Yellow River And The Estuary Of N-alkanes, Are Fatty Acids Characteristic Analysis

This paper based on the task of 973 "Study on carbon flux of the typical river in China ".According to the approach which can be useful in studying the source of organic matter. We studied n-alkanes and fatty acids for biomakers and discussed the source of organic matter and temporal-spatial distribution in the mainstream and estuary of Huanghe .: The distribution of n-alkanes is divided three parts: the upstream, reservoir and estuary. This distribution markedly subjected to terrigenous influence. Aquatic origin makes a major contribution to n-alkanes in the reservoir and estuary. According to carbon number, we can conclude the different aquatic and terrigenous origin. At the linjin station in the estuary, UCM signified a petroleum input. Fatty acids show a bimodal distribution. Such contributions suggest the particulate fatty acid come from aquatic origin. The carbon number changes in the different station, as the result that bacteria is the most contribution to aquatic origin. So the percent of aquatic matter varied smoothly with chl-a.According to seasonal variation, we can divide the compose of n-alkanes to three parts : from April to July (spring) , from August to October (summer, autumn) from November to February (winter). In the higher molecular range C₂₃-C₃₄, there is an odd/even carbon number predominance maximizing at C₂₉. C₁₅ — C₁₉ has a seasonal variation . The concentration of n-alkanes changes smoothly with flow, because of sand turbulence by human. The origin of fatty acid changes with season. From April to July, in the lower molecular range, an odd carbon number predominance can be observed, aquatic matter makes an important contribution. In August, it is reverse. The origin mainly comes from terrigenous inputs. but December to February ,when TSS and the two kind of organic matter reach the minimum, POC has a high value, this phenomena need deep study. In summer, the percent of aquatic origin is higher than the result of the mainstream of Huanghe. The percent of aquatic origin in fatty acid decreased with chl-a. The concentration of n-alkanes in the dry season is similar to that in the mainstream of Huanghe. But the odd/even carbon number is not obvious, signifying an weaker terrigenous inputs. Fatty acid with C_24:0/C_16:0 is lower than that in the mainstream of Huanghe and in the huayuankou station in April, 2004. The contribution of aquatic originis more than the river. The concentration of n-alkanes and the percent of terrigenous inputs in the dry season decreased with the increase of salinity, and fatty acids is different from n-alkanes. Marine phytoplankton is one part of sea origins, which is different from the mainstream and estuary of Huanghe. The concentration of n-alkanes in the flood season is lower than in the dry season. Terrigenous inputs make an important contribution, but it is lower than the mainstream of Huanghe and September at huayuankou station. Fatty acids is similar to that in the shore, but it is lower than that in the estuary. This survey is different from other cruises in the flood season. There is a positive relation between the total concentration of n-alkanes and fatty acids and salinity, but when the salinity is lower than 2O%o, the terrigenous percentage of n-alkanes and fatty acids decrease with the increase of salinity. When the salinity is higher than 20 %o, the terrigenous percentage of n-alkanes and fatty acids increase with the increase of salinity. However ,there is a positive relation between the total concentration of n-alkanes and fatty acids and TSS> POC, maybe influenced by the accomendation of reservoir . Artificial and natural factors cause the origin from marine have an indistinct rule with chl-a. The distribution of particulate n-alkanes and fatty acids in August is similar to that in 2004. It is suggested that terrestrial organic matter makes an important role in the particulate organic input in Huanghe, owing to the similar change between in the dry season and in the low flowoSediment n-alkanes show a single-modal with maximum at C29^ C31. The distribution of fatty acids is similar to particulate samples, but its terrigenous advantage is strong than the particulate samples . North line contrasted with south line, terrestrial organic is weaker , such result suggested that sands came out from estuary diffuse from north to south. It can conclude terrestrial organic make an important contribution to surface sediment near to the mouth of Huanghe.