哈尔滨尘暴天气沉降物的物质组成及其对物源的限制

Material characteristics of dust fallouts during the dust-storm weather in Harbin: Constraint on the provenance

本文对哈尔滨尘暴事件(2011年5月11日)的干沉降和湿沉降粉尘进行了粒度、REE和Sr-Nd同位素组成分析。同时,为了限制尘暴粉尘的源区,还对东北沙地(科尔沁沙地和呼伦贝尔沙地)进行了表土采样。结果显示,干沉降粉尘呈双峰态粒度分布,众数值分别为3.6μm和28μm,而湿沉降呈单峰态粒度分布,众数值为6μm。哈尔滨尘暴事件粉尘的粒度分布模式可与黄土高原黄土、红黏土及世界上其他地区的长距离搬运粉尘相对比。这些尘暴粉尘来自遥远的源区。干沉降和湿沉降粉尘表现出相同的REE模式和Sr-Nd同位素组成,它们来自科尔沁沙地和浑善达克沙地。现代尘暴事件的干沉降与湿沉降粉尘相同的物质来源暗示了黄土高原黄土的细颗粒和粗颗粒组分有相同的风尘源区。

The dry-and wet-deposited dust depositions of the dust-storm event in Harbin on May 11,2011 as well as the surface sediments from the potential sources were collected for investigation of grain-size,REE and Sr-Nd isotopic compositions.Some conclusions have been reached:The dry-deposited dusts are marked by bimodal grain-size distributions with fine mode at 3.6μm and coarse mode at 28μm whereas the wet-deposited dusts are indicative of unimodal grain-size modes with a fine mode at 6μm.The grain-size modes for Harbin dust-storm dusts are compatible with CLP loess and Pliocene eolian red clay as well as the eolian dust entrained for a long distance in other regions of the world.These dust-storm depositions have a derivation from distinct sources.There are identical REE patterns and Sr-Nd isotopic compositions for dry-and wet-deposited dusts,suggestive of the derivation from Horqin Sandy Land and,to a certain extent,Onqin Daga Sandy Land.The corresponding Sr-Nd isotopic compositions for dry-and wet-deposited dusts give clues to suggest that fine grains in the CLP loess deposits are expected to be of derivation identical to coarse grains.