不同前处理对湖泊沉积物粒度测量结果的影响

Influence of Different Pre-treatments on Grain-size Measurement of Lake Sediments

选择两个不同湖泊的沉积物为研究对象,通过对比不同前处理后的测量结果,比较了各种前处理方法的优劣,并提出两种较好的前处理方法.结果显示不同湖泊沉积物和同一湖泊的不同样品对各种前处理方法的响应并不相同,从整体上来看,经过去离子水浸泡后并用超声波分散的方法效果最好,目前最常用的传统的前处理方法结果也较好.测量结果还显示,经过(NaPO3)6处理后再用超声波分散容易使频率分布曲线出现细粒次峰,产生双峰分布的型式,原因也许与(NaPO3)6的分散作用使颗粒絮凝作用减小,增强超声波对颗粒的直接撞击作用,使颗粒被击碎从而产生双峰分布有关.

As an important environmental index, grain-size character of lake sediments has been widely used in the lake sediment and environmental change studies, accurate measurement is an indispensable requisition for its application. In the depositing process of the lake sediments, chemical and physical change can be taken place and some organic matter, some carbonate may form, organic matter and carbonate can make the sediments cement, and the cementation is not helpful for the grain-size measurement , so pre-treatments is very necessary to get accurate grain-size data. There are some differences in the pre-treatments of lake sediments measurement in different laboratories. Here we present our experimental data of lake sediment grain-size measurement from two different lakes. Based on different pre-treatments, the results of the measurements were analyzed and compared, and two preferable pre-treatment methods were presented. The results indicate that the sediments from different lakes have different responds to different pre-treatment, it can be seen from the whole samples that the pre-treatment that dipping in the distilled water and dispersed by ultrasonic( method F-10 in the text) obtained the best dispersing effect, and the traditional pre-treatment (method E-3 in the text) , which is also the most common use one, also got rather good results. Whereas pre-treated by (NaPO3 )6could make the sediment particles easily to be shattered by ultrasonic and then another very thin particle peak appeared, possibly (NaPO3 )6 , as a kind of dispersant, decreasing the flocculation effect between the particles and then the direct striking effect to the particles of the ultrasonic strengthened, under the strong striking, particles can be broken up. We believe that the bimodal distribution curves do not reflect the real condition of the samples, and this kind of abnormal distribution can bring false environmental information, more attention need to pay to this phenomena when measuring the grain-size of the lake sediments.