The Geochemical Research Of Organic Carbon In The Intertidal Zone Of The Yellow River Delta

In order to explore the horizontal and vertical distribution of organic carbon, andknow the perservation and degradation in the intertidal of the Yellow River Delta,surface and core sediments samples were collected and analyzed in May, August,November,2012and March,2013. Via the study on the total organic carbon (TOC),13C and the trace of organic molecules, the results and conclusions are demonstratedas followed.The surface organic carbon in the sediments of Yellow River Delta ranged at0.06-0.40%(0.19%at ave.). It was gradually reduced from the middle to the northand south. The most organic carbon was in November,2012, then August,2012, andthen May,2012. The organic carbon in core ranged at0.13-0.35%(0.20%at ave.),and it waved from the surface to the deep layers. The downstream of the Yellow Riverhad lower organic carbon, which ranged at0.08%-0.16%(0.13%at ave.)The surface13C ranged from-20.43‰to-24.26‰in the sediments of YellowRiver Delta and ranged from-25.10‰to-26.32‰in the sediments of thedownstream of the Yellow River and ranged from-23.55‰to-24.61‰vertically,which indicated mixed source of terrigenous and sea; the source of the sea is bigger inMay and August but less in November and March.Lipids were divided into categories, free fatty acids, bound fatty acids andmineral fatty acids.36kinds of fatty acid molecules were detected in sedimentssamples, including14species of saturated fatty acids,4branched chain fatty acids,11monounsaturated fatty acids and7polyunsaturated fatty acids.22neutral lipids weredetected, including phytol,10sterols and11alcohols.Total fatty acids in the surface sediments of Yellow River Delta ranged at13.46-98.56μg/g (40.18μg/g at ave.) and had no correlation with organic matter. Freefatty acids dominated by28.4-86.7%(58.4%at ave.). The most fatty acids were inMarch,2013, then May,2012, and then November,2012. Fatty acid reduced gradually from north to south in March,2013and August,2012and waved in May,2012, andNovember,2012. Total fatty acids in the surface sediments of the Yellow River were34.9-42.5%of the delta which ranged at5.72-34.42μg/g (17.19μg/g at ave.), andbound fatty acids dominated by24.5-77.7%(46.9%at ave.). Total fatty acids rangedat9.04-28.37μg/g (17.66μg/g at ave.) vertically which tended to decrease from thesurface to the deep and then increase until stabilization, and free fatty acids dominatedby37.7-59.3%(49.4%at ave.).The total neutral lipids were12.3-33.3%of the total fatty acids which ranged at4.48-12.08μg/g (6.82μg/g at ave.) in the delta. Free neutral lipids dominated by73.8-96.7%(86.6%at ave.). The most neutral lipids were in November,2012, thenMarch,2013, and then May,2012. Total neutral lipids in the surface sediments of theYellow River were9.6-19.6%of the delta which ranged at0.43-2.37μg/g (1.20μg/gat ave.), and bound total neutral lipids dominated by22.7-61.9%(37.4%at ave.).Total neutral lipids ranged at1.05-3.11μg/g (2.25μg/g at ave.) vertically whichtended to increase from the surface to the deep and then decrease and then increaseuntil stabilization, and bound fatty acids increased in the deep which could bedominated by52.2%.The fatty acids in the delta originated most from multiple sources, then algaesources, and then bacterial sources, finally, the terrigenous. While the fatty acids inthe surface sediments of the Yellow River originated most from bacterial sources.Vertically,60%of free fatty acids originated from multiple sources, bound fatty acidsoriginated most from bacterial sources. The neutral lipids originated most from algaesources, then multiple sources.Primary productivity contributed little and grain size had a significant impact onorganic matter in the Yellow River Delta.