Sources And Preservation Of Organic Carbon And Lipids In The Intertidal Areas Of The Yellow River Delta

In order to explore the preservation and degradation of organic carbon and lipids in the intertidal of the Yellow River Delta, surface and core sediments samples were collected and analyzed in the July 2008. Via the study on the total organic carbon (OC) and compound specific composition of fatty acids and neutral lipids, the sources and transportation pattern of organic carbon were discussed in the intertidal areas. The results and conclusions are demonstrated as followed:The surface organic carbon was located at 0.10-0.21 % (averaged at 0.13 %) in the intertidal zone of the Yellow River Delta. The highest values were discovered in the middle area, decreasing to both offshore and and the sea areas. The organic carbon in core ranged at 0.10-0.82 % (averaged at 0.22 %), presenting the pattern of highest in the surface layer, rapid decreasing from surface to subsurface layers and then relative low in deep layers. The organic carbon ranked at a low level compared with other estuaries, bays and coastal areas.Total fatty acids in the surface sediments ranged at 9.60-51.81μg/(g dry weight) (averaged at 25.45μg/(g dry weight)). Presents middle by the north to the south high, to the south and the distributed rule which reduces to the north, simultaneously north and middle the tidal zone total fat acid content elevates gradually by the near bank to the disembark, the south tidal zone gradually reduces. The free fatty acids dominated by 53.52-97.37 %, while the bound ones accounted for 2.63-46.48 %. The distribution of free fatty acids was obviously affected by GuangLi River, presenting an extremely high content near to the river mouth and gradually decreasing to the ope n sea. Meanwhile, both the free and bound fatty acids followed a similar pattern in that, the contents decreased from the middle area to nearshore and offshore areas.The total fatty acids waved and decreased from surface to bottom, ranging at 5.38-31.02μg/(g dry weight) and averaging at 18.51μg/(g dry weight). Free fatty acids continuously decreased from surface to bottom, with the bound fatty acids opposite. It was suggested that the transformation from free fatty acids to bound ones increased with depth going down and the transformation rate of free fatty acids was larger than the decomposition rate.The total neutral lipids ranged at 2.46-21.76μg/(g dry weight) and averaged at 8.68 μg/(g dry weight) with the pattern of higher in the centrals of south and north areas but lower near shore and offshore areas. The free neutral lipids dominated for 67.70-95.66 %. The free/bound ratios of lipids followed a similar pattern with that of total neutral lipids but higher in the north and lower in the south.Different from that of fatty acids, the vertical distribution of neutral lipids waved and increased with depth down, ranging at 2.44-7.11μg/(g dry weight) and averaging at 4.42μg/(g dry weight). The free neutral lipids dominated in the whole column, decreasing from 88.46 % in the surface to 51.70 % in the bottom, while the bound one followed an opposite variation correspondingly. This relative variation fit with that of free and bound fatty acids, which indicating a gradual transformation with depth down.Classified by its potential functions, the lipids were grouped into sources from terrestrial high plant, micro algae and bacteria. The results show that micro algae and bacteria were the major sources for lipids with a similar percentage, while terrestrial high plant accounted for 3.5 % only. It was indicated that the lipids primarily originated from productions in situ.It could be summarized that both free and bound bacteria lipids waved and decreased from surface to bottom, that of algae lipids varied and decreased, while that of terrestrial high plant decreased from surface to subsurface and then kept at a relative stable state. Meanwhile, a higher preservation of all the lipids was discovered in deep layers.