基于图像法和激光法的山东半岛黄岛海滩沉积物粒度特征对比

以新型快速成像及处理技术为基础的动态图像法可为单个样品快速建立百万至上亿个颗粒的图像及粒度、粒形参数数据库,可直观表现天然沉积物的海量颗粒的大小和形状信息,但目前对其与激光法测试结果之间的异同尚缺乏深入理解。本文对采自山东半岛黄岛地区黄海沿岸3处海滩共190个样品进行动态图像粒度分析,通过等效投影面积径(等积径)计算均值粒径、分选系数、偏度、峰度等粒度参数,并与激光法测试结果进行对比。结果表明:1)现代海滩沉积物图像法统计粒径比激光法稍粗,但二者之间的差异较之细粒沉积物较多的类型(如冲洪积物)而言已经很小;2)现代海滩沉积物图像法粒度分析较之激光法分选更优,偏度和峰度均更小;3)图像法和激光法粒度分析结果在沉积环境判别中具有相近的功能,但图像法对沉积环境和动力条件的响应更为敏感。这些认识为动态图像粒度分析技术的应用推广和资料解释提供了新的理论与技术支持。

COMPARISONS OF GRAIN-SIZE ANALYSIS RESULTS OF BEACH SEDIMENTS IN THE HUANGDAO DISTRICT,QINGDAO,BASED ON IMAGING AND LASER METHODS

The dynamic image method,based on rapid image-processing technology,can quickly create a massive database of grain size,shape and parameters for natural sediment,directly represent the size and shape information of grains up to a hundred million for each sample.However,at present,there is still a lack of deep understanding of the similarities and differences between them and the test results of other traditional methods.In this paper,8 groups of samples were collected from the Yellow Sea coast of Huangdao District(35°53'~36°08'N,120°01'~120°18'E),Qingdao City,Shandong Province.Among them,1 group of samples is taken from the apex to the front of the Fenghe River Delta,1 group from the beach between Fenghe River and Yinzhuhe River,4 groups from two intertidal zones located at Jinshatan Beach(two groups)and the Yinshatan Beach(two groups),respectively,and 2 groups from two short profiles located at the front of the Fenghe River Delta and near the high tide level of Yinshatan Beach,respectively.A total of 190 samples were analyzed by dynamic-image grain-sizer and laser grain-sizer,respectively.The results of dynamic image method are based on the equivalent-projection area diameter to calculate the median grain-size,mean grain-size,sorting,skewness,kurtosis and others,and compare them with the corresponding parameters by laser one.The results show that:(1)The comparison of grain-size frequency distributions shows that the major difference between two methods is concentrated on the finer tail,and the portion of finer grains by laser method usually far exceeds that by image one.As to the cumulative frequency curve,the laser method usually shows more complex segments than the imaging one.(2)The comparison of grain-size data indicates that the grain-size by imaging method in the study area is slightly coarser than that of the laser one(the direct contrast is between 0.004~0.448 phi,and the difference under the same measurement range is 0.005~0.441 phi;the maximum difference of physical size is about 36%).The difference value is much lower than that of the sediment rich in the fine-grained material(such as the Jinshajiang River alluvium of 0.68~2.40 phi).This indicates that the difference between two methods is closely related to the type and characteristics of the deposit.(3)The sorting coefficient(0.37~1.02)by image method in this study is always smaller than that by laser one(0.41~1.09),showing that the sorting by image method is better than that by laser one;the absolute value of skewness by image method is always smaller than that by laser one,and the kurtosis by image method is also smaller than that by laser one.(4)The grain-size analysis results by two methods in this study have not reflected the characteristics of mature beach,which may be related to sand input by both rivers and/or human.However the results by two methods have similar function in sedimentary environment discrimination.The comparison between the sample groups of different sedimentary environments shows that the image method is more sensitive to the sedimentary environment and dynamic conditions.(5)The above conclusions are still valid after the same measurement range.These understandings provide new theoretical and technical support for the application of dynamic image granularity analysis technology and its data interpretation.