长江口底床沉积物粒度分布特征及测定方法对比研究

Sediment distribution patterns in the Yangtze Estuary and comparison of particle size measurement methods

通过传统法(吸管—筛析综合法)和激光法(采用美国Coulter激光粒度仪,LS-100Q)两种方法对179个长江口底床沉积物分别进行了粒度测量。结果显示,长江口内上半段和北港要明显粗于南港,以砂至粉砂质砂为主,而由南港至口外及杭州湾北部均以黏土质粉砂为主;而对于口外,粉砂质砂覆盖了北面的大部,要明显粗于南面的黏土质粉砂。南支口外以现代沉积物为主,而北支口外沉积物受控于更新世残留砂。在测量方法方面,传统法与激光法测得结果的相对大小,随着不同样品粒径的变化存在明显的分布规律。同时,对平均粒径、中值粒径、标准偏差、峭度和偏度五个粒度参数进行了回归分析,得出了可靠的换算公式,可运用于今后的粒度参数转换。

Sediment grain size analyses for 179 seabed samples in the Yangtze Estuary were conducted by both traditional （pipette and sieving） and laser （Coulter, LS-100Q, USA） methods. Our results show that the sediments in the North Channel and the upper reach of the inner Yangtze Estuary are mainly sands and silty sands, usually coarser than those in the South Channel. The deposits in the South Channel and the Northern Hangzhou Bay are mainly clayey silt. Meanwhile, silty sands cover the most northern part of the outer estuary, and are apparently coarser than the clayey silty in the southern part of the outer estuary. The sediments in the outer estuary off the South Channel mainly refect the modern deposits, while the sediments off the North Channel are dominated by relict Pleistocene sands. As to the measurement methods, there are apparent distribution patterns of relative size from the two methods. Moreover, regression analyses for the fve parameters, including mean size, median size, standard deviation, skewness, and kurtosis, were conducted to obtain reliable conversion formulas for the two methods. These can be used in future studies for comparison with historical data.