Organic matter composition (isotopic composition and biomarker characterisation) from Lake Paringa and soils from Westland, New Zealand (NERC Grant NE/P013538/1)

The dataset contains geochemical measurements which quantify the amount and source of carbon in organic matter of sediments from Lake Paringa, New Zealand. Measurements were made on a 6 m sediment core collected in 2015 from the lake bed using a Mackereth corer (PA6m1a). The core was correlated to master core PA1 which has a well-established age-depth model based on accelerator mass spectrometry measurements of the radiocarbon (14C) content of terrestrial macrofossils (Howarth et al., 2016). In addition, soil samples were collected using a soil auger from two elevation transects in westland, New Zealand in 2016 and 2017 (from Mt. Fox and Alex Knob). All sediment samples were freeze dried and ground to homogenise them prior to geochemical analyses. Organic carbon concentration (%) and the stable isotopic composition of organic carbon (δ13C) was measured (Frith et al., 2018) following the removal of carbonate minerals (0.25 M hydrochloric acid for 4 hours at approximately 70 °C) by combustion of sediment at 1,020 °C in a Costech Elemental Analyser coupled via a CONFLO III to a Thermo Scientific Delta V Advantage stable isotope mass spectrometer. Total nitrogen content (N, %) and its isotopic composition (δ15N) was measured by combustion of untreated samples in a Costech Elemental Analyser with a CARBOSORB trap to inhibit large CO2 peaks from affecting measurements. A subset of samples were selected for analysis of the radiocarbon activity (14C, reported as F14C) of bulk organic matter by accelerator mass spectrometry after graphitization. A subset of sediment samples from the lake core and soil samples were selected for the analysis of biomarker abundance and their hydrogen isotope composition. We focused on the extraction of n-alkanes from aliquots of lake sediment (~2 g) using established methods (Wang et al., 2020). These measurements are reported in the dataset as the abundance of n-alkanes (chain lengths C21 to C35) in ug/g of sediment (and sum of chain lengths and ratios - carbon preference index). Finally, the dataset includes outputs of organic matter provenance: modelled elevation and depth, as described in Wang et al., (2020). In the datafile, the sample elevation and depth are provided. The labels for data are as follows. For down core sediment samples from Lake Paringa, they are labelled with the core code (PA6m1), and the sampling interval in centimetres (PA6m1_x). Soil samples from an elevation transect from Mt Fox (MF-YY-a) are labelled with a distinct code for each site (YY) and sub-code for each soil depth (a). Soil samples from an elevation transect of Alex Knob (5.Z.z) are labelled based on sub-site (Z) and soil depth (z).

该数据集收录了新西兰帕林加湖沉积物有机质中碳元素的含量及其来源的地球化学测量数据。测量于2015年通过对湖床进行6米沉积物柱样采集（使用Mackereth柱样采集器PA6m1a）而完成。该柱样与具有基于加速器质谱法测定的陆地宏化石碳-14（14C）含量所建立的年龄-深度模型的基准柱样PA1进行对比。此外，2016年和2017年（从福克斯山和亚历克斯诺布山）在西兰西部的两个海拔梯度带中，利用土壤钻采集了土壤样本。所有沉积物样本均经过冷冻干燥并研磨以实现均质化，随后进行地球化学分析。有机碳浓度（%）及有机碳的稳定同位素组成（δ13C）在去除碳酸盐矿物（0.25 M盐酸在约70°C下反应4小时）后，通过在Costech元素分析仪中于1,020°C燃烧沉积物，并与Thermo Scientific Delta V Advantage稳定同位素质量光谱仪的CONFLO III耦合进行测量（Frith等人，2018年）。总氮含量（N，%）及其同位素组成（δ15N）通过在Costech元素分析仪中燃烧未经处理的样本，并使用CARBOSORB陷阱抑制大型CO2峰来影响测量而获得。一部分样本经过石墨化后，通过加速器质谱法分析了大量有机物的放射性碳活动度（14C，以F14C表示）。沉积物柱样和土壤样本的一部分被选用于分析生物标志物丰度和其氢同位素组成。我们专注于从湖泊沉积物的等份（约2克）中提取n-烷烃（链长C21至C35）的常规方法（Wang等人，2020年）。这些测量结果在数据集中以沉积物中n-烷烃的丰度（链长C21至C35）以ug/g计（以及链长总和与比值——碳选择指数）的形式报告。最后，数据集还包括了有机质来源的模型化海拔和深度输出，如Wang等人（2020年）所述。在数据文件中，提供了样本的海拔和深度。数据标签如下：对于帕林加湖下沉积物样本，以柱样代码（PA6m1）和采样间隔（厘米，PA6m1_x）进行标记；来自福克斯山海拔梯度带的土壤样本以每个地点（YY）的独特代码和每个土壤深度的子代码（a）进行标记；来自亚历克斯诺布山海拔梯度带的土壤样本则根据次级地点（Z）和土壤深度（z）进行标记。