Description: Compound-specific radiocarbon dating often requires working with small samples of 〈 100 µg carbon (µgC). This makes the radiocarbon dates of biomarker compounds very sensitive to biases caused by extraneous carbon of unknown composition, a procedural blank, which is introduced to the samples during the steps necessary to prepare a sample for radiocarbon analysis by accelerator mass spectrometry (i.e., isolating single compounds from a heterogeneous mixture, combustion, gas purification and graphitization). Reporting accurate radiocarbon dates thus requires a correction for the procedural blank. We present our approach to assess the fraction modern carbon (F14C) and the mass of the procedural blanks introduced during the preparation procedures of lipid biomarkers (i.e. n-alkanoic acids) and lignin phenols. We isolated differently sized aliquots (6-151 µgC) of n-alkanoic acids and lignin phenols obtained from standard materials with known F14C values. Each compound class was extracted from two standard materials (one fossil, one modern) and purified using the same procedures as for natural samples of unknown F14C. There was an inverse linear relationship between the measured F14C values of the processed aliquots and their mass, which suggests constant contamination during processing of individual samples. We used Bayesian methods to fit linear regression lines between F14C and 1/mass for the fossil and modern standards. The intersection points of these lines were used to infer F14Cblank and mblank and their associated uncertainties. We estimated 4.88±0.69 μgC of procedural blank with F14C of 0.714±0.077 for n-alkanoic acids, and 0.90±0.23 μgC of procedural blank with F14C of 0.813±0.155 for lignin phenols. These F14Cblank and mblank can be used to correct AMS results of lipid and lignin samples by isotopic mass balance. This method may serve as a standardized procedure for blank assessment in small-scale radiocarbon analysis.

Description: The dataset comprises contents and mass-accumulation rates of lignin phenols in sediment cores from the Bering Sea (cores SO202/1_18-3 and SO202/1_18-6). Eight lignin-derived phenols were analyzed in our study. They can be classified into three groups according to their plant sources and structures: Vanillyl phenols (V) consisting of vanillin (Vl), acetovanillone (Vn) and vanillic acid (Vd). 2. Syringyl phenols (S), comprising syringealdehyde (Sl), acetosyringone (Sn) and syringic acid (Sd). 3. Cinnamyl phenols (C) that include p-coumaric acid (p-Cd) and ferulic acid (Fd). Besides, we also included some other oxidation products that do not necessarily originate from lignin, such as 3,5-dihydroxybenzoic acid (3,5Bd). Contents are calculated relative to total organic carbon contents and to the dry weight of the sediment. Indicators for vegetation development (S/V and C/V), wetland extent (3,5Bd/V) and degree of organic matter degradation ((Ad/Al)s and (Ad/Al)v) are given. Moreover, TOC and dry bulk density of the two sediment cores are also shown in this dataset.

Description: The dataset comprises contents and mass-accumulation rates of lignin phenols in sediment core from the Okhotsk Sea (core SO178-13-6). Eight lignin-derived phenols were analyzed in our study. They can be classified into three groups according to their plant sources and structures: Vanillyl phenols (V) consisting of vanillin (Vl), acetovanillone (Vn) and vanillic acid (Vd). 2. Syringyl phenols (S), comprising syringealdehyde (Sl), acetosyringone (Sn) and syringic acid (Sd). 3. Cinnamyl phenols (C) that include p-coumaric acid (p-Cd) and ferulic acid (Fd). Besides, we also included some other oxidation products that do not necessarily originate from lignin, such as 3,5-dihydroxybenzoic acid (3,5Bd). Contents are calculated relative to total organic carbon contents and to the dry weight of the sediment. Moreover, indicators for vegetation development (S/V and C/V), wetland extent (3,5Bd/V) and degree of organic matter degradation ((Ad/Al)s and (Ad/Al)v) are given.

Description: The dataset comprises contents and mass-accumulation rates of lignin in sediment cores from the Bering Sea (core SO202-18-3/6) and the Okhotsk Sea (cores SO178-13-6). These data have been obtained on these two cores: SO202-18-3/6 for the dry bulk density, sedimentation rate, and sea surface temperatures; lignin phenols concentrations are available for both cores. Moreover, contents of 3,5-dihydroxybenzoic acid are given. Contents are calculated relative to total organic carbon contents and to the dry weight of the sediment.