Total petroleum hydrocarbons from marine sediments sampled for the Davis STP project

This metadata record contains an Excel file containing total petroleum hydrocarbon data from analysis of marine sediments collected at Davis Station from December 2009 to March 2010. Refer to the Davis STP reports lodged under metadata record Davis_STP for the full Davis Sewage Treatment Project methods and result details. Davis STP - Total petroleum hydrocarbonsHydrocarbons were extracted from a 10g sub-sample of homogenised wet soil by tumbling overnight with a mixture of 10 mL of deionised water, 10 mL of dichlormethane (DCM), and 1 mL of DCM spiked with internal standards: 254 mg/L bromoeicosane; 55.2 mg/L 1,4 dichlorobenzene; 51.2 mg/L p-terphenyl; 52.2 mg/L tetracosane-d50; and 255 mg/L cyclo-octane. Samples were then centrifuged for 5 minutes at 1000 rpm, this was repeated a further 3 times to ensure complete separation of the organic and aqueous fractions. The DCM fraction was then extracted and placed into GC-vials.Extracts were analysed for total petroleum hydrocarbons (TPH) by gas chromatography using flame ionisation detection (GC-FID; Agilent 6890N with a split/splitless injector) and an auto-sampler (Agilent 7683 ALS). Separation was achieved using an SGE BP1 column (25 m x 0.22 mm ID, 0.25 µm film thickness). 1 µL of extract was injected (5:1 pulsed split) at 310° C and 17.7 psi of helium carrier gas. After 1.3 minutes, the carrier gas pressure was adjusted to maintain constant flow at 3.0 mL/min for the duration of the oven program. The oven temperature program was started at 36 °C (held for 3 minutes) and increased to 320 °C at 18 °C/min. Detector temperature was 330 °C.TPH concentrations were determined using a calibration curve, generated from standard solutions of special Antarctic blend diesel (SAB), and standard diesel. TPH was measured using the ratio of the total detector response of all hydrocarbons to the internal standard peak response.List of compounds analysed-    C8-C28 individual hydrocarbon components-    Naphthalene-    Biomarkers (phytanes)-    Total signal and area, and resolved compounds from C8 to C40, over specific ranges (e.g. C9-C18, SAB)Reporting limit-    0.3 mg.kg-1 on a dry matter basis (DMB) for individual components-    2.5-160 mg.kg-1 on a dry matter basis (DMB) for various calculated rangesAnalytical uncertainty-    Analytical precision: (a) 3 samples extracted and analysed in triplicate, (b) 3 extracts analysed by GC-FID in duplicate; only 1 of each set greater than RL (160): (a) RSD = 2%, (b) RSD = 0.4%-    Site heterogeneity: reproducibility (RSD) of mean data from site replicate samples (mostly duplicates) was 24% (mean, SD 20%, range 4-60%, n=8)-    From the limited data on reproducibility summarised above, it can be concluded that site heterogeneity contributes most to the uncertainty of the TPH data for the site locations.Background of the Davis STP project Refer to the Davis STP reports lodged under metadata record Davis_STP.

本元数据记录附带一份Excel文件，内含2009年12月至2010年3月在戴维斯站（Davis Station）采集的海洋沉积物样品分析所得的总石油烃（total petroleum hydrocarbons, TPH）数据。完整的戴维斯污水处理项目（Davis Sewage Treatment Project, STP）方法与结果细节，请参阅元数据记录Davis_STP下存档的戴维斯STP报告。

戴维斯STP-总石油烃
将10g均质湿土壤子样品与10mL去离子水、10mL二氯甲烷（dichloromethane, DCM）以及1mL添加了内标的二氯甲烷混合液进行过夜翻滚振荡，其中内标组分及浓度分别为：254mg/L溴二十烷、55.2mg/L 1,4-二氯苯、51.2mg/L对三联苯、52.2mg/L氘代二十四烷（tetracosane-d50）、255mg/L环辛烷。随后将样品以1000转每分钟离心5分钟，重复该操作3次以确保有机相与水相完全分离。提取二氯甲烷相并转移至气相色谱进样小瓶中。

提取物采用配有火焰离子化检测器（gas chromatography with flame ionisation detection, GC-FID；安捷伦（Agilent）6890N，配备分流/不分流进样口）及自动进样器（Agilent 7683 ALS）的气相色谱仪，对其中的总石油烃进行分析。色谱分离使用SGE BP1色谱柱（25m×0.22mm内径，0.25μm膜厚）。进样体积为1μL，采用5:1脉冲分流模式，进样口温度设为310℃，载气氦气初始压力为17.7psi。1.3分钟后，调整载气压力以维持柱流速恒定为3.0mL/min，直至升温程序结束。升温程序初始温度为36℃（保持3分钟），随后以18℃/min的速率升温至320℃。检测器温度设置为330℃。

总石油烃浓度通过校准曲线计算得到，校准曲线由南极专用混合柴油（Special Antarctic Blend Diesel, SAB）标准溶液及普通柴油标准溶液绘制得到。总石油烃的定量基于所有烃类的总检测器响应与内标峰响应的比值。

本次分析的化合物清单包括：
- C8-C28单体烃组分
- 萘
- 生物标志物（植烷类）
- 特定碳数范围内（如C9-C18、SAB）的总信号与峰面积，以及C8至C40的分离化合物

报告限：
- 单个组分以干重计（dry matter basis, DMB）的报告限为0.3mg·kg⁻¹
- 各类计算范围的总石油烃以干重计的报告限为2.5-160mg·kg⁻¹

分析不确定度：
- 分析精密度：(a) 3份样品分别进行三次重复提取与分析；(b) 3份提取物分别进行两次GC-FID分析；仅每组中1份样品的浓度高于报告限（160mg·kg⁻¹）：(a) 相对标准偏差（relative standard deviation, RSD）为2%，(b) RSD为0.4%
- 场地异质性：场地重复样品（多为平行样）的平均数据重现性（RSD）为24%（平均值，标准差20%，范围4%-60%，n=8）
- 基于上述有限的重现性数据，可以得出结论：场地异质性是导致该采样点总石油烃数据不确定度的主要来源。

戴维斯STP项目背景 请参阅元数据记录Davis_STP下存档的戴维斯STP报告。