 1002μatm, and had an average of 615μatm during the mixing of fresh and salt waters. High value was observed in Fresh Water Side (FWS) due to Yellow River water input and decreased by mixing of fresh and salt water. The carbonate system was the main control factors of pCO2 while the temperature, photosynthesis and biological aerobic respiration were not.2. The distributions of inorganic carbon, organic carbon and nutrients were all impacted by the fresh water input and saltwater dilution. Inorganic carbon had obviously high concentration in FWS which had a negative correlation with salinity during mixing of fresh and salt water. In the Salt Water Side (SWS) the drop of PIC and DIC concentration were 99% and 25%, respectively. When TSS=569mg/L, the ratio of DIC/PIC is 1, which indicate that inorganic carbon transport in the Yellow River Estuary was mainly in the form of DIC. Organic carbon showed a negative correlation with salinity too, the concentration of POC and DOC dropped by 92% and 35%, respectively. When TSS=250mg/L, the ratio of DOC/POC is 1, which indicate that organic carbon transport in the Yellow River Estuary was mainly in the form of POC. Concentrations of nitrate, nitrite and silicate were decreased conservatively, ammonia had high value in SWS than that in FWS, phosphate had low value in SWS because of sharp drop at the beginning of mixing of fresh and salt water.3. The pCO2 of adjacent water of the Yellow River Estuary ranged from 311-723μatm, and had an average of 480μatm. In the Estuarine water affected by the diluted water from the Yellow River, carbonate showed a significantly high value and led to high pCO2 by carbonate system. Input of fresh water in wet season over years maintained high level of pCO2 in the south of estuarine water. Two thirds of the survey area was a source of pCO2. The temperature, photosynthesis and biological aerobic respiration were not main control factors.4. The distributions of carbon system parameters were not only determined by the fresh water from Yellow River in dry season. As the small amount, only the distributions in estuarine water showed relatively high concentration. Accumulation of materials input by fresh water over years and secondary pollution of sediments in the south of estuary were the reasons that maintained high surface and bottom concentrations in this area in dry season.5. The results indicated that fresh water from the Yellow River was the main source of the NO3-N, NO2-N and SiO3-Si, which had high-value areas of surface concentration in the estuary. The concentrations of NH4-N and PO4-P in the estuary were lower than the average levels which meant diluted water was not the main source. Significantly concentrations of inorganic nitrogen observed in the south shoal area were not directly caused by input of diluted water from Yellow River, while the water exchange in the Yellow River Delta Wetland and the accumulations of materials from diluted water were the main reasons which resulted the high concentrations in dry season. The coastal flow from Bo Hai Sea led to the obvious high-value area of PO4-P in the north of the Yellow River Estuary.6. The N/P ratios in surface and bottom seawater were 248 and 141 respectively, which meant severe phosphorus limiting eutrophication in the survey area; the eutrophication indices (EI) were lower than 0.6 and two-thirds of the survey area reached first class standard besides relatively heavy pollution in the south shoal. As a main factor affecting the water quality, inorganic nitrogen which had a high concentration needed enough attention.
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