西宁市大气降尘粒度特征分析

西宁地处青藏高原东北缘,是柴达木沙尘暴东移的必经之道和沉降区.对西宁3个采样点2013年1月至8月收集的尘暴与非尘暴以及混合降尘进行粒度分析,发现:1)西宁尘暴与非尘暴降尘粒度特征无明显差别,以粉质亚砂土为主,平均粒径Ф值介于5.76~5.23,频率曲线呈近似正态分布,分选较差;2)兰州与西宁的非尘暴降尘物源可能存在明显的差异;3)干法测量粗颗粒组分明显高于湿法,超细颗粒组分湿法高于干法,干法测量有利于获取尘暴降尘的原始粒度特征;4)西宁尘暴和非尘暴降尘粒度特征与西宁黄土样品粒度特征十分相似,说明现代降尘是地质时代风尘活动的继续,现代风积作用仍在进行.

Grain-size Distributions Analysis of Xining Dust

Xining, located in the northeastern margin of the Tibetan Plateau, is an important dust dep- osition area and necessary passage which Qaidam sandstorm moves to the east. We analyzed grain--size distributions of the dust of sandstorm and none--sandstorm, sampling from 3 sites in Xining from January to August, 2013. The results show that. 1） there is no significant difference in the grain--size distributions between the dust of sandstorm and non--sandstorm. The dust of sandstorm and non--sandstorm is mainly composed of silty sand loam which average grain--size of Ф value is between 5.76 and 5.23. Its frequency curve is similar to normal distribution and its sorting is poor; 2） the source of none--sandstorm dust between Lanzhou and Xining may have obvious differences; 3） the coarse components under scirocco measurement are significantly higher than those of hydro measurement. The ultrafine grain components of hydro measurement are higher than those of scirocco measurement, the scirocco measurement is helpful to obtain the original characteristics of particle size of the dust; 4） the characteristics of grain--size of the sandstorm and none--sandstorm dust in Xining are similar to the characteristics of the loess sample grain-- size in Xining, which illustrates that the modern dust is a continuation of the dust activity in geological time and the modern dust deposition is still going on.