浙闽沿岸南部泥质沉积中心表层沉积物粒度特征及其季节性差异

Grain-size Characteristics of the Surface Sediments and Their Seasonal Variability in the Mud Depocenter off the Southern Zhejiang-Fujian Coast

通过对浙闽沿岸南部泥质沉积中心15个站位夏季和冬季表层沉积物的粒度分析和对比,探讨了表层沉积物粒度的分布特征、季节性差异及其影响因素。研究结果表明,各站样品以黏土质粉砂为主,各粒度参数差别较小,平均粒径和标准偏差呈显著的负相关,偏态和尖态呈弱负相关。粒级—标准偏差曲线上,在4.92～6.46和25.32～33.27μm之间存在高峰值,在11.16～13.39μm之间为低谷值。粒度分布具有季节性差异,冬季样品各粒度参数分布范围均高于夏季,平均粒径(值)总体上比夏季的要小,偏态和尖态等值线的梯度明显大于夏季的。在粒级—标准偏差曲线上,冬季样品的变化程度要显著高于夏季的。粒度分布的差异主要受物质来源和海洋动力环境的季节性变化影响。

Samples of surface sediments at 15 stations in the mud depocenter off the southern Zhejiang-Fujian coast were collected in both summer and winter seasons. The distribution pattern,seasonal variability of grain-size of the surface sediments in this area and their influential factors were discussed based on the grain-size measurements. The results indicate that surface sediments were mainly clayey silts with slight variations in the grain size parameters such as median grain size （ Mz） ,standard deviation （ SD） ,skewness （ Sk） and kurtosis （ Kg）. There exists an evidently negative correlation between Mz and SD,while a weakly negative correlation is found between Sk and Kg. Two peak values around 4. 92 ～ 6. 46 and 25. 32 ～ 33. 27 μm,and a low value around 11. 16 ～ 13. 39 μm are identified from the SD of grain-size curves. Meanwhile,significant seasonal variability is found as indicated by the large differences between the parameters of surface sediments collected in summer and winter season. The ranges of all the four parameters in the winter samples are higher than those in the summer samples,while the  values of Mz in winter samples are generally smaller than those in the summer samples. And the gradients of Sk and Kg are larger than those in the summer samples at the same station. The variability in SD of grain size in the winter samples was evidently higher than that in the summer samples. The variations of the parameters of surface sediments in this area are mostly attributed to sediment sources and the seasonal difference in marine dynamic environment.