Distributions And Sources Of Hydrocarbons In The Yellow River And Its Estuary

The Yellow River is the second longest river in China.As one of the highest tubidriver in the world,it has important effect on carbon cycle of North-west Pacific Ocean.To better understand the distributions and sources of organic matter in the YellowRiver and its Adjacent Sea,n-alkanes,fatty acids and polycyclic aromatichydrocarbons (PAHs) were choosed as the biomakers.The distributions and sourcesof the three kinds of hydrocarbons in water,suspended and sedimentary particles fromthe Yellow River and its Adjacent Sea were discussed,and the size distributions ofPAHs and n-alkanes in suspended particles at Lijin Hydrographic Station were studied.The following five sections were discussed in the present thesis:①The distributionand sources of n-alkanes in the Yellow River;②The distribution and sources of fattyacids in the Yellow River;③The distribution and sources of PAHs in the YellowRiver;④Compositional feature of hydrocarbons in suspended particles from theYellow River Estuary and its implication to transport and distribution of organiccarbon。⑤Compositional feature of hydrocarbons in sediment particles from theYellow River Estuary and its implication to transport and distribution of organiccarbon。The particulate samples from the Yellow River in surface water were collected inautumn,2003 and July,2007 respectively.The results show that the concentrations ofn-alkanes,fatty acids and PAHs are 7.01μg/g-33.62μg/g,2.11μg/g-14.59μg/g and118.27 ng/L-979.15 ng/L respectively.The hydrocarbons in the suspended particulatesamples from the Yellow River show a spatial characteristic.Terrestrial organic mattermakes a major contribution for particulate n-alkanes and aquatic organic matter makesa major contribution for particulate fatty acids.More terrestrial organic matter isfound in the upper reaches than that in lower reaches.The relative proportions of 16 PAHs in all stations are similar,and the 2-3 ring PAHs play a most important role inall the stations except Yinchuan.Source analysis reveals that PAHs mainly originatefrom coal burning.PAHs originating from combustion of petroleum cannot be ignoredin Yinchuan and Tongguan.The concentrations of benzo[a]pyrene are all abovedrinking water standards in most of the stations sampled except Guide and Liujiaxia.The concentrations of n-alkanes and fatty acids show a marked seasonal differencein the Yellow River Estuary.In April,the content of alkane is 7.01μg/g-33.62μg/g,and the content of fatty acid is 2.11μg/g-14.59μg/g.The contents of both alkane andfatty acid increase with the increasing of the salinity.L/Hs of n-alkane are rangedfrom 0.41 to 0.65.Aquatic organic matter plays an important role in the higher salinityregions,and terrestrial organic matter plays an important role at salinity of 1-13;inSeptember,the content of alkane is 11.83μg/g-74.80μg/g,and the content of fattyacid is 8.81μg/g-49.23μg/g.The contents of both alkane and fatty acid increase withthe decreasing of the distance from the coast.The L/Hs are similar to that in April inlow salinity and L/Hs are lower than that in April in high salinity,which is seem as theresult of sediment resuspension.The content of PAHs in the freshwater is 393.16 ng/g,which is lower than 781.35 ng/g,the content of PAHs in the mixing zone.The PAHsmainly originate from coal burning in the freshwater,and PAH inputs could comefrom petroleum.and coal burning in the mixing zone。Suspended particle samples from the Yellow River estuary were sorted into fivegrain size fractions to explore the effect of grain size distribution on organic mattercontent and composition.The results show that there are distinct differences in theorganic material associated with individual grain size fractions corresponding todifferences in content and composition.PAHs and n-alkanes are more abundant in thefiner fractions and fine particles (＜32μm) play a significant role in organic matter.This investigation shows that particulate n-alkanes in the Yellow River estuary consistof a mixture of compounds from terrigenous and riverine biogenic n-alkanes and morebiogenic n-alkanes accumulate in finer particles.Particulate PAHs are related tocombustion/pyrolysis processes of coal/wood combustion,and less pyrolytic PAHsare found in the particles with diameter from 32 to 63μm. Concentrations of n-alkane,fatty acids and PAHs are 0.38μg/g-2.55μg/g,0.08-0.26μg/g and 0.371μg/g-0.650μg/g in the sediments from the Yellow River Estuary,respectively.Significant differences are observed between the north route and thesouth route.With the effect of the water from the Yellow River in the south route,thehydrocarbons increase with the increasing of the distance from the coast.The fartheraway from the river,the less terrestrial organic matter is observed in the estuary.ThePAHs mainly originate from coal burning.The 4-ring PAHs are predominant insediment PAHs.With the effect of the oilfield near the Huanghe delta,the levels ofthree kinds of hydrocarbons show the highest level in the mouth.The UCM ofn-alkane is found and PAHs origin from the mixture of combustion and petroleum inthe sample from the N 1 location.