Organic Carbon In The Main Stream Of The Huanghe (yellow) River And Carbon Transport In The Sand And Water Regulation Period In Lijin Gauge Station

Organic carbon (particulate and dissolved) was investigated during 4 cruises from 2003 to 2009 along the Huanghe River and in the Huayuankou gauge station. Investigations on the carbon parameters also were conducted in the "sand and water regulation" (S&W) periods in 2005,2006,2008 and 2009. Results and analysis suggest that:1. POC and DOC range from 0.65 to 39.95 mg/L and 1.57 to 4.77 mg/L respectively, in the Huanghe main stream where strong spatial differences in organic carbon are observed. Discharge is clearly connected with the change of concentrations of POC and DOC, during a whole hydrologic year in the Huayuankou gauge station in the middle reach of the River.2. Reservoirs and S&W, two of the human activities, have different effects on the transport of organic carbon in the Huanghe River. There are stronger plankton activities in the reservoirs, leading to more contributions to organic carbon, and DOC is dominated there. Whereas, POC is the main form of organic carbon during the S&W period when a great amount of organic carbon is exported.3. POC% (POC content) in the Huanghe River is lower than the average of the global rivers, but follows similar patterns of other rivers, decreasing logthomo-logically with the increase of TSS concentration. POC transport is controlled by the paticle size in the Huanghe River.More than 80 percent POC is concentrated in the particles with low-size of 16μm, and above 95 percent in the particles with low-size of 32μm. Loess serves as the main source of POC in the Huanghe, whilst contribution from planktons is weak.4. DOC along the Huanghe changes following non-clear principles. Largely, DOC concentration shows negatively linear with discharge during a hydrological year in the Huayuankou gauge station. In the S&W periods, DOC concentration maintains thanks to that released from particulate organic carbon under the impact of high load sand.5. Degradable degree of both DOC and POC is low in the Huanghe River. TSS concentration is the controlling factor of the export of DOC and POC. POC is the dominate form of organic carbon export when TSS is higher than 364 mg/L, while DOC becomes the main form when TSS is lower than that value. Although the TSS limit value changes due to biogeochemical factors, it shows little impact from the S&W.6. During the S&W period, pCO2, PIC and POC increase dramatically, while DOC and DIC increase slightly along with the climbing of discharge and TSS. There is a large increase in the carbon fluxes output to the estuary, among of which 80% is inorganic carbon, especially the PIC. TSS controls the particulate carbon whilst the dissolved carbon is mainly result from the transform from particulate carbon. Strong carbonate buffering and biological aerobic respiration are the most important processes maintaining the high pCO2 in the S&W period.