环境磁学样品干燥过程中的磁性效应

Environmental Magnetism Research on the Magnetic Effects by Different Drying Processes to Tidal Flat Sediments

对长江口南岸潮滩沉积物柱样和表层样品的烘干、风干和冻干法处理 ,然后进行系统磁性测量和水分、有机质的测定。实验结果得知 :以冻干法为参照 ,烘干和风干方法对样品的磁参数的稳定性影响很小 ,但研究质地粘重样品时 ,应避免采用风干方法或校正风干样含水量质量后计算相关的磁参数。有机质的含量与主要磁参数成正相关 。

Magnetic effects in sediment of Yangtze River estuary tidal flat is studied in laboratory by different drying treatments. Three treatments,including oven drying , air drying and lyophilization are applied in the core (total length:21 cm,sampled from high tidal flat) and tidal flat surface (0～5 cm) sediment samples(high, middle and low tidal flat), and then the magnetic properties,water and total organic matter contents has been measured systematically. Results show that oven drying, air drying and lyophilization treatment processes de affect the most of magnetic minerals .The SIRM- χ crossplot of the core samples shows linearly significant correlation, the upper part sub samples of the core have high value of SIRM and χ , the bottom part have low value of SIRM and χ .According to F 300mT , S -20mT and S -100mT , ferrimagnetic minerals dominate the magnetic properties in the Yangtze River estuary tidal flat sediments. The particle size of whole core become finer from bottom to upper sub samples. The differences of the three samples treatments are insignificant, according to type of magnetic minerals, consistence of dominated magnetic minerals, concentration of magnetic minerals and particle size, in the whole core sub samples and its variations. The oven drying is still effective sample treatment, and the lyophilization is the best sample drying method of the three. Under the general condition, the effect of oven drying and air drying samples to magnetic change, compare with lyophilization, is so little that it does not result in magnetic parameters wrong interpretation. However,for clay samples, air drying samples will cause much difference in the value of magnetic parameters, thus its air drying water contents after magnetic measurement should be avoided or calibrated. Another result shows that organic matter contents are positively correlated with main magnetic parameters.This study has some limits because of only test for the tidal flat sediment samples, so if do some further deduction on this topic, more studies on various sediments and soils samples are necessary.