Pretreatment Method of Grain Size Measurement of Marine Sediments in Paleoenvironment Research
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摘要: 对深海沉积物样品进行粒度测试前，应根据研究目的，在预处理过程中有效去除碳酸盐和生物硅，同时完好保留陆源碎屑组分，才能使测试结果准确反映古气候和古环境变化。对采于南海的样品分别加入不同剂量浓度为10％的盐酸或浓度为25％的醋酸，以及不同剂量的NaOH或Na2CO3，同时利用有机元素分析仪、硅钼蓝比色法、环境扫描电子显微镜分析、观察不同方法的预处理效果，并结合粒度测试的结果认为，对于碳酸盐，盐酸和醋酸均可将其有效去除，但由于少量盐酸仍会对陆源矿物组分造成破坏，因此应使用酸性较弱的醋酸；对于生物硅，大剂量的Na2CO3仍难将其有效去除，而使用小剂量的NaOH即可去除干净，但需控制剂量以避免破坏矿物组分。针对南海沉积物中的各种生物组分含量，确定了醋酸和NaOH的使用剂量并建立了预处理流程。Abstract: To yield grain size results of marine sediments reflecting variation of paleoenvironment and paleoclimate without distortion, biogenic carbonate and opal in samples should be effectively removed while terrigenous component should be undamaged during pretreatment procedure before measurement. To find the appropriate pretreatment method, marine sediments from South China Sea were treated with different dosages of hydrochloric acid (10%) or acetic acid (25%) and different dosages of NaOH and Na2CO3, then organic element analyzer, silicamolybdenum blue colorimetry and ESEM were used to evaluate the effects combined with the results of grain size measurement. The synthetic outcomes reveal that both of hydrochloric acid and acetic acid can eliminate biogenic carbonate well, however, because even a few dosage of the former can destroy terrigenous mineral component, the latter should be adopted during pretreatment procedure owing to its lower acidity; a large dosage of Na2CO3 still can't eliminate biogenic opal effectively but only a few dosage of NaOH can work well, so the latter should be used with restricted dosage to avoid destroying mineral component. According to biogenic content in marine sediments from SCS, the quantities of acetic acid (25%) and NaOH were determined and pretreatment procedure was established.
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Key words:
- marine sediments /
- grain size /
- pretreatment procedures /
- biogenic carbonate /
- biogenic opal
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