The Lignin Characteristics Of Sediment Core T08in The Fujian-zhejiang Coastal Mud Area Of East China Sea And The Significance For Environmental Evolution

Marginal seas with high productivity and organic carbon burial played animportant role in global carbon cycle. Long-term and continuous organic carbonburial was recorded in the sediments inshelf seas. It was necessary to detect theorganic matter in the sediment for looking for the rules of variation trends andproviding data to establish models. Lignin is a unique component of vascular plantswith high chemical stability and resistance to degradation. Thus, it is a goodbiomarker of terrestrial organic matters and has been applied widely in thegeochemistry study.In this work, the TOC, C/N, δ¹³C and the parameters of lignin in T08coresediments located in the Fujian and Zhejiang coastal mud in the inner shelf of EastChina Sea were analyzed,combining with previous data the TOC, C/N, δ¹³C, and thevariation trends of them were discussed. The vegetation source and degradation levelof the terrestrial organic carbon were indicated based on S/V, C/V,（Ad/Al）Vand（Ad/Al）Sparameters. The chronology of the core T08was roughly estimatedaccording to the core PC-6located close to the core T08. The impact of theenvironment and climate change on the input, migration and burial of the terrigenousorganic matter was studied through the trends of the lignin contents. The majorconclusions of the study are as following:（1） The TOC%in core T08changed within0.35%⁰.86%with a decreasingtrend as the depth increased.The TN%in core T08is between0.001%⁰.13%. Thevalue of TN%was low between0-68cm and fluctuated within smaller range with adecreasing trend as the depth increased.. The TN%also presented fluctuations in a dcreasing trend with depth increasing below68cm. In addition, TN and TOC hadpoor correlations.（2） The C/N values in core T08can be divided into three stages: From0to-28cm,C/N fluctuated within larger range as the depth increased, ranged from10.12to25.50, the average was14.70; From-29to-67cm, the fluctuation range of the C/Nvalue was relatively large from20.47to348.41. The C/N ratio increased with depthincreasing, and then gradually decreased; Below-68cm, it ranged from5.13to9.63and its average value was6.85. The δ¹³C‰of total organic matter ranged from-22.42‰to21.51‰and its average was-21.96‰, the values showed an increasingtrend as the depth increased, which reflected that the terrigenous input in this areawas reduced from now to the past, and also indicated that the organic matter in T08core sediments mainly were from the sea sources.（3） The Σ8and Λ8in core T08ranged from0.141to0.476mg/10gds and0.249to0.741mg/100mgOC respectively, the contents of lignin above-110cm were higherthan that below-110cm. In addition, both Σ8and Λ8had no clear correlations withTOC%（R2Σ8≈0.32，R2Λ8≈0）, which indicated that the sea source may be the mainsource of organic matter in core T08. The correlation coefficients of the contents ofP、S、V and C series monomer with the total lignin phenols of the11monomers wereR2P≈0.56，R2S≈0.75，R2V≈0.90and R2C≈0.30. S series monomer and V seriesmonomer had the similar vertical distribution, illustrating that S and V had the samesources, the distribution trend of the C series monomer was not the same with the Sand V series.（4） S/V in core T08ranged from0.29to1.14, with a mean value of0.73, C/Vranges from0.03to0.33, with a mean value of0.12. The relationship of S/V andC/V reflected that the source of lignin in core T08were mainly herbaceous tissue ofangiosperms, but a few were found to be woody tissue; According to the LPVI, itcan be divided into three parts: the first part was from0cm to-55cm in which therewere no big changes in range, with a mean of47.6; the second part from-56cm to-69cm had an intense fluctuation, most LPVI values ranged from8to27, but at-59cm,-61cm,-65cm and-68cm, LPVI value were greater than27, even greater than 67at-59cm and-61cm; The third part from-70cm to the bottom, LPVI had avariation range of29.6to172.9with a average of69, amost value were more than67.Taken a consideration with LPVI, lignin in T08core should had a mixed vegetationsources which contained woody angiosperms and gymnosperms grass.（5） Degradation parameters （Ad/Al）Vin core T08with a mean of0.38variedfrom0.3to0.5. This vertical distribution pattern was similar to that of （Ad/Al）Switha mean of0.31. The mean value of P/（V+S） was0.41: from0to-121cm, the averagevalue （0.38which is less than0.39） showed that the demethyl/demethoxydegradation of lignin was weak in this stage; Blow-121cm, its mean value（0.45which is between0.39and0.63） showed that lignin in this stage had a moderatedemethyl/demethoxy degradation. So it indicated that lignin in core T08experienceda moderate degradation by microorganism. There was a negative correlation betweenPon/P and P/（V+S）, indicating that the contribution of other sources to P seriesproduction had increase and the lignin had decreased as the degradation strengthened.Another negative correlation between Λ8and P/（V+S） suggested thatdemethyl/demethoxy degradation was important in core T08which may affect thecontents of lignin.（6） According to the similar location of the core PC-6and core T08, we inferedthat the chronology of core T08was from0-3.0⁴.0ka B.P. In-75cm^-219cm, thefluctuation range of the lignin content was large which reflected the East AsianWinter Monsoon was relatively strong; the lignin content was relatively stable from0to-75cm, indicating that East Asian Winter Monsoon was relatively stable. Thelignin content above-75cm in core T08changed slightly, reflecting that thetemperature varied relatively small; the lignin content fluctuated larger with highvalue indicating that temperatures alternated frequently and climate changes wasextremely unstable; the degree of degradation below-161cm was greater than above-161cm, reflecting that the air temperature of the former was higher than the latter.