珠江(广州河段)表层沉积物粒度分布特征

沉积物的粒度是控制沉积物中污染物分布的主要因素之一。在珠江(广州河段)表层沉积物粒度组分监测结果的基础上,运用矩法计算公式对各粒度分布参数(平均值、标准差、偏度和尖度)进行了计算,并对沉积物粒度分布特征进行了全面的分析。结果表明:全河段沉积物中砂的平均含量最高,粉砂其次,粘土的含量普遍较低。平均粒径的平均值为0.50 mm,属于砂的粒级范围。在22个断面中,有5个断面的分选系数超过0.5,属于分选中等级别;其余17个断面的分选系数均小于0.5,属于分选好的级别。在22个断面中,出现正偏度和负偏度的断面各占一半。各断面的尖度值在1.00～13.70之间,除1个断面为正态曲线外,其余均为窄峰型。

Grain size distributional characteristics of the surface sediments in the Pearl River (Guangzhou section)

Grain size is one of the main factors to control the pollutant distribution in sediment.Based on monitoring of percentage of grain sizes of the surface sediments in the Pearl River(Guangzhou section),grain size distributional parameters(average value,standard deviation,skewness and kurtosis) were calculated using moment method,and a systematic study was carried out on grain size distributional characteristics.The results showed the highest,middle and the lowest average value of the percentage of grain sizes occurred for the sand,powder sand and clay,respectively.The average value of grain sizes of the River was 0.50 mm,belonging to the grain size scope of sand.There were five sites with standard deviation over 0.5,belonging to moderate sorting degree.Other 17 sites belonged to good sorting degree with standard deviation below 0.5.Sites(with positively skewed) had the same amount with sites(with negatively skewed).The value of kurtosis was between 1.00 and 13.70.Most sites appeared sharp kurtosis in grain size distribution,but one site was normal.