The area of East China Sea(ECS)inner shelf is an important sink of suspended particulates from Yangtze River(YR)and materials originated from YR basin.In this study,the parameters of lignin and alkane biomarkers in surface sediment samples from ECS inner shelf were determined to distinguish the sources and to trace the transport of terrigenous organic matters in the region.Our dataset showed that total alkanes with carbon numbers from 10 to 38(T-alkanes)were significantly correlated to both TAR(terrigenous/aquatic ratio)and HMW/LMW(the ratio of high molecular weight to low molecular weight alkanes)(r=0.88,P<0.05 for both),indicating that the majority of T-alkanes was predominantly originated from terrestrial sources,and T-alkanes are important constituents of terrestrial organic matters in the study area.The area was probably affected by petroleum pollution to a certain degree,as indicated by the values of carbon preference index(CPI),odd-over-even carbon number predominance(OEP)and the ratio of pristane to phytane(Pr/Ph).The values of Pr/n-C_(17) and Ph/n-C_(18) suggested a strong reductive sedimentary condition in the region with no obvious biodegradation.The content of eight lignin phenols(Σ8)decreased from the coast to the open sea,indicative of riverine input and hydrodynamic transport of terrigenous organic matters.Lignin degradation parameters presented an increasing trend from the coastline toward the open sea.The lignin vegetation parameters and alkane index(AI)suggested the predominance of non-woody angiosperms in the YR basin.The obvious correlation betweenΛ8(Σ8 normalized to 100 mg organic carbon),TAR and HMW/LMW reveals the significantly concurrent input of lignin and alkanes from terrestrial sources.
Lignin serves as one of the most important molecular fossils for tracing Terrestrial Organic Matters （TOMs） in marine environment. Extraction and derivatization of lignin oxidation products （LOPs） are crucial for accurate quantification of lignin in marine sediment. Here we report a modification of the conventional alkaline cupric oxide （CuO） oxidation method, the modification consisting in a solid phase extraction （SPE） and a novel on-column derivatization being employed for better efficiency and reproducibility. In spiking blanks, recoveries with SPE for the LOPs are between 77.84% and 99.57% with relative standard deviations （RSDs） ranging from 0.57% to 8.04% （n=3）, while those with traditional liquid-liquid extraction （LLE） are from 44.52% to 86.16% With RSDs being from 0.53% to 13.14% （n=3）. Moreover, the reproducibility is greatly improved with SPE, with less solvent consumption and shorter processing time. The average efficiency of on-column derivatization for LOPs is 100.8%±0.68%, which is significantly higher than those of in-vial or in-syringe derivatization, thus resulting in still less consumption of derivatizing reagents.Lignin in the surface sediments sampled from the south of Yangtze River estuary, China, was determined with the established method. Recoveries of 72.66% to 85.99% with standard deviation less than 0.01mg/10g dry weight are obtained except for p-hydroxybenzaldehyde. The lignin content ∑8 （produced from 10g dry sediment） in the research area is between 0.231 and 0.587mg. S/V and C/V ratios （1.028 ± 0.433 and 0.192±0.066, respectively） indicate that the TOMs in this region are originated from a mixture of woody and nonwoody angiosperm plants; the high values or （Ad/Al）v suggest that the TOMs has been highly degraded.
ZHANG TingLI XianguoSUN ShuwenLAN HaiqingDU PeiruiWANG Min
Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (K 37 U ') in sediment core ZY2 from the central mud area.The SST records varied between 14.1 and 16.5°C (15.6°C on average),with 3 phases:(1) A high SST phase at 6.2-5.9 cal ka BP;(2) A low and intensely fluctuating SST phase at 5.9-2.3 cal ka BP;and (3) A high and stable SST phase since 2.3 cal ka BP.Variation of the SST records is similar to intensity of the Kuroshio Current (KC),and corresponds well in time to global cold climate events.However,the amplitude of the SST response to cooling events was significantly different in different phases.The SST response to global cooling event was weak while the KC was strong;and the SST response was strong while the KC was weak.The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a shelf branch of the KC and a compensating current induced by the East Asia winter monsoon.The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling,and both the Kuroshio and East Asian winter monsoon play important roles in the modulation mechanism.The SST records display a periodicity of 1482 years.The same period was found in the KC records,indicating that variation of the SST records in the central South Yellow Sea is strongly affected by KC intensity.The same period was also found in Greenland ice cores and North Atlantic and Arabian Sea sediment cores,showing a regional response of marine environmental variability in the East China Seas to that in the global oceans.
WANG LiBoYANG ZuoShengZHANG RongPingFAN DeJiangZHAO MeiXunHU BangQi
We present lipid biomarker records of two cores （ZYI and ZY3） from the central South Yellow Sea mud area to investigate the changes in sources and transport processes of the sedimentary organic matter （OM） throughout the Holocene. Based on the analysis of marine biomarker content （EPB （Phytoplankton Biomarker, total content of brassicasterol, dinosterol and C37-alkenones） and crenarchaeol）, and terrestrial biomarkers （En-alkanols and brGDGTs） as well as TMBR＇ and BIT index values, the marine organic matter （MOM） and terrestrial organic matter （TOM） deposition history was reconstructed. Changes in TOM and MOM were related to variations in land vegetation density and marine productivity, as well as transport processes dominated by the oceanic circulation system. The marine biomarker contents from the South Yellow Sea have generally in- creased throughout the Holocene, indicating that the increased MOM contents were mainly controlled by the strengthening of the circulation system. The terrestrial biomarkers, on the other hand, were more variable, indicating more complex influence of TOM burial in the Yellow Sea. During the Early Holocene （7200-6000 cal yr BP）, the moderate TOM input revealed by the terrestrial proxy records may result from abundant land source supply by strong river transport despite the lack of transport via circulation system. The Mid-Holocene （6000-3000 cal yr BP） was characterized by decreased terrestrial biomarker contents. The balance between the decrease in land source supply and increase of transportation by the current system of the TOM resulted in the lower but stable contents of TOM. During the Late Holocene （3000 cal yr BP to present）, the TOM deposition in the South Yellow Sea increased as the current system was further enhanced and thus transported more TOM to the central South Yellow Sea, although the land supply of TOM was further reduced.
