哈尔滨沙尘沉降物的粒度组成及其源地分析

Grain-size Distributions of Harbin Fallouts and Its Source Areas

对2002年3月20日和2006年3月10日哈尔滨沙尘沉降物进行收集,同时还对城市松散的地表裸土进行了采样。粒度分析结果显示,沙尘沉降物粒度组成存在一定的差异。2002年沉降物的粉砂占71.2%,砂粒组分占21.7%,粘粒组分含量仅占7.1%;2006年沉降物的粉砂含量占73.6%,粘粒占19.8%,砂粒占6.6%。总体上看,2002年沉降物粒度比2006年沉降物明显偏粗。2002年沙尘沉降物粒度组成表现出明显的三峰分布特征,而2006年沉降物则呈双峰分布特征,说明哈尔滨沙尘沉降物是由多种不同成因的组分构成。城市地表裸土中可供远程搬运的细颗粒物质（〈63μm）含量较多,在60%以上,可为沙尘天气提供较多的粉尘物质。认为哈尔滨沙尘沉降物中砂粒级的粗颗粒物质是就地起沙,属于近源堆积;长期悬浮颗粒（〈18μm）主要来源于远距离的外源输入,包括黄土高原在内的西北地区可能为哈尔滨沙尘提供了一定量的粉尘物质;而短期悬浮颗粒（18～63μm）主要是区域内部沙尘天气产生,来源于城市地表裸土。2002年沙尘以内源输入为主,但外源输入也占据一定比例,而2006年沙尘主要以外源输入为主,内源输入占据的比例相对较小。

The two fallouts, respectively collected on March 20, 2002 and March 10, 2006 in Harbin city, were carried out grain-size analysis. The results showed that there exist many differences between two sand-dust dust falls. The silt content of dustfall in 2002 amount to 71.2%, sand 19.8% and clay 7.1%. The silt content of dust fall in 2006 account for 73.6%, and clay come to 19.8%, and sand come up to 6.6%. In general, the grain size of dust fall in 2002 was evidently much courser than that of dust fall in 2006. The grain-size distribution of fallouts in 2002 exhibit three-peaked characteristic, however, that of fallouts in 2006 was characterized by bimodal distributions, showing that two fallouts in Harbin area both were composed of many kinds of components with different causes. It was considered that the coarse particle materials of 〉63 μm, from two sand-dust fallouts in Harbin city, were from local ground offering plentiful sand-sized particles, and were near-source deposits. The long-term suspended particles （〈18 μ m） were mainly from long-distance outer-source input. The short-term suspended particles of 18-63 μ m were possibly from regional inner sand-dust weather, and may also mixed the existence of outer-source import of mid-short distance. The sand-dust deposits in Harbin were the admixture of both coarse grains transmitted in short distance and fine grains transported in long distance, among others, 2002 sand dust gave priority to inner-source input, but also was of a certain proportion of outer-source input, and 2006 sand dust mainly dominated by outer-source input, and possessed less scale of inner-source input.