Environmental Proxies in the Liupanshan Basin Lake-Level Study (chroma, magnetic susceptibility, CaCO3 and Hg content)

The sample for this study comes from the Liupanshan Basin, specifically the Liwaxia Formation. The specific experimental method is as follows: Chromaticity: Take an appropriate amount of sample and place it on a glass slide for compaction and flattening. Use the CM-700 d-type spectrophotometer produced by Konica Minolta in Japan to measure the three flat surface areas of the sample. During the testing process, ensure a constant background light source to obtain three sets of L, a *, and b * data results and calculate their average. The wavelength range of the testing instrument is 400~700 nm, the measurement wavelength interval is 10 nm, the testing aperture is 8 mm, and the standard deviation of chromaticity values is less than 0.04. Magnetization: Weigh the sample by about 8 g, pack it into a 2 × 2 × 2 cm cube sample box, press it tightly, weigh it, and use a British made Bartington MS2 magnetic susceptibility meter to measure the volumetric magnetization value. Each sample is measured continuously in the x, y, and z directions for three values, and then the average magnetization value is obtained. Obtain the mass magnetization value according to the formula: χ=к/ρ, where ρ is the ratio of the sample mass to the box volume. The content of calcium carbonate is determined by gas flow method. Excess hydrochloric acid is added and reacted with a weighed sample of about 0.1-0.2 g. After the reaction is complete, the carbon dioxide produced by the interaction between carbonate rock and hydrochloric acid is calculated by the volume change in the gas flow tube, and the content of calcium carbonate is converted accordingly. Hg concentration test: Use Lumex PYRO-915 mercury analyzer to measure the Hg concentration of the sample, weighing 0.05~0.1 g per sample. To ensure the stability of the instrument's measurement accuracy, a standard sample is inserted after every five measurements. Total organic carbon: weigh and grind to about 0.2 g of 200 mesh rock sample with a water permeable crucible, use 1:7 diluted hydrochloric acid to pickle the sample for 12 hours, then use distilled water to pickle the sample, wash the sample to neutral and dry it, and use CS-902G high-frequency infrared carbon sulfur analyzer in Oil and Gas Analysis and Testing Center of Northwest Institute of Ecological Resources and Environment, Chinese Academy of Sciences to measure.

本研究的样品采自六盘山盆地，具体为李家洼组（Liwaxia Formation）。具体实验方法如下：
1. 色度测试：称取适量样品置于载玻片上压实整平，采用日本柯尼卡美能达（Konica Minolta）生产的CM-700d型分光光度计，对样品的三个平整表面区域进行测试。测试过程中需保证背景光源恒定，获取三组L、a*、b*数据结果并计算平均值。该测试仪器的波长范围为400~700 nm，测量波长间隔为10 nm，测试孔径为8 mm，色度值的标准偏差小于0.04。
2. 磁化率测试：称取约8 g样品，装入2×2×2 cm的立方体样品盒中压实密封，再次称量后，采用英国产Bartington MS2型磁化率仪测定体积磁化率。每个样品分别沿x、y、z三个方向连续测量三次，取平均值得到平均磁化率。根据公式χ=κ/ρ换算得到质量磁化率，其中ρ为样品质量与样品盒体积的比值。
3. 碳酸钙含量测定：采用气流法测定碳酸钙含量，称取约0.1~0.2 g的样品，加入过量盐酸与样品反应。待反应完全后，通过气流管内的体积变化计算碳酸盐与盐酸反应生成的二氧化碳量，据此换算得到碳酸钙的含量。
4. 汞（Hg）浓度测试：采用Lumex PYRO-915型汞分析仪对样品的汞浓度进行测定，每个样品称样量为0.05~0.1 g。为保证仪器测量精度的稳定性，每完成5次测量后插入一次标准样品校准。
5. 总有机碳测试：称取约0.2 g研磨至200目粒径的岩样，置于透水坩埚中，先用体积比1:7的稀盐酸浸泡样品12小时，随后用蒸馏水漂洗样品，直至洗至中性后烘干。将处理后的样品送至中国科学院西北生态资源环境研究院油气分析测试中心，采用CS-902G型高频红外碳硫分析仪进行测试。